HEAT EXCHANGER AND METHOD OF OPERATING THE SAME

Abstract

An evaporative heat exchanger includes first and second stacked plates forming a first fluid flow path between a first end and a second end. The first stacked plate defines a plane. Third and fourth stacked plates define a second fluid flow path. A fluid flow plate is positioned between the first and second stacked plates, and has a plurality of flow channels extending substantially parallel to the plane between the first end and the second end. At least one of the first and second stacked plates defines slots that form a portion of the first fluid flow path so that fluid flowing along the first fluid flow path flows along the flow channels in the first direction, then flows along at least one of the slots, then flows into adjacent flow channels and then along the adjacent flow channels in a second direction parallel to the first direction.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. application Ser. No. 12/572,310, filed Oct. 2, 2009 which claims priority to U.S. Provisional Patent Application Ser. No. 61/102,458, filed Oct. 3, 2008, the entire contents of both of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to heat exchangers, and more particularly to evaporative heat exchangers having a number of stacked plates at least partially defining two separate and substantially adjacent fluid flow paths

SUMMARY OF THE INVENTION

Attempts to use stacked plate style heat exchangers in applications where one of the fluids experiences a change of phase from a liquid to a vapor have been problematic. In such applications the fluid that is evaporating exists, over at least a portion of its flow path through the heat exchanger, as a two-phase fluid having both vapor and liquid fractions. The vapor fraction tends to separate from the liquid fraction due to the substantial differences in densities between the phases, making it difficult to achieve a uniform distribution of the fluid over the multiple parallel passages. This maldistribution effect can be especially pronounced when the flow path through the heat exchanger is circuitous, requiring the fluid to make multiple changes in flow direction. When the distribution is not uniform, the performance of the heat exchanger tends to suffer. Separation of the phases of the evaporating fluid can result in liquid flooding of certain regions, with slugs of the liquid forced through the heat exchanger at a non-constant rate. For this reason, evaporative heat exchangers have often been of a construction wherein the evaporating fluid does not require redistribution along its flow path.

In certain evaporative heat exchanger applications, it may be especially beneficial to arrange the flow passages so that the hot fluid and the evaporating fluid pass through the heat exchanger in a counter-flow or in a concurrent flow orientation to one another. A counter-flow orientation may be desirable when the hot fluid is to be cooled to as low a temperature as possible, or when the evaporating fluid is to be superheated to as high a temperature as possible. A concurrent flow orientation may be desirable when the hot fluid and the evaporating fluid are to exit the heat exchanger at one common temperature. Examples of such applications include, but are not limited to, air-conditioning and refrigeration chillers, Rankine cycle evaporators, and water and/or fuel vaporizers for fuel processing and fuel cell applications. A disadvantage of using a tube and fin evaporator construction in such applications is the difficulties that it poses in arranging the hot and cold fluid flows in a circuiting arrangement other than cross-flow.

According to one embodiment of the invention, a stacked plate evaporative heat exchanger for the transfer of heat from a first fluid to a second fluid to vaporize the second fluid includes a plurality of separate parallel flow passages to direct the first fluid through the heat exchanger, and a plurality of parallel arranged fluid flow plates for the second fluid interleaved with the parallel flow passages for the first fluid. The fluid flow plates have a first and second set of flow channels extending from a first end of the fluid flow plate to a second end of the fluid flow plate to define a first flow pass for the second fluid. The fluid flow plates further have a third set of flow channels to define a second flow pass for the second fluid parallel to the first pass. A first collection manifold is located at the second end to receive at least a portion of the second fluid flow from the first pass and transfer it to the second pass. A second collection manifold is located between the first and second ends and intersects the second set of flow channels and at least some of the third set of flow channels, but not the first set of flow channels, to receive at least a portion of the second fluid from the first pass and transfer it to the second pass.

In some embodiments, the fluid flow plate is constructed by corrugating a thin sheet of material. The second collection manifold may be defined by slots passing through the corrugations of the fluid flow plate.

In some embodiments, the plurality of separate parallel flow passages are arranged to direct the first fluid through the heat exchanger in a direction approximately perpendicular to the first and second flow passes for the second fluid. In some embodiments the plurality of separate parallel flow passages are arranged to direct the first fluid in two or more sequential passes through the heat exchanger.

In some embodiments, the pressure resistance and heat transfer performance of the heat exchanger may be improved by having a uniformly narrow channel width for the flow channels of the fluid flow plates. In some embodiments the second collection manifold can consist of one or more slots extending through the fluid flow plate. In some embodiments the one or more slots can each have a slot width that is approximately equal to the channel width.

In some embodiments, the fluid flow plates include a fourth set of flow channels to additionally define the second flow pass, and a fifth set of flow channels to define a third pass downstream of the first and second passes A third collection manifold is located at the first end of the fluid flow plate to receive at least a portion of the second fluid from the second pass and transfer it to the third pass. A fourth collection manifold is located between the first and second ends and intersects the fourth set of flow channels and at least some of the fifth set of flow channels, but not the third set of flow channels, to receive at least a portion of the second fluid from the second pass and transfer it to the third pass. In some such embodiments the fluid flow plates include additional flow passes downstream of the third pass.

In some embodiments, the plurality of separate parallel flow passages are at least partially defined by a plurality of stamped plates. Each of the stamped plates can include a recessed area to receive one of the fluid flow plates.

In some embodiments, the present invention provides an evaporative heat exchanger operable to at least partially vaporize fluid. The heat exchanger can include a number of parallel flow passages extending through the heat exchanger, together the flow passages define a first fluid flow path, and a number of substantially parallel stacked plates interleaved with the parallel flow passages. Each plate can have a first end and a second end spaced apart from the first end and at least partially define a first set of flow channels extending from the first end to the second end and a second set of flow channels extending from the first end to the second end parallel to the first set of flow channels. The first and second sets of flow channels together can comprise a first flow pass of a second fluid flow path. Each plate can also include a third set of flow channels extending from the first end to the second end and comprising a second flow pass of the second fluid flow path substantially parallel to the first flow pass of the second fluid flow path, a first collection manifold adjacent to the second end and connecting the first and second passes, and a second collection manifold between the first end and the second end, the second collection manifold intersecting the second set of flow channels and at least some of the third set of flow channels. The can plate separate the first set of flow channels from the second collection manifold.

In some embodiments, the present invention provides an evaporative heat exchanger that is operable to at least partially vaporize fluid. The heat exchanger includes first and second stacked plates that define a first fluid flow path between the first and second stacked plates. The first and second stacked plates each have a first end and a second end, and the first stacked plate defines a plane. Third and fourth stacked plates define a second fluid flow path between the third and fourth stacked plates. The third stacked plate is positioned adjacent the second stacked plate. A fluid flow plate is positioned between the first and second stacked plates. The fluid flow plate has flow channels extending in a first direction between the first end and the second end. The first direction is substantially parallel to the plane. At least one of the first and second stacked plates and the fluid flow plate includes slots that form a portion of the first fluid flow path so that fluid flowing along the first fluid flow path flows along at least one of the flow channels in the first direction and then flows in a second direction into at least one of the slots. The second direction is non-parallel to the plane. The fluid then flows in a third direction toward an adjacent one of the flow channels. The third direction is substantially parallel to the plane. The fluid then flows in a fourth direction into the adjacent one of the flow channels. The fourth direction is substantially non-parallel to the plane. Finally, the fluid flows in a fifth direction along the adjacent one of the flow channels. The fifth direction is substantially parallel to the plane.

In some embodiments, the present invention provides an evaporative heat exchanger that is operable to at least partially vaporize fluid. The heat exchanger includes first and second stacked plates that define a first fluid flow path between the first and second stacked plates. The first and second stacked plates each have a first end and a second end, and the first stacked plate defines a plane. Third and fourth stacked plates define a second fluid flow path between the third and fourth stacked plates. The third stacked plate is positioned adjacent the second stacked plate. A fluid flow plate is positioned between the first and second stacked plates. The fluid flow plate has flow channels that extend in a first direction between the first end and the second end. The first direction is substantially parallel to the plane. At least one of the first and second stacked plates includes slots that form a portion of the first fluid flow path so that fluid flowing along the first fluid flow path flows along at least one of the flow channels in the first direction, then flows along at least one of the slots, then flows into an adjacent one of the flow channels and then along the adjacent flow channel in a second direction, substantially parallel to the first direction.

Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a heat exchanger according to some embodiments of the present invention.

FIG. 2 is a partially exploded isometric view of the heat exchanger of FIG. 1.

FIG. 3 is an isometric view of certain portions of the heat exchanger of FIGS. 1 and 2.

FIG. 4 is similar to FIG. 3 but with certain details removed to more clearly show fluid flow paths.

FIGS. 5a-c are diagrammatic illustrations of possible fluid flow paths through a heat exchanger according to embodiments of the present invention.

FIG. 6 is an isometric view of a heat exchanger according to another embodiment of the present invention.

FIG. 7 is an isometric view of certain portions of the heat exchanger of FIG. 6.

FIG. 8 is an isometric view of a heat exchanger according to another embodiment of the present invention.

FIG. 9 is an isometric view of certain portions of the heat exchanger of FIG. 8.

FIG. 10 is an exploded view of FIG. 9.

FIG. 11 is a cross-sectional view taken along line 11-11 of FIG. 8.

FIG. 12 is a close-up view of a portion of FIG. 11.

FIGS. 13-16 illustrate alternative embodiments of stacked plate assemblies of heat exchangers according to some embodiments of the present invention.

FIG. 17 illustrates an alternative embodiment of a plate for use in any of the heat exchangers described here.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.

FIGS. 1 and 2 illustrate a heat exchanger 1 according to some embodiments of the present invention. The heat exchanger 1 is adapted to receive a first fluid flow 2 and a second fluid flow 3 and to place them in heat exchange relation with one another so as to transfer heat from one of the fluid flows to the other of the fluid flows. The heat exchanger 1 is especially well suited for use when the fluid flow 2 is a hot gas flow and the fluid flow 3 is a liquid or partially liquid flow having a boiling point or bubble point temperature that is lower than the entering temperature of the fluid flow 2, so that heat can be transferred from the first fluid flow 2 to the second fluid flow 3 in order to substantially vaporize the second fluid flow 3.

In some such applications, the heat that is so transferred may be sufficient to fully vaporize the second fluid flow 3, whereas in other applications the heat may be sufficient to vaporize only a portion of the first fluid flow 3. Furthermore, in some applications, the heat that is transferred from the first fluid flow 2 to the second fluid flow 3 may exceed the amount of latent heat required to fully vaporize the second fluid flow 3, so that the second fluid flow 3 exits the heat exchanger 1 as a superheated vapor.

The heat exchanger 1 shown in FIGS. 1 and 2 may be especially useful as an evaporator in a Rankine cycle waste heat recovery system for an internal combustion engine. In such a system, the first fluid flow 2 can be a flow of exhaust gas from the internal combustion engine, and the second fluid flow 3 can be a Rankine cycle working fluid such as water, ammonia, ethanol, methanol, R245fa or similar refrigerants, or a combination thereof. The utility of the heat exchanger 1 is not limited to such applications, however, and no limitations to the use of a heat exchanger according to the present invention are implied unless expressly recited in the claims.

As best seen in FIG. 2, the heat exchanger 1 includes a plurality of parallel arranged stamped shells 5, each of which is adapted to house a fluid flow plate 4 for the second fluid flow 3. The heat exchanger 1 further includes a plurality of convoluted fin structures 6 for the first fluid flow 2 interleaved with the stamped shells 5, and a plurality of stamped shells 7 located between the convoluted fin structures 6 and the fluid flow plates 4 in order to maintain separation between the first and second fluid flows 2 and 3 traveling through the heat exchanger 1. While reference is made herein to stamped shells 5, 7, in some embodiments, the shells 5, 7 can be formed in manners other than stamping. Alternatively or in addition, the shells 5, 7 can be positioned along or form less than the entire first and second fluid flows 2, 3.

In the illustrated embodiment of FIGS. 1 and 2, the stamped plates 5 and 7 are adapted to form sealed edges along the length of the heat exchanger 1. The heat exchanger 1 further includes a top plate 8 and a bottom plate 9, as well as header plates 10 to define an inlet and outlet for the first fluid flow 2. The components of the heat exchanger 1 may be joined to one another by brazing, soldering, welding, or other methods known in the art.

Features of the fluid flow plates 4 and stamped shells 5 will now be further described with reference to FIGS. 3 and 4. The stamped shells 5 include a fluid inlet port 11 to receive the second fluid flow 3 and a fluid outlet port 12 through which the second fluid flow 3 can exit the heat exchanger 1. Between the inlet port 11 and the outlet port 12 the second fluid flow 3 is routed through multiple flow passes defined by the stamped shell 5 and the fluid flow plate 4, with the flow passes extending between parallel ends 40, 41 of the fluid flow plate 4. In the exemplary embodiment shown in FIGS. 3 and 4, a fluid flow would encounter eight passes as it travels from inlet port 11 to outlet port 12. The eight passes are depicted using dashed lines in FIG. 4, with arrows indicating the direction of flow through each pass. It should be recognized that the desirable number of passes would vary with the application, and that heat exchangers having fewer than or more than eight passes are possible.

In the depicted embodiment, the fluid flow plate 4 is a corrugated thin metal sheet. Each of the eight fluid passes 14-21 comprise a plurality of flow channels 13 defined by corrugations of the fluid flow plate 4. The crests of the corrugations may be rounded as shown, or they may be some other shape such as, for example, flat or peaked. During fabrication of the heat exchanger 1, the crests of the corrugations can be bonded to the adjacent surfaces of the stamped plates 5 and 7 in order to define the flow channels 13. Alternatively or in addition, the crest of the corrugations can engage correspondingly shaped recesses or protrusions on the adjacent surfaces of the stamped plates 5 and 7 to seal the flow channels 13. Adjacent ones of the channels 13 are generally non-communicative with each other, except in the manifold regions to be described later on.

The inlet port 11 is directly connected to the channels 13 comprising the fluid pass 14 at the end 40, so that a portion of the second fluid flow 3 can enter the space between the stamped shell 5 and an adjacent stamped shell 7 or top plate 8 and can flow through the fluid pass 14. After traveling through the pass 14, the fluid can transfer to the pass 15 by way of the collection manifold 22 located at the end 41, and additionally by way of the collection manifold 23 located between the ends 40 and 41. It should be observed that the collection manifold 23 does not intersect some of the channels 13 comprising the pass 14, so that any fluid traveling through these channels is forced to travel the entire length of the channels and through the manifold 20. Additionally, the collection manifold 23 as shown does not intersect some of the channels 13 comprising the pass 15, and any fluid traveling through those channels must come from the collection manifold 22.

After flowing through the pass 15, the fluid can transfer to the pass 16 by way of the collection manifold 24 located at the end 40, and additionally by way of the collection manifold 25 located between the ends 40 and 41. Again, the collection manifold 25 as shown does not intersect some of the channels comprising the pass 15 and does not intersect some of the channels comprising the pass 16.

As can be inferred from inspection of FIGS. 3 and 4, the number of channels comprising any one pass need not be equal to the number of channels comprising any other pass. In fact, it may be preferable in some embodiments for the number of channels per pass to increase from the first pass to the second pass and so forth, as is the case for the embodiment of FIGS. 3 and 4. The reduced number of channels in the upstream passes can aid in achieving a uniform distribution of flow among the channels when the flow is all or mostly liquid and consequently has a relatively high density. As the flow moves downstream and the vapor quality increases, the mean density of the flow decreases and a greater number of channels can be used in order to accommodate the increased volumetric flow rate without compromising flow distribution.

In the illustrated embodiment, the collection manifold 25 consists of three approximately parallel slots 25a, 25b and 25c extending through the fluid flow plate 4. In different embodiments, the collection manifold can consist of more or fewer slots, so that the flow area in the collection manifold can be adjusted. Some advantages can be found, however, in having multiple slots to comprise the manifold rather than one larger slot. A smaller slot width will result in a smaller hydraulic diameter than a larger slot width, and this will reduce the negative impact on heat transfer performance caused by removal of the corrugations in the slot area. Additionally, a smaller slot width will provide greater structural support to resist deformation of the shells 5, 7 when the second fluid flow 3 is at a substantially higher pressure than the first fluid flow 2, as is frequently the case in evaporative systems. It should be understood by those having skill in the art that the proper slot width and number of slots may vary depending on the application.

In a manner similar to that described above, the fluid flows through the pass 16, then by way of the manifolds 26 and 27 through the pass 17, then by way of the manifolds 28 and 29 through the pass 18, then by way of the manifolds 30 and 31 through the pass 19, then by way of the manifolds 32 and 33 through the pass 20, then by way of the manifolds 34 and 35 through the pass 21, after which the fluid exits the heat exchanger 1 through outlet port 12.

The manifolds 24, 28 and 32 at the end 40 are separated from each other by protrusions 36 that extend from the wall of the recess in the plate 5 that houses the fluid flow plate 4. These protrusions extend approximately to the end 40 of the fluid flow plate 4 in order to provide a highly tortuous flow path for the fluid to flow directly from one of the manifolds 24, 28 and 32 to an adjacent one of the manifolds 24, 28 and 32 without passing through two of the flow passes in the plate 4. Similar protrusions 36 prevent or substantially inhibit bypass flow from the inlet port 11 to the manifold 24, and between the manifolds 22, 26, 30 and 34 located at the end 41.

In some embodiments, the bypass prevention may be improved by providing notches in the fluid flow plate 4 to receive portions of the protrusions 36 therein in order to provide an even more tortuous flow path. In some embodiments the protrusions 36 may be joined to one or more of the corrugations comprising the channels 13 of the fluid flow plate 4 to completely block such bypass flow. In some such embodiments, the joining can be accomplished by creating a brazed joint. In such embodiments, the protrusions 36 can block off one end of one or more of the channels 13 located between adjacent passes in the fluid flow plate 4 in order to direct substantially all of the fluid flow through the passes. In some embodiments, the flow blocking protrusions 36 may alternatively extend from the fluid flow plate 4 to engage the wall of the plate 5.

The flow manifolds 26, 28, 30, 32 and 34 also can be seen to include a flow area constriction region defined by features 37 that extend partially into the manifolds from the wall of the plate 5, the purpose of which will be described later.

Turning now to FIGS. 5a-c, some of the aspects of the present invention will be described. FIG. 5a illustrates a portion of the fluid flow path for the second fluid flow 3 as it passes through a heat exchanger 1 according to some embodiments of the present invention. The arrows represent the overall flow direction of the fluid in the various depicted sections of the fluid flow path.

The portion of the fluid flow path shown in FIG. 5a includes a pass A and a pass B located adjacent to and immediately downstream from the pass A, each of the passes A, B comprising a plurality of parallel flow channels such as the channels 13 of the embodiment of FIG. 3. The passes A and B may be any two adjacent passes along the fluid flow path. For example, they could represent any adjacent pair of the passes 14-21 in the embodiment of FIGS. 3 and 4.

The passes A and B extend from an end 38 of the fluid flow plate 4 to an end 39 of the fluid flow plate 4. Additional (not shown) flow passes may be located upstream and/or downstream of the passes A and B. The ends 38 and 39 can correspond to the ends 40 and 41, respectively, in the embodiment of FIGS. 3 and 4 if the pass A corresponds to one of the even-numbered passes 14, 16, 18 or 20. Likewise, the ends 38 and 39 can correspond to the ends 41 and 40, respectively, in the embodiment of FIGS. 3 and 4 if the pass A corresponds to one of the odd-numbered passes 15, 17 or 19.

The passes A and B are fluidly connected to one another by way of manifolds C and D, where manifold C is located at the end 39 and manifold D is located between the ends 38 and 39. The pass A comprises a set of channels Al that directly connect to the manifold C, and another set of channels A2 that directly connect to both manifolds C and D.

The channels comprising the pass B are each connected to at least one of the manifolds C and D. As shown in FIG. 5a, in some embodiments, some of the channels comprising the pass B are connected to the manifold C but are not connected to the manifold D, while the other of the channels comprising the pass B are connected to both manifolds C and D. In other embodiments, such as the one shown in FIG. 5b, some of the channels comprising the pass B are connected to the manifold D but are not connected to the manifold C. In still other embodiments, all of the channels comprising the pass B may be connected to both manifolds C and D.

When a heat exchanger including a flow plate 4 according to the embodiment of FIG. 5a is operated as an evaporative heat exchanger, with the evaporating fluid flowing as a two-phase fluid through pass A, the liquid and vapor phases of the portion of the fluid in the set of channels A2 will tend to separate from one another when the fluid encounters the manifold D. Due to its lower density, the vapor phase will experience a much greater pressure drop than the liquid phase will in passing from the manifold D back into the channel region between manifolds D and C. As a result, the vapor phase portion of the fluid traveling in the channels of section A2 will tend to flow in greater proportion through the manifold D. The liquid phase portion, in contrast, is more likely to continue straight through into the manifold C.

As a result of having the set of channels Al only connect to the manifold C, the entirety of the fluid traveling in the set of channels A1 will be directed into manifold C. This can prevent the accumulation of liquid in manifold C, as any vapor present in the set of channels A1 will “push” the liquid through into the pass B. In the embodiment of

FIG. 5a, in some embodiments, it is preferable to include a local constriction of the manifold C, such as by the presence of the partial flow blocking feature 37. Including such a local constriction can prevent the entirety of the flow in manifold C from flowing all the way to the end of that manifold and into only the last few channels of the pass B. When the fluid reaches the local constriction, a substantial portion of the fluid will be directed into the manifold D, from where it can then be distributed into the channels of pass B that are directly connected to manifold D.

In the alternative embodiment of FIG. 5b, the manifold C does not extend to all of the channels of pass B, and all of the fluid in the manifold C is directed into the manifold D, from where it can then be distributed to the channels of pass B.

In the embodiment of FIG. 5c, an additional flow pass E immediately adjacent to pass B is shown. The passes B and E are fluidly connected to one another by a manifold F located at the end 38 of the flow plate 4, and by a manifold G located between the ends 38 and 39. One set B1 of the channels of pass B are connected only to the manifold F, while a separate set B2 of the channels are connected to both manifolds F and G, so that the manifolds F and G can provide similar benefits as was described with reference to the manifolds C and D. It should be readily apparent that this pattern can be repeated as necessary in order to provide the desirable number of flow passes for a particular application.

FIG. 6 illustrates another embodiment of a heat exchanger 101 of the present invention. A hot fluid flow 102 and an evaporating fluid flow 103 are directed into and out of the heat exchanger 101 through ports in the top plate 108 of the heat exchanger 101. Such an embodiment can operate as a liquid chiller in a refrigeration or climate control system, wherein the hot fluid flow 102 is a liquid that is chilled by evaporation of a refrigerant flow 103. As seen in FIG. 7, in such an application, the fluid flow plate 104 can include openings 111, 112 corresponding to the port locations for the fluid flow 103. The flow 103 is distributed by way of the openings 111 to the plurality of layers 105 containing the flow plates 104. Within the fluid flow plate 104, the fluid flow 103 is directed though multiple passes of the parallel arranged flow channels 113, as indicated by the arrows in FIG. 7.

The flow 113 is distributed into the first pass by way of the manifolds 115 and 116. From the first pass, the flow 113 is distributed into the second pass by way of the manifolds 117 and 118, which serve the purpose of the manifolds C and D of FIGS. 5a-c. Specifically, it can be seen that some of the channels 113 belonging to the first pass are connected to the manifold 117 but not to the manifold 118, whereas others of the channels are connected to both manifolds 117 and 118.

Some of the flow channels 113 may be blocked by a ring 115 surrounding a port 110 through which the flow 102 is collected from the plurality of flow layers 107 interleaved with the flow layers 105. A portion 118a of the manifold 118 is located so as to intersect those channels and allow for the fluid passing through those channels to bypass around the ring 115.

The flow 103 is directed into the second pass from the manifolds 117 and 118, and is directed from the second pass into the third pass through the manifolds 119 and 120. The fluid is directed from the third pass to the fourth pass through the manifolds 121 and 122, and from the fourth pass to the fifth pass through the manifolds 123 and 124. The manifolds 125 and 126 redirect the fluid from the fifth pass into the port 112, through which the fluid 103 is removed from the heat exchanger 101.

Similar to the first pass, some of the channels in the fifth flow pass are blocked by a ring 114 surrounding the inlet distribution port 106 for the fluid 102. A portion 124c of the manifold 124 is located such that a portion of the fluid 103 can be directed into those channels despite the flow blockage due to the ring 114.

The manifolds 117, 119, 121 and 123 have local constrictions caused by protrusions or extensions 128 protruding from the fluid flow plate 104 into the manifold areas. These extensions 128 serve a similar function as the previously described protrusions 37.

The manifolds 117, 121 and 125 are separated from one another by protrusions 136 extending from the wall of the plate 105, said protrusions being received into notches 127 in the fluid flow plate 104. The manifolds 115, 119 and 123 are similarly separated from one another.

FIGS. 8-12 illustrate another embodiment of a heat exchanger 201 of the present invention. The illustrated embodiment of FIGS. 8-12 incorporates many of the features described and illustrated with respect to the embodiments of FIGS. 1-7. The discussion of the embodiments of FIGS. 8-12 will primarily focus on the features that are not disclosed in the description or figures of the embodiments of FIGS. 1-7. As shown in FIGS. 8-12, the heat exchanger 201 includes a hot fluid flow 202 and an evaporating fluid flow 203. The hot fluid flow 202 is shown flowing generally from left to right, but can flow generally right to left in other embodiments. The evaporating fluid flow 203 flows generally from right to left, but can flow generally left to right in other embodiments. The illustrated heat exchanger 201 is a counter flow heat exchanger. However, in other embodiments, the heat exchanger 201 can have one or more portions of the heat exchanger arranged as parallel flow, cross flow, counter-cross flow or other type of heat exchanging flow relationship.

The illustrated heat exchanger 201 includes a plurality of stacked plate assemblies. One of the stacked plate assemblies is shown in FIGS. 9 and 10. Each of the stacked plate assemblies includes a fluid flow plate 204, first and second stamped shells 205a, 205b, a convoluted fin 206 and first and second stamped shells 207a, 207b. The plurality of stacked plate assemblies are positioned between a top plate 208 and a bottom plate 209 (shown in FIG. 11).

The hot fluid flow 202 flows into the heat exchanger 201 at a first collection region 210a and exits the heat exchanger 201 at a second collection region 210b. The hot fluid flow 202 flows from the first collection region 210a between the first and second stamped shells 207a, 207b and along convolutions defined by the convoluted fin 206 prior to flowing into the second collection region 210b.

The evaporating fluid flow 203 flows into the heat exchanger 201 at a fluid inlet 211 and flows out of the heat exchanger 201 at a fluid outlet 212. The evaporating fluid flow 203 travels along a circuitous flow path between the fluid inlet 211 and the fluid outlet 212. The circuitous flow path extends between first and second parallel ends 240, 241 of the heat exchanger 201. The circuitous flow path includes a plurality of fluid passes 214, 215, 216, 217, 218 and 219 (see stamped shell 205a of FIG. 10). The circuitous flow path is defined by a plurality of flow channels 213 formed in the fin 204 and a plurality of slots formed in the stamped shells 205a, 205b. The plurality of slots include a plurality of groups of substantially parallel slots. In the illustrated embodiment, the first and second stamped shells 205a, 205b have corresponding slots. However, in other embodiments, the first and second stamped shells 205a, 205b can have offset slots or differing numbers and/or configurations of slots.

A first group of the plurality of slots includes slots 225a, 225b, 225c and 225d which are positioned adjacent to the fluid inlet port 211 and adjacent the first parallel end 240. A second group of the plurality of slots includes slots 227a, 227b and 227c spaced from the fluid inlet port 211 and positioned adjacent the second parallel end 241. A coordinate axis is included on FIG. 9 for clarity. The evaporating fluid flow 203 in the fluid pass 214 travels along the flow channels 213 of the fluid flow plate 204 (along the Y axis) between the first group of slots 225a-225d and the second group of slots 227a-227c. The first group of slots 225a-225d allows the fluid to move between adjacent flow channels 213 in the fluid flow plate 204. Specifically, the fluid can flow along the Z axis into the slots 225a-225d, then along the X axis in the slots 225a-225d, then finally along the Z axis into one or more of the adjacent flow channels 213. The first group of slots 225a-225d and the fluid pass 214 are relatively narrow (when measured along the X axis) when compared to the second group of slots 227a-227c and the fluid pass 215. Each of the slots in the first group of slots 225a-225d is spaced apart a greater distance (when measured along the Y axis) than each of the slots in the second group of slots 227a-227c.

The second group of slots 227a-227c functions as a turn-around so that the fluid flow reverses direction and flows back toward the parallel end 240 along the fluid pass 215. Specifically, the fluid flows in the Y direction along some of the flow channels 213 from the first parallel end 240 toward the second parallel end 241, then into any of the slots 227a-227c which allows the fluid to flow along the X direction into adjacent flow channels 213. When the fluid is in the adjacent flow channels 213, the fluid can flow in the Y direction along the fluid pass 215 from the second parallel end 241 toward the first parallel end 240. Because the second group of slots 227a-227c and the fluid pass 215 are wider (when measured along the X axis) than the first group of slots 225a-225d and the fluid pass 214, the second group of slots 227a-227c is in fluid connection with a greater number of flow channels 213 than the first group of slots 225a-225d. The flow channels 213 that are fluidly connected to the first group of slots 225a-225d form fluid pass 214 and permit fluid to flow from the first parallel end 240 to the second parallel end. The flow channels 213 that are fluidly connected to the second group of slots 227a-227c but are fluidly separated from the first group of slots 225a-225d form fluid pass 215 and permit fluid to flow from the second parallel end 241 to the first parallel end 240.

After the fluid is allowed to turn around in the second group of slots 227a-227c, the fluid flows along the Y axis in the fluid pass 215 toward a third group of slots 229a, 229b, 229c, 229d and 229e positioned adjacent the first parallel end 240 and the first group of slots 225a-225d. Similar to the discussion above, the third group of slots 229a-229e allows the fluid to move between adjacent flow channels 213 in the fluid flow plate 204. Specifically, the fluid can flow along the Z axis into the slots 229a-229e, then along the X axis in the slots 229a-229e, then finally along the Z axis into one or more of the adjacent flow channels 213. The slots 227a-227c of the second group are narrower (when measured along the X axis) and fewer in number than the slots 229a-229e of the third group. Because the third group of slots 229a-229e are wider (when measured along the X axis) than the second group of slots 227a-227c, the third group of slots 229a-229e is in fluid connection with a greater number of flow channels 213 than the second group of slots 227a-227c. The flow channels 213 that are fluidly connected to the third group of slots 229a-229e but are fluidly separated from the second group of slots 227a-227c form fluid pass 216 and permit fluid to flow from the first parallel end 240 to the second parallel end 241. Therefore, the fluid is allowed to turn around in the third group of slots 229a-229e and move from fluid pass 215 to fluid pass 216.

After the fluid turns around in the third group of slots 229a-229e, the fluid flows along the flow channels 213 of the fluid pass 216 from the first parallel end 240 toward a fourth group of slots 231a, 231b, 231c, 231d, 231e, 231f and 231g adjacent the second parallel end 241. The fourth group of slots 231a-231g, like the second and third groups of slots 227a-227c and 229a-229e discussed above, functions as a turn-around for fluid flowing along the flow channels 213. Specifically, fluid that flows along the fluid pass 216 toward the fourth group of slots 231a-231g can flow along the Z axis into the slots 231a-231g, then along the X axis in the slots 231a-231g, then finally along the Z axis into one or more of the adjacent flow channels 213. The slots 229a-229e of the third group are narrower (when measured along the X axis) and fewer in number than the slots 231a-231g of the fourth group. Because the fourth group of slots 231a-231g are wider (when measured along the X axis) than the third group of slots 229a-229e, the fourth group of slots 231a-231g is in fluid connection with a greater number of flow channels 213 than the third group of slots 229a-229e. The flow channels 213 that are fluidly connected to the fourth group of slots 231a-231g but are fluidly separated from the third group of slots 229a-229e form fluid pass 217 and permit fluid to flow from the second parallel end 241 to the first parallel end 240. Thus, the fourth group of slots 231a-231g permits the fluid to turn around and move from the fluid pass 216 to the fluid pass 217. Fluid pass 217 is wider (when measured along the X axis) than fluid pass 216.

After the fluid turns around in the fourth group of slots 231a-231g, the fluid flows along the flow channels 213 of the fluid pass 217 from the second parallel end 241 toward a fifth group of slots 233a, 233b, 233c, 233d, 233e, 233f, 233g, 233h and 233i adjacent the first parallel end 240. The fifth group of slots 233a-233i, like the second, third and fourth groups of slots 227a-227c, 229a-229e and 231a-231g discussed above, functions as a turn-around for fluid flowing along the flow channels 213. Specifically, fluid that flows along the fluid pass 217 toward the fifth group of slots 233a-233i can flow along the Z axis into the slots 233a-233i, then along the X axis in the slots 233a-233i, then finally along the Z axis into one or more of the adjacent flow channels 213. The slots 233a-233i of the fifth group are wider (when measured along the X axis) and greater in number than the slots 231a-231g of the fourth group. Because the fifth group of slots 233a-233i are wider (when measured along the X axis) than the fourth group of slots 231a-231g, the fifth group of slots 233a-233i is in fluid connection with a greater number of flow channels 213 than the fourth group of slots 231a-231g. The flow channels 213 that are fluidly connected to the fifth group of slots 233a-233i but are fluidly separated from the fourth group of slots 231a-231g form fluid pass 218 and permit fluid to flow from the first parallel end 240 to the second parallel end 241. Thus, the fifth group of slots 233a-233i permits the fluid to turn around and move from the fluid pass 217 to the fluid pass 218.

After the fluid turns around in the fifth group of slots 233a-233i, the fluid flows along the flow channels 213 of the fluid pass 218 from the first parallel end 240 toward a sixth group of slots 235a, 235b, 235c, 235d, 235e, 235f, 235g, 235h, 235i, 235j and 235k adjacent the second parallel end 241. The sixth group of slots 235a-235k, like the second, third, fourth and fifth groups of slots 227a-227c, 229a-229e, 231a-231g and 233a-233i discussed above, functions as a turn-around for fluid flowing along the flow channels 213. Specifically, fluid that flows along the fluid pass 218 toward the sixth group of slots 235a-235k can flow along the Z axis into the slots 235a-235k, then along the X axis in the slots 235a-235k, then finally along the Z axis into one or more of the adjacent flow channels 213. The slots 235a-235k of the sixth group are wider (when measured along the X axis) and greater in number than the slots 233a-233i of the fifth group. Because the sixth group of slots 235a-235k are wider (when measured along the X axis) than the fifth group of slots 233a-233i, the sixth group of slots 235a-235k is in fluid connection with a greater number of flow channels 213 than the fifth group of slots 233a-233i. The flow channels 213 that are fluidly connected to the sixth group of slots 235a-235k but are fluidly separated from the fifth group of slots 233a-233i form fluid pass 219 and permit fluid to flow from the second parallel end 241 to the first parallel end 240. Thus, the sixth group of slots 235a-235k permits the fluid to turn around and move from the fluid pass 218 to the fluid pass 219. Fluid pass 219 is wider (when measured along the X axis) than fluid pass 218.

With continued reference to FIG. 10, the illustrated first and second stamped shells 207a and 207b are substantially mirror images and define a first collection opening 245a that forms a portion of the first collection region 210a and a second collection opening 245b that forms a portion of the second collection region 210b. In the illustrated embodiment, the first and second collection openings 245a, 245b are substantially triangular. However, in other embodiments, the first and/or section collection openings 245a, 245b can have differing shapes and configurations.

The illustrated first and second stamped shells 205a and 205b are substantially mirror images and define first collection openings 247a, 247b that form a portion of the first collecting region 210a and second collection openings 249a, 249b that form a portion of the second collecting region 210b. In the illustrated embodiment, the first and second collection openings 247a, 247b, 249a, 249b are substantially triangular. However, in other embodiments, the first and/or section collection openings 247a, 247b, 249a, 249b can have differing shapes and configurations. In the illustrated embodiment, the first and second collection openings 247a, 247b, 249a, 249b each have dimples 251a, 251b, 253a, 253b that provide points at which the first and second stamped plates 205a, 205b can be connected (for example, by brazing). In other embodiments, other arrangements of dimples or other shapes can be utilized to connect the first and second stamped plates 205a, 205b adjacent the first and second collection openings 247a, 247b, 249a, 249b.

Turning now to FIGS. 11 and 12, the plurality of stacked plate assemblies are shown in cross-section. FIG. 12 is a close up of the portion of FIG. 11 surrounded by the circle 12. The fluid flow plates 204 are omitted from FIG. 12 for clarity. In the illustrated embodiment, each of the stacked plate assemblies has a substantially identical configuration and has corresponding positions and quantities of slots. While only slots 231e, 231f and 231g are illustrated in each of the first and second stamped shells 205a, 205b, each of the first, second, third, fourth, fifth and sixth groups of slots 225a-225d, 227a-227c, 229a-229e, 231a-231g, 233a-233i and 235a-235k are present in each of the first and second stamped shells 205a, 205b. However, in non-illustrated configurations, one or more of the stacked plate assemblies can have a different configuration and/or different locations and quantities of slots than the remaining stacked plate assemblies.

Turning now to FIG. 13, a portion of an alternate embodiment of a stacked plate assembly is illustrated. Similar to the embodiment of FIGS. 8-12, the illustrated stacked plate assembly includes a fluid flow plate 304 positioned between first and second stamped shells 305a, 305b. The embodiment of FIG. 13 further includes a third stamped shell 305c positioned adjacent the first stamped shell 305a and a fourth stamped shell 305d positioned adjacent the second stamped shell 305b. The fluid flow plate 304 and the first, second, third and fourth stamped shells 305a, 305b, 305c and 305d are sandwiched between first and second stamped shells 307a, 307b. While the first and second stamped shells 307a, 307b are illustrated at opposite ends of the fluid flow plate 304, the first and second stamped shells 307a, 307b are positioned in pairs adjacent both the third stamped shell 305c and the fourth stamped shell 305d. Similar to the embodiments described above, the assemblies formed by the fluid flow plate 304 and the stamped shells 305a, 305b, 305c and 305d are interleaved with the pairs of stamped shells 307a, 307b. Although not illustrated, a convoluted fin can be provided between the first stamped shell 307a and the second stamped shell 307b.

The first, second, third and fourth stamped shells 305a, 305b, 305c, 305d each include a plurality of groups of slots. The slots are substantially identical in each of the first, second, third and fourth stamped shells 305a, 305b, 305c, 305d. The slots illustrated in FIG. 13 substantially correspond to the slots in the first and second stamped shells 205a, 205b shown in FIGS. 8-12 and described in detail above. Specifically, the groups of slots form substantially rectangular shapes. In other, non-illustrated embodiments, the slots in one or more of the stamped shells can differ in quantity and/or location across the respective stamped shell.

Turning now to FIG. 14, a portion of an alternate embodiment of a stacked plate assembly is illustrated. Similar to the embodiment of FIG. 13, the illustrated stacked plate assembly includes a fluid flow plate 404 positioned between first and second stamped shells 405a, 405b, as well as a third stamped shell 405c positioned adjacent the first stamped shell 405a and a fourth stamped shell 405d positioned adjacent the second stamped shell 405b. The fluid flow plate 404 and the first, second, third and fourth stamped shells 405a, 405b, 405c and 405d are sandwiched between first and second stamped shells 407a, 407b. Like the embodiments of FIGS. 1-13, the first, second, third and fourth stamped shells 405a, 405b, 405c and 405d have identical slots. In contrast to the embodiments of FIGS. 1-13, many of the slots in each group of slots have different widths. Specifically, many of the slots positioned adjacent outer edges of the first, second, third and fourth stamped shells 405a, 405b, 405c and 405d are wider than the slots positioned inward from the outer edges. In the illustrated embodiments, many of the groups of slots form a substantially trapezoidal shape. In other embodiments, one or more of the groups can include slots that form substantially trapezoidal shapes whereas one or more of the groups can include other, non-trapezoidal shapes and configurations.

Turning now to FIG. 15, a portion of an alternate embodiment of a stacked plate assembly is illustrated. Similar to the embodiments of FIGS. 13 and 14, the illustrated stacked plate assembly includes a fluid flow plate 504 positioned between first and second stamped shells 505a, 505b, as well as a third stamped shell 505c positioned adjacent the first stamped shell 505a and a fourth stamped shell 505d positioned adjacent the second stamped shell 505b. The fluid flow plate 504 and the first, second, third and fourth stamped shells 505a, 505b, 505c and 505d are sandwiched between first and second stamped shells 507a, 507b. Like the embodiments of FIGS. 1-14, the first, second, third and fourth stamped shells 505a, 505b, 505c and 505d have identical slots. In contrast to the embodiments of FIGS. 1-14, the groups of slots each form a substantially parallelogram shape. Specifically, the slots adjacent an outer edge of the stamped shells 505a, 505b, 505c and 505d are positioned closer to a second parallel end 541 than the slots spaced from the outer edge. However, the slots in each group of slots have a substantially uniform length. In other embodiments, at least one of the groups of slots can have the slots adjacent the outer edge positioned closer to a first parallel end 540 than the slots spaced from the outer edge.

Turning now to FIG. 16, a portion of an alternate embodiment of a stacked plate assembly is illustrated. Similar to the embodiments of FIGS. 13-15, the illustrated stacked plate assembly includes a fluid flow plate 604 positioned between first and second stamped shells 605a, 605b, as well as a third stamped shell 605c positioned adjacent the first stamped shell 605a and a fourth stamped shell 605d positioned adjacent the second stamped shell 605b. The fluid flow plate 604 and the first, second, third and fourth stamped shells 605a, 605b, 605c and 605d are sandwiched between first and second stamped shells 607a, 607b. Like the embodiments of FIGS. 1-15, the first and second stamped shells 605a and 605b have identical slots. However, the third and fourth stamped shells 605c and 605d do not have any slots. Similar to the embodiments of FIGS. 1-13, the groups of slots each form a substantially rectangular shape.

FIG. 17 illustrates a stamped shell 705 that can be utilized with any of the heat exchangers described and illustrated herein. Like the stamped shells 205a and 205b, the illustrated stamped shell 705 includes first, second, third, fourth, fifth and sixth fluid passes 714, 715, 716, 717, 718 and 719 that extend between first and second parallel ends 740, 741. The illustrated stamped shell 705 also includes a first group of slots 725, a second group of slots 727, a third group of slots 729, a fourth group of slots 731, a fifth group of slots 733 and a sixth group of slots 735. The third, fourth, fifth and sixth groups of slots 729, 731, 733 and 735 substantially correspond to the slots described above and illustrated in FIGS. 8-12. In contrast to the slots of the embodiment of FIGS. 8-12, each of the slots of the first group of slots 725 form a bypass between the first flow pass 714 and the second flow pass 715. Specifically, the first group of slots 725 include a first portion that extends across at least a portion of the first flow pass 714 and a second portion that extends across at least a portion of the second flow pass 715. The first portion of the first group of slots 725 is narrower than the second portion when measured in the direction extending between first and second parallel ends 740, 741. Additionally, the first group of slots 725 extend at a non-parallel angle with respect to the other groups of slots 727, 729, 731, 733 and 735. In particular, the first portion of the first group of slots 725 extend at a non-parallel angle with respect to the second portion of the first group of slots. Further in contrast to the embodiment of FIGS. 8-12, each of the slots of the second group of slots 727 is thinner in the direction extending between the first and second parallel ends 240, 241.

Other configurations of plates and slots can be utilized with the heat exchangers of the present invention and the illustrated embodiments are given by way of example only.

Various alternatives to the certain features and elements of the present invention are described with reference to specific embodiments of the present invention. With the exception of features, elements, and manners of operation that are mutually exclusive of or are inconsistent with each embodiment described above, it should be noted that the alternative features, elements, and manners of operation described with reference to one particular embodiment are applicable to the other embodiments.

The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention.

Claims

1. An evaporative heat exchanger operable to at least partially vaporize fluid, the heat exchanger comprising:

first and second stacked plates defining a first fluid flow path between the first and second stacked plates, the first and second stacked plates each having a first end and a second end, and the first stacked plate defines a plane;

third and fourth stacked plates defining a second fluid flow path between the third and fourth stacked plates, wherein the third stacked plate is positioned adjacent the second stacked plate; and

a fluid flow plate positioned between the first and second stacked plates, the fluid flow plate having a plurality of flow channels extending in a first direction between the first end and the second end, wherein the first direction is substantially parallel to the plane;

wherein at least one of the first and second stacked plates and the fluid flow plate defines a plurality of slots, wherein the plurality of slots form a portion of the first fluid flow path such that fluid flowing along the first fluid flow path flows along at least one of the flow channels in the first direction and then flows in a second direction into at least one of the plurality of slots, wherein the second direction is non-parallel to the plane, and then flows in a third direction toward an adjacent one of the flow channels, wherein the third direction is substantially parallel to the plane, and then in a fourth direction into the adjacent one of the flow channels, wherein the fourth direction is substantially non-parallel to the plane, and then in a fifth direction along the adjacent one of the flow channels, wherein the fifth direction is substantially parallel to the plane.

2. The heat exchanger of claim 1, wherein at least one of the slots is an elongate slot extending along the third direction.

3. The heat exchanger of claim 1, wherein the second direction is substantially perpendicular to the plane.

4. The heat exchanger of claim 1, wherein the first direction is substantially perpendicular to the third direction.

5. The heat exchanger of claim 1, wherein the first direction is substantially parallel to the fifth direction.

6. The heat exchanger of claim 1, wherein at least one of the plurality of slots is formed in the first plate.

7. The heat exchanger of claim 1, wherein at least one of the plurality of slots is formed in the second plate.

8. The heat exchanger of claim 1, wherein the plurality of slots include at least one slot formed in the first plate and at least one slot formed in the second plate.

9. The heat exchanger of claim 1, wherein the plurality of slots includes a first group of slots and a second group of slots, wherein the first group of slots is formed in the first plate and wherein the second group of slots is formed in the second plate.

10. The heat exchanger of claim 1, wherein the fluid flow plate has convolutions that form adjacent the peaks and valleys, and wherein the plurality of flow channels are defined by peaks and valleys.

11. The heat exchanger of claim 1, wherein the plurality of slots include at least one group of elongate slots each extending in the third direction, substantially perpendicular to the first direction.

12. The heat exchanger of claim 1, further comprising a convoluted fin positioned between the third and fourth plates.

13. An evaporative heat exchanger operable to at least partially vaporize fluid, the heat exchanger comprising:

first and second stacked plates defining a first fluid flow path between the first and second stacked plates, the first and second stacked plates each having a first end and a second end, and the first stacked plate defines a plane;

third and fourth stacked plates defining a second fluid flow path between the third and fourth stacked plates, wherein the third stacked plate is positioned adjacent the second stacked plate; and

a fluid flow plate positioned between the first and second stacked plates, the fluid flow plate having a plurality of flow channels extending in a first direction between the first end and the second end, wherein the first direction is substantially parallel to the plane;

wherein at least one of the first and second stacked plates defines a plurality of slots, wherein the plurality of slots form a portion of the first fluid flow path such that fluid flowing along the first fluid flow path flows along at least one of the flow channels in the first direction, then flows along at least one of the plurality of slots, then flows into an adjacent one of the flow channels and then along the adjacent flow channel in a second direction, substantially parallel to the first direction.

14. The heat exchanger of claim 13, wherein the plurality of slots are elongate and extend in a third direction, wherein the third direction is non-parallel to the plane.

15. The heat exchanger of claim 14, wherein the third direction is substantially perpendicular to the first direction.

16. The heat exchanger of claim 13, wherein at least one of the plurality of slots is an elongate slot.

17. The heat exchanger of claim 13, wherein the plurality of slots includes a first plurality of slots formed in the first plate and a second plurality of slots formed in the second plate.

18. The heat exchanger of claim 17, wherein each the first plurality of slots are substantially aligned with a corresponding one of the second plurality of slots in a direction substantially perpendicular to the plane.

19. The heat exchanger of claim 13, wherein the fluid flow plate has convolutions that form adjacent peaks and valleys, and wherein the plurality of flow channels are defined by the peaks and valleys.

20. The heat exchanger of claim 13, further comprising a convoluted fin positioned between the third and fourth plates.