GB1570027A

GB1570027A - Scraped-surface heat exchanger

Info

Publication number: GB1570027A
Application number: GB771677A
Authority: GB
Original assignee: A Johnson and Co London Ltd
Current assignee: A Johnson and Co London Ltd
Priority date: 1977-02-23
Filing date: 1977-02-23
Publication date: 1980-06-25

Description

(54) A SCRAPED-SURFACE HEAT EXCHANGER (71) We, A. JOHNSON AND COM PANY (LONDON) LIMITED, a British company, of Villiers House, 41-47 Strand, London, WC2N 5LE, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:: According to the invention, there is provided a scraped-surface heat exchanger comprising a stator surrounding a rotor, the stator having a plurality of annular projections extending inwardly towards the axis of rotation of the rotor, each projection having a first flank which is the upper flank when the heat exchanger is appropriately positioned, with the axis of rotation of the rotor vertical, and which then slopes downwardly, proceeding towards said axis, the rotor carrying scrapers which scrape the first flanks and the opposite flanks of the projections as the rotor rotates.

Preferably, the annular spaces, into which the space within the stator is divided by the projections, communicate with one another at locations radially inwardly of the tips of the projections. Preferably, the whole of each flank is scraped. The scraping scrapes off films. of the material being treated, which form on the projections. The scraped-off material is mixed with the remainder of the material and proceeds with it along the rotor.

The scrapers may press against the flanks as a result of the scrapers possessing resilience and,' or as a result of the pressure of the fluid material and or by springs. They could be pivotally mounted ori vanes projecting from the rotor.

The heat exchange could be effected with gas or liquid heat exchange medium flowing through the stator, for example along it in the same direction as, or in counter-current with, a fluid material to be heated or cooled which flows along the rotor between the rotor and the stator.

The projections preferably taper, proceeding towards the axis of rotation of the rotor, and they are preferably hollow, the spaces within them being for one of the two fluids involved in the heat exchange. Thus the projections could be of sheet material.

The spaces within them could communicate with one another at their extremities remote from the rotor, so that the above-mentioned gas or liquid can flow into and out of them, from one to another along the stator. Preferably, the connections between the spaces within adjacent projections are staggered circumferentially so that the gas or liquid entering the space within one projection has to flow part of the way around the axis of rotation of the rotor before it can leave that space and flow into the space within the next projection. The space within each projection could be divided into two or more parts, for example by virtue of each projection being made up of two or more segments distributed around the axis of rotation of the rotor. The two flanks of each projection or of each segment of each projection could also be provided by separate members.

The above-mentioned first flanks and the opposite flanks of the projections are referred to below as upper flanks and lower flanks, respectively, but that does not mean that the heat exchanger necessarily operates with the axis of rotation of the rotor vertical, or, if it is vertical, with the first flanks uppermost. The lower flanks of the projections preferably slope downwardly, proceeding away from said axis. The greater part of each upper flank and/or each lower flank could be planar. Alternatively, the greater part of each upper flank and/or each lower flank could be concavely or convexly rounded in order to give the projections greater strength if they are of sheet material.

It is highly desirable so to construct the stator that when the heat exchanger is positioned with the upper flanks of the projections uppermost and the axis of the stator vertical, liquids of low viscosity in the space within the stator, for example low-viscosity liquids used in the heat exchange or lowviscosity liquids for cleaning the heat exchanger after use, will drain completely from the stator and will not, for example, form pools on the upper flanks of the projections.

The tips of the projections could be convexly rounded. There could be, alternatively or additionally, concave rounding between the roots of adjacent projections. Preferably the scrapers or additional scrapers scrape also these convexly and/or concavely rounded parts. Preferably, each annular space between two adjacent projections receives at least one scraper blade which scrapes one flank of one projection and the opposite flank of the other projection and preferably also the part between the roots of the two projections and half of the tip of each of the two projections. The blades may be of plastics material and may be held in slots in plates, for example circular plates, mounted on the rotor and co-axial with it.

The stator may comprise a stack of annular parts each of which provides only one of the pojections.

An example in accordance with the invention is described below with reference to the accompanying drawings, in which: Figure 1 shows a side view of a rotary scraped-surface heat exchanger, in section, Figure 2 shows a plan view of a disc on the rotor of the heat exchanger, and Figure 3 shows a scraper mounted on the disc.

The heat exchanger shown in Figures 1 to 3 operates with its rotor 1 rotating about a vertical axis 2. The rotor is preferably of stainless steel and is of regular hexagonal cross-section over the greater part of its length and along that part are regularly distributed circular discs 3. the faces of which are perpendicular to the axis 2. The discs have regular hexagonal holes 4 through them at their centres and they are formed with radial slots 5.

A stator surrounding the rotor comprises a stack of similar annular members 6 (there will usually be more than the three shown) held between flanges 7 and 8 of a housing by bolts 9 provided with nuts 10. Each annular member comprises a collar 6A and a sheet metal part 6B, preferably stainless steel, which affords an annular projection extending inwardly toards the axis 2. The upper flank 6C of each projection is slightly concave but over the whole of its length it slopes downwardly proceeding towards the axis 2. so that pools of low-viscosity liquid cannot remain on the flanks 6C of the projections when it is desired to drain the heat exchanger with the axis of the stator, which is the axis 2, vertical.The lower flank 6D of eachprojection is also slightly concave and over the whole of its length slopes downwardly, proceeding away from the axis 2.

The tip 6E of each projection is convexly rounded and there is concave rounding at 6F between the roots of adjacent projections. Seals 11 between the collars 6A and between the end collars and the flanges 7 and 8 are compressed by the bolts 9 and nuts 10. The collars are formed with bosses 12 formed with screw-threaded holes 13 to receive connections for supplying heat exchange fluid to and taking it from hollows 14 within the projections 6B.

Each slot 5 receives a plastics scraper blade 15 which, when free from stress is flat and wider than the space between the lower flank 6D of one projection 6B and the upper flank 6C of the next. The scraper blades are forced into arcuate form as shown in Figure 3 and sharp edges of them scrape, in each case, the whole of one flank 6D, one flank 6C and one concavely rounded part 6F and halves of each of two projection tips 6E. The blades have holes 16 through them.

Fluids which are to be in heat-exchange relationship are pumped along the heat exchanger, for example in counter-current, in one case through the hollows 14 in turn and in the other case in through or out of a connection 17 at the lower end of the housing, through the space between stator and rotor and out of or in through the upper end of the housing and being continually scraped off all points on the projections 6B.

The scraped-surface heat exchanger described above and shown in the accompanying drawings is also described, illustrated and claimed in our co-pending Patent Application No 7900823 (Serial No 1570026).

WHAT WE CLAIM IS: 1. A scraped-surface heat exchanger comprising a stator surrounding a rotor, the stator having a plurality of annular projections extending inwardly towards the axis of rotation of the rotor, each projection having a first flank which is the upper flank when the heat exchanger is appropriately positioned, with the axis of rotation of the rotor vertical, and which then slopes downwardly, proceeding towards said axis. the rotor carrying scrapers which scrape the first flanks and the opposite flanks of the projections as the rotor rotates.

2. A heat exchanger according to claim 1 in which the projections taper, proceeding towards the axis of rotation of the rotor.

3. A heat exchanger according to claim 1 or 2 in which the projections are hollow, the spaces within them being for one of the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. stator that when the heat exchanger is positioned with the upper flanks of the projections uppermost and the axis of the stator vertical, liquids of low viscosity in the space within the stator, for example low-viscosity liquids used in the heat exchange or lowviscosity liquids for cleaning the heat exchanger after use, will drain completely from the stator and will not, for example, form pools on the upper flanks of the projections. The tips of the projections could be convexly rounded. There could be, alternatively or additionally, concave rounding between the roots of adjacent projections. Preferably the scrapers or additional scrapers scrape also these convexly and/or concavely rounded parts. Preferably, each annular space between two adjacent projections receives at least one scraper blade which scrapes one flank of one projection and the opposite flank of the other projection and preferably also the part between the roots of the two projections and half of the tip of each of the two projections. The blades may be of plastics material and may be held in slots in plates, for example circular plates, mounted on the rotor and co-axial with it. The stator may comprise a stack of annular parts each of which provides only one of the pojections. An example in accordance with the invention is described below with reference to the accompanying drawings, in which: Figure 1 shows a side view of a rotary scraped-surface heat exchanger, in section, Figure 2 shows a plan view of a disc on the rotor of the heat exchanger, and Figure 3 shows a scraper mounted on the disc. The heat exchanger shown in Figures 1 to 3 operates with its rotor 1 rotating about a vertical axis 2. The rotor is preferably of stainless steel and is of regular hexagonal cross-section over the greater part of its length and along that part are regularly distributed circular discs 3. the faces of which are perpendicular to the axis 2. The discs have regular hexagonal holes 4 through them at their centres and they are formed with radial slots 5. A stator surrounding the rotor comprises a stack of similar annular members 6 (there will usually be more than the three shown) held between flanges 7 and 8 of a housing by bolts 9 provided with nuts 10. Each annular member comprises a collar 6A and a sheet metal part 6B, preferably stainless steel, which affords an annular projection extending inwardly toards the axis 2. The upper flank 6C of each projection is slightly concave but over the whole of its length it slopes downwardly proceeding towards the axis 2. so that pools of low-viscosity liquid cannot remain on the flanks 6C of the projections when it is desired to drain the heat exchanger with the axis of the stator, which is the axis 2, vertical.The lower flank 6D of eachprojection is also slightly concave and over the whole of its length slopes downwardly, proceeding away from the axis 2. The tip 6E of each projection is convexly rounded and there is concave rounding at 6F between the roots of adjacent projections. Seals 11 between the collars 6A and between the end collars and the flanges 7 and 8 are compressed by the bolts 9 and nuts 10. The collars are formed with bosses 12 formed with screw-threaded holes 13 to receive connections for supplying heat exchange fluid to and taking it from hollows 14 within the projections 6B. Each slot 5 receives a plastics scraper blade 15 which, when free from stress is flat and wider than the space between the lower flank 6D of one projection 6B and the upper flank 6C of the next. The scraper blades are forced into arcuate form as shown in Figure 3 and sharp edges of them scrape, in each case, the whole of one flank 6D, one flank 6C and one concavely rounded part 6F and halves of each of two projection tips 6E. The blades have holes 16 through them. Fluids which are to be in heat-exchange relationship are pumped along the heat exchanger, for example in counter-current, in one case through the hollows 14 in turn and in the other case in through or out of a connection 17 at the lower end of the housing, through the space between stator and rotor and out of or in through the upper end of the housing and being continually scraped off all points on the projections 6B. The scraped-surface heat exchanger described above and shown in the accompanying drawings is also described, illustrated and claimed in our co-pending Patent Application No 7900823 (Serial No 1570026). WHAT WE CLAIM IS:

1. A scraped-surface heat exchanger comprising a stator surrounding a rotor, the stator having a plurality of annular projections extending inwardly towards the axis of rotation of the rotor, each projection having a first flank which is the upper flank when the heat exchanger is appropriately positioned, with the axis of rotation of the rotor vertical, and which then slopes downwardly, proceeding towards said axis. the rotor carrying scrapers which scrape the first flanks and the opposite flanks of the projections as the rotor rotates.

two fluids involved in the heat exchange.

4. A heat exchanger according to claim 3 in which the projections are of sheet material.

5. A heat exchanger according to claim 3 or 4 in which the spaces within the projections communicate with one another at their extremities remote from the rotor, so that said one of the fluids can flow into and out of them, from one to another along the stator.

6. A heat exchanger according to claim 5 in which the connections between the spaces within adjacent projections are staggered circumferentially so that said one of the fluids entering the space within one projection has to flow part of the way around the axis of rotation of the rotor before it can leave that space and flow into the space within the next projection.

7. A heat exchanger according to claim 6 in which the space within each projection is divided into a plurality of parts.

8. A heat exchanger according to claim 7 in which the division is effected by each projection being made up of two or more segments distributed around the axis of rotation of the rotor.

9. A heat exchanger according to any one of claims 1 to 8 in which the two flanks of each projection are provided by separate members.

10. A heat exchanger according to claim 8 in which the two flanks of each segment of each projection are provided by separate members.

11. A heat exchanger according to any preceding claim in which said opposite flanks of the projections slope downwardly, proceeding away from said axis.

12. A heat exchanger according to any preceding claim in which the greater part of each upper flank is concavely rounded.

13. A heat exchanger according to any preceding claim in which the greater part of each said opposite flank is concavely rounded.

14. A heat exchanger according to any preceding claim in which the tips of the projections are convexly rounded.

15. A heat exchanger according to any preceding claim in which there is concave rounding between the tips of adjacent projections.

16. A heat exchanger according to any preceding claim in which in each annular space between two adjacent projections there is at least one scraper blade which scrapes one flank of one projection and the opposite flank of the other projection.

17. A heat exchanger according to any preceding claim in which the blades are held in slots in plates mounted on the rotor.

18. A heat exchanger according to any preceding claim in which the stator comprises a stack of annular parts each of which provides only one of the projections.