WO2019121766A1

WO2019121766A1 - Building unit for magnetocaloric heat exchanger

Info

Publication number: WO2019121766A1
Application number: PCT/EP2018/085629
Authority: WO
Inventors: Colman Carroll; Dietmar Bender; Herve Dietsch; Christian Eichholz; Benjamin SCHMIDT-HANSBERG
Original assignee: Basf Se
Priority date: 2017-12-18
Filing date: 2018-12-18
Publication date: 2019-06-27

Abstract

Described are building units for a heat exchanger block for a magnetocaloric heat exchanger, magnetocaloric heat exchangers comprising a heat exchanger block comprising two or more of said building units, as well as processes for manufacturing said building units and said magnetocaloric heat exchangers.

Description

Building unit for magnetocaloric heat exchanger

The present application relates to a building unit for a heat exchanger block for a magnetocaloric heat exchanger, to magnetocaloric heat exchangers comprising a heat exchanger block comprising two or more of said building units, as well as to processes for manufacturing said building units and said magnetocaloric heat exchangers. Magnetocaloric materials and magnetocaloric heat exchangers are known in the art, see e.g. WO 2011/018348 A2, US 8,763,407 B2 and FR 3 004 795.

Related art is also

JP 2007 291437 A

US 201 1/048690 A1

US 2017/336108 A1

US 2014/020881 A1

US 2014/020881 A1.

In the design of a magnetocaloric heat exchanger, a couple of challenging, and in some cases even opposing requirements has to be considered, inter alia maximum interface area between solid (magnetocaloric material) and fluid (heat transfer medium) phase in order to enhance the heat transfer, maximum magnetocaloric density for the sake of efficient use of the magnetic field volume, and minimum resistance against the flow of the heat transfer medium for reducing the pressure drop, as well as mechanical stability against the stress exerted from the flow of the heat transfer medium and from the cycles of introduction into and removal from the magnetic field. Further constraints result from restrictions in the processability of magnetocaloric materials, which are usually brittle, into shaped bodies having fine structures, which are necessary for complying with the above- mentioned requirements, and from the need of efficient manufacturing of such shaped bodies.

These and other problems are solved by a building unit according to the present invention for a magnetocaloric heat exchanger and by a magnetocaloric heat exchanger according to the present invention, as well as by the processes according to the present invention for manufacturing said building unit units and said magnetocaloric heat exchangers. In a first aspect, the present invention relates to a building unit for a magnetocaloric heat exchanger,

said building unit comprising a shaped body made up of a one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials, said shaped body comprising

a base plate, said base plate having a first surface and a second surface opposite to each other

and arranged on said first surface of said base plate a fluid flow structure comprising

two or more parallel ridges protruding from said base plate

- one or more grooves each extending between two of said ridges

wherein

said base plate has a base plate thickness B

said ridges have a height H

at least one of said grooves has a width C of 200 pm or less, preferably of 100 pm or less, more preferably of 50 pm or less, measured at half of height H

at least one of said ridges has a width W of 200 pm or less, preferably of 100 pm or less, more preferably of 50 pm or less, measured at half of height H

wherein for said at least one of said groove and said at least one ridge adjacent to said groove

0.5 < H/B < 2

0.5 < H/C < 2 0.5 < H/W < 2.

Accordingly, said building unit according to the present invention comprises a shaped body made up of a one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials. Said binding agent binds said particles of said one or more magnetocaloric materials within said shaped body. Without wishing to be bound by theory it is assumed that said binding agent forms a matrix wherein said particles of one or more magnetocaloric material are embedded. In certain preferred cases, said binding agent is in a cured state.

Said shaped body comprises a base plate, said base plate having a first surface and a second surface opposite to each other. Arranged on said first surface of said base plate is a fluid flow structure allowing for the flow of a heat transfer medium (herein also referred to as a heat transfer fluid) along predetermined flow paths. Said fluid flow structure comprises two or more parallel ridges protruding from said base plate and one or more grooves each extending between two of said ridges. Said grooves allow for flow of a heat transfer fluid. Each groove has two adjacent ridges confining said groove. Preferably, the ridges protruding from said base plate and the grooves extending between said ridges cover a large part of the first surface of said shaped body, so that a large number of grooves with adjacent ridges extend over said first surface of said shaped body.

Usually, the second surface of said base plate of said shaped body is at substantially even level, i.e. has no protrusions and no recesses.

Ideally, the ridges and grooves have a rectangular cross section, i.e., each groove has a bottom area extending substantially parallel to the second surface of said base plate and two walls extending substantially perpendicular to the second surface of said base plate, and each ridge has a top area extending substantially parallel to the second surface of said base plate. Herein, it is understood that said second surface of said base plate is the surface of the base plate which faces away from the fluid flow structure.

However, due to material flow limitations during manufacturing the fluid flow structure by means of an embossing roll (see below), there may occur some deviation from an ideal rectangular cross section, resulting in rounding of the corners, compared to the above- described ideal rectangular cross section so that the real cross section of the grooves is close to U-shape, and the real cross section of the ridges is close to an upside-down U. Herein, the cross section of each groove has a dip and two walls, and the cross section of each ridge has a peak. Said base plate has a base plate thickness B which corresponds to the perpendicular distance between the second surface of said base plate (i.e. the surface of the base plate which faces away from the fluid flow structure) and the height level of the bottom resp. dip of a groove. Preferably, said base plate thickness B is in the range of from 10 pm to 200 pm, preferably 10 pm to 100 pm, more preferably 10 pm to 50 pm.

Said ridges each have a height H which corresponds to the perpendicular distance (perpendicular with respect to the second surface of the base plate) between the height level of the bottom resp. dip of a groove adjacent to said ridge and the height level of the top area resp. peak of said ridge. Said height H is 200 pm or less, preferably in the range of from 10 pm to 100 pm, preferably of from 20 pm to 50 pm.

The sum of base plate thickness B and height H of the ridges is substantially constant throughout the whole shaped body. Preferably, said base plate thickness B is substantially constant throughout the whole shaped body, and all ridges have the same height H. Accordingly, said bottoms resp. dips of all grooves are substantially at the same height level respective to the second surface of the base plate.

In said fluid flow structure,

wherein for said at least one groove and said at least one ridge adjacent to said groove

0.5 < H/B < 2, preferably 1 < H/B < 2

0.5 < H/C < 2, preferably 1 < H/C < 2

0.5 < H/W < 2. preferably 1 < H/W < 2. In case the cross-sections of the ridges and grooves are ideally rectangular, as described above, said width C of said groove and said width W of said ridge are constant over the whole height H of said ridges. In a preferred building unit according to the present invention,

all grooves have a width C of 200 pm or less, preferably of 100 pm or less, more preferably of 50 pm or less, measured at half of height H, wherein preferably all grooves have the same width C

- all ridges have a width W of 200 pm or less, preferably of 100 pm or less, more preferably of 50 pm or less, measured at half of height H, wherein preferably all ridges have the same width W

and for all of said grooves and their adjacent ridges

0.5 < H/B < 2, preferably 1 < H/B < 2

0.5 < H/C < 2, preferably 1 < H/C < 2

0.5 < H/W < 2. preferably 1 < H/W < 2.

The fluid flow structure as described herein consists of very fine structures, which due to the plurality of tiny channels and narrow but relatively high (in relation to their width W) ridges provides for a large interface area between the magnetocaloric material and the heat transfer fluid as well as for short heat conducting pathways and for a low pressure drop of the fluid flow.

Figures 1a and 1 b show side views of examples of a shaped body 1 as described above. Said shaped body 1 comprises a base plate 2, said base plate 2 having a first surface 2a and a second surface 2b opposite to each other. Arranged on said first surface 2a of said base plate 2 is a fluid flow structure comprising a plurality of ridges 3 protruding from said base plate 2 and a plurality of grooves 4 each extending between two of said ridges 3. Said second surface 2b of said base plate 2 of said shaped body 1 is at substantially even level, i.e. has no protrusions and no recesses.

All figures are schematically and not drawn to scale. In figure 1a, said ridges 3 and grooves 4 have a rectangular cross section. Each groove 4 has a bottom area extending substantially parallel to the second surface 2b of said base plate 2 and two walls extending substantially perpendicular to the second surface 2b of said base plate 2, and each ridge 3 has a top area extending substantially parallel to the second surface 2b of said base plate 2. The bottoms of all grooves 4 are substantially at the same height level respective to the second surface 2b of base plate 2. The top areas of all ridges 3 are substantially at the same height level respective to the second surface 2b of base plate 2. Said base plate 2 has a base plate thickness B which corresponds to the perpendicular distance between the second surface 2b of said base plate 2 (i.e. the surface of the base plate 2 which faces away from the fluid flow structure) and the height level of the bottoms of the grooves 4. Said ridges 3 each have a height H which corresponds to the perpendicular distance between the height level of the bottoms of said grooves 4 and the height level of the top areas of said ridges 3. The base plate thickness B is substantially constant over the whole shaped body 1 , and all ridges 3 have the same height H. The grooves 4 have a width C measured at half of height H, and the ridges 3 have a width W measured at half of height H, wherein 0.5 < H/B < 2 0.5 < H/C < 2 0.5 < H/W < 2. In figure 1 b, said ridges and grooves have a cross section deviating from a rectangular cross section in such manner that the corners are rounded. In figure 1 b, said rounding is exaggerated for illustrative purposes. The cross section of each groove 4 has a dip (deepest point of the cross section of said groove) and two walls partly extending in a direction substantially perpendicular to the second surface 2b of said base plate 2, and the cross section of each ridge 3 has a peak (highest point of the cross section of said groove). The dips of all grooves 4 are substantially at the same height level respective to the second surface 2b of base plate 2. The peaks of all ridges 3 are substantially at the same height level respective to the second surface 2b of base plate 2. Said base plate 2 has a base plate thickness B which corresponds to the perpendicular distance between the second surface 2b of said base plate 2 (i.e. the surface of the base plate 2 which faces away from the fluid flow structure) and the height level of the dips of the grooves 4. Said ridges 3 each have a height H which corresponds to the perpendicular distance between the height level of the dips of said grooves 4 and the height level of the peaks of said ridges 3. The base plate thickness B is substantially constant over the whole shaped body 1 , and all ridges 3 have the same height H. The grooves 4 have a width C measured at half of height H, and the ridges 3 have a width W measured at half of height H wherein, 0.5 < H/B < 2, 0.5 < H/C < 2, 0.5 < H/W < 2.

In some preferred types of building units according to the present invention, said ridges extend continuously from one edge to another edge (typically the opposite edge) of the first surface of said base plate. This type of building unit is advantageous due to its uncomplicated structure which reduces the efforts for manufacturing such building unit.

Figure 2 shows a plane view (view from above) of an example of a shaped body 1 having a fluid flow structure as described above. Said fluid flow structure comprises a plurality of parallel ridges 3 extending continuously from one edge to the opposite edge of the first surface 2a of base plate 2, thereby defining a plurality of grooves 4 extending continuous- ly from one edge to the opposite edge of the first surface 2a of a base plate 2. Said grooves 4 act as channels for the flow of a heat transfer fluid.

In other, particularly preferred types of building units according to the present invention, said fluid flow structure comprises

- one or more regions having parallel ridges protruding from said base plate and grooves extending between said ridges

and one or more regions without protruding ridges

wherein said grooves open out into said region without protruding ridges.

In this type of building unit the ridges do not extend continuously from one edge to anoth- er edge of said base plate, because the first surface of the base plate is partially covered by one or more regions without protruding ridges. Said regions without protruding ridges are even and are at the same height level relative to the second surface of the base plate like the bottoms resp. dips of said grooves which open out into said region without protruding ridges. In the direction of fluid flow, regions having parallel ridges protruding from said base plate and grooves extending between said ridges alternate with regions without protruding ridges. Preferably such region without protruding ridges has a dimension extending parallel to the width C of said grooves which is significantly larger than the width C of said grooves. Preferably, said region without protruding ridges is of rectangular shape. Said regions without protruding ridges act as fluid redistribution regions, i.e. they allow intermixing of the fluid flow streams emerging from the plurality of grooves which open out into said region without protruding ridges. Due to the fluid redistribution achieved by means of said fluid redistribution region, any risk of channeling and inhomogeneous distribution of the heat transfer fluid is significantly reduced. Nevertheless, it is preferable to keep the area of the first surface of the base plate, which is covered by the above- defined fluid redistribution regions, significantly smaller than the area of the first surface of the base plate which is covered by regions having protruding ridges ad defined above, so that the above-defined advantages of said ridges and grooves are not compromised by the presence of fluid redistribution regions. In a particularly preferred building unit of the above-described type, said fluid flow structure comprises at least

a first region having a plurality of parallel ridges protruding from said base plate and grooves extending between said ridges a second region having a plurality of parallel ridges protruding from said base plate and grooves extending between said ridges

and one region without protruding ridges, said region extending between said first region having protruding ridges and said second region having protruding ridges wherein

the grooves extending between said protruding ridges of said first region having protruding ridges open out into one side of said region without ridges and the grooves extending between said protruding ridges of said second region having protruding ridges open out into the opposite side of said region without ridges.

Typically, said region without protruding ridges which extends between said first region having protruding ridges and said second region having protruding ridges is of rectangular shape, and the long sides of said rectangular region without protruding ridges extend perpendicularly to the ridges in said first region having protruding ridges and perpendicu- larly to the ridges in said second region having protruding ridges. The grooves extending between said protruding ridges of said first region having protruding ridges open out into the first long side of said rectangular region without ridges, and the grooves extending between said protruding ridges of said second region having protruding ridges open out into the second, opposite long side of said rectangular region without ridges. The width Z of said rectangular region (corresponding to the length of the short sides of said rectangle region) without protruding ridges defines the distance between said first region having protruding ridges and said second region having protruding ridges. Preferably said distance is small compared to the length L of the grooves in said first region having protruding ridges and to the length of the grooves in said second region having protruding ridges, more specifically preferably 25 % or less of the length of the grooves in said first region having protruding ridges and in said second region having protruding ridges.

Figure 3 shows a plan view (view from above) of an example of shaped body 1 having a fluid flow structure as described above. Said fluid flow structure comprises three regions having parallel ridges 3a, 3b, 3c protruding from said base plate 2 and grooves 4a, 4b, 4c extending between said ridges 3a, 3b, 3c, and two fluid redistribution regions 5a, 5b which are regions without protruding ridges. In the direction of fluid flow, regions having parallel ridges 3a, 3b, 3c protruding from base plate 2 and grooves 4a, 4b, 4c extending between said ridges 3a, 3b, 3c alternate with fluid redistribution regions 5a, 5b. Said fluid redistribution regions 5a, 5b are at the same height level (relative to the second surface of the base plate) like the bottoms resp. dips of said grooves 4a, 4b, 4c which open out into said fluid redistribution regions 5a, 5b. Fluid redistribution region 5a extends between a first region having protruding ridges 3a and a second region having protruding ridges 3b. Fluid redistribution region 5b extends between a first region having protruding ridges 3b and a second region having protruding ridges 3c. Each fluid redistribution regions 5a, 5b is of rectangular shape. The long sides of said rectangular fluid redistribution regions 5a, 5b extend perpendicularly to the ridges 3a, 3b, 3c. The grooves 4a extending between protruding ridges 3a open out into one long side of rectangular fluid redistribution region 5a, and the grooves 4b extending between protruding ridges 3b open out into the opposite long side of rectangular fluid redistribution region 5a. The grooves 4b extending between protruding ridges 3b open out into one long side of rectangular fluid redistribution region 5b, and the grooves 4c extending between protruding ridges 3c open out into the opposite long side of rectangular fluid redistribution region 5b. The width Z of said rectangular fluid redistribution region 5a (corresponding to the length of the short sides of said rectangle) defines the distance between said region having protruding ridges 3a and said region having protruding ridges 3b. The width Z of said rectangular fluid redistribution region 5b (corresponding to the length of the short sides of said rectangle) defines the distance between said region having protruding ridges 3b and said region having protruding ridges 3c. In both cases, Z is small compared to the length L of the grooves 4a, 4b, 4c, more specifically less than 25 % of the length of the grooves 4a, 4b, 4c. As explained above, said shaped body is made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials. Typically, each mixture comprises a binding agent and particles of one magnetocaloric material. In specific cases, each mixture consists of a binding agent and particles of one magnetocaloric material. Herein, said magnetocaloric materials are preferably selected from the group consisting of

(1 ) compounds of the general formula (I)

(Fei-xAx)2+v(Pi-yZ_y)i +w (I )

where

A represents one or more elements selected from the group consisting of Mn, Co,

Cr and Ni,

Z represents one or more elements selected from the group consisting of B, C, Se,

Ge, Ga, Si, Sn, N, As and Sb,

0 < x < 1 0 < y < 1

-0.2 < v < 0.2

-0.1 < w < 0.1

(2) compounds of one the general formulae (II) and (III) and (IV)

La(FexAh-x)i3Hy or La(FexSii-x)i3Hy (II)

where

x is a number from 0.7 to 0.95,

y is a number from 0 to 3;

La(Fe_xAl_yCoz)i3 or La(Fe_xSi_yCo_z)i3 (III)

where

x is a number from 0.7 to 0.95,

y is a number from 0.05 to 1 - x,

z is a number from 0.005 to 0.5;

LaMn_xFe2-xGe (IV)

where

x is a number from 1.7 to 1.95 and

(3) Heusler alloys of the MnTP type where T is a transition metal and P is a p-doping metal having an electron count per atom e/a in the range from 7 to 8.5,

(4) compounds of the general formula (V)

Gd5(SixGei-_x)4 (V)

where x is a number from 0.2 to 1 ,

(5) manganites of the perovskite type,

(6) compounds of one of the general formulae (VI) and (VII)

Tb5(Si₄-xGe_x) (VI)

where x = 0, 1 , 2, 3, 4,

XTiGe (VII)

where X selected from the group consisting of Dy, Ho, Tm, (7) compounds of one of the general formulae (VIII) - (X!)

Mn₂-xZ_xSb (VIII)

Mn₂Z_xSbi-x (IX)

where

Z is selected from the group consisting of Cr, Cu, Zn, Co, V, As, Ge, x is from 0.01 to 0.5,

Mn₂-xZxAs (X)

Mn₂ZxAsi-x (XI)

where

Z is selected from the group consisting of Cr, Cu, Zn, Co, V, Ge,

x is from 0.01 to 0.5.

Most preferably, said magnetocaloric materials are selected from the group consisting of compounds of the general formula (I) as defined above. Most preferred are compounds of the general formula (I)

( Fe 1 ₂ P 1 -yZy)l (I)

where

A represents Mn, and optionally one or more elements selected from the group consisting of Co, Cr and Ni,

Z represents Si and optionally one or more elements selected from the group con- sisting of B, C and N

0 < x < 1 , preferably 0.3 < x < 0.7

0 < y < 1 , preferably 0.25 < x < 0.7

-0.2 < v < 0.2, preferably -0.12 < v < 0.12, further preferably -0.1 < v < 0.1 ,

-0.1 < w < 0.1 , preferably -0.05 < v < 0.05, further preferably -0.02 < v < 0.02. A compound of general formula (I) typically comprises a main phase having an Fe₂P- structure. Usually said main phase occupies 90 % or more of the volume of said compound of general formula (I). Compounds of general formula (I) and methods for preparation thereof are known in the art. Magnetocaloric materials which contain manganese, iron, silicon and phosphorus, and methods for their preparation are disclosed in WO 2011/083446A1 and US 2011/0220838 A1. Preferred magnetocaloric materials of a composition according to formula (I), which contain manganese, iron, silicon and phosphorus, have a composition according to formula (la)

(Mn_xFei-x)2+uP_ySiv (la)

wherein

-0.12 < u < 0.10, preferably -0.05 < u < 0.05

0.3 < x < 0.7 preferably 0.35 < x < 0.65

0.3 < y < 0.75, preferably 0.4 < y < 0.7

0.25 < v < 0.7, preferably 0.3 < v < 0.6

0.95 < (y + v) < 1.05, preferably 0.98 < (y + v) < 1.02

Magnetocaloric materials which contain manganese, iron, silicon, phosphorus, and boron, and methods for their preparation are disclosed in WO 2015/018610, WO 201/018705 and WO 2015/01867. Preferred magnetocaloric materials of a composition according to formula (I), which contain manganese, iron, silicon, phosphorus and boron, have a composition according to formula (lb)

(MnxFei-x)2+_uPySivBw (lb)

wherein

-0.12 < u < 0.10, preferably -0.05 < u < 0.05

0.3 < x < 0.7 preferably 0.35 < x < 0.65

0.3 < y < 0.75, preferably 0.4 < y < 0.7

0.25 < v < 07, preferably 0.3 < v < 0.6

0.005 < w < 0.1 , preferably 0.01 < w < 0.08

0.95 < (y + v + w) < 1.05, preferably 0.98 < (y + v + w) < 1.02.

Magnetocaloric materials which contain manganese, iron, silicon, phosphorus, nitrogen and optionally boron and methods for their preparation are disclosed in WO2017/072334. Preferred magnetocaloric materials which contain manganese, iron, silicon, phosphorus, nitrogen and optionally boron, have a composition according to formula (lc) (MnxFei-x)2_+uPySivN_rBw (lc)

wherein

-0.12 < u < 0.10, preferably -0.05 < u < 0.05

0.3 < x < 0.7 preferably 0.35 < x < 0.65,

0.3 < y < 0.75, preferably 0.4 < y < 0.7

0.25 < v < 0.7, preferably 0.3 < v < 0.6,

0.001 < r < 0.1 , preferably 0.005 < r < 0.07,

0 < w < 0.1 , preferably 0.01 < w < 0.08

(y + v + w) < 1.05, preferably < 1.02, preferably < 1

(y + v + w + r) > 0.95, preferably > 0.98, preferably > 1.

Preferred magnetocaloric materials of a composition according to formula (I), which contain manganese, iron, silicon, phosphorus and nitrogen have a composition according to formula (Id)

(Mn_xFei-x)2+_uP_ySivNr (Id)

wherein

-0.12 < u < 0.10, preferably -0.05 < u < 0.05

0.3 < x < 0.7 preferably 0.35 < x < 0.65,

0.3 < y < 0.75, preferably 0.4 < y < 0.7

0.25 < v < 0.7, preferably 0.3 < v < 0.6

0.001 < r < 0.1 , preferably 0.005 < r < 0.07

(y + v) < 1.05, preferably < 1.02, preferably < 1

(y + v + r) > 0.95, preferably ³ 0.98, preferably ³ 1.

Preferred magnetocaloric materials of a composition according to formula (I), which contain manganese, iron, silicon, phosphorus, nitrogen and boron have a composition according to formula (le)

(Mn_xFei-x)2+_uPySivNrBw (le)

wherein

-0.12 < u < 0.10, preferably -0.05 < u < 0.05 0.3 < x < 0.7 preferably 0.35 < x < 0.65,

0.3 < y < 0.75, preferably 0.4 < y < 0.7

0.25 < v < 0.7, preferably 0.3 < v < 0.6

0.001 < r < 0.1 , preferably 0.005 < r < 0.07

0.005 < w < 0.1 , preferably 0.01 < w < 0.08

(y + v + w) < 1.05, preferably < 1.02, preferably < 1

(y + v + w + r) > 0.95, preferably > 0.98, preferably > 1.

Magnetocaloric materials which contain manganese, iron, silicon, phosphorus, carbon, and optionally one or both of boron and nitrogen, and methods for their preparation are disclosed in a patent application having the application number PCT/EP2017/063901.

Preferred magnetocaloric materials of a composition according to formula (I), which contain manganese, iron, silicon, phosphorus and carbon, have a composition according to formula (If)

(Mn_xFei-x)2+_uPySivCz (If)

wherein

-0.12 < u < 0.10, preferably -0.05 < u < 0.05

0.3 < x < 0.7 preferably 0.35 < x < 0.65

0.3 < y < 0.75, preferably 0.4 < y < 0.7

0.25 < v < 0.7, preferably 0.3 < v < 0.6

0.001 < z < 0.15, preferably 0.003 < z < 0.12

0.95 < (y + v) < 1.05, preferably 0.98 < (y + v) < 1.02.

Preferred magnetocaloric materials of a composition according to formula (I), which contain manganese, iron, silicon, phosphorus, carbon and boron, have a composition according to formula (Ig)

(Mn_xFei-x)2+iiPySivC_zBw (Ig)

wherein

-0.12 < u < 0.10, preferably -0.05 < u < 0.05

0.3 < x < 0.7 preferably 0.35 < x < 0.65 0.3 < y < 0.75, preferably 0.4 < y < 0.7

0.25 < v < 0.7, preferably 0.3 < v < 0.6

0.001 < z < 0.15, preferably 0.003 < z < 0.12

0.005 < w < 0.1 , preferably 0.01 < w < 0.08

0.95 < (y + v + w) < 1.05, preferably 0.98 < (y + v + w) < 1.02.

Preferred magnetocaloric materials of a composition according to formula (I), which contain manganese, iron, silicon, phosphorus, carbon and nitrogen, have a composition according to formula (Ih)

(Mn_xFei-x)2+uPySivCzNr (Ih)

wherein

-0.12 < u < 0.10, preferably -0.05 < u < 0.05

0.3 < x < 0.7 preferably 0.35 < x < 0.65

0.3 < y < 0.75, preferably 0.4 < y < 0.7

0.25 < v < 0.7, preferably 0.3 < v < 0.6

0.001 < z < 0.15, preferably 0.003 < z < 0.12

0.001 < r < 0.1 , preferably 0.005 < r < 0.07

(y + v) < 1.05, preferably < 1.02, preferably < 1

(y + v + r) > 0.95, preferably > 0.98, preferably > 1 .

Preferred magnetocaloric materials of a composition according to formula (I), which contain manganese, iron, silicon, phosphorus, carbon, boron and nitrogen, have a composition according to formula (li)

(Mn_xFei-x)2+uPySivCzNrB_w (li)

wherein

-0.12 < u < 0.10, preferably -0.05 < u < 0.05

0.3 < x < 0.7 preferably 0.35 < x < 0.65

0.3 < y < 0.75, preferably 0.4 < y < 0.7

0.25 < v < 0.7, preferably 0.3 < v < 0.6

0.001 < z < 0.15, preferably 0.003 < z < 0.12 0.001 < r < 0.1 , preferably 0.005 < r < 0.07

0.005 < w < 0.1 , preferably 0.01 < w < 0.08

(y + v + w) < 1.05, preferably < 1.02, preferably < 1

(y + v + w + r) > 0.95, preferably > 0.98, preferably > 1. Preferably, said magnetocaloric materials comprise, more preferably consist of particles having a size distribution characterized by

a D90 value of 10 pm or less and/or

a D50 value of 6 pm or less and/or

a D10 value of 2 pm or less and/or

as determinable by sieving analysis. Preferably the D90 value is 10 pm or less, the D50 value is 6 pm or less and the D10 value is 2 pm or less. Said particles are spherical or non-spherical or a mixture of both. For a non-spherical particle, d is determined by the smallest cross-sectional dimension of said particle. Commonly, for economical reasons non-spherical particles obtained by crushing larger objects of the corresponding magne- tocaloric material are used, because producing spherical particles is a rather elaborate process, which may suffer from a low yield. The optimal particle size is determined by the dimensions of the fluid flow structure to be obtained, i.e. height and width of the ridges and the width of the grooves to be formed. More specifically the finer the fluid structure to be formed the smaller particle size is needed. Said binding agent is preferably selected from the group consisting of polyester polyurethanes having a glass transition temperature in the range of from -45 °C to -5 °C. The glass transition temperature is determined by differential scanning calorimetry (DSC). Determination of glass transition temperatures by means of DSC is known in the art.

Polyester polyurethanes are known in the art. In polyurethanes of this kind, the diol com- ponent is selected from the group of polyesters. In the shaped body, said binding agent is in the cured state.

In said mixtures comprising a binding agent and particles of one or more magnetocaloric materials, preferably the total weight fraction of the particles of said magnetocaloric materials is in the range of from 90 wt.-% to 98 wt.-%, more preferably from 92 wt.-% to 97 wt.-%, based on the total weight of said particles of magnetocaloric materials and said binding agent. A high weight fraction of the particles of magnetocaloric materials is desir- able in order to achieve a high magnetocaloric density for the sake of efficient use of the magnetic field volume. On the other hand, a certain amount of binding agent is indispens- ible in order to allow for embedding of the particles of said magnetocaloric material into a matrix formed from said binding agent, thereby holding together said particles and main- taining the desired shape of the shaped body.

In some preferred types of building units according to the present invention, the whole shaped body is made up of one single mixture comprising a binding agent and particles of one or more magnetocaloric materials, preferably particles of one magnetocaloric material. This type of building unit is advantageous due to its uncomplicated composition which reduces the efforts for manufacturing such building unit.

In other particularly preferred types of building units according to the present invention, said shaped body consists of three or more portions each comprising particles of a magnetocaloric material having a different Curie temperature, wherein said portions are arranged alongside each other by ascending or descending Curie temperature Tc of the magnetocaloric materials in the direction of the ridges and grooves of the fluid flow structure, wherein in each case the difference between the Curie temperatures of the magnetocaloric materials of two adjacent portions is in the range of from 0.5 K to 4 K.

In a building unit of this preferred type, said shaped body consists of three or more portions each made up of a mixture comprising a binding agent and particles of a magneto- caloric material, wherein said magnetocaloric materials of said different mixtures each have a different Curie temperature. Within said shaped body, said three or more portions are arranged alongside each other by ascending or descending Curie temperature Tc of the magnetocaloric materials in the direction of the ridges and grooves of the fluid flow structure (i.e. in the direction of the flow of the heat transfer fluid). Accordingly, said three or more portions are arranged alongside each other by ascending or descending Curie temperature Tc of the magnetocaloric materials in the flow direction of the heat transfer fluid. In each case the difference between the Curie temperatures of the magnetocaloric materials of two adjacent portions is in the range of from 0.5 K to 4 K.

Preferably 3 to 40 portions, typically each in are in the form of a rectangular stripe having a width of 0.1 to 10 mm, are arranged alongside each other by ascending or descending Curie temperature Tc of the magnetocaloric materials in the direction of the ridges and grooves of the fluid flow structure (i.e. in the direction of the flow of the heat transfer fluid). Accordingly, the length direction of said stripes extends perpendicular to the grooves and ridges of the fluid flow structure, and the heat transfer fluid flows perpendicular to the length direction of stripes. Thus, during flowing along a groove, the heat transfer fluid passes portions each made up of a different mixture comprising a binding agent and particles of a magnetocaloric material, wherein said magnetocaloric materials of said different mixtures each have a different Curie temperature. In some cases each groove extends over a plurality of such stripes. This is especially the case for building units having shaped bodies with ridges and grooves extending continuously from one edge to another edge of the base plate.

Alternatively, especially in building units having, in the direction of fluid flow, regions having parallel ridges protruding from said base plate and grooves extending between said ridges alternating with fluid redistribution regions as described above, each of said regions may be arranged on an individual portion comprising a magnetocaloric material having a different Curie temperature wherein in each case the difference between the Curie temperatures of the magnetocaloric materials of two adjacent portions is in the range of from 0.5 K to 4 K. Figure 4 shows a side view and a plan view (view from above) of an example of a shaped body 1 consisting of three rectangular portions 1a, 1 b, 1c, each comprising particles of a magnetocaloric material having a different Curie temperature. The magnetocaloric material in portion 1a has Curie temperature Tc1 , the magnetocaloric material in portion 1 b has Curie temperature Tc2, and the magnetocaloric material in portion 1 b has Curie temperature Tc3.

Said three portions 1a, 1 b, 1c are arranged alongside each other by ascending or descending Curie temperature Tc of the magnetocaloric materials in the direction of the ridges 3 and grooves 4 of the fluid flow structure (In the side view said ridges and groves are not visible, because they extend parallel to the plane of the paper). Accordingly, said three portions 1a, 1 b, 1 c are arranged alongside each other by ascending or descending Curie temperature Tc of the magnetocaloric materials in the flow direction of the heat transfer fluid. In each case the difference between the Curie temperatures of the magnetocaloric materials of two adjacent portions is in the range of from 0.5 K to 4 K. Thus, Tc1 differs from Tc2 by 0.5 K to 4 K, and Tc2 differs from Tc3 by 0.5 K to 4 K. A building unit having a shaped body consisting of three or more portions each comprising particles of a magnetocaloric material having a different Curie temperature, wherein said portions are arranged alongside each other by ascending or descending Curie temperature Tc of the magnetocaloric materials in the flow direction of the heat transfer fluid as described above is advantageous because by combining magnetocaloric materials having different Curie temperatures the temperature span wherein a magnetocaloric device may provide efficient cooling resp. heating is increased, compared to a magnetocaloric device comprising a single magnetocaloric material. It is known that the magnetocaloric effect of a magnetocaloric material depends on the temperature and has its maximum in the vicinity of the Curie temperature of said material. Thus, in order to optimize the performance of the magnetocaloric heat exchanger it is desirable that at each position of the flow path of the heat transfer fluid across the magnetocaloric heat exchanger the Curie temperature coincides with the temperature deter- mined for said position by the temperature gradient between the cold side heat exchanger and the hot side heat exchanger. In order to approach these preferable condition, a magnetocaloric heat exchanger preferably comprises three or more different magnetocaloric materials arranged in succession by ascending or descending Curie temperature along the flow path of the heat transfer fluid, i.e. the magnetocaloric material having the highest Curie temperature is arranged at one end of the flow path of the heat transfer fluid, the magnetocaloric material having the second highest Curie temperature follows and so on, and the magnetocaloric material having the lowest Curie temperature is placed at the opposite end of the flow path of the heat transfer fluid. The end of the flow path of the heat transfer fluid where the magnetocaloric material having the highest Curie temperature is located corresponds to the hot side of the magnetocaloric heat exchanger, and the end of the flow path of the heat transfer fluid where the magnetocaloric material having the lowest Curie temperature is located corresponds to the cold side of the magnetocaloric heat exchanger.

In such a magnetocaloric heat exchanger, cooling resp. heating of each magnetocaloric material (with the exception of the first one) to a temperature near its Curie temperature is effected by the preceding magnetocaloric material, and each magnetocaloric material (with the exception of the last one) effects cooling resp. heating of the succeeding magnetocaloric material to a temperature near its Curie temperature. In other words, the first magnetocaloric material effects cooling down resp. heating up the second magnetocaloric material to a temperature near the Curie temperature of the second magnetocaloric material, and so on with any further magnetocaloric material contained in the cascade. This way, the cooling effect achieved can be greatly increased in comparison with a magnetocaloric heat exchanger comprising a single magnetocaloric material.

The number of different magnetocaloric materials and their Curie temperatures are se- lected depending on the temperature span to be covered in the desired application. Preferably, the difference in the Curie temperatures between the magnetocaloric material with the highest Curie temperature and the magnetocaloric material with the lowest Curie temperature corresponds to said temperature span.

The Curie temperature of a magnetocaloric material depends on the chemical composi- tion of the magnetocaloric material. Thus, the above-mentioned three or more magnetocaloric materials having a different Curie temperature may be magnetocaloric materials having different chemical composition. For many types of magnetocaloric materials, especially for those of above-defined general formula (I), it is well-known that slight variation of the stoichiometry (i.e. of the proportions between the different elements present in said material) has a significant influence on the Curie temperature. Alternatively, magnetocaloric materials having different Curie temperatures at identical stoichiometry are obtainable by varying the temperature of the heat treatment applied in the preparation of such materials, as described in non-prepublished patent application of application number PCT/EP2017/071885. In some preferred types of building units according to the present invention, said building unit consists of a shaped body as defined above, preferably a shaped body having one or more of the above-defined preferred features. This type of building unit is advantageous due to the absence of parts made up of materials which do not contribute to the magnetocaloric effect. In other particularly preferred types of building units according to the present invention, said building unit comprises a shaped body as defined above, preferably a shaped body having one or more of the above-defined preferred features, and a substrate which does not comprise any magnetocaloric material, said substrate having a first surface and a second surface opposite to each other, wherein said first surface of said substrate is attached to the second surface of the base plate of said shaped body. Optionally said building unit further comprises a second shaped body as defined above, preferably a shaped body having one or more of the above-defined preferred features, wherein said second surface of said substrate is attached to the second surface of the base plate of said second shaped body. More specifically, in some cases said preferred type of building unit comprises a shaped body as defined above, preferably a shaped body having one or more of the above- defined preferred features, and a substrate which does not comprise any magnetocaloric material, wherein said substrate is attached to the second surface of the base plate of said shaped body. This type of building unit is advantageous, because the substrate imparts mechanical stability to the shaped body to which it is attached, and facilitates handling of the building unit. Herein, said second surface of said base plate of said shaped body is at substantially even level, i.e. has no protrusions and no recesses. The substrate usually origins from the method of manufacturing a building unit according to the present invention, see third aspect of the present invention as described below.

In some cases, a building unit of the above-defined type consists of a shaped body as defined above, preferably a shaped body having one or more of the above-defined preferred features, and a substrate which does not comprise any magnetocaloric material, wherein said substrate is attached to the second surface of the base plate of said shaped body.

Figure 5 shows a side view of an example of a building unit of the above-defined type. Said building unit 100 consists of a shaped body 1 as defined above, preferably a shaped body having one or more of the above-defined preferred features, and a substrate 11 which does not comprise any magnetocaloric material. Said substrate 11 is attached to the second surface 2b of the base plate 2 of said shaped body 1.

In other cases a building unit of the above-defined type comprises a first shaped body and a second shaped body as defined above, and a substrate which does not comprise any magnetocaloric material, said substrate having a first surface and a second surface opposite to each other, wherein said first surface of said substrate is attached to the second surface of the base plate of said first shaped body and said second surface of said substrate is attached to the second surface of the base plate of said second shaped body. Herein, said first shaped body and said second shaped body preferably have one or more of the above-defined preferred features. The second surface of the base plate of said first shaped body is at substantially even level, i.e. has no protrusions and no re- cesses, and the second surface of the base plate of said second shaped body is at substantially even level, i.e. has no protrusions and no recesses. This type of building unit is advantageous, because one substrate imparts mechanical stability to two shaped bodies attached to said substrate, thereby reducing the volume fraction occupied by the substrate (which does not contribute to the magnetocaloric effect) relative to the total volume of substrate and shaped bodies comprising particles of one or more magnetocaloric materials.

Preferably, said first shaped body and said second shaped body are of identical composition, shape, structure and dimensions. More specifically, the fluid flow structures of the first shaped body and the second shaped body are like mirror images with regard to each other.

In preferred cases, a building unit of the above-defined type consists of a first shaped body and a second shaped body as defined above, and a substrate which does not comprise any magnetocaloric material, said substrate having a first surface and a second surface opposite to each other, wherein said first surface of said substrate is attached to the second surface of the base plate of said first shaped body and said second surface of said substrate is attached to the second surface of the base plate of said second shaped body. Figure 6 shows a side view of an example of a building unit of the above-defined type.

Said building unit 200 consists of a first shaped body T as defined above, preferably in the form of a shaped body having one or more of the above-defined preferred features, a second shaped body 1” as defined above, preferably in the form of a shaped body having one or more of the above-defined preferred features, and a substrate 11 which does not comprise any magnetocaloric material. Said substrate 11 has a first surface and a second surface opposite to said first surface . The first surface of said substrate 11 is attached to the second surface 2b’ of the base plate 2’ of said first shaped body T and the second surface of said substrate 11 is attached to the second surface 2b” of the base plate 2” of said second shaped body 1”. The fluid flow structure having protruding ridges 3 and grooves 4’ extending between said protruding ridges of said first shaped body T and the fluid flow structure having protruding ridges 3” and grooves 4” extending between said protruding ridges of said second shaped body 1” are like mirror images with regard to each other.

Said substrate is preferably in a form selected from the group consisting of foils, films, webs, panes and plates. Preferably, said substrate has a thickness in the range of from 0.1 pm to 100 pm, preferably 1 pm to 25 pm more preferably 1 pm to 15 pm, most preferably 1 pm to 10 pm. Preferably, said substrate comprises one or more materials from the group consisting of organic polymers and metals. Preferred organic polymers are polyethylene terephthalate PET, polyethylene naphthalate PEN, polypropylene PP, polyeth- ylene PE, polyamide, polyimide and Aram id. Preferred metals are aluminum, copper and stainless steel. Most preferably, said substrate is in a form selected from the group consisting of foils, films, webs, panes and plates, has a thickness in the range of from 0.1 pm to 100 pm, preferably 1 pm to 25 pm, more preferably 1 pm to 15 pm, most preferably 1 pm to 10 pm, and comprises one or more materials from the group consisting of organic polymers and metals. Typically, the lateral dimensions (dimensions perpendicular to the base plate thickness B) of a building unit according to the present invention are both in the range of from 0.1 mm to 50 mm.

In a second aspect, the present invention relates to a magnetocaloric heat exchanger comprising a heat exchanger block comprising two or more building units, preferably 50 to 1000 building units, according to the first aspect of the present invention, preferably building units having one or more of the above-defined preferred features, subsequently stacked on top of one another

wherein in each case between two building units stacked one on top of the other - the ridges protruding from the base plate of the shaped body of the first building unit engage the second surface of the base plate of the shaped body of the second building unit stacked on top of said first building unit,

or

the ridges protruding from the base plate of the shaped body of the first building unit engage the substrate attached to the base plate of the shaped body of the second building unit stacked on top of said first building unit

or

the ridges protruding from the base plate of a shaped body of the first building unit engage the ridges protruding from the base plate of a shaped body of the second building unit stacked on top of said first building unit.

When two or more building units according or the present invention are stacked on top of each other, the ridges act as spacers with regard to the adjacent building unit, allowing for substantially uniform spacing between adjacent building units, and accordingly uniform flow of the heat exchanger fluid over each building unit. In a first preferred type of heat exchanger blocks according to the present invention, two or more building units are subsequently stacked on top of one another, so that in each case between two building units stacked one on top of the other the ridges protruding from the base plate of the shaped body of the first building unit engage the second surface of the base plate of the shaped body of the second building unit stacked on top of said first building unit. In this type of heat exchanger block, the stacked building units do not comprise a substrate. Preferably each of the stacked building units consists of a shaped body as defined above, preferably a shaped body having one or more of the above-defined preferred features (for examples of such shaped body, see figure 1a and

1 b).

Figure 7a shows an example of a heat exchanger block according to said first preferred type. In heat exchanger block 7a three building units 10a, 10b, 10c are stacked on top of each other. Each of the stacked building units consists of a shaped body as defined above, preferably a shaped body having one or more of the above-defined preferred features. In each case between two building units stacked one on top of the other the ridges protruding from the base plate of the shaped body of the first building unit engage the second surface of the base plate of the shaped body of the second building unit stacked on top of said first building unit. More specifically, the ridges protruding from the base plate of the shaped body of the lowermost building unit 10a engage the second surface of the base plate of the shaped body of the middle building unit 10b, and the ridges protruding from the base plate of the shaped body of the middle building unit 10b engage the second surface of the base plate of the shaped body of the uppermost build- ing unit 10c.

In a second preferred type of heat exchanger blocks according to the present invention, two or more building units are subsequently stacked on top of one another, so that in each case between two building units stacked one on top of the other the ridges protruding from the base plate of the shaped body of the first building unit engage the substrate attached to the base plate of the shaped body of the second building unit stacked on top of said first building unit. In this type of heat exchanger block, the stacked building units each comprise a substrate. Preferably each of the stacked building units consists of a shaped body as defined above, preferably a shaped body having one or more of the above-defined preferred features, and a substrate, preferably a substrate having one or more of the above-defined preferred features, attached to the second surface of the base plate of said shaped body (for an example of such building unit, see figure 5).

Figure 7b shows an example of a heat exchanger block according to said second preferred type. In heat exchanger block 7b, three building units 100a, 100b, 100c are stacked on top of each other. Each of the stacked building units consists of a shaped body as defined above, preferably a shaped body having one or more of the above- defined preferred features and a substrate 11a, 11 b, 11c, preferably a substrate having one or more of the above-defined preferred features, attached to the second surface of the base plate of said shaped body. In each case between two building units stacked one on top of the of other the ridges protruding from the base plate of the shaped body of the first building unit engage the substrate attached to the base plate of the shaped body of the second building unit stacked on top of said first building unit. More specifically, the ridges protruding from the base plate of the shaped body of the lowermost building unit 100a engage the substrate 1 1 b attached to the base plate of the shaped body of the middle building unit 100b, and the ridges protruding from the base plate of the shaped body of the middle building unit 100b engage the substrate 1 1 c attached to the base plate of the shaped body of the uppermost building unit 100c.

In a third preferred type of heat exchanger blocks according to the present invention, two or more building units are subsequently stacked on top of one another, so that the ridges protruding from the base plate of a shaped body of the first building unit engage the ridges protruding from the base plate of a shaped body of the second building unit stacked on top of said first building unit. In this type of heat exchanger block, the stacked building units each comprise a first and a second shaped body as defined above, and a substrate which does not comprise any magnetocaloric material, said substrate having a first and a second surface opposite to each other, wherein said first surface of said sub- strate is attached to the second surface of the base plate of said first shaped body and said second surface of said substrate is attached to the second surface of the base plate of said second shaped body. Thus, in the direction of stacking, each building unit has a first (lower) and a second (upper) shaped body, and accordingly a first (lower) and a second (upper) fluid flow structure. Preferably each of the stacked building units consists of a first and a second shaped body as defined above, preferably said shaped bodies each having one or more of the above-defined preferred features, and a substrate, preferably a substrate having one or more of the above-defined preferred features, said substrate having a first surface and a second surface opposite to each other, wherein said first surface of said substrate is attached to the second surface of the base plate of said first shaped body and said second surface of said substrate is attached to the second surface of the base plate of said second shaped body (for an example of such building unit, see figure 6).

Herein the fluid flow structures of adjacent stacked building units are designed so that fitting of the ridges of the fluid flow structure of one building unit into the grooves of the adjacent fluid flow structure of the adjacent building unit is precluded. This is achieved e.g. by providing said building unit with fluid flow structures wherein the width W of the ridges is larger than the width C of said grooves of the adjacent building unit, thereby precluding that the ridges of the fluid flow structure of one building unit to fit into the grooves of the adjacent fluid flow structure of the adjacent building unit. Thus, the ridges of adjacent building units cooperate to define a combined fluid flow structure wherein the adjacent fluid flow structures of two building units stacked on top of the other cooperate with each other.

Figures 7c and 7d show examples of a heat exchanger block according to said third preferred type. In heat exchanger block 7c resp. 7d, in each case three building units 200a, 200b, 200c resp. 200d, 200e, 200f are stacked on top of each other. Each of the stacked building units consists of a first and a second shaped body as defined above, and a substrate 1 1a, 1 1 b, 1 1 c, 1 1 d, 1 1 e, 1 1f which does not comprise any magnetocaloric material, said substrate having a first and a second surface opposite to each other, wherein said first surface of said substrate is attached to the second surface of the base plate of said first shaped body and said second surface of said substrate is attached to the second surface of the base plate of said second shaped body (cf. figure 6). In each building unit, the fluid flow structures of first shaped body and the second shaped body are like mirror images with regard to each other. In each case, the ridges protruding from the base plate of a shaped body of the first building unit engage the ridges protruding from the base plate of a shaped body of the second building unit stacked on top of said first building unit. More specifically, the ridges protruding from the base plate of the upper shaped body of the lowermost building unit 200a, 200d engage the ridges protruding from the base plate of the lower shaped body of the middle building unit 200b, 200e, and the ridges protruding from the base plate of the upper shaped body of the middle building unit 200b, 200e engage the ridges protruding from the base plate of the lower shaped body of the uppermost building unit 200c, 200f.

The examples of figures 7c and 7d differ with regard to the relative positions of the ridges and grooves of adjacent fluid flow structures of building units 200a, 200b, 200c resp. 200d, 200e, 200f. In the example shown in figure 7c, the three building units 200a, 200b, 200c are subsequently stacked on top of one another, so that the positions of the grooves of the fluid flow structure of each building unit are shifted with regard to the positions of the grooves in the adjacent fluid flow structures of the adjacent building units. More specifically, the grooves of the upper fluid flow structure of the lowermost building unit 200a are shifted with regard to the grooves of the lower fluid flow structure of the middle building unit 200b, so that the grooves of the upper fluid flow structure of the lowermost building unit 200a do not match with the grooves of the lower fluid flow structure of the middle building unit 200b, and the grooves of the upper fluid flow structure of the middle building unit

200b are shifted with regard to the grooves of the lower fluid flow structure of the upper- most building unit 200c, so that the grooves of the upper fluid flow structure of the middle building unit 200b do not match with the grooves of the lower fluid flow structure of the uppermost building unit 200c.

In the example shown in figure 7d, the three building units 200d, 200e, 200f are subsequently stacked on top of one another, so that the grooves of the fluid flow structure of each building unit match with the grooves in the adjacent fluid flow structures of the adjacent building units. More specifically, the grooves of the upper fluid flow structure of the lowermost building unit 200d match with the grooves of the lower fluid flow structure of the middle building unit 200e, and the grooves of the upper fluid flow structure of the middle building unit 200e match with the grooves of the lower fluid flow structure of the uppermost building unit 200f.

The height of a heat exchanger block (dimension in the direction in which the building units are stacked on top of each other) is in the range of from 0.1 cm to 4 cm, depending on the thickness of the individual building units and the number of building units. Usually the height of the heat exchanger block is shorter than both of the lateral directions of the building units.

Magnetocaloric heat exchangers as such are known in the art, see e.g. WO 201 1/018348 A2, US 8,763,407 B2 and FR 3 004 795.

A magnetocaloric heat exchanger according to the present invention may further comprise a casing surrounding said heat exchanger block. The casing can be made of any suitable material. Typically casings are made of plastics such as glass-reinforced polypropylene, carbon-fiber reinforced polyetheretherketone or glass-fiber reinforced epoxy. Metals like steel and aluminum are also possible, but are not preferred. Preferably the heat exchanger block is fixed in the casing by means of a two component (2K) epoxy resin. An example of a magnetocaloric heat exchanger 7 according to the present invention, which comprises a heat exchanger block consisting of three building units 10a, 10b, 10c as defined above and casing 6 surrounding said heat exchanger block 4 is shown in figure 8. Herein, the ridges protruding from the base plate of the uppermost building unit 10c engage with top plate 6a of the casing 6. A magnetocaloric heat exchanger according to the present invention typically comprises further construction elements. Details thereof are known to the skilled person. Said further construction elements typically comprise means for applying a changing external magnet- ic field to the heat exchanger block and means (typically in the form of tubing and/or piping) for charging and discharging a heat transfer fluid, distributing said heat transfer fluid to the stacked building units in order to allow parallel flow of the heat transfer fluid over the stacked building units, and collecting the heat transfer fluid emerging from the stacked building units over which the hat transfer fluid has flown. The tubing/piping connects the heat exchanger block according to the invention material with the hot side and the cold side of the magnetocaloric heat exchanger.

The magnetocaloric heat exchanger according to the present invention is typically installed within a magnetocaloric device, e.g. a magnetocaloric cooling device. This device may be configured to use multiple magnetocaloric heat exchangers which all contribute to the device performance.

In a third aspect, the present invention relates to a process for manufacturing a building unit as defined above, preferably a building unit having one or more of the above-defined preferred features, for a magnetocaloric heat exchanger, said process comprising the steps

providing one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials

providing a substrate which does not comprise any magnetocaloric material, said substrate having a first and a second surface opposite to each other

- applying said one or more mixtures to said first surface of said substrate, to form a coated substrate having a coating layer made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials disposed on said substrate, said coating layer having a first surface facing away from said substrate and opposite to said first surface a second surface in contact with said substrate

treating said first surface of said coating layer by means of an embossing roll, the surface of said embossing roll exhibiting a structure which is a negative with respect to the fluid flow structure of the building unit to be manufactured

optionally curing said binding agent

- obtaining said building unit by forming a piece of said coated substrate having lateral dimensions corresponding to said building unit

wherein optionally before or after forming said piece having lateral dimensions corresponding to said building unit, said substrate is removed from said second surface of said coating layer. For the process according to the present invention, one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials are provided, and a substrate which does not comprise any magnetocaloric material, said substrate having a first and a second surface opposite to each other, is provided. Typically, each of said mixtures comprises a binding agent and particles of one magnetocaloric material, or consists of one a binding agent and particles of one magnetocaloric material. Preferred magnetocaloric materials are as described above in the context of the first aspect of the present invention. Preferred particle size distribution of the particles of the magnetocaloric materials is as described above in the context of the first aspect of the present invention.

Said binding agent is preferably selected from the group consisting of polyester polyurethanes having a glass transition temperature in the range of from -45 °C to -5 °C. Upon processing, polyester polyurethanes exhibit thermoplastic behavior. More specifically, said polyester polyurethanes are ductile and flexible, which allows for tight conformation of the mixture comprising said binding agent selected from the group consisting of the above-defined polyester polyurethanes and particles of one or more magnetocaloric materials to the contours of the embossing roll, so that building units with appropriate contour accuracy can be obtained.

In said mixtures comprising a binding agent and particles of one or more magnetocaloric materials, the total weight fraction of the particles of said magnetocaloric materials is in the range of from 90 wt.-% to 98 wt.-%, preferably from 92 wt.-% to 97 wt.-%, based on the total weight of said particles of magnetocaloric materials and said binding agent. Optionally, the mixture comprises further constituents which serve to facilitate processa- biltiy of said mixture, but are removed during processing (mainly during the step of curing) and accordingly are not present in the shaped body finally obtained from said mixture. For instance, the mixture comprises a solvent or a mixture of solvents for dissolving the binding agent. This is especially preferred for binding agents selected from the group of polyester polyurethanes as described above. Preferred solvents for binding agents selected from the group of polyester polyurethanes as described above are propylene glycol mono methyl ether acetate (PGMEA), ethylacetate, acetone/toluene (volume ratio 2: 1 ) and methylethylketone/ethylacetate (volume ratio 1 :1 ).

Said substrate is preferably in a form selected from the group consisting of foils, films, webs, panes and plates. Preferably, said substrate has a thickness in the range of from 0.1 pm to 100 pm, preferably 1 pm to 25 pm, more preferably 1 pm to 15 pm, most pref- erably 1 mih to 10 mih. Preferably said substrate comprises one or more materials from the group consisting of organic polymers and metals. Preferred organic polymers are polyethylene terephthalate PET, polyethylene naphthalate PEN, polypropylene PP, polyethylene PE, polyamide, polyimide and Aram id. Preferred metals are aluminum, copper and stainless steel. Most preferably, said substrate is in a form selected from the group consisting of foils, films, webs, panes and plates, has a thickness in the range of from 0.1 pm to 100 pm, preferably 1 pm to 25 pm, more preferably 1 pm to 15 pm, most preferably 1 pm to 10 pm, and comprises one or more materials from the group consisting of organic polymers and metals. In the process according to the present invention, said one or more mixtures are applied to said first surface of said substrate, to form a coated substrate having a coating layer made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials disposed the first surface on said substrate. Said coating layer has a first surface facing away from said substrate and opposite to said first surface a second surface in contact with said substrate.

Figure 9 shows an example of a coated substrate 13 as described above. Said coated substrate 13 consists of a coating layer 12 made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials, and a substrate 11. Said substrate 11 has a first surface 1 T and a second surface 11” opposite to each other. Said coating layer 12 is disposed on said first surface 1 T of said substrate 11. Said coating layer has a first surface 12a facing away from said substrate 1 1 and opposite to said first surface 12a a second surface 12b in contact with said substrate 11.

In preferred processes according to the present invention, said mixtures are applied to said surface of said substrate by means of a coating technique, e.g. slot-die coating. Those techniques are known to the skilled person.

Preferably, said coating layer has a thickness in the range of from 30 pm to 200 pm (as measured prior to treating the first surface of said coating layer by means of an embossing roll).

In the process according to the present invention, said first surface of said coating layer is treated by means of an embossing roll, the surface of said embossing roll exhibiting a structure which is a negative with respect to the fluid flow structure of the building unit to be manufactured. In this manner, the desired fluid flow structure is imparted to the first surface of the coating layer, thereby transforming the coating layer into a shaped body as defined above.

The surface of the embossing roll exhibits a structure which is a negative with respect to the fluid flow structure of the building unit to be manufactured, i.e. a structure which is inverted with regard to the fluid flow structure to be imparted to the surface of the coating layer treated by means of the embossing roll. Accordingly the structure at the surface of the embossing roll has recessed areas at those positions where the intended fluid flow structure has protruding areas (ridges as defined above) and has protruding areas at those positions where the intended fluid flow structure has recessed areas (grooves as defined above, and optionally fluid redistribution regions i.e. without protruding ridges into which said grooves open out).

The technique of embossing is known to the skilled person. Typically, embossing is achieved by guiding the coated substrate through a pair of cylinder-shaped rolls rotating in opposite direction. Preferably this is achieved by a calendaring machine equipped with said pair of rolls. The pair of rolls consists of a first roll acting on the coating layer and a second roll supporting the substrate. Said first roll is the embossing roll. The surface of said embossing roll exhibits a structure which is a negative with respect to the fluid flow structure of the building unit to be manufactured (as explained above). Preferably the embossing roll has a core made of copper and disposed on the surface of said core a coating made of hard chromium. Said coating exhibits said structure which is a negative with respect to the fluid flow structure of the building unit to be manufactured. Preferably, the supporting roll has a hard rubber coating. Typically, said rubber coating has a thickness in the range of from 0.2 mm to 0.4 mm, preferably 0.25 to 0.25 mm, and a shore D hardness SH 90. Typically, embossing is carried out with a line force in the range of from 60 N/mm to 160 N/mm, and the coated substrate moves through the pair of rolls with a speed of 0.1 m/min to 1 m/min, preferably 0.25 m/min to 0.75 m/min, most preferably 0.4 m/min to 0.6 m/min.

Compared to other techniques, which basically may allow for preparing fine structures like the above-defined fluid flow structures, e.g. 3D-printing and rapid prototyping, the em- bossing technique used according to the present invention has the advantage that the entire structure is obtained in a single process cycle, thereby increasing the throughput. In contrast, manufacturing of structures having a certain thickness by means of 3D printing requires carrying out a large number of printing steps, because the higher the thick- ness of the structure, the larger the number of layers to be printed to build up the desired structure.

Preferably, embossing is carried out as a hot embossing process. Preferably, said embossing roll is kept at a temperature in the range of from 40 °C to 60 °C, while said sup- porting roll is not heated.

Figure 10 shows an example of a setup used in the embossing step of the process according to the present invention. A coated substrate 13 consisting of a substrate 11 and a coating layer 12 made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials disposed on a first surface 1 1’ of a substrate 11 is guided through a pair of cylinder-shaped rolls 15 and 16 rotating in opposite direction. The pair of rolls 15, 16 consists of a first roll 15 acting on the coating layer 12 and a second roll 16 supporting the substrate 1 1. Said first roll 15 is the embossing roll. The surface of said embossing roll exhibits a structure 15a which is a negative with respect to the fluid flow structure of the building unit to be manufactured. After having passed the pair of rolls 15, 16, the surface of the coating layer 12 exhibits a fluid flow structure comprising ridges 3 and grooves 4 as described above.

In some preferred processes according to the invention, after furnishing the coating layer with the desired fluid flow structure by means of embossing (as described above), the binding agent is cured. Whether curing is performed or not, depends on the used binding agent. Use of curable binding agents and curing them after embossing has the advantage of improving the form stability of the fluid flow structure. Preferably said binding agent is selected from the group consisting of polyester polyurethanes having a glass transition temperature in the range of from -45 °C to -5 °C, and curing said polyester polyurethane is carried out at a temperature of 200 °C or less, preferably in the range of from 120 °C to 190°C.

Thereafter, in the process according to the present invention, a building unit according to the present invention is obtained by forming a piece of said coated substrate having lateral dimensions corresponding to said building unit. Usually, this is done by cutting to size said coated substrate, or punching out from the coated substrate a piece of said coated substrate having lateral dimensions corresponding to said building unit. Alternatively, the substrate provided for the above-described process is a substrate already cut to size of the building unit to be manufactured. However, this approach is less preferred because it inhibits performing the steps of coating, embossing and curing in a continuous manner for large areas. Therefore, it is preferred to provide a substrate having at least one lateral dimension (usually, a length) significantly larger than a lateral dimension of the building unit to be manufactured, thereby allowing for performing the steps of coating, embossing and curing in a continuous manner for large areas, so that a large number of building units can be obtained when said substrate is processed.

Optionally, in the process according to the present invention, before or after forming said piece having lateral dimensions corresponding to said building unit, said substrate is removed from said second surface of said coating layer. In such cases the substrate is preferably peeled off from the coating layer. Preferably, this is done before forming said piece having lateral dimensions corresponding to said building unit, e.g. before said coated substrate is cut to size. A process according to the present invention, wherein said substrate is removed from said second surface of said coating layer, allows for manufacturing a building unit which consists of a shaped body as described above, preferably a shaped body having one or more of the above-defined preferred features. An example of such shaped body is shown in figure 1.

In another preferred type of process according to the present invention, said substrate is not removed from said second surface of said coating layer. A process according to the present invention, wherein said substrate is not removed from said second surface of said coating layer, allows for manufacturing a building unit which comprises a shaped body as defined above, preferably a shaped body having one or more of the above-defined preferred features, and a substrate which does not comprise any magnetocaloric material, said substrate having a first and a second surface opposite to each other, wherein said first surface of said substrate is attached to the second surface of the base plate of said shaped body. An example of such a building unit is shown in figure 5. Optionally said building unit further comprises a second shaped body as defined above, preferably a shaped body having one or more of the above-defined preferred features, and said second surface of said substrate is attached to the second surface of the base plate of said second shaped body.

In certain cases, a process according to the invention is preferred, wherein said substrate is not removed from said second surface of said coating layer, said process comprising the steps of

providing one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials providing a substrate which does not comprise any magnetocaloric material, said substrate having a first surface and a second surface opposite to each other applying said one or more mixtures to said first surface of said substrate and to said second surface of said substrate, to form a coated substrate having a first coating layer made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials disposed on said first surface of said substrate, and a second coating layer made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials disposed on said second surface of said substrate, each of said coating layers having a first surface facing away from said substrate and opposite to said first surface a second surface in contact with said substrate

treating the first surface of said first coating layer and the first surface of said second coating layer each by means of an embossing roll, the surface of said embossing roll in each case exhibiting a structure which is a negative with respect to the fluid flow structure of the building unit to be manufactured

optionally curing said binding agent

obtaining said building unit by forming a piece of said coated substrate having lateral dimensions corresponding to said building unit.

This preferred process according to the present invention allows for manufacturing a building unit which comprises a first and a second shaped body as defined above, and a substrate which does not comprise any magnetocaloric material, said substrate having a first and a second surface opposite to each other, wherein said first surface of said substrate is attached to the second surface of the base plate of said first shaped body and said second surface of said substrate is attached to the second surface of the base plate of said second shaped body. An example of such a building unit is shown in figure 6.

For this preferred process according to the present invention, one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials are provided, and a substrate which does not comprise any magnetocaloric material, said substrate having a first and a second surface opposite to each other, is provided. P re- ferred mixtures and substrates are as described above.

In said preferred process according to the present invention, said one or more mixtures are applied to said first surface and to said second surface of said substrate, to form a coated substrate having a first coating layer made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials dis- posed on said first surface of said substrate, and a second coating layer made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials disposed on said second surface of said substrate. Each of said coating layers has a first surface facing away from said substrate and opposite to said first sur- face a second surface in contact with said substrate.

Figure 11 shows an example of a coated substrate 14 as described above. Said coated substrate 14 consists of a first coating layer 12’ made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials, a second coating layer 12” made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials, and a substrate 11. Said substrate 11 has a first surface 11’ and a second surface 11” opposite to each other. Said first coating layer 12’ is disposed on said first surface 1 1’ of said substrate 11. Said second coating layer 12” is disposed on said second surface 1 1” of said substrate 1 1. Said first coating layer 12’ has a first surface 12a’ facing away from said substrate 11 and opposite to said first surface 12a’, a second surface 12b’ in contact with said first surface 11’ of said substrate 1 1. Said second coating layer 12” has a first surface 12a” facing away from said substrate 1 1 and opposite to said first surface 12a”, a second surface 12b” in contact with said second surface 11” of said substrate 11.

Preferably, said mixtures are applied to said first and said second surface of said sub- strate by means of a coating technique, e.g. slot-die coating.

Preferably, said first and second coating layer has a thickness in the range of from 30 pm to 200 pm (as measured prior to treating the first surface of said first coating layer and the first surface of said second coating layer, resp., by means of an embossing roll). Preferably, said first coating layer and said second coating layer have substantially the same thickness.

In said preferred process according to the present invention, the first surface of said first coating layer and the first surface of said second coating layer are each treated by means of an embossing roll, the surface of said embossing roll in each case exhibiting a structure which is a negative with respect to the fluid flow structure of the building unit to be manufactured. In this manner, the desired fluid flow structure is imparted to the first surface of the first coating layer, thereby transforming the first coating layer into a first shaped body as defined above, and the desired fluid flow structure is imparted to the first surface of the second coating layer, thereby transforming the second coating layer into a second shaped body as defined above. Preferably, embossing of the coated substrate is done by means of a pair of structured embossing rollers, one acting on the first surface of said first coating layer, the other one acting on the first surface of said second coating layer. Preferably, the fluid flow structures which are imparted to said first coating layer and said second coating layer are like mirror images with regard to each other. Figure 12 shows an example of a setup used in the embossing step of the above-defined preferred process according to the present invention. A coated substrate 14 (cf. figure 1 1 ) consisting of a substrate 1 1 , first coating layer 12’ made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials disposed on a first surface 1 1’ of said substrate and a second coating layer 12” made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials disposed on a second surface 1 1” of said substrate a is guided through a pair of cylinder-shaped rolls 15’ and 15” rotating in opposite direction. The pair of rolls 15’, 15” consists of a first embossing roll 15’ acting on the first coating layer 12’ and a second embossing roll 15” acting the second coating layer 12”. The surfaces of said embossing rolls 15’, 15” exhibit structures 15a’, 15a” which are a negative with respect to the fluid flow structure of the building unit to be manufactured. After having passed the pair of rolls, the surface of the first coating layer 12’ exhibits a fluid flow structure comprising ridges 3’ and grooves 4’ as described above, and the surface of the second coating layer 12” exhibits a fluid flow structure comprising ridges 3” and grooves 4” as described above. The fluid flow structure on the first coating layer 12’ and the fluid flow structure on the second coating layer 12” are like mirror images with regard to each other.

Optionally, in said preferred process according to the present invention, after furnishing the first and the second coating layer with the desired fluid flow structure by means of embossing (as described above), the binding agent is cured. Whether curing is performed or not, depends on the used binding agent. Use of curable binding agents and curing them after embossing has the advantage of improving the form stability of the fluid flow structure. Preferably said binding agent is selected from the group consisting of polyester polyurethanes having a glass transition temperature in the range of from -45 °C to -5 °C, and curing said polyester polyurethane is carried out at a temperature of 200 °C or less, preferably in the range of from 120 °C to 190°C.

Thereafter, in said preferred process according to the present invention, a building unit as defined above is obtained as described above by forming a piece of said coated substrate having lateral dimensions corresponding to said building unit. Usually, this is done by cutting to size said coated substrate, or punching out from the coated substrate a piece of said coated substrate having lateral dimensions corresponding to said building unit.

In some preferred processes according to the present invention, only one mixture comprising a binding agent and particles of one or more magnetocaloric materials, preferably particles of one magnetocaloric material, are applied to a surface of said substrate. By doing so, a building unit comprising a shaped body made up of one mixture comprising a binding agent and particles of one or more magnetocaloric materials, preferably particles of one magnetocaloric material, is obtained.

Another particularly preferred type of process according to the present invention compris- es the steps

providing three or more mixtures each comprising a binding agent and particles of a magnetocaloric material, each magnetocaloric material having a different Curie temperature,

applying each of said three or more mixtures to a portion of the surface of said substrate by ascending or descending Curie temperature Tc of the magnetocaloric materials to form a coated substrate having a coating layer consisting of three or more portions each comprising particles of a magnetocaloric material having a dif- ferent Curie temperature disposed on said substrate, wherein said three or more portions are arranged alongside each other by ascending or descending Curie temperature Tc of the magnetocaloric materials, wherein in each case the difference between the Curie temperatures of the magnetocaloric materials of two adjacent portions is in the range of from 0.5 to 4 K, said coating layer having a first sur- face facing away from said substrate and opposite to said first surface a second surface in contact with said substrate,

treating said first surface of said coating layer by means of an embossing roll, the surface of said embossing roll exhibiting a structure which is a negative with respect to the fluid flow structure of the building unit to be manufactured, so that the ridges and grooves of the fluid flow structure extend perpendicular to said three or more portions each comprising particles of a magnetocaloric material having a different Curie temperature.

This preferred process according to the present invention allows for manufacturing a building unit according to the present invention comprising a shaped body, wherein said shaped body consists of three or more portions each comprising particles of a magnetocaloric material having a different Curie temperature, wherein said portions are arranged alongside each other by ascending or descending Curie temperature Tc of the magnetocaloric materials in the direction of the ridges and grooves of the fluid flow structure, wherein in each case the difference between the Curie temperatures of the magnetocaloric materials of two adjacent portions is in the range of from 0.5 K to 4 K. An example of such shaped body is shown in figure 4.

For this preferred process according to the present invention, three or more mixtures each comprising a binding agent and particles of one magnetocaloric material are provid- ed, wherein in each mixture the magnetocaloric material has a different Curie temperature, and a substrate which does not comprise any magnetocaloric material, said substrate having a first and a second surface opposite to each other, is provided. Preferred mixtures and substrates are as described above.

In said preferred process according to the present invention, each of said three or more mixtures is applied to an individual portion of said surface of said substrate by ascending or descending Curie temperature Tc of the magnetocaloric materials. Thus, the first mixture comprising a magnetocaloric material having the highest resp. lowest Curie temperature is applied to a first portion of the surface of said substrate, the second mixture comprising a magnetocaloric material having the next higher resp. lower Curie tem- perature with respect to the magnetocaloric material in the first mixture is applied to a second portion alongside said first portion of the surface of said substrate, the third mixture comprising a magnetocaloric material having the next higher resp. lower Curie temperature with respect to the magnetocaloric material in the second mixture is applied to the third portion alongside said second portion of the surface of said substrate etc. Thus, a coated substrate is formed having a coating layer consisting of three or more portions each comprising particles of a magnetocaloric material having a different Curie temperature disposed on said substrate. In said coating layer, said three or more portions are arranged alongside each other by ascending or descending Curie temperature Tc of the magnetocaloric materials. The magnetocaloric materials are selected so that in each case the difference between the Curie temperatures of the magnetocaloric materials of two adjacent portions is in the range of from 0.5 K to 4 K. Said coating layer has a first surface facing away from said substrate and opposite to said first surface a second surface in contact with said substrate. Preferably, said mixture is applied to said surface of said substrate by means of a coating technique, e.g. slot-die coating. Preferably, said layer has a thickness in the range of from 30 pm to 200 pm (as measured prior to treating the first surface of said coating layer by means of an embossing roll.) In said preferred process according to the present invention, the first surface of said coating layer is treated by means of an embossing roll, the surface of said embossing roll exhibiting a structure which is a negative with respect to the fluid flow structure of the building unit to be manufactured. Treating the first surface of said coating layer by means of an embossing roll is carried out so that the ridges and grooves of the fluid flow struc- ture extend perpendicular to said three or more portions each comprising particles of a magnetocaloric material having a different Curie temperature. In this manner, the desired fluid flow structure is imparted to the first surface of the coating layer thereby transforming the coating layer into a shaped body as defined above. An example of such shaped body is shown in figure 4. Preferably, said embossing roll is kept at a temperature in the range of from 40 °C to 60 °C.

Optionally, in said preferred process according to the present invention, after furnishing the coating layer with the desired fluid flow structure by means of embossing (as described above), the binding agent in the coating layer is cured. Whether curing is per- formed or not depends on the used binding agent. Use of curable binding agents and curing them after embossing is performed has the advantage of improving the form stability of the fluid flow structure. Preferably said binding agent is selected from the group consisting of polyester polyurethanes having a glass transition temperature in the range of from -45 °C to -5 °C, and curing said polyester polyurethane is carried out at a temperature of 200 °C or less, preferably in the range of from 120 °C to 190°C.

Thereafter, in said preferred process according to the present invention, a building unit as defined above is obtained as described above by forming a piece of said coated substrate having lateral dimensions corresponding to said building unit. Usually, this is done by cutting to size said coated substrate, or punching out from the coated substrate a piece of said coated substrate having lateral dimensions corresponding to said building unit. In a fourth aspect, the present invention relates to a process for manufacturing a magnetocaloric heat exchanger, comprising the steps of

providing two or more building units, preferably 50 to 1000 building units, according to the first aspect of the present invention as defined above, or manufacturing two or more building units, preferably 50 to 1000 building units, by the process according to the third aspect of the present invention as defined above

forming a heat exchanger block by subsequently stacking said building units on top of one another, wherein in each case between two building units stacked one on top of the other

- the ridges protruding from the base plate of the shaped body of the first building unit engage the second surface of the base plate of the shaped body of the second building unit stacked on top of said first building unit, or

the ridges protruding from the base plate of the shaped body of the first building unit engage the substrate attached to the base plate of the shaped body of the second building unit stacked on top of said first building unit or

In the process according to the fourth aspect of the present invention, a heat exchanger block is formed by subsequently stacking said building units on top of one another. Preferably, said two or more, preferably 50 to 1000 building units are those which have one or more of the above-defined preferred features. In a process for manufacturing a first preferred type of heat exchanger blocks as defined above in the context of the second aspect of the present invention, the two or more building units are subsequently stacked on top of one another, so that in each case between two building units stacked one on top of the other the ridges protruding from the base plate of the shaped body of the first building unit engage the second surface of the base plate of the shaped body of the second building unit stacked on top of said first building unit. In this type of heat exchanger block, the stacked building units do not comprise a substrate. Preferably each of the stacked building units consists of a shaped body as defined in above, preferably a shaped body having one or more of the above-defined preferred features. An example of a stack obtainable in this manner is shown in figure 7a. In a process for manufacturing a second preferred type of heat exchanger blocks as defined above in the context of the second aspect of the present invention, the two or more building units are subsequently stacked on top of one another, so that in each case between two building units stacked one on top of the other the ridges protruding from the base plate of the shaped body of the first building unit engage the substrate attached to the base plate of the shaped body of the second building unit stacked on top of said first building unit. In this type of heat exchanger block, the stacked building units each comprise a substrate. Preferably each of the stacked building units consists of a shaped body as defined in above, preferably a shaped body having one or more of the above-defined preferred features, and a substrate, preferably a substrate having one or more of the above-defined preferred features, attached to the second surface of the base plate of said shaped body. An example of a stack obtainable in this manner is shown in figure 7b.

In a process for manufacturing a third preferred type of heat exchanger blocks as defined above in the context of the second aspect of the present invention, the two or more building units are subsequently stacked on top of one another, so that the ridges protruding from the base plate of a shaped body of the first building unit engage the ridges protruding from the base plate of a shaped body of the second building unit stacked on top of said first building unit. In this type of heat exchanger block, the stacked building units each comprise a first and a second shaped body as defined above, and a substrate which does not comprise any magnetocaloric material, said substrate having a first and a second surface opposite to each other, wherein said first surface of said substrate is attached to the second surface of the base plate of said first shaped body and said second surface of said substrate is attached to the second surface of the base plate of said second shaped body. Preferably each of the stacked building units consists of a first and a second shaped body as defined above, preferably said shaped bodies each having one or more of the above-defined preferred features, and a substrate, preferably a substrate having one or more of the above-defined preferred features, said substrate having a first and a second surface opposite to each other, wherein said first surface of said substrate is attached to the second surface of the base plate of said first shaped body and said second surface of said substrate is attached to the second surface of the base plate of said second shaped body. Herein the fluid flow structures of adjacent stacked building units are designed so that fitting the ridges of the fluid flow structure of one building unit into the grooves of the fluid flow structure of the adjacent building unit is precluded. This is achieved e.g. by providing said building with fluid flow structures wherein the width W of the ridges is larger than the width C of said grooves of the adjacent building unit, thereby precluding that the ridges of the fluid flow structure of one building unit to fit into the grooves of the fluid flow structure of the adjacent building unit. Thus, the ridges of adjacent building units cooperate to define fluid flow structure. Examples of stacks obtainable in this manner are shown in figure 7c and 7d.

The process for manufacturing a magnetocaloric heat exchanger may include assembling of further parts of the magnetocaloric heat exchanger with said heat exchanger block. For details of said further parts, reference is made to the disclosure provided in the context of the second aspect of the present invention.

Preferably, the process for manufacturing a magnetocaloric heat exchanger as defined above further comprises providing a casing surrounding said heat exchanger block. Preferably the heat exchanger block is fixed in the casing by means of a two component (2K) epoxy resin.

Example

A mixture comprising

a binding agent in the form of a polyester polyurethane having a glass transition temperature of -28 °C dissolved in a solvent

- and particles of a magnetocaloric material having a composition according to formula Mn1.17Feo.71 Po.49Sio.51 and a Curie temperature of 32 °C

was provided. The particle size of the magnetocaloric material has a D90 value of 5 pm (size distribution analyzed by a Retsch camsizer). In said mixture the total weight fraction of the particles of said magnetocaloric material is 92.5 % based on the total weight of said particles of said magnetocaloric material and said binding agent. The weight ratio between polyester polyurethane and solvent was about 1 :6.

A substrate in the form of an aluminum foil having a thickness of 20 pm was provided.

Said mixture was applied to one surface of said substrate by means of slot die coating, thereby forming a coated substrate having a coating layer made up of said mixture dis- posed on said substrate. The coating layer had a thickness of 120 pm. Said coating layer had a first surface facing away from said substrate and opposite to said first surface a second surface in contact with said substrate.

Said first surface of said coating layer was treated by means of an embossing roll. The surface of said embossing roll exhibited a structure which is negative with respect to a fluid flow structure comprising a plurality of continuous parallel ridges and a plurality of parallel continuous grooves each extending between two of said ridges, wherein said ridges have a height H of 70 pm and a width W of 50 pm, and said grooves have a width C of 70 pm. Said fluid flow structure does not contain any regions without protruding ridges. Embossing was carried out by means of a calander equipped with a pair of cylindershaped rolls, i.e. an embossing roll acting on the coating layer and a supporting roll supporting the substrate. The embossing roll had a core made of copper and a coating made of hard chromium and was kept at a temperature of about 57 °C. The supporting roll had a hard rubber coating having a thickness of 0.3 mm, and a shore D hardness SH 90. The supporting roll was not heated. Embossing was carried out with a line force of

157 N/mm, and the coated substrate moved through the pair of cylinder-shaped rolls with a speed of 0.5 m/min.

After embossing the binding agent was cured by subjecting the coated substrate to a temperature of about 135 °C. During curing the solvent was removed by evaporation. Pieces having lateral dimensions of 2 cm x 1 .5 cm were punched out from the coated substrate. The substrate was not removed from said second surface of said coating layer.

In this way, a plurality of building units were obtained, each consisting of

a shaped body made up of a mixture comprising a binding agent in the form of a cured polyester polyurethane and particles of a magnetocaloric material having the composition and Curie temperature given above

and a substrate in the form of an aluminum foil having a thickness of 20 pm, said aluminum foil having a first and a second surface opposite to each other, wherein said first surface of said aluminum foil is attached to the second surface of the base plate of said shaped body. In each building unit, said shaped body comprises

and arranged on said first surface of said base plate a fluid flow structure compris ing a plurality of parallel ridges protruding from said base plate and a plurality of grooves each extending between two of said ridges

wherein said ridges extend continuously from one edge to the opposite edge of said first surface of said base plate

said base plate has a base plate thickness B of 90 pm,

said ridges have a height H of 70 pm

- said grooves have a width C of 70 pm, measured at half of height H

said ridges have a width W of 50 pm, measured at half of height H

Said fluid flow structure does not contain any regions without protruding ridges. The cross section of the grooves and ridges exhibited some deviation from a rectangular shape, i.e. the corners were slightly rounded. For said ridges and grooves, H/B = 0.77, H/C = 1 and H/W = 1.4. Said grooves allow for the flow of a heat transfer fluid.

100 of the above-described building units were stacked subsequently on top of each other wherein in each case between two building units stacked one on top of the other the ridges protruding from the base plate of the shaped body of the first building unit engage the substrate attached to the base plate of the shaped body of the second building unit stacked on top of said first building unit.

In this way, a heat exchanger block was obtained consisting of 100 building units as described above, wherein in each case between two building units stacked one on top of the other the ridges protruding from the base plate of the shaped body of the first building unit engage the substrate attached to the base plate of the shaped body of the second building unit stacked on top of said first building unit, so that the ridges protruding from the base plate of the shaped body of the first building unit and the substrate attached to the base plate of the shaped body of the second building unit stacked on top of said first building unit cooperate to define channels for the flow of a heat transfer fluid. The heat exchanger block has a total height of about 2 cm. The heat exchanger block was sur- rounded by an encasing made of glass-fiber reinforced plastic. In said encasing the heat exchanger block was fixed by means of a two component (2K) epoxy resin.

Claims

1. Building unit for a magnetocaloric heat exchanger,

said building unit comprising a shaped body made up of a one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric ma- terials

said shaped body comprising

and arranged on said first surface of said base plate a fluid flow structure com- prising

two or more parallel ridges protruding from said base plate one or more grooves each extending between two of said ridges wherein

said base plate has a base plate thickness B, wherein said base plate thickness B is in the range of from 10 pm to 200 pm, preferably 10 pm to 50 pm

said ridges have a height H, wherein said height H is 200 pm or less, preferably in the range of from 10 pm to 100 pm, further preferably of from 20 pm to 50 pm

- at least one of said grooves has a width C of 200 pm or less, preferably of 50 pm or less, measured at half of height H

at least one of said ridges has a width W of 200 pm or less, preferably of 50 pm or less, measured at half of height H

0.5 < H/B < 2

0.5 < H/C < 2

0.5 < H/W < 2.

2. Building unit according to claim 1 wherein

said ridges extend continuously from one edge to another edge of said first surface of said base plate.

3. Building unit according to claim 1 or 2, wherein said fluid flow structure comprises - one or more regions having parallel ridges protruding from said base plate and grooves extending between said ridges

and one or more regions without protruding ridges

wherein said grooves open out into said region without protruding ridges.

4. Building unit according to any of claims 1 to 3, wherein said binding agent is se- lected from the group consisting of polyester polyurethanes having a glass transition temperature in the range of from -45 °C to -5 °C.

5. Building unit according to any of claims 1 to 4 wherein said shaped body consists of three or more portions each comprising particles of a magnetocaloric material having a different Curie temperature, wherein said portions are arranged alongside each other by ascending or descending Curie temperature of the magnetocaloric materials in the direction of the ridges and grooves of the fluid flow structure, wherein in each case the difference between the Curie temperatures of the magnetocaloric materials of two adjacent portions is in the range of from 0.5 K to 4 K.

6. Building unit according to any of claims 1 to 5, comprising

a shaped body as defined in any of claims 1 to 5

a substrate which does not comprise any magnetocaloric material, said substrate having a first and a second surface opposite to each other, wherein said first surface of said substrate is attached to the second surface of the base plate of said shaped body

- optionally a second shaped body as defined in any of claims 1 to 5, wherein said second surface of said substrate is attached to the second surface of the base plate of said second shaped body.

7. Building unit according to claim 6, wherein said substrate

is in a form selected from the group consisting of foils, films, webs, panes and plates

and/or

has a thickness in the range of from 0.1 pm to 100 pm, preferably 1 pm to 25 pm, more preferably 1 pm to 15 pm, most preferably 1 pm to 10 pm and/or

comprises one or more materials from the group consisting of organic polymers and metals.

8. Magnetocaloric heat exchanger comprising a heat exchanger block comprising two or more building units, preferably 50 to 1000 building units, according to any of claims 1 to 7 subsequently stacked on top of one another

wherein in each case between two building units stacked one on top of the other the ridges protruding from the base plate of the shaped body of the first building unit engage the second surface of the base plate of the shaped body of the second building unit stacked on top of said first building unit or

9. Process for manufacturing a building unit as defined in any of claims 1 to 7 for a magnetocaloric heat exchanger, comprising the steps

providing a substrate which does not comprise any magnetocaloric material, said substrate having a first and a second surface opposite to each other applying said one or more mixtures to said first surface of said substrate, to form a coated substrate having a coating layer made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials disposed on said substrate, said coating layer having a first surface facing away from said substrate and opposite to said first surface a second surface in contact with said substrate,

treating said first surface of said coating layer by means of an embossing roll, the surface of said embossing roll exhibiting a structure which is a negative with respect to the fluid flow structure of the building unit to be manufac- tured

optionally curing said binding agent

obtaining said building unit by forming a piece of said coated substrate having lateral dimensions corresponding to said building unit

wherein optionally before or after forming said piece having lateral dimen- sions corresponding to said building unit, said substrate is removed from said second surface of said coating layer.

10. Process according to claim 9, wherein said substrate is not removed from said second surface of said coating layer.

11. Process according to claim 10, comprising the steps of

- providing one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials

providing a substrate which does not comprise any magnetocaloric material, said substrate having a first and a second surface opposite to each other applying said one or more mixtures to said first surface of said substrate and to said second surface of said substrate, to form a coated substrate having a first coating layer made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials disposed on said first surface of said substrate, and a second coating layer made up of one or more mixtures each comprising a binding agent and particles of one or more magnetocaloric materials disposed on said second surface of said substrate, each of said coating layers having a first surface facing away from said substrate and opposite to said first surface a second surface in contact with said substrate treating the first surface of said first coating layer and the first surface of said second coating layer each by means of an embossing roll, the surface of said embossing roll exhibiting a structure which is a negative with respect to the fluid flow structure of the building unit to be manufactured

- optionally curing said binding agent

12. Process according to claim 9, wherein said substrate is removed from said second surface of said coating layer.

13. Process according to any of claims 9 to 12, comprising the steps of

providing a substrate which does not comprise any magnetocaloric material, said substrate having a first and a second surface opposite to each other applying each of said three or more mixtures to a portion of the surface of said substrate by ascending or descending Curie temperature Tc of the magnetocaloric materials to form a coated substrate having a coating layer consisting of three or more portions each comprising particles of a magneto- caloric material having a different Curie temperature disposed on said substrate, wherein said three or more portions are arranged alongside each other by ascending or descending Curie temperature Tc of the magnetocaloric materials, wherein in each case the difference between the Curie temperatures of the magnetocaloric materials of two adjacent portions is in the range of from 0.5 to 4 K, said coating layer having a first surface facing away from said substrate and opposite to said first surface a second surface in contact with said substrate,

treating said first surface of said coating layer by means of an embossing roll, the surface of said embossing roll exhibiting a structure which is a nega- tive with respect to the fluid flow structure of the building unit to be manufactured, so that the ridges and grooves of the fluid flow structure extend perpendicular to said three or more portions each comprising particles of a magnetocaloric material having a different Curie temperature.

14. Process according to any of claims 9 to 13, wherein said binding agent is selected from the group consisting of polyester polyurethanes as defined in claim 4, and curing said polyester polyurethane is carried out at a temperature of 200 °C or less, preferably in the range of from 120 °C to 190°C.

15. Process for manufacturing a magnetocaloric heat exchanger, comprising the steps of

providing two or more building units, preferably 50 to 1000 building units, according to any of claims 1 to 7 or manufacturing two or more building units, preferably 50 to 1000 building units, by the process according to any of claims 9 to 14

the ridges protruding from the base plate of the shaped body of the first building unit engage the second surface of the base plate of the shaped body of the second building unit stacked on top of said first building unit,

or