EP2515064B1

EP2515064B1 - Heat exchanger

Info

Publication number: EP2515064B1
Application number: EP20110003326
Authority: EP
Inventors: Charlie Penny; Adrian Ware; Laurent Amann; Steven Fairhurst; Christopher Aylward
Original assignee: Senior UK Ltd
Current assignee: Senior UK Ltd
Priority date: 2011-04-20
Filing date: 2011-04-20
Publication date: 2014-06-04
Anticipated expiration: 2031-04-20
Also published as: EP2515064A1

Description

Field of the Invention

The present invention relates to heat exchangers.

Background to the Invention

There are many heat exchanger applications where a hot gas inlet and a cooled gas outlet need to be in close proximity to each other due to space constraints. Such applications include automotive cooling systems, such as cars, trucks and rail locomotives, and medical equipment applications, nuclear power industry applications and the like.
Typically, a known heat exchanger, used for example for cooling a gas flow, comprises an external casing, a heat exchange plate or tube assembly comprising one or a plurality of heat exchange plates or tubes, one or more coolant inlets for allowing a coolant fluid to enter the casing and permeate around the heat exchange plate or tube assembly ,one or more coolant outlets for allowing the coolant fluid to drain from the casing, one or more gas inlets for allowing gas to enter the heat exchange assembly, and one or more gas outlets to allow gas to exhaust from the heat exchange plate or tube assembly.
The heat exchange plates or tubes are held rigidly in the casing by a bulkhead or connecting plate which extends across an end of the casing.
In an "I" type heat exchanger, there is a first bulkhead at a first end of the cooling plate assembly, and a second bulkhead at a second end of the heat exchange plate or tube assembly, and fluid to be cooled or heated flows between the first and second ends along a plurality of passages or conduits in the cooling plates.
In a known "U" shaped heat exchanger, a plurality of cooling plates are held in parallel in a side by side relationship connected by a single connecting plate or bulkhead at one end of the heat exchanger, so that both inlets and outlets of the fluid to be cooled can be presented on a same face at a same end of the heat exchanger.
In US2008/0110595 there is disclosed a heat exchanger according to the preamble of claim 1 with an external bypass. The heat exchanger includes stacked flat tubes located above and parallel to a corrugated tube. The stacked flat tubes are configured and arranged to form a fluid cooling passage for allowing a coolant to flow in at least two directions. The corrugated tube provides a fluid conduit at the base of the heat exchanger and therefore heat exchange is primarily effected by the thermal relationship between an upper surface of the corrugated tube and the lowermost stacked flat tube.

Summary of the Invention

A problem with known heat exchangers is that the boiling of a liquid coolant, for example either water or a water and anti-freeze mixture, within a high temperature heat exchanger can cause localized stress concentrations and failure of the heat exchanger.
A heat exchanger will exchange the greatest proportion of heat where the inlet gas is at its hottest. Consequently, the highest proportion of heat exchange will occur at and in close proximity to the inlet bulkhead.
Many prior art heat exchangers have a restriction to coolant flow near to the bulkhead due to the need to interface the gas carrying conduits into the bulkhead. Even where there is no restriction to coolant flow, then there is no defined path to increase coolant flow at the bulkhead.
The relatively low coolant flow rate near the gas inlet end, combined with the increased heat exchange can cause the coolant at or near the bulkhead to boil and lead to a failure of the heat exchanger at or near the bulkhead.
Specific embodiments herein describe a plate cooler type heat exchanger having a near inlet coolant channel at or near the interface between the hot fluid inlet header and the start of the heat exchange section (often formed by a bulkhead) at which a gas inlet is present. The inlet end coolant channel is aimed at increasing the coolant flow across the interface between the inlet header and the heat exchanger and around the bulkhead, and thereby reducing the likelihood of localised boiling. Reducing localised boiling near the inlet to the heat exchange assembly may improve the reliability of the cooler device.
According to a first aspect of the present invention, there is provided a cooling plate assembly for cooling a fluid flow using a liquid coolant, said assembly comprising:

a plurality of cooling plates (200), each cooling plate comprising a plurality of fluid conduits (203) through which fluid can flow; and
said cooling plate assembly comprising a fluid inlet region, a fluid outlet region, and a heat exchange region
characterised by,
a set of first coolant channels (407 - 412; 800) arranged between said plurality of cooling plates and positioned immediately adjacent to said fluid inlet region, each of said first coolant channels extending in a direction transverse to a main flow direction of said plurality of fluid conduits, said fluid conduits being sealed from said set of first coolant channels, and at least one of said first coolant channels allowing a relatively higher coolant flow rate in a direction transverse to a main length of said fluid conduits than occurs in a region further away from said inlet region.

The embodiments encompass a heat exchanger gas conduit with a smoother gas side surface at and near the bulkhead, which reduces the heat transfer co-efficient and thus reduces the risk of localised boiling at or near the bulkhead.
Other aspects are as recited in the claims herein.

Brief Description of the Drawings

For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which:

Referring to Figure 1 herein, there is illustrated schematically in external view, a heat exchanger according to a first specific embodiment;
Referring to Figure 2 herein, there is illustrated schematically in view from above, an individual cooling plate according to a first specific embodiment;
Referring to Figure 3 herein, there is illustrated schematically a cooling plate assembly of the heat exchanger of Figure 1 herein;
Referring to Figure 4 herein, there is illustrated schematically in detail, a first end of the cooling plate assembly of Figure 3 herein;
Referring to Figure 5A herein, there is illustrated schematically in view from one side, the cooling plate assembly of Figure 3 herein;
Referring to Figure 5B herein, there is illustrated schematically a plot of coolant temperature and gas temperature between first and second ends of the cooling plate assembly as shown in Figure 5A herein;
Referring to Figure 6 herein, there is illustrated schematically in external view, a "U" shaped heat exchanger according to a second specific embodiment having gas inlets and gas outlets on one end of the cooler;
Referring to Figure 7 herein, there is illustrated schematically a cooling plate assembly of the "U" shaped heat exchanger of Figure 6 herein;
Referring to Figure 8 herein, there is illustrated schematically in close up detail a close up of a bulkhead and cooling plates at the first end of the "U" shaped heat exchanger of Figures 6 and 7 herein;
Referring to Figure 9 herein, there is illustrated schematically in view from one side a third embodiment heat exchanger comprising a plurality of individual cooling plates;
Referring to Figure 10 herein, there is illustrated schematically in view from above a fourth embodiment heat exchange plate; and
Referring to Figure 11 herein, there is illustrated schematically in view from one side a heat exchange plate assembly according to a fourth specific embodiment.

Detailed Description

There will now be described by way of example a specific mode contemplated by the inventors. In the following description numerous specific details are set forth in order to provide a thorough understanding. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the description.
In this specification there are described embodiments of heat exchangers for exchanging heat between a first fluid, which in the general case can be a gas or a liquid and a second fluid, which in the general case can be a gas or a fluid. In various places for ease of description, the heat exchanger embodiments are referred to as coolers, and the fluids are specified as gases or liquids, and embodiments are described where a liquid, e.g. water and / or a water/ antifreeze mixture is used to cool a gas, e.g. an engine exhaust gas. However although these are specific embodiments, in the general case, the heat exchanger uses a liquid coolant and the fluid to be cooled may comprise a gas or a gas/ liquid mixture, or even a liquid, and the invention is limited only by the features of the claims
In this specification, for ease of terminology, the interface between the fluid inlets of one or more heat exchange plates or heat exchange tubes will be referred to as the "inlet header". In some embodiments a plurality of cooling plates are connected together at their fluid inlet ends by a bulkhead plate, which extends in a direction transverse to a main length direction of the heat exchange plates or tubes. In other embodiments, the ends of a plurality of cooling plates may be connected together without the use of a separate bulkhead plate. In either case, the region of the heat exchange plates or tubes where the fluid flow enters the plates or tubes is referred to as the "inlet header".
Specific embodiments described herein address the problem of localized boiling of a coolant fluid near a gas inlet and bulkhead of a heat exchanger. Localized boiling may lead to high component temperature and premature component failure. In the specific embodiments, these problems are addressed by:

1. Directing a higher proportion of the coolant flow to the inlet header region of the gas conduits, compared to the regions of the gas conduits in the center region of the heat exchanger ; and / or
2. Minimizing the turbulence in the gas near the inlet header, by reducing turbulence inducing features in the gas flow, and thereby lowering the heat transfer co-efficient on the gas side, in the region near the bulkhead.

In the embodiments described herein, the solution is addressed by implementing the following improved features:

The gas conduit or conduits is/ are shaped such that the gas cooling plate(s) narrow at or near the inlet header.
A relatively narrowed cooling plate at or near the inlet header results in a smoother and larger flow path for the coolant to flow through, thus increasing coolant flow at the inlet header; thus reducing the risk of localized boiling at or near the inlet header.
The conduit surface initially encountered by the gas flow (on the gas side of the heat exchanger) and the section following the initial gas side surface is more planar than the central section of the conduit, thus the gas side heat transfer coefficient is reduced; thus reducing the risk of localized boiling at or near the inlet header.

There is provided a heat exchanger gas conduit with a smoother gas side surface at and near the bulkhead, which reduces the heat transfer co-efficient and thus reduces the risk of localised boiling at or near the bulkhead.
Referring to figure 1 herein, there is illustrated schematically in perspective view, an "I" type heat exchanger 100 comprising an external casing 101; a cooling plate assembly; one or more coolant inlets 102 for allowing a coolant fluid to enter the casing and permeate around the cooling plate assembly, and one or more coolant outlets 103 for allowing the coolant fluid to exit from the casing; one or more gas inlet connectors 104 for allowing gas to enter the cooling plate assembly, and one or more gas outlet connectors 105 to allow gas to exhaust from the cooling plate assembly.
The cooling plate assembly comprises a plurality of plates stacked side by side, held rigid, and spaced apart from each other at their ends, between a first bulkhead and a second bulkhead.
A fluid to be cooled, for example a hot gas, enters the heat exchanger at a first end and exits the heat exchanger at a second end. The coolant surrounds one or a plurality of cooling plates through which a fluid to be cooled (in this case a gas) passes, and heat is transferred between the fluid to be cooled and the coolant. The gas flow and coolant fluid flow are separated by metal walls of the cooling plate assembly. Heat is transferred between the gas flow and the coolant fluid by conduction of heat from the gas flow to the metal walls of the cooling plates, and from the metal cooling plates to the coolant fluid.
A cooling plate assembly which fits in the outer casing will now be described with reference to figures 2 to 5 herein.
Referring to Figure 2 herein, there is illustrated schematically in view from above, one heat exchanger plate of the "I° type plate heat exchanger of figure 1 herein, hereafter referred to as a cooling plate. The heat exchanger comprises one or a plurality of such cooling plates.
Each cooling plate 200 comprises a pair of flat metal plates joined together at their sides 201, 202, and forming a plurality of fluid conduits or passages 203 there between (herein also referred to as gas conduits), each fluid conduit extending between first and second ends 204, 205 respectively of the cooling plate.
The upper plate comprises a plurality of generally semi-cylindrical protrusions 206 extending along the lengths of the plate, which form gas passages or conduits. Along each gas conduit, the plurality of protrusions 206 are alternated with a plurality of indents 207. A main axial direction of the substantially semi-cylindrical protrusions is arranged along a direction between the first and second ends.
Similarly, each lower plate of each cooling plate comprises a plurality of substantially semi-cylindrical protrusions 206 and a plurality of indents 207 arranged in rows and columns between a first end and a second end of the lower plate. The lower plate comprises a plurality of generally semi-cylindrical indents and protrusions extending along the length of the plate, which form the opposite walls of the gas passages or conduits
In each cooling plate, for each gas channel, the plurality of protrusions in the upper plate line up opposite the plurality of indents in the lower plate, and the plurality of protrusions on the lower plate line up opposite the corresponding respective plurality of indents in the upper plate with the result that the protrusions and indents along each gas conduit creates a serpentine tubular gas conduit in which the gas flow follows a serpentine path along the conduit inside the cooling plate, between the upper and lower plates, which causes continuous turbulence and mixing of the gas allowing the gas to contact the interior surfaces of the gas conduits and thereby achieves efficient heat transfer between the gas and the metal of the cooling plate. The edges of the plates are sealed together in a gas tight manner.
On the upper plate, the plurality of indents or depressions are arranged in rows and columns, and separating the plurality of raised protrusions, the arrangement being that for each gas conduit between the first and second ends of the upper plate, each conduit is periodically interrupted by a plurality of said indents / depressions.
Similarly, on the lower plate, there are a corresponding plurality of lines of protrusions and depressions or indents, arranged in rows and columns over the lower plate, the arrangement being that for each conduit extending between the first and second ends of the lower plate, the internal bore of that conduit or passage are periodically interspersed with a plurality of said indents / depressions, creating a substantially serpentine gas flow path.
As the upper and lower plates are fixed together, the depressions of the upper plate line up with the corresponding respective protrusions of the lower plate, and vice versa the depressions of the lower plate line up adjacent to the corresponding respective protrusions on the upper plate, the result being a plurality of tubular fluid or gas conduits / passages channels extending between the first and second ends of the cooling plate, each of which have a serpentine path. The gas passages cross a central plane of the cooling plate, as the gas flow undulates passing between the semi-circular protrusions of the upper and lower plates.
Providing the serpentine fluid conduits, causes the fluid to undulate, and generates turbulence in the fluid flow and thereby enhances the heat transfer between the upper and lower plates of each cooling plate and the gas flow.
In the cooling plate of Figure 2 herein, the depressions or indents on the external surface of the cooling plate line up in a direction transverse to the main gas flow direction, allowing coolant to penetrate between the cooling plates when the cooling plates are stacked together, and allowing coolant flow over the outside surfaces of the cooling plates.
There is also shown a substantially flat surface 212 on the upper plate of the cooling plate at the first end, and a second substantially smooth flat planar surface 213 at the second end. Similarly, the lower plate at the first end has a flat smooth surface extending across the width of the plate, and at the second end the lower plate has a further flat smooth surface extending across a width of the plate. These surfaces are provided to engage with a plurality of corresponding slots in the bulkheads 300, 301, so that during manufacture, the ends of the cooling plates can be inserted into the slots, and brazed or soldered to the bulkhead.
At the ends of the cooling plate, there are also provided a set of protrusions 214 and indents 215 which are relatively longer than the other indents 207 and protrusions 206. These extended indents and protrusions provide relatively larger width coolant channels extending across the width of the cooling plates at each end of the cooling plate. This allows a relatively higher flow rate of coolant across the ends of the cooling plates at the near inlet and near outlet ends of the cooling plates, than in the more central heat exchange area between the ends, and allows enhanced access of coolant to the joint between the cooling plates and the bulkheads. This helps to provide more efficient cooling at the interface between the cooling plates and the bulkhead at the inlet header.
The enhanced length protrusions and indents at the ends of the cooling plates also provide a relatively straighter bore to the gas passages at the inlet end and the outlet end compared to the more undulating bore of the gas passages in the central heat exchange region. This results in slightly reduced heat transfer from gas to cooling plate metal in the near inlet region, thereby assisting in reducing the temperature at the inlet end of the cooling plate and at the joint between the cooling plate and the bulkhead. Similarly, the extended length indents / protrusions at the other end provide a region of slightly reduced heat exchange from gas to cooling plate, and a slightly increased heat exchange from cooling plate to coolant, at the gas outlet end. In this embodiment, the cooling plates and the cooling plate assembly are symmetrical, and the assembly can be reversed so that the outlet can be used as the inlet end and vice versa.
Referring to Figure 3 herein, there is illustrated schematically in view from one side a cooling plate assembly of the heat exchanger of figure 1 herein.
The first ends of the plurality of cooling plates are connected to the first bulkhead 300, for example by brazing or soldering. Similarly, the plurality of second ends of the plurality of cooling plates are connected to the second bulkhead 301 by brazing or soldering.
The plurality of cooling plates are held by the first and second bulkheads, so that the plates are stacked on top of each other, with a gap there between to allow passage of coolant fluid between adjacent cooling plates.
The entire assembly shown in Figures 2 and 3 herein is encased in a rectangular box section casing, having a coolant inlet and a coolant outlet. One or more gas inlets and gas outlets are provided to the casing, and there is an inlet header region between the main gas inlet connector on the casing between the main gas inlet connector 104. and the inlet ends of the cooling plate assembly.
Each cooling plate has at least one gas inlet and at least one gas outlet, and in the embodiment shown, there are a plurality of gas inlets 302 to the plurality of cooling plates, protruding through the first bulkhead, and at the second end, there are a plurality of gas outlets 303 of the individual cooling plates protruding from the second bulkhead.
Referring to Figure 4 herein, there is illustrated schematically in close up, a view of the first end of the "I' shaped cooling plate assembly. Each cooling plate has a corresponding respective single gas inlet 400 - 406.
Since each cooling plate is substantially symmetrical, the gas flow can be reversed in the opposite direction, from the second to the first end without any substantial difference in performance.
In the side view of Figure 4 herein, there are shown viewed between and parallel to the main planes of the cooling plates, a plurality of coolant cross channels 407 - 412 formed between a plurality of relatively longer substantially semi-cylindrical protrusions 214 of the upper plates of the cooling plates, and the lower plates of a neighboring cooling plates immediately adjacent. These channels near to the bulkhead 300 allow coolant to flow in a direction across the width of the cooling plate in a region near to the bulkhead and allowing relatively high coolant flow rates and direct coolant contact with an inner surface 413 of the bulkhead 300, thereby allowing efficient heat transfer from the bulkhead 300 to the coolant, and heat transfer to the coolant fluid from the portions of the cooling plate where the cooling plates join the bulkhead.
As shown in Figures 3 and 4 herein, portions of the flat surfaces which protrude from the bulkheads on the interior of the cooling plate assembly provide a plurality of substantially straight through channels 407 - 412 for the coolant to flow across the first bulkhead and parallel to the first bulkhead, in contact with the bulkhead between the first and second sides of the cooling plate assembly. Similarly, the regions of substantially flat plate immediately adjacent to the second bulkhead 301 at the other (second) end of the cooling plate assembly form a plurality of substantially straight coolant channels immediately adjacent the second bulkhead, allowing efficient access of the cooling fluid to the bulkhead, and to the joints between the cooling plates and the second bulkhead.
In Figures 3 and 4, since the cooling plates are substantially symmetrical, the cooling plate assembly can be reversed so that gas can flow through in either direction, so that either bulkhead can be used as the fluid inlet or the fluid outlet.
Referring to Figure 5A herein, there is illustrated schematically the "I" shaped plate heat exchanger of Figure 1 herein, in view from one side.
In Figure 5B herein, there is shown schematically a comparison of gas temperature, and coolant temperature along the length of the cooling plate assembly.
Referring to Figure 5A herein, an "I" plate heat exchanger is illustrated in view from one side. At a first inlet end 500 (the inlet header end), there is provided a plurality of coolant channels extending in a direction transverse to the overall flow direction of fluid to be cooled, the coolant channels being of a relatively larger cross sectional area, and allowing a relatively high coolant flow rate in a direction parallel to a main plane of the inlet bulkhead of the plate cooler, compared to a plurality of coolant fluid cross channels 501 nearer the centre of the heat exchanger.
Similarly, at a second end 502 of the "I" plate heat exchanger there is provided a second set of cross channels 503 providing coolant flow in a direction transverse to a main direction of gas flow, and parallel to a main plane of the second (outlet) bulkhead plate, the second set of channels having relatively greater flow capacity and relatively greater cross sectional area in a direction transverse to a direction of coolant flow along the channels, than other coolant channels extending across the cooler away from the bulkhead.
Referring to Figure 5B herein, there is illustrated a plot of coolant temperature (round points) and gas temperature (diamond points) against the length along the cooling plate assembly.
The inlet header end is at the left hand of the graph in Figure 5B and the outlet end is at the right hand side of the graph in Figure 5B.
The coolant temperature, shown by circular dots is relatively reduced immediately adjacent to the bulkhead, due to the presence of the near-inlet cooling channels extending in a direction transverse to the direction of gas flow along the cooling plates. Similarly, there is a corresponding slight reduction in coolant temperature immediately adjacent to the gas outlets and the second bulkhead.
The gas temperature, shown on the diamond shaped line in Figure 5B, which reduces gradually as the gas passes along the cooling plates, from the inlet header end to the outlet end.
The temperature of the coolant fluid near the inlet end is relatively reduced, whilst the temperature profile of the gas / fluid along the length of the assembly shows a gradual decline to an acceptable gas outlet temperature.
Referring to Figure 6 herein, there is illustrated schematically in perspective view, a second heat exchanger 600 according to a second specific embodiment. The second heat exchanger comprises a substantially "U" shaped canister type heat exchanger.
The "U" shaped heat exchanger 600 comprises a first section for cooling condensate gas, and a second section for cooling an "anode off" gas, being a gas which is given off an anode of a fuel cell, and which may be electrically charged.
The first and second heat exchange sections share a casing 601, and a liquid coolant supply which flows into the casing via a coolant inlet pipe or tube 602, and leaves the casing via a coolant outlet pipe or tube, 603. The first section comprises a gas inlet 604 and a gas outlet 605, which feed gas into and out of the first heat exchange section.
The second heat exchange section for cooling the anode gas comprises a a heat exchange plate assembly, said heat exchange plate assembly comprising a plurality of heat exchange plates stacked side by side and held rigid and spaced apart from each other by a bulkhead plate. The heat exchange plate assembly comprises a plurality of gas inlets 606 - 608, accessible extemally via the bulkhead; a plurality of gas outlets 609 - 611 accessible externally via the bulkhead; at least one fluid inlet connector 612, to allow anode off gas to enter the casing; and at lease one fluid outlet connector 613 to allow cooled anode off gas to exit the casing. There is also provided a condensate drain 614 to collect condensate from the cooling plates.
The anode off gas outlet 613 and condensate drain 614 each lead to a condensate tank for collecting condensate. The anode off gas inlet 612, the anode off gas outlet 613, and the condensate drain 614 may each comprise standard pipe connectors.
Referring to Figure 7 and 8 herein, there is illustrated schematically in view from one side, the cooling plate assembly of the substantially "U" shaped heat exchanger of Figure 6 herein. Figure 7 illustrates schematically, the cooling plate assembly, absent of its external casing.
Figure 8 illustrates schematically in close up view, a detail of the connection between the plurality of cooling plates and the bulkhead of the heat exchanger.
Referring to Figure 7 herein, shown in view from one side, a plurality of cooling plates 700 - 704 are arranged side by side and spaced apart from each other to allow coolant fluid to percolate between the cooling plates to cool the outer surfaces of the cooling plates. At a first end 705, bulkhead 706 joins the plurality of cooling plates together. The cooling plates may be inserted into a substantially "U" shaped canister, such that the cooling plates are suspended inside the canister, held at their first ends 707 by the bulkhead.
Each cooling plate comprises an upper plate and a lower plate connected together around their perimeters, and forming at a first end, a gas inlet and a gas outlet, so that the plurality of gas inlets and the plurality of gas outlets of the cooling plates are all presented on a same face of the heat exchanger.
Each cooling plate comprises a plurality of gas passages or conduits formed as a plurality of protrusions and indents or depressions, similarly as described herein before with reference to the first embodiment. However, in the "U" shaped cooling plates, the conduits extend in parallel from the first end to the second end 708, arc around in a semi circle at the second end, and return from the second end to the first end. Thus, gas enters on one side of the cooling plate, travels around a "U" shaped gas conduit, and exits at the first end.
In this embodiment, the gas outlet of one cooling plate is arranged to locate on a same side of the heat exchanger as a gas inlet of the adjacent cooling plate in the stack, with the plurality of gas inlets and outlets all on the same face. Hence each plate has a gas inlet region and a gas outlet region located side by side at the first side of the cooling plate.
Gas enters the plurality of cooling plates at the respective inlet regions, and exhausts from the plurality of cooling plates at the respective outlet regions. In this case, since the channels are "U" shaped, the inlet header of one cooling plate lies adjacent an outlet header of another cooling plate.
Gas travelling along each gas conduit experiences an alternating side to side serpentine path, as it encounters alternate indents and protrusions along a length of the gas conduit.
Fluid coolant flows across a width of the cooling plates in a direction transverse to a length between the two ends of the cooling plates, via a plurality of fluid channels formed by the plurality of indents or depressions in the otherwise substantially cylindrical gas conduits.
Referring to figure 8 herein, immediately adjacent the bulkhead 706, there are provided a plurality of fluid coolant channels 800, which are relatively increased in cross sectional area in a direction transverse to a main direction of the gas flow. These regions allow coolant fluid to contact the inner surface 801 of the bulkhead 706, thereby allowing efficient cooling of the bulkhead.
The increased size coolant fluid channels 800 immediately adjacent to the bulkhead and the joint between the bulkhead and the cooling plates reduces the occurrence of overheating of the coolant fluid near to the joint, and allows the bulkhead and the joint between the bulkhead and each cooling plate to be continuously in contact with liquid coolant to dissipate heat.
Additionally, each gas conduit has a respective near inlet region 802 - 806 which has a relatively straight and smooth bore, compared to the main heat exchange region between the gas inlet and gas outlet of each conduit. This allows the gas to pass relatively freely through this initial section of the gas passage, with low induction of turbulence, which helps reduce the heat transfer between the gas and the metal walls of the cooling plate in the immediate near inlet region of cooling plate. The internal bore of the gas passage is relatively more undulating in the main heat exchange region than at the gas inlet and gas outlet ends, and the fluid flow in through these parts of the conduits is more turbulent.
Referring to Figure 9 herein, there is illustrated schematically in view from one side a third embodiment heat exchanger comprising a plurality of individual cooling plates 900-905.
Two separate arrangements are possible. In a first arrangement, similar to the "I" plate arrangement of Figures 1-5, the plates are located adjacently, but without the need for a bulkhead at either end. In this arrangement, all of the inlets are arranged at one end of the heat exchanger plate assembly and all of the outlets are arranged at the other (outlet) end.
In a second arrangement, where the cooling plates are "U" shaped cooling plates each cooling plate having a gas inlet and a gas outlet at the same end, with the gas inlet and gas outlet on opposite sides of the cooling plate, the gas outlet of a first cooling plate for example 900 is co-located with a gas inlet of a second adjacent cooling plate, for example 901. Similarly, the gas outlet of the second cooling plate 901 is co-located adjacent to a gas inlet of the third cooling plate 902 and so on, down the stack of cooling plates.
In either case, adjacent to the inlet region of each cooling plate is provided an indent, across the width of the cooling plate, so that when the cooling plates are stacked one on top of the other as shown in Figure 9, a plurality of coolant channels are formed 906-912 to allow coolant to flow across a width of the cooling plate and in a direction transverse to a main gas flow direction. Since the coolant cross channels 906-912 are provided immediately adjacent to the inlet header of each cooling plate, this allows coolant to flow across the width of the cooling plates in a direction perpendicular to the main direction of gas flow, so that the inlets of the cooling plates are cooled relatively more efficiently.
Similarly, as shown in the first and second embodiments herein, each cooling plate has a plurality of gas conduits extending along the cooling plate, where each gas conduit forms a serpentine gas path, there being enough space for coolant to flow between the plates, so that heat exchange can occur between the fluid or gas flowing through the conduits of the cooling plates, and the coolant which flows within the casing and externally around the outside of the cooling plates.
In the embodiments of figure 9 herein, the cooling plates are held together at their ends in contact with each other and without the need for a connecting bulkhead between the individual plates. This means that the gas inlets and outlets of the cooling plates can be relatively larger in cross sectional area than if a connecting bulkhead plate were used. An outer connecting plate may surround the cooling plates to hold them together in contact with each other within the outer casing. The ends of the cooling plates may be brazed or dip soldered together at their inlet and outlet ends.
The increased fluid flow across the gas inlet ends of the cooling plates helps to reduce the temperature of the inlet ends of the cooling plates, and reduce any stresses where the cooling plates contact each other and / or the surrounding plate at the inlet end.
Referring to Figures 10 and 11 herein, there is shown schematically a cooling plate assembly of a "I" type heat exchanger unit according to a fourth specific embodiment.
The heat exchanger comprises one or a plurality of such cooling plates, held in an outer casing, by first and second bulkhead plates, one at each end of the heat exchange plate. The external casing comprises one or more coolant inlets for allowing a cooling fluid to enter the casing and permeate around the cooling plate assembly and one or more coolant outlets which allow the coolant fluid to exit the casing, one or more gas inlet connectors to allow the gas to enter the cooling plate assembly and one or more gas outlet connectors to allow the gas to exhaust from the heat exchange assembly. In external view, the external casing may be similar to that shown in Figure 1 herein.
Referring to Figure 10 herein, there is illustrated schematically in view from above, one cooling plate of an "I" type plate heat exchanger.
Each cooling plate 1000 comprises a pair of flat metal plates joined together at their sides 1001, 1002, and forming a plurality of fluid conduits or passages 1003 there between (herein also referred to as gas conduits), each fluid conduit extending between first and second ends 1004, 1005 respectively of the cooling plate.
The upper plate comprises a plurality of generally semi-cylindrical protrusions 1006 extending along the lengths of the plate, which form gas passages or conduits. Along each gas conduit, the plurality of protrusions 1006 are alternated with a plurality of scallop shaped indents 1007. A main axial direction of the substantially semi-cylindrical protrusions is arranged along a direction between the first and second ends.
Similarly, each lower plate of each cooling plate comprises a plurality of substantially semi-cylindrical protrusions 1006 and a plurality of scallop shaped indents 1007 arranged in rows and columns between a first end and a second end of the lower plate. The plurality of generally semi-cylindrical indents and protrusions extending along the lengths of the lower plate form the opposite walls of the gas passages or conduits
In each cooling plate, for each gas channel, the plurality of protrusions in the upper plate line up opposite the plurality of indents in the lower plate, and the plurality of protrusions on the lower plate line up opposite the corresponding respective plurality of indents in the upper plate with the result that the protrusions and indents along each gas conduit creates a serpentine tubular gas conduit in which the gas flow follows a serpentine path along the conduit inside the cooling plate, between the upper and lower plates, which causes continuous turbulence and mixing of the gas within the gas conduit, allowing the gas to contact the interior surfaces of the gas conduits and thereby achieves efficient heat transfer between the gas and the metal of the cooling plate. The edges of the plates are sealed together in a gas tight manner.
On the upper plate, the plurality of indents or depressions are arranged in rows and columns, the arrangement being that for each gas conduit between the first and second ends of the upper plate, each conduit is periodically interrupted by a plurality of said indents / depressions.
Similarly, on the lower plate, there are a corresponding plurality of lines of protrusions and depressions or indents, arranged in rows and columns over the lower plate, the arrangement being that for each conduit extending between the first and second ends of the lower plate, the internal bore of that conduit or passage is periodically interspersed with a plurality of said indents / depressions, creating a substantially serpentine gas flow path.
As the upper and lower plates are fixed together, the depressions of the upper plate line up with the corresponding respective protrusions of the lower plate, and vice versa the depressions of the lower plate line up adjacent to the corresponding respective protrusions on the upper plate, the result being a plurality of tubular fluid or gas conduits / passages channels extending between the first and second ends of the cooling plate, each of which have a serpentine path. The gas passages cross a central plane of the cooling plate, as the gas flow undulates passing between the semi-circular protrusions of the upper and lower plates.
Providing the serpentine fluid conduits causes the fluid flow to undulate, and generates turbulence in the fluid flow and thereby enhances the heat transfer between the upper and lower plates of each cooling plate and the gas flow.
In the cooling plate of Figure 10 herein, the depressions or indents on the external surface of the cooling plate line up in a direction transverse to the main gas flow direction, allowing coolant to penetrate between the external surfaces of the adjacent cooling plates when the cooling plates are stacked together, and allowing coolant flow over the outside surfaces of the cooling plates.
There is also shown a substantially flat surface 1012 on the upper plate of the cooling plate at the first end, and a second substantially smooth flat planar surface 1013 at the second end. Similarly, the lower plate at the first end has a flat smooth surface extending across the width of the plate, and at the second end the lower plate has a further flat smooth surface extending across a width of the plate. These surfaces are provided to engage with a plurality of corresponding slots in the bulkheads 1100, 1101, so that during manufacture, the ends of the cooling plates can be inserted into the slots, and brazed or soldered to the bulkhead.
At the ends of the cooling plate, the individual gas conduits have a near-bulkhead region in which the internal bore of the gas passage is relatively smooth and uninterrupted by protrusions or depressions. The length of the relatively smooth bore may extend in the range 5% to 10% of the length of the whole cooling plate, and in this example, approximately 7% of the length of the cooling plate. The individual near-bulkhead regions of the gas conduits are slightly divergent in the direction of the inlets 1102 into the cooling plate, so as to provide a smooth gas passage, and to reduce the amount of heat transfer between the gas and the insides of the gas passage at the gas conduit immediate inlet region, compared to the central region of the cooling plates, beyond the inlet region, where the gas passage follows a convoluted path.
Additionally, these extended smooth regions 1105 of the gas conduit shape the outside of the cooling plates in the near bulkhead regions, to provide relatively larger width coolant channels extending across the width of the cooling plates at each end of the cooling plate. This allows a relatively higher flow rate of coolant across the ends of the cooling plates at the near inlet and near outlet ends of the cooling plates, than in the more central heat exchange area between the ends, and allows enhanced access of coolant to the joints between the cooling plates and the bulkheads. This helps to provide more efficient cooling at the interface between the cooling plates and the bulkhead at the inlet header.
The enhanced length smooth bore portions at the end of the cooling plates provide a relatively straighter bore to the gas passages at the inlet end and the outlet end compared to the more undulating bore of the gas passages in the central heat exchange region. This results in slightly reduced heat transfer from gas to cooling plate metal in the near inlet region, thereby assisting in reducing the temperature at the inlet end of the cooling plate and at the joint between the cooling plate and the bulkhead. Similarly, the extended length smooth bore portions at the other end provide a region of slightly reduced heat exchange from gas to cooling plate, and a slightly increased heat exchange from cooling plate to coolant, at the gas outlet end. In this embodiment, the cooling plates and the cooling plate assembly are symmetrical, and the assembly can be reversed so that the outlet can be used as the inlet end and vice versa.
Referring to Figure 11 herein, there is illustrated schematically in view from one side a cooling plate assembly of the heat exchanger of Figure 1 herein.
The first ends of the plurality of cooling plates are connected to the first bulkhead 1100, for example by brazing or soldering. Similarly, the plurality of second ends of the plurality of cooling plates are connected to the second bulkhead 1101 by brazing or soldering.
The plurality of cooling plates are held by the first and second bulkheads, so that the plates are stacked on top of each other, with a gap there between to allow passage of coolant fluid between adjacent cooling plates.
The entire assembly shown in Figures 10 and 11 herein is encased in a rectangular box section casing, having a coolant inlet and a coolant outlet. One or more gas inlets and gas outlets are provided to the casing, and there is an inlet header region between the main gas inlet connector on the casing between the main gas inlet connector 104, and the inlet ends of the cooling plate assembly.
Each cooling plate has at least one gas inlet and at least one gas outlet, and in the embodiment shown, there are a plurality of gas inlets 1102 to the plurality of cooling plates, protruding through the first bulkhead, and at the second end, there are a plurality of gas outlets 1103 of the individual cooling plates protruding from the second bulkhead.

Claims

A cooling plate assembly for cooling a fluid flow using a liquid coolant, said assembly comprising:
a plurality of cooling plates (200), each cooling plate comprising a plurality of fluid conduits (203) through which fluid can flow; and

said cooling plate assembly comprising a fluid inlet region, a fluid outlet region and a heat exchange region;

characterised by,

a set of first coolant channels (407 - 412; 800) arranged between said plurality of cooling plates and positioned immediately adjacent to said fluid inlet region, each of said first coolant channels extending in a direction transverse to a main flow direction of said plurality of fluid conduits, said fluid conduits being sealed from said set of first coolant channels, and at least one of said first coolant channels allowing a relatively higher coolant flow rate in a direction transverse to a main length of said fluid conduits than occurs in a region further away from said inlet region.
The cooling plate assembly as claimed in claim 1, wherein each said first coolant channel (407 - 412; 800) is formed between a lower section of one said cooling plate, and an upper section of another said cooling plate.
The cooling plate assembly as claimed in claim 1, wherein each said coolant channel is formed between a lower section of one cooling plate and an upper section of another said cooling plate and the cooling plates are joined to form an interface between said fluid conduits and a gas header.
The cooling plate assembly as claimed in any one of the preceding claims, comprising a second set of coolant channels (501) positioned further away from said inlet region than said first coolant channels, wherein a flow path of a said first coolant channel enables greater coolant flow rate in a direction transverse to the main fluid flow direction, than occurs in said second set of coolant channels (501).
The cooling plate assembly as claimed in any one of the preceding claims, comprising a second set of coolant channels (501) positioned further away from said inlet region, than said set of first coolant channels (407 - 412; 800), wherein a cross sectional area of a said first coolant channel in a direction transverse to a main fluid flow direction in said fluid conduits, is in the range 1.2 to 5 times a cross sectional area of a said second coolant channel in the same direction.
The cooling plate assembly as claimed any one of the preceding claims, comprising:
a first bulkhead plate (300) at a first end of said assembly;

a second bulkhead plate (301) at a second end of said assembly; and

said plurality of cooling plates (200) extending between said first and second bulkhead plates;

wherein there are provided a set of said first coolant channels (407 - 412; 800) immediately adjacent to said first bulkhead, and a further set of said first coolant channels positioned immediately adjacent to said second bulkhead.
The cooling plate assembly as claimed in any one of claims 1 to 5, comprising a single bulkhead (706) connecting together a plurality of substantially "U" shaped said cooling plates.
The cooling plate assembly as claimed in claim 7, wherein there are provided a set of said first coolant channels immediately adjacent a set of fluid inlets of said substantially "U" shaped cooling plates.
The cooling plate assembly as claimed in claim 7, wherein there are provided a set of said first coolant channels (800) immediately adjacent a set of fluid inlets of said substantially "U" shaped cooling plates and immediately adjacent a set of fluid outlets of said plurality of substantially "U" shaped cooling plates.
A cooling plate assembly, as claimed in claim 1,wherein:
said fluid conduits are each provided with a relatively extended smooth internal surface (1105) immediately adjacent said fluid inlet region, for minimising turbulence of fluid flow in said fluid conduits adjacent to said fluid inlet region.
A heat exchanger comprising:
a cooling plate assembly as claimed in any one of the preceding claims; and

an outer canister (101; 601);

at least one coolant inlet (102; 602) for allowing coolant to flow into said canister; and

at least one coolant outlet (103; 603) for allowing coolant to flow out of said canister.
A heat exchanger, comprising a cooling plate assembly as claimed in any one of claims 1 to 10, wherein the fluid conduit is a gas conduit with a smoother gas side surface at and near the bulkhead, which reduces the heat transfer co-efficient and thus reduces the risk of localised boiling at or near the bulkhead.
A cooling plate assembly as claimed in any one of claims 1 to 10, having at least one cooling plate (200; 700 - 704) comprising:
an upper plate;

a lower plate;

said upper plate and lower plate being connected together along first and second edges (201; 202) in a fluid tight manner;

said upper and lower plates forming a plurality of fluid conduits (203) extending along a length of said cooling plate, through which a first fluid can flow;

said upper and lower plates comprising a plurality of protrusions (206) and depressions (207) for allowing a fluid coolant to pass over an outer surface of said cooling plate in a direction transverse to a first fluid flow direction in said fluid conduits;

characterised by

said fluid conduits (203) being sealed from an outer surface of said cooling plate; and

said protrusions (206) and depressions (207) are arranged such that a region immediately adjacent one end (204; 205) of said cooling plate, on at least one of said upper or lower plates, provides for allowing a relatively higher coolant flow rate across a width of said cooling plate in a direction transverse to a main length of said fluid conduits, in a region immediately adjacent said end of said cooling plate than occurs in a region further away from said end.
The cooling plate assembly as claimed in claim 13, wherein:
said fluid conduits extend between a first end (204) and a second end (205) of said at least one cooling plate; and

at least one end of said cooling plate is provided with a region immediately adjacent to said end, which is clear of said protrusions (206) on at least one of said upper or lower plates, for allowing a relatively higher coolant flow rate across the width of said cooling plate immediately adjacent to said end.
The cooling plate assembly as claimed in claim 13 or 14, wherein said at least one cooling plate comprises a substantially "U" shaped plate, having a plurality of fluid inlets and a plurality of fluid outlets at a same said end.
The cooling plate assembly as claimed in claim 13 or 14, wherein said at least one cooling plate comprises:
a plurality of fluid inlets at a first end (204) of said cooling plate; and

a plurality of fluid outlets at a second end (205) of said cooling plate.