WO2018157192A1

WO2018157192A1 - Heat exchanger

Info

Publication number: WO2018157192A1
Application number: PCT/AU2018/000029
Authority: WO
Inventors: John Leslie Graham Mcnab
Original assignee: Ficom Pty Ltd
Priority date: 2017-03-03
Filing date: 2018-03-02
Publication date: 2018-09-07

Abstract

A heat exchanger plate including a planar sheet extending longitudinally and laterally to define a first surface and a second surface, and having two lateral edges and two longitudinal edges, wherein a region along each longitudinal edge is bent to form a longitudinal flange including a flange surface which is offset a distance from and parallel to the first surface of the planar sheet, and an array of spaced apart projections, wherein the spaced apart projections extend from the first surface of the sheet in the same direction and distance as the flange surfaces.

Description

HEAT EXCHANGER

TECHNICAL FIELD

[0001] The present invention relates to a cross-flow heat exchanger. In a particular form the present invention relates to an improved heat exchanger plate for a cross-flow heat exchanger.

BACKGROUND

[0002] Cross-flow plate-type heat exchangers use a number of stacked heat exchanger plates, aligned parallel to each other and separated by a defined spacing. When transferring heat from one airstream to another two perpendicular airstreams flow through channels formed between the plates. Each airstream flows into alternating channels, arranged perpendicular to one another, so while the airstreams pass near each other they never mix. Heat energy from the hot stream flowing through one side of the exchanger is transferred to the cold stream flowing through the other side of the exchanger via the plates.

[0003] Such heat exchangers are particularly useful in air conditioning applications, such as when it is desired to transfer heat energy to or from a waste heat air stream to or from a fresh air stream. Another application is in indirect evaporative air conditioning, where one air stream is cooled by the addition of water and heat is then transferred into this stream by another air stream which enters the conditioned space. The use of the heat exchanger results in dry cool air being introduced to the conditioned space rather than moist cool air. This aids in improving the comfort level in the conditioned space, and can also result in the delivery of colder air.

[0004] In some heat exchangers, the plates are manufactured from plastic, and feature an array of small projections (often referred to as turbulating projections) which provide two functions: separating the plates to provide a space for the air flow through the heat exchanger, and for providing turbulence to the air flow, increasing heat transfer efficiency.

[0005] These plastic heat exchanger plates have historically been formed using a vacuum forming method which resulted in sharpness and thinning of the turbulating projections, leading to high failure rates and an unacceptably short life. The tips would fail causing a gradual leakage of air from the high pressure side to the low pressure side of the plate. These failed tips were difficult to detect and the leakage between hot and cold streams would reduce the overall performance of the heat exchanger.

[0006] Additionally, the method used to seal two adjoining plates at their edges involved forcing the edges of two plates together and adhering the plates with a resilient paint to form a joint. This method is costly, the paint is difficult to apply evenly, and the joints often fail prematurely as a result of residual loads from the plates trying to return to a straight condition. The joining method also affected the rigidity of the edges of the plates leading to uneven plate spacing and poor uniformity of airflow resulting in reduced efficiency of heat transfer for a given heat exchange surface area.

[0007] The number of plates per unit height affects the heat transfer surface area and pressure drop. It is therefore advantageous to be able to adjust the height of the turbulating projections to suit different applications. Previous manufacture methods made it difficult to reliably or affordably achieve this, as new tooling is required for different projection heights, and by varying projection heights, there are variances in the residual loads on the plate edges during the joint forming process.

[0008] It is against this background and the problems and difficulties associated therewith that the present invention has been developed.

[0009] Certain objects and advantages of the present invention will become apparent from the following description, taken in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed.

SUMMARY

[0010] According to a first aspect of the present invention, there is provided a heat exchanger plate including a planar sheet extending longitudinally and laterally to define a first surface and a second surface, and having two lateral edges and two longitudinal edges, wherein a region along each longitudinal edge is bent to form a longitudinal flange including a flange surface which is offset a distance from and parallel to the first surface of the planar sheet, and an array of spaced apart projections, wherein the spaced apart projections extend from the first surface of the sheet in the same direction and distance as the flange surfaces.

[001 1] In one form, the two lateral edges and two longitudinal edges are of equal length.

[0012] In one form, the projections are arranged such that when a heat exchanger plate is rotated 90 degrees relative to another heat exchanger plate, the projections of the two plates are nonconcentric.

[0013] In one form, the projections are arranged along spaced apart diagonal rows, wherein each diagonal row is separated by a lateral distance 'a^", and adjacent projections along each diagonal row are separated by a lateral distance 'b\ [0014] In one form, the longitudinal distance 'a^" is equal to double the longitudinal distance 'b\ [0015] In one form, the plate further includes bevelled corners. [0016] In one form, the plate is manufactured from a thermoplastic.

[0017] According to a second aspect of the present invention, there is provided a heat exchanger plate pack including a plurality of said heat exchanger plates, wherein the plates are stacked such that there is a bottom plate, and a plurality of plates stacked above it, wherein each successive plate is rotated 90 degrees relative to the preceding plate, such that the longitudinal edge of each successive plate is aligned with the lateral edge of the plate preceding it, such that the flange surfaces and projections of each preceding plate support the second surface of the plate succeeding it, wherein a channel is formed between preceding and succeeding plates, and wherein each channel is oriented at 90 degrees to its adjacent channel.

[0018] According to a third aspect of the present invention, there is provided a method of forming a heat exchanger plate from a planar sheet extending longitudinally and laterally to define a first surface and a second surface, and having two lateral edges and two longitudinal edges, the method including the steps of bending a region along each longitudinal edge is bent to form a longitudinal flange with a flange surface which is offset a distance from and parallel to the first surface of the planar sheet, and forming an array of spaced apart projections, wherein the spaced apart projections extend from the first surface of the sheet in the same direction and distance as the flange surfaces.

[0019] According to a fourth aspect of the present invention, there is provided a method of

manufacturing a heat exchanger plate pack comprising a plurality of said heat exchanger plates, wherein the plurality of heat exchanger plates includes at least a first and second heat exchanger plate, the method includes placing the second heat exchanger plate on top of the first heat exchanger plate such that the lateral edges of the second heat exchanger plate are aligned with the longitudinal edges of the first heat exchanger plate, and the flange surfaces and projections of the first heat exchanger plate supporting the second surface of the second heat exchanger plate, and welding the flange surfaces of the first plate to the second surface of the second heat exchanger plate.

BRIEF DESCRIPTION OF DRAWINGS

[0020] Embodiments of the present invention will be discussed with reference to the accompanying drawings wherein: [0021] Figure 1 is a plan view of an improved heat exchanger plate;

[0022] Figure 2A is a top perspective view of a the heat exchanger plate of Figure 1 ;

[0023] Figure 2B is a bottom perspective view of a portion of the heat exchanger plate of Figure 1 ;

[0024] Figure 3A is a top perspective view of a plurality of stacked heat exchanger plates as shown in Figure 1;

[0025] Figure 3B is an enlarged view of Figure 3A in the region of circle A;

[0026] Figure 4A is a bottom perspective view of a plurality of stacked heat exchanger plates as shown in Figure 1 ;

[0027] Figure 4B is an enlarged view of Figure 4A in the region of circle C;

[0028] Figure 5 is a side exploded view of three stacked heat exchanger plates as shown in Figure 1;

[0029] Figure 6 is a top perspective exploded view of three stacked heat exchanger plates as shown in Figure 1, detailing the relationship between adjacent plates;

[0030] Figure 7 is a schematic view of a portion of two stacked heat exchanger plates, detailing the relationship between their corresponding turbulating projections;

[0031] Figure 8 is a perspective view of an assembled cross flow plate type heat exchanger installed in a schematic evaporative air conditioning unit, and including a plurality of the heat exchanger plates as shown in Figure 1, according to an embodiment;

[0032] Figure 9 is a schematic view of a heat exchanger plate production line, according to an embodiment; and

[0033] Figures 10A to 10E are schematics of the forming process of the heat exchanger plate of Figure 1, according to an embodiment.

DESCRIPTION OF EMBODIMENTS

[0034] Referring to Figures 1 to 2B, there is shown a heat exchanger plate 1 according to an

embodiment. The heat exchanger plate 1 comprises a thin planar sheet 2 extending longitudinally and laterally to define a first surface 3 and a second surface 4. The plate 1 has two lateral edges (first and second lateral edges 5, 6) and two longitudinal edges (first and second longitudinal edges 7, 8) wherein a region along each longitudinal edge 7, 8 is bent to form a longitudinal flange (first and second longitudinal flanges 9, 1 1) with a flange surface (first and second flange surfaces 10, 12) which is offset a distance from and parallel to the first surface 3 of the sheet 2. The plate 1 also comprises bevels 13 at each corner.

[0035] The plate 1 features an array of spaced apart projections 14, whose tips 15 extend from the first surface 3 of the sheet 2 in the same direction and distance as the flange surfaces 10, 12. The projections 14 are formed such that a complimentary recess 16 is formed in the second surface 4 of the plate 1.

[0036] As best shown in Figure 1, the projections 14 are arranged along spaced apart diagonal rows, where the lateral distance 'a^" between adjacent diagonal rows is equal to double the lateral distance 'b' between adjacent projections along each row. This arrangement of the projections 14 is such that when a heat exchanger plate is rotated 90 degrees relative to another heat exchanger plate 1, the projections 14 of the two plates are nonconcentric (as best shown in Figure 7 and discussed in more detail below).

[0037] Referring now to Figure 3 A and 4A, where there are shown top and bottom perspective views of a plate pack 100 comprising a plurality of heat exchanger plates 1 stacked on top of each other. It can be seen how each plate is rotated 90 degrees relative to the plate(s) adjacent to it, such that the longitudinal edge of one plate is aligned with the lateral edge of the plate(s) adjacent to it. As can be seen more clearly in Figures 3B and 4B, the plate at the bottom of the pack supports the second plate that rests on top of it, with the second surface of the second plate supported by the two flange surfaces to define first and second joins, the second surface also supported upon by the tips of the projections of the bottom plate.

[0038] Figures 5 and 6 provide further perspectives detailing the relationship between adjacent heat exchanger plates, with side and top perspective exploded views of three stacked heat exchanger plates respectively.

[0039] Referring now to Figure 7, where there is shown a schematic top view of two stacked heat exchanger plates 1, where the location of the bottom plate^'s projections 21 1 is highlighted in order to demonstrate how when the top plate is rotated 90 degrees relative to the bottom plate, the projections of the two plates 21 1, 221 are nonconcentric. This is important, because if the projections 21 1, 221 of the two plates were concentric, the projection 21 1 tips of the bottom plate would undesirably nest in the corresponding recesses formed in the projections 221 of the top plate, and the space between the two plates would collapse. [0040] Referring again to Figures 3B and 4B, where it can be seen that a first channel 170 is defined between the first (top) surface of the first plate 1 10, the second (bottom) surface of the second plate 120 and the longitudinal flanges 1 1 1 of the first plate 1 10. It can then be seen that the third plate 130 rests upon the second plate 120 such that a second channel 180 is defined between the first (top) surface of the second plate 120, the second (bottom) surface of the third plate 130 and the longitudinal flanges 121 of the second plate 120. This pattern repeats itself, with a channel being formed between each adjacent plate, and by virtue of the 90 degree rotation of each plate relative to its adjacent plate(s), each channel is oriented at 90 degrees to its adjacent channel, facilitating cross-flow of air streams between adjacent plates, such that there is a first set of channels oriented in one direction, and a second set of channels oriented at 90 degrees to the first set of channels.

[0041] Referring now to Figure 8, where there is shown a perspective view of an assembled cross flow plate type heat exchanger 1000 including a plurality of the heat exchanger plates arranged in a pack 1300. The heat exchanger includes a first blower 1 100 which blows a first hot airstream 1 150 through the first set of channels, and a second blower 1200 which blows a second cold airstream 1250 through the second set of channels. Whereby heat energy from the hot airstream is transferred to the cold airstream via the heat exchanger plates.

[0042] Referring now to Figure 9, where there is shown a schematic of a production line 300 for the heat exchanger plate, according to an embodiment. The plate may be manufactured from a thermoplastic material, which in this instance is drawn from a roll of thermoplastic film 305, which is driven through a series of modules before it becomes a finished plate, where the width of the film 305 is equal to the eventual width of the plate 1, avoiding the need to subsequently trim the plate 1 to the correct width. The film 305 is driven using edge rollers 310 which reduce jams and fouling compared to other drive systems.

[0043] The first module is the thermoforming module 400 which forms the projections 14 in the film 305. The second module is the cutting module 500, which cuts the film 305 to the correct length. The third module is the bending module 600, which forms the longitudinal flanges 10, 12 to complete the plate 1. The final module is the plate stacking and welding module 700 which forms the complete heat exchanger plate pack 100. In a preferred form of the invention a controller (not shown) coordinates the functions of modules 400, 500, 600 and 700. In a non-preferred form these functions are coordinated manually by an operator.

[0044] Referring to Figures 10A to IOC where a schematic of the thermoforming module 400 is shown. The thermoforming module 400 features a top female mould 401 which is fixed in place and comprises an array of holes 402 arranged to match the arrangement of the projections 14 of the plate 1. The holes 402 therefore forming the female part of the mould where the projections 14 are formed in the film 305. The female mould 401 is manufactured from aluminium to ensure maximal thermal conductivity and even temperature distribution, however any suitable material could be used. The female mould 401 is stiffened and supported in order to ensure that deflection of the mould 401 is minimised under the pressure loads exerted upon it during the thermoforming process. The support arrangement allows the mould 401 to expand without deflections in the plane of the plate.

[0045] The thermoforming module 400 further comprises an array of projection forming pins 403 which have a diameter of approximately 2mm with a 5mm diameter flat head at their base to allow them to be anchored to a bottom pin retaining plate 405. The forming pins 403 are manufactured from steel and have a tip formed to produce the required radius in the tip of the projection 15.

[0046] The bottom pin retaining plate 405 is located below the female mould 401 with the purpose of anchoring and controlling the vertical movement of the forming pins 403. The retaining plate 405 is made from stainless steel to minimise thermal deformation and to maximise rigidity so that the forming pins 403 move up to the female mould 401 uniformly. Uniform movement of the forming pins 403 is critical to ensure that all of the projections 14 formed in the film 305 are of a uniform height.

[0047] The pin retaining plate 405 is vertically actuated by nine cams (not shown) which push on the pin retaining plate 405 at 9 points over the area of the plate to ensure that it moves uniformly. The cams are driven using a single motor (not shown) through precision drive chains (not shown) to control the movement and reduce backlash and hysteresis to acceptable levels when compared to gears. Alternative modes of precision actuation may also be possible, such as the use of linear actuators, or hydraulic cylinders.

[0048] Located directly above the pin retaining plate 405 is a pin retaining plate 406, which is fixed to the pin retaining plate 405 and has a complimentary hole 408 for each forming pin 403 arranged in an array to match the arrangement of the projections 14. The pin retaining plate 406 acts to anchor the forming pins 403 securely to the pin retaining plate 405, and to ensure that the forming pins 403 are held securely in their vertical axis.

[0049] Above the pin retaining plate 406 and below the female mould 401 is the film holding plate 407. The film holding plate 407 also has a hole 408 for each forming pin 403 arranged in an array to match the arrangement of the projections 14. The purpose of the film holding plate 407 is to support the film 305 as it is fed into the thermoforming module 400, and then to move up and put pressure on the film 305 to hold it in place prior to the forming pins 403 entering the female mould 401 to form the projections 14 in the film 305. After the thermoforming process, the film holding plate 407 moves back down to support the film as it exits the thermoforming module 400. [0050] The film holding plate 407 is attached to the pin retaining plate 406 and bottom pin retaining plates 405, 406 using springs 409. The springs 409 allow the film holding plate 407 to move up and down along with the pin retaining plate 405, while allowing the film holding plate 407 to absorb some load during the thermoforming process. By absorbing some of the load, crushing of the film 305 is prevented. The film holding plate 407 is manufactured from aluminium to ensure rapid and uniform temperature changes associated with the heating of the film 305 and plates for forming the projections 14, and rapid cooling of the film 305 and plates to complete the thermoforming process.

[0051] Prior to forming the projections 14, the female mould 401, film holding plate 407 and film 305 must be heated to the required temperature to soften the film 305. The thermoforming module 400 is contained in an insulated body and is heated using an electric air heater which includes ducting to direct air heated to approximately 105 degrees C to the female mould 401, the film holding plate 407, and the film 305. Once the required temperature is met, the cams turn, moving the forming pins 403 up through the film holding plate 407, engaging the film 305 and forming the projections 14 in the film 305 against the top female mould 401.

[0052] By virtue of the cam drive system, the height of the projections 14 are able to be quickly and accurately varied without any change in tooling. This is achieved by varying the amount that the cams are rotated, which varies the distance that forming pins 403 move into the female mould 401. This offers a distinct advantage over previous manufacture methods which required new tooling for different projection heights.

[0053] After forming, cold air is directed through separate ducting to rapidly cool the female mould 401, the film 305 and the film holding plate 407 to below 85 Degrees C. This forced quick setting of the plastic makes the projections permanent 14 and increases the production rate of the thermoforming module 400. The female mould 401 and film holding plate 407 remain closed together during this operation with the forming pins 403 still within the projections 14 and engaged with the top female mould 401.

[0054] After cooling, the cams lower the forming pins 403 so that they disengage from the female mould 401 and the film 305. When the springs 409 become unloaded, the film holding plate 407 then lowers away from the female mould 401. The female mould 401 may be fitted ejecting with pins (not shown) that lower through the female mould 401 to push the film 305 out of the female mould 401 in the event that the projections 14 become stuck in the holes 402 of the female mould 401. [0055] With the partially formed film 305 now resting on the film holding plate 407, edge rollers 310 then drive the film 305 out of the thermoforming module 400 and toward the cutting module 500. The thermoforming module 400 takes approximately 3 minutes to form the projections 14 in the film 305.

[0056] The cutting module 500 comprises a reciprocating circular cutting blade (not shown), however in alternate embodiments it could be a guillotine style blade. In use, the edge rollers 310 index the partially formed film 305 to a position in order to cut its trailing edge (simultaneously cutting the leading edge of the next plate to be formed). The plate length is set according to the allowance for bends such that once the plate is bent, when the plate length equals the plate width. After cutting, edge rollers 310 then drive the partially formed film 305 toward the bending module 600, while the unformed film 305 is indexed back into the thermoforming module 400, where the thermoforming cycle recommences.

[0057] Referring now to Figures 10D and 10E where a schematic of the bending module 600 is shown. The bending module 600 comprises a moveable double edged female mould 610 which features a leading edge bender 61 1, a trailing edge bender 612 and a central plate 613 and is designed to alternately form the leading and trailing edge longitudinal flanges in the film 305. The female mould 610 is configured to close over a fixed male mould 620 in order to form the longitudinal flanges 9, 10 of the heat exchanger plate 1. The bending module 600 also comprises cutting blades (not shown) which cut the bevelled corners 13 of the plate 1 at the same time that the longitudinal flanges 9, 10 are formed. The bending module 600 also comprises an electric air heater which heats the female mould 610and the film 305 during the bending process via ducting.

[0058] As the leading edge of the partially formed film 305 exits the cutting module 500, it is indexed to the correct position in the bending module 600 via the edge rollers 310. The female mould 610 is then closed on the leading edge of the film 305 such that the leading edge bender 61 1, the central plate 613 and the fixed male mould 620 work to form the two bends required to form the first longitudinal flange 9, and the two bevelled corner 13 cuts along the leading edge in one operation. While the operation takes place, heat is applied via the electric air heater in order to make the two bends forming the longitudinal flange 9 permanent. The female mould 610 is then raised and the partially formed film 305 is indexed until its trailing edge is at the correct position in the bending module 600, where the bending and cutting operation is repeated, this time using the trailing edge bender 612.

[0059] The offset distance of the flange surfaces 10, 12 to the first surface 3 of the plate 1 is able to be quickly and accurately varied by adjusting how far the female mould 610 is closed over the male mould 620. [0060] Indexing of the film 305 is achieved using the edge rollers 310 and sensors (not shown) which detect when the film 305 is in the correct position.

[0061] In alternative embodiments, the cutting and bending operations could be performed

simultaneously, whereby a single module could cut a first plate^'s trailing edge (simultaneously cutting the leading edge of a subsequent second plate), and at the same time, trailing longitudinal edge of the first plate and the leading longitudinal edge of the second plate could be bent and cut to form the

corresponding longitudinal flanges and bevelled corners.

[0062] The now fully formed heat exchanger plate 1 is then driven out of the bending module by edge rollers 310 toward a plate stacking and welding module 700. The plate stacking and welding module comprises a rotatable and height adjustable platform 710 and an edge welder. The edge welder comprising two opposing heated blades which are capable of being driven toward and apart from each other.

[0063] In use, a first heat exchanger plate is driven by edge rollers 310 on to the platform 710. The platform is then rotated 90 degrees and lowered by a height equal to the height of a single heat exchanger plate. A second heat exchanger plate is then placed on top of the first heat exchanger plate, such that the second heat exchanger plate is oriented 90 degrees relative to the first heat exchanger plate. The edge welder is then positioned with one blade above, and the other blade below the first joint, in order to perform a welding operation. The welding operation consisting of the two heated blades being driven toward each other to apply an even, gentle pressure along the joint in order to weld the two plate edges together. The two blades are then driven apart from each other, and the platform is rotated 180 degrees such that the second joint of the two plates is positioned adjacent the edge welder. The edge welder then repeats the welding operation along the second joint.

[0064] The heated blades of the edge welder are driven using precision pneumatic cylinders and limit switches and are stiffened to ensure an even pressure on the joint during welding.

[0065] The bevelled corners 13 cut at each of the corners of the plates 1 are required to allow the edge welding of each plate to the next.

[0066] The platform 710 is then rotated 90 degrees and again indexed down by a height equal to the height of a single heat exchanger plate, with the process then repeating until a complete plate pack is formed. Indexing of the platform 710 is achieved using linear actuators. [0067] It will be appreciated that the geometry of the plate design allows for a single plate geometry to be used to assemble individual plates at 90 degrees to each other and hence form the plate pack. This prevents the need for two different thermoforming modules for each plate geometry. The new method of manufacture delivers greater consistency and ease of adjustment in the spacing between adjacent plates, while also delivering improvements to the resiliency of the plate stack.

[0068] The joining of adjacent plates using the flange surfaces and the edge welding process instead of forcing plate edges together and applying resilient paint performs the following critical functions:

[0069] The flat flange surface of the bottom plate mates with the flat second surface of the top plate, which improves the reliability of the joint.

[0070] The two bends that form the longitudinal flanges stiffen the longitudinal edges of each plate, minimising deformation of the plate along the edge, improving the uniformity of the space between the adjacent plates, which improves airflow and therefore efficiency.

[0071] Using the bent longitudinal flanges reduces pressure on the joints as there are no residual loads acting against the joints.

[0072] Throughout the specification and the claims that follow, unless the context requires otherwise, the words "comprise" and "include" and variations such as "comprising" and "including" will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers.

[0073] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of suggestion that such prior art forms part of the common general knowledge.

[0074] It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that the invention is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention as set forth and defined by the following claims.

Claims

1. A heat exchanger plate including:

a planar sheet extending longitudinally and laterally to define a first surface and a second surface, and having two lateral edges and two longitudinal edges;

wherein a region along each longitudinal edge is bent to form a longitudinal flange including a flange surface which is offset a distance from and parallel to the first surface of the planar sheet; and an array of spaced apart projections, wherein the spaced apart projections extend from the first surface of the sheet in the same direction and distance as the flange surfaces.

2. The heat exchanger plate as claimed in claim 1, wherein the two lateral edges and two longitudinal edges are of equal length.

3. The heat exchanger plate as claimed in claim 1 or 2, wherein the projections are arranged such that when a heat exchanger plate is rotated 90 degrees relative to another heat exchanger plate, the projections of the two plates are nonconcentric.

4. The heat exchanger plate as claimed in any of the preceding claims, wherein the projections are arranged along spaced apart diagonal rows, wherein each diagonal row is separated by a lateral distance 'a^", and adjacent projections along each diagonal row are separated by a lateral distance 'b\

5. The heat exchanger plate as claimed in claim 4, wherein the longitudinal distance 'a^" is equal to double the longitudinal distance 'b\

6. The heat exchanger plate as claimed in any of the preceding claims, wherein the plate further includes bevelled corners.

7. The heat exchanger plate as claimed in any of the preceding claims, wherein the plate is manufactured from a thermoplastic.

8. A heat exchanger plate pack including a plurality of heat exchanger plates as claimed in any of the preceding claims, wherein the plates are stacked such that there is a bottom plate, and a plurality of plates stacked above it, wherein each successive plate is rotated 90 degrees relative to the preceding plate, such that the longitudinal edge of each successive plate is aligned with the lateral edge of the plate preceding it, such that the flange surfaces and projections of each preceding plate support the second surface of the plate succeeding it, wherein a channel is formed between preceding and succeeding plates, and wherein each channel is oriented at 90 degrees to its adjacent channel.

9. A method of forming a heat exchanger plate from a planar sheet extending longitudinally and laterally to define a first surface and a second surface, and having two lateral edges and two longitudinal edges, the method including the steps of bending a region along each longitudinal edge is bent to form a longitudinal flange with a flange surface which is offset a distance from and parallel to the first surface of the planar sheet, and forming an array of spaced apart projections, wherein the spaced apart projections extend from the first surface of the sheet in the same direction and distance as the flange surfaces.

10. A method of manufacturing a heat exchanger plate pack comprising a plurality of heat exchanger plates as claimed in any of claims 1 to 7, wherein the plurality of heat exchanger plates includes at least a first and second heat exchanger plate, the method includes: placing the second heat exchanger plate on top of the first heat exchanger plate such that the lateral edges of the second heat exchanger plate are aligned with the longitudinal edges of the first heat exchanger plate, and the flange surfaces and projections of the first heat exchanger plate supporting the second surface of the second heat exchanger plate; and

welding the flange surfaces of the first plate to the second surface of the second heat exchanger plate.