PLATE HEAT EXCHANGER WITH FLOW DIRECTING BAFFLES

Abstract

A plate heat exchanger includes a stack of plate pairs arranged within a housing. Comb-like baffles extend into flow gaps between the plate pairs to direct a fluid flow in a sinusoidal pattern within the flow gaps. The flow gaps are divided into two sub-sets of flow gaps, preferably alternatingly arranged along the height of the stack. Legs of some baffles extend into a first sub-set but not into the second sub-set, while legs of some baffles extend into the second sub-set but not into the first sub-set. The baffles are arranged so that the sinusoidal pattern in the second sub-set is phase-shifted form the sinusoidal pattern in the first sub-set.

Claims

1. A plate heat exchanger comprising: a housing defining a volume for a fluid to flow through; a stack of plate pairs arranged within the housing, each plate pair having a longitudinal direction and a transverse direction, the dimension of the plate pairs in the longitudinal direction being greater than the dimension of the plate pairs in the transverse direction; a plurality of flow gaps arranged between adjacent ones of the plate pairs in a stacking direction of the stack and between outermost ones of the plate pairs and walls of the housing, the plurality of flow gaps consisting of a first subset of the plurality of flow gaps and a second subset of the plurality of flow gaps, the flow gaps of the first subset and the flow gaps of the second subset being alternately ordered in the stacking direction; and a plurality of comb-like baffles extending into the plurality of flow gaps in order to define a sinusoidal flow path for the fluid extending in the longitudinal direction within each one of the flow gaps, wherein the sinusoidal flow paths in the flow gaps of the second subset are phase-shifted from the sinusoidal flow paths in the flow gaps of the first subset.

2. The plate heat exchanger of claim 1, wherein the sinusoidal flow paths in flow gaps of the second subset are phase-shifted from the sinusoidal flow paths in the flow gaps of the first subset by no more than 90°.

3. The plate heat exchanger of claim 1, wherein the sinusoidal flow paths in flow gaps of the second subset are phase-shifted from the sinusoidal flow paths in the flow gaps of the first subset by 60°.

4. The plate heat exchanger of claim 1, wherein the plate pairs are provided with an array of outwardly directed dimples, adjacent ones of the plate pairs being joined together through the dimples, the dimples being arranged in rows that extend in the transverse direction, and wherein the comb-like baffles are arranged between the rows of dimples.

5. The plate heat exchanger of claim 1, wherein the plurality of comb-like baffles are arranged in a repeating pattern along the longitudinal direction.

6. The plate heat exchanger of claim 5, wherein an instance of the repeating pattern consists of four of the comb-like baffles.

7. The plate heat exchanger of claim 5, wherein the repeating pattern includes a first comb-like baffle extending from a first longitudinal edge of each plate pair, followed by a second comb-like baffle extending from a second longitudinal edge of each plate pair, followed by a third comb-like baffle extending from the second longitudinal edge of each plate pair, followed by a fourth comb-like baffle extending from the first longitudinal edge of each plate pair.

8. The plate heat exchanger of claim 7, wherein a spacing in the longitudinal direction between said first comb-like baffle and said second comb-like baffle is greater than a spacing in the longitudinal direction between said second comb-like baffle and said third comb-like baffle.

9. A plate heat exchanger comprising: a housing defining a volume for a fluid to flow through; a stack of plate pairs arranged within the housing, each plate pair having a longitudinal direction and a transverse direction, the dimension of the plate pairs in the longitudinal direction being greater than the dimension of the plate pairs in the transverse direction, adjacent ones of the plate pairs being spaced apart to define a plurality of flow gaps between the plate pairs for the fluid to pass through, each one of the plate pairs having a first edge and a second edge both extending in the longitudinal direction; one or more first flow baffles arranged within the housing, each of the one or more first flow baffles having a plurality of legs extending in the transverse direction from the first edges of the plate pairs into a first subset of the plurality of flow gaps but not into a second subset of the plurality of flow gaps, said plurality of legs extending more than half of the dimension of the plate pairs in the transverse direction, terminal ends of said plurality of legs being spaced away from the second edges of the plate pairs to allow the fluid to flow between said terminal ends and a wall of the housing adjacent to the second edges; one or more second flow baffles arranged within the housing, each of the one or more second flow baffles having a plurality of legs extending in the transverse direction from the second edges of the plate pairs into the second subset of flow gaps but not into the first subset of flow gaps, said plurality of legs extending more than half of the dimension of the plate pairs in the transverse, terminal ends of said plurality of legs being spaced away from the first edges of the plate pairs to allow the fluid to flow between said terminal ends and a wall of the housing adjacent to the first edges; one or more third flow baffles arranged within the housing, each of the one or more third flow baffles having a plurality of legs extending in the transverse direction from the second edges of the plate pairs into the first subset of flow gaps but not into the second subset of flow gaps, said plurality of legs extending more than half of the dimension of the plate pairs in the transverse direction, terminal ends of said plurality of legs being spaced away from the first edges of the plate pairs to allow the fluid to flow between said terminal ends and a wall of the housing adjacent to the first edges; and one or more fourth flow baffles arranged within the housing, each of the one or more fourth flow baffles having a plurality of legs extending in the transverse direction from the first edges of the plate pairs into the second subset of flow gaps but not into the first subset of flow gaps, said plurality of legs extending more than half of the dimension of the plate pairs in the transverse, terminal ends of said plurality of legs being spaced away from the second edges of the plate pairs to allow the fluid to flow between said terminal ends and a wall of the housing adjacent to the second edges.

10. The plate heat exchanger of claim 6, wherein the flow gaps of the first subset and the flow gaps of the second subset are alternatingly arranged in a stacking direction of the stack.

11. The plate heat exchanger of claim 7, wherein the housing includes a wall that is spaced apart from a terminal one of the plate pairs at a first end of the stack in the stacking direction to define a flow gap for the fluid to pass through, and wherein each of the one or more first flow baffles and each of the one or more third flow baffles have an additional long leg that extends in the transverse direction into that flow gap.

12. The plate heat exchanger of claim 8, wherein the housing includes a wall that is spaced apart from a terminal one of the plate pairs at a second end of the stack in the stacking direction opposite the first end to define a flow gap for the fluid to pass through, and wherein each of the one or more second flow baffles and each of the one or more fourth flow baffles have an additional long leg that extends in the transverse direction into that flow gap.

13. The plate heat exchanger of claim 6, wherein each of the one or more first flow baffles is aligned with one of the one or more second baffles in the longitudinal direction and wherein each of the one or more third flow baffles is aligned with one of the one or more fourth baffles in the longitudinal direction.

14. The plate heat exchanger of claim 6, wherein the first, second, third, and fourth flow baffles are all staggered along the longitudinal direction.

15. The plate heat exchanger of claim 11, wherein the first, second, third, and fourth flow baffles are arranged in a repeating pattern along the longitudinal direction

16. The plate heat exchanger of claim 12, wherein the repeating pattern consists of one of the first flow baffles followed by one of the second flow baffles followed by one of the third flow baffles followed by one of the fourth flow baffles.

17. The plate heat exchanger of claim 13, wherein a spacing in the longitudinal direction between the first and the second flow baffles of the repeating pattern is greater than a spacing in the longitudinal direction between the second and the third flow baffles of the repeating pattern.

18. The plate heat exchanger of claim 14, wherein the spacing in the longitudinal direction between the first and the second flow baffles of the repeating pattern is exactly twice the spacing in the longitudinal direction between the second and the third flow baffles of the repeating pattern.

19. The plate heat exchanger of claim 14, wherein a spacing in the longitudinal direction between the third and the fourth flow baffles of the repeating pattern is equal to the spacing in the longitudinal direction between the first and the second flow baffles of the repeating pattern.

20. The plate heat exchanger of claim 14, wherein a spacing in the longitudinal direction between the fourth flow baffle of one instance of the repeating pattern and the first flow baffle of an immediately following instance of the repeating pattern is equal to the spacing in the longitudinal direction between the second and the third flow baffles of the repeating pattern.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 is a perspective view of a plate heat exchanger in a housing, according to some embodiment of the invention.

[0037] FIG. 2 is a partially exploded perspective view of a stack of plate pairs to be used in the plate heat exchanger of FIG. 1.

[0038] FIG. 3 is a partial cut-away view of the plate heat exchanger of FIG. 1.

[0039] FIG. 4 is a perspective view of an embodiment of the plate heat exchanger of FIG. 1, with the housing and other components removed to illustrate certain details of the heat exchanger.

[0040] FIG. 5 is a section view taken along the lines V-V of FIG. 4.

[0041] FIG. 6 is the section view of FIG. 5 with certain components hidden from view for the sake of clarity.

[0042] FIGS. 7A and 7B are plan views of the embodiment of FIG. 4, showing two different flow gaps between plate pairs of the heat exchanger.

[0043] FIG. 8 is a plan view of the embodiment of FIG. 4, illustrating flow paths for a fluid through the flow gaps of FIGS. 7A and 7B.

[0044] FIG. 9 is a perspective view of another embodiment of the plate heat exchanger of FIG. 1, with the housing and other components removed to illustrate certain details of the heat exchanger.

[0045] FIGS. 10A and 10B are plan views of the embodiment of FIG. 9, showing two different flow gaps between plate pairs of the heat exchanger.

[0046] FIG. 11 is a plan view of the embodiment of FIG. 9, illustrating flow paths for a fluid through the flow gaps of FIGS. 10A and 10B.

DETAILED DESCRIPTION

[0047] 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 accompanying 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.

[0048] A heat exchanger 1 according to some embodiments of the invention is depicted in FIG. 1. The heat exchanger 1 is configured to transfer heat between a first fluid flow that enters the heat exchanger 1 through an inlet port 31 and exits the heat exchanger 1 through an outlet port 34, and a second fluid flow that enters the heat exchanger 1 through an inlet port 32 and exits the heat exchanger 1 through an exit port 33.

[0049] The heat exchanger 1 can be particularly useful in exchanging heat between two liquid flows. By way of example, the first fluid flow can be a flow of coolant such as water, ethylene glycol, propylene glycol, or a glycol-water mixture. Also by way of example, the second fluid flow can be a flow of lubricating oil, or hydraulic oil, or a combustible fuel such as LNG or LPG. In some applications the heat exchanger 1 can be used to cool the second fluid by transferring heat from the second fluid to the first fluid as they pass through the heat exchanger 1. In other applications the heat exchanger 1 can be used to heat the second fluid by transferring heat from the first fluid to the second fluid as they pass through the heat exchanger.

[0050] In some particular embodiments, the heat exchanger 1 is used as a vaporizer for LNG or LPG. The LNG or LPG enters the heat exchanger 1 through the inlet port 32 in a liquid or a two-phase liquid-vapor state, and flows through flow structures of the heat exchanger 1 while simultaneously a flow of liquid coolant enters the heat exchanger 1 and flows through other flow structures of the heat exchanger 1. As the two fluid flow through the heat exchanger, heat is convectively transferred from the higher temperature coolant to the lower temperature LNG or LPG. The transfer of heat into the LPG or LNG vaporizes the liquid fraction of the LPG or LNG, so that it exits the heat exchanger 1 through the outlet port 33 as a fully vapor state flow. The coolant exits the heat exchanger 1 at a reduced temperature though the outlet port 34.

[0051] As shown in FIG. 1 and FIG. 3, the heat exchanger 1 includes an outer housing 2 to contain the flow structures for the fluids. In the exemplary embodiment, the housing 2 is constructed of several walls, particularly walls 7-13, which are joined together to define a fluid volume 4 for the first fluid to pass through. The housing 2 can be constructed of a metal such as aluminum or steel. It should be understood, however, that the housing 2 need not be constructed of metal, and can in some instances be constructed, at least in part, of other materials such as, for example, plastic. In at least some embodiments, the housing can be provided as a part of another component. For example, the housing 2 can be provided as a cavity or sump within an engine block.

[0052] The ports 32 and 33 extend though apertures in a top wall 10 of the housing 2, thereby allowing for the connection of fluid lines to transport the second fluid into and out of the heat exchanger 1. It should be understood, however, that one or both of the ports for that fluid can alternatively be arranged on other walls of the housing 2. The port 31 extends through the wall 12 of the housing 2 and the port 34 extends through the wall 13 of the housing 2, but again it should be understood that one or both of these ports can alternatively be arranged on other walls of the housing 2. The placement of the ports 31-34 as shown in the exemplary embodiment can provide increased heat exchanger effectiveness by providing for an overall counter-flow orientation between the two fluid flows. However, in some cases it may be beneficial to rearrange the ports to achieve, for example, a concurrent-flow or parallel-flow orientation.

[0053] Arranged within the housing 2 of the heat exchanger 1 is a stack 3 of plate pairs 5, shown in the partially exploded view of FIG. 2, which is housed within the internal fluid volume 4 of the housing 2, as shown in partially cut-away FIG. 3. The plate pairs 5 are stacked together in a stacking direction, indicated by the arrow 22, to form the stack 3. Such a heat exchanger construction, referred to herein as a plate heat exchanger construction, allows for the flow of the second fluid to pass through the interior of the plate pairs 5 as the flow of the first fluid passes through the fluid volume 4. That flow of the first fluid passes through flow gaps 6 that are arranged between adjacent ones of the plate pairs 5, as will be described, so that the first fluid flows over the external surfaces of the plate pairs 5 in order to exchange heat with the second fluid as that second fluid flows through the plate pairs 5.

[0054] Each of the plate pairs 5 extends in a longitudinal direction, indicated by the arrow 20. The overall flow of both the first fluid and the second fluid are preferably aligned with the longitudinal direction, and are preferably arranged to be in counter-flow orientation with one another in order to maximize the heat exchange effectiveness. To that end, the longitudinal direction 20 is preferably greater than the transverse direction of the plate pairs 5 (indicated by the arrow 21) that is perpendicular to that longitudinal direction 20.

[0055] In order to convey the second fluid into and out of the plate pairs 5, an inlet manifold 35 extends in the stacking direction 22 through the stack 3 at a first end of the stack 3 in the longitudinal direction 20, and an outlet manifold 36 similarly extends through the stack 3 at a second end of the stack 3 in the longitudinal direction. The manifolds 35 and 36 can be at least partially defined by, for example, flanged apertures that are formed into the plates of the plate pairs 5. Annularly shaped spacer rings 37 can be arranged at in the flow gaps 6 between adjacent plate pairs 5 At the manifold locations in order to further define the manifolds. The inlet fitting 32 is aligned with the inlet manifold 35 to deliver the flow of second fluid into the manifold 35 in order to distribute that flow among the various plate pairs 5 of the stack 3, and the outlet fitting is aligned with the outlet manifold 36 in order to remove the flow from the manifold 36 after it has discharged into that manifold 36 form the various plate pairs 5.

[0056] Multiple baffles 7, shown generally in FIG. 3, are assembled to the stack 3 in order to route the first fluid through the flow gaps 6 so that the rate of heat transfer between the fluids can be increased. The baffles 7 each include legs 17 (best seen in FIG. 6), each of which extends into one of the flow gaps 6 between the plates that bound that flow gap 6, in order to block the direct passage of the first fluid at that location along the longitudinal direction 20.

[0057] The baffles 7 are comb-like baffles, with a spine 39 from which the legs 17 extend. The spine 39 extends in the stacking direction 22 of the stack 3 alongside one of the longitudinal edges of the plate pairs 5, and is preferably disposed against the adjacent wall of the housing 2 in order to block any of the fluid from bypassing the baffle 7 between the stack 3 and the housing 2. In order to enable improved bypass flow blocking in the case where the housing walls are not uniform, the spines 39 can be provided with sealing lips that conform to the housing walls.

[0058] The legs 17 extend into the flow gaps 6 in the transverse direction 21 from one of the longitudinal edges of the plate pairs 5. Preferably, the legs 17 extend for a distance that is more than half of the overall dimension of the plate pairs 5 in the transverse direction, but less than the full extent of that overall dimension. A terminal end 18 of each leg 17 is thereby spaced away from the longitudinal edge of the plate pair opposite the longitudinal edge from which the leg extends. For instance, the terminal ends 18 of those legs 17 that extend from a first longitudinal edge 15 of the plate pairs (e.g. the legs of the baffles 7a and 7d as shown in FIGS. 7A and 7B) are spaced away from a second longitudinal edge 16, and the terminal ends 18 of those legs 17 that extend from the second longitudinal edge 16 of the plate pairs (e.g. the legs of the baffles 7b and 7c as shown in FIGS. 7A and 7B) are spaced away from the first longitudinal edge 15. As a result of those spacings, the fluid is able to flow between those terminal ends 18 and a corresponding wall 8 or 9 of the housing 2, so that the first fluid can continue to flow in the longitudinal direction 20.

[0059] As can be seen in FIGS. 5 and 6, any one of the baffles 7 has legs 17 that extend into some, but not all, of the flow gaps 6. The flow gaps 6 are separated into a first subset 6a of the flow gaps, and a second subset 6b of the flow gaps. Preferably, the flow gaps of the first subset 6a and the flow gaps of the second subset 6b are alternatingly ordered along the stacking direction 22, as shown in FIG. 5. Each of the baffles 7 has legs 17 that extend into one subset of the flow gaps but not into the other one of the subsets. For example, with specific reference to FIGS. 7A and 7B, the legs of the flow baffles 7a and 7c extend into the flow gaps of the first subset 6a, but not into the flow gaps of the second subset 6b, and the legs of the flow baffles 7b and 7d extend into the flow gaps of the second subset 6b, but not into the flow gaps of the first subset 6a. Each of the flow baffles can be provided with notches 38 that allow the edges of the plate pairs to be received into the baffle 7 for proper assembly of the flow baffles 7.

[0060] In addition to having legs 17 that extend into the flow gaps 6 between adjacent plate pairs 5, the baffles 7 are also provided with an additional leg 17 that is arranged in a similar flow gap between a terminal one of the plate pairs 5 and an adjacent wall of the housing 2. The flow baffles 7a and 7c have such an additional leg 17 that extends into a flow gap between the terminal plate pair 5 at a first end 23 of the stack and an adjacent wall 10 of the housing 2, while the flow baffles 7b and 7d have such an additional leg 17 that extends into a flow gap between the terminal plate pair 5 at a second end 24 of the stack and an adjacent wall 11 of the housing 2.

[0061] The flow baffles can be arranged in a pattern along the longitudinal direction 20 so that a sinusoidal flow pattern of the first fluid through the flow gaps is developed. The sinusoidal pattern that is developed in the first subset of flow gaps can be independent of the sinusoidal pattern that is developed in the second subset. FIG. 8 represents the path of fluid through the flow gaps of the first subset 6a with the meandering solid arrow 29, and the path of fluid through the flow gaps of the second subset 6b with the meandering dashed arrow 30.

[0062] The sinusoidal flow path 29 results from a repeating pattern by which the baffles 7a and 7c are arranged along the longitudinal direction 20. As shown in FIG. 7A, the flow baffles 7a and 7c (i.e. the flow baffles 7 with legs that extend into the first subset of flow paths 6a) are alternatingly arranged at a regular interval along the longitudinal direction 20. A flow baffle 7a is followed by a flow baffle 7c that is spaced some further distance along the longitudinal direction 20, followed by another flow baffle 7a that is again spaced some further distance along. This pattern can repeat itself additional times along the length of the plate pairs in the longitudinal direction 20, but (as is seen in the embodiment of FIG. 4) it need not repeat. The period of the sinusoidal flow pattern is determined by the distance between subsequent occurrences of the same flow baffle (e.g. the flow baffle 7a). It should be noted that, while the exemplary embodiment of FIGS. 4-8 show a constant spacing between the flow baffles of a given subset of flow gaps, in some alternative embodiments a non-constant spacing can be used, in which case the sinusoidal flow path will have a non-constant period.

[0063] In a similar fashion, as shown in FIG. 7B, the flow baffles 7b and 7d (i.e. the flow baffles 7 with legs that extend into the second subset of flow paths 6b) are alternatingly arranged at a regular interval along the longitudinal direction 20 in order to create the sinusoidal flow path 30 within those flow gaps. In the exemplary embodiment of FIGS. 4-8, the baffles 7b are aligned, along the longitudinal direction 20, with the baffles 7a, and the baffles 7d are similarly aligned with the baffles 7c. As a result, the sinusoidal flow paths 29 and 30 both have the same period, and are phase-shifted from one another by approximately 180°.

[0064] FIG. 9 depicts an alternative embodiment of a plate stack 3′ that can be used within the heat exchanger 1. The plate stack is constructed using the same plate pairs 5 as the stack 3, but has a different arrangement of comb-like baffles 7. As shown in FIGS. 10A and 10B, the stack 3′ also has flow baffles 7a and 7c that have legs extending into the flow gaps of a first subset 6a′, and flow baffles 7b and 7d that have legs extending into the flow gaps of a second subset 6b′. The baffles 7a and 7c again are alternatingly arranged along the longitudinal direction with a constant spacing, and extend into the flow gaps from opposing longitudinal edges 15 and 16, respectively. Likewise, the baffles 7b and 7d again are alternatingly arranged along the longitudinal direction with a constant spacing, and extend into the flow gaps from opposing longitudinal edges 16 and 15, respectively. Accordingly, as depicted in FIG. 11, sinusoidal flow patterns 29′ and 30′ are produced within the subsets 6a′ and 6b′, respectively.

[0065] In contrast with the embodiment of FIG. 4, however, the flow baffles with legs extending into the second subset 6b′ are staggered, in the longitudinal direction, from the flow baffles with legs extending into the first subset 6a′, resulting in a phase-shift between the flow patterns 29′ and 30′ that is less than 180°.

[0066] In the embodiment of FIG. 9, the flow baffles 7 are arranged in a fully staggered, repeating pattern whereby, along the longitudinal direction, a first flow baffle 7a is followed by a second flow baffle 7b followed by a third flow baffle 7c followed by a fourth flow baffle 7d, followed again by another instance of that pattern. It can further be seen, in FIGS. 10A and 10B, that the spacing in the longitudinal direction between a baffle 7a and the subsequent baffle 7b is greater than the spacing between that baffle 7b and the subsequent baffle 7c. Furthermore, the spacing between a baffle 7c and the subsequent baffle 7d is the same as the spacing between a baffle 7a and the subsequent baffle 7b, and the spacing between a baffle 7d and the subsequent baffle 7a is the same as the spacing between a baffle 7b and the subsequent baffle 7c. This spacing pattern has the result that the phase shift between the flow patterns 29′ and 30′ is less than 90°. In the case where all the spacings are equal, the phase shift would be equal to 90°.

[0067] The flow gaps 6 between adjacent ones of the plate pairs 5 can be created through a pattern of outwardly directed dimples 14 that are formed into the plates. These dimples 14 are arranged in a regularly repeating array, and are further arranged so that the locations of the dimples on adjacent plate pairs 5 coincide with one another, so that the plate pairs 5 can be joined together (for example, by brazing) to form the completed stack 3 or 3′ with the requisite flow gaps 6. The legs 17 of the comb-like flow baffles 7 can be sized to have a height that is generally equal to twice the height of the dimples 14 (with some allowance for manufacturing tolerances) so that the legs 17 can fill the gap between the plate pairs 5 in order to block the flow of the first fluid.

[0068] The pattern of the dimples 14 is such that the dimples 14 are arranged in rows that extend in the transverse direction 21, with the rows spaced apart, in the longitudinal direction 20, to provide spaces for the legs 17 of the flow baffles 7. The spacing between flow baffles 7 can, then, be expressed as an integer multiple of the spacing between transverse rows of the dimples 14. In the exemplary embodiment of FIG. 9, as can be seen from FIGS. 10A and 10B, the period of the sinusoidal flow path 29′ (equal to the spacing between successive ones of the first flow baffles 7a) and the period of the sinusoidal flow path 30 (equal to the spacing between successive ones of the second flow baffles 7b) are both equal to six dimple row spacings. Each dimple row spacing is, therefore, equal to a 60° portion of the sinusoidal path.

[0069] If those flow baffles 7 whose legs extend from the same longitudinal edge of the plate pairs 5 (e.g. the flow baffles 7b and 7c) were to be aligned in pairs along the longitudinal direction, then the phase shift between the sinusoidal flow patterns would be zero. Consequently, the phase shift can be calculated by the offset between the baffle 7b and the baffle 7c of an instance of the repeating pattern, or by the offset between the baffle 7d of one instance and the baffle 7a of the subsequent instance. In the exemplary embodiment of FIG. 9, that offset is equal to a single dimple row spacing, which is equivalent to a phase shift of 60°.

[0070] By causing the first fluid to flow in a sinusoidal pattern through the flow gaps 6, the heat transfer performance of the heat exchanger 1 is improved. This is at least in part due to higher Reynolds numbers in the fluid flow immediately upstream of each baffle 7, where the flow of fluid is directed from the longitudinal direction 20 to the transverse direction 21. The inventors have found that, once the fluid flows through the gap between the end 18 of the flow baffle legs and the opposing wall of the housing 2 to continue on in the longitudinal direction 20, a “dead zone” of low Reynolds number flow is formed immediately downstream of the baffle. The rate of convective heat transfer is thus reduced in this region immediately downstream. While such an undesirable decrease in local heat transfer performance can be partially remedied by increasing the number of flow baffles, and decreasing the spacing therebetween, such a modification would increase the pressure drop through the heat exchanger, which is often undesirable.

[0071] By offsetting the baffles on adjacent ones of the flow gaps 6, the zones of low convective heat transfer on one outwardly facing surface of each plate pair 5 can be aligned with the zones of high convective heat transfer on the other outwardly facing surface of the pair. This allows for a more uniform rate of heat transfer that is higher than would be achieved without flow baffles.

[0072] In some applications, the increased rate of heat transfer resulting from the described baffle arrangements might only be necessary over a portion of each plate pair. For instance, it may be desirable to provide the increased rate of heat transfer only at an end of the stack 3 in the longitudinal direction 20 (i.e. near the inlet port 31 or the outlet port 32) in order to provide enhanced heat transfer in a region of the heat exchanger 1 that otherwise would have limited heat transfer effectiveness due to a reduced approach temperature difference between the two fluids in that region.

[0073] The heat exchanger 1 can find particular utility as a vaporizer for LNG or LPG. In such an application, the LNG or LPG would be the fluid that is directed to flow through the plate pairs 5, while liquid coolant flows through the flow gaps 6 in order to transfer heat to the LNG or LPG, thereby vaporizing the fluid. The LNG or LPG enters the heat exchanger 1 at a very low temperature, which can create a risk of freezing the liquid coolant near the inlet port 32 of the LNG or LPG. By providing the baffles as described, particularly in that region, the risk of freezing can be reduced.

[0074] While the legs 17 as depicted in the exemplary embodiments extend perpendicularly to the longitudinally extending edges 15 and 16 of the plate pairs 5, the legs 17 can alternatively extend in the transverse direction 21 in a non-perpendicular fashion. For example, it can be observed that the dimples 14, in addition to being arranged in rows that run in the transverse direction 21, are also arranged in rows that run at an approximately 45° angle to both the transverse direction 21 and the longitudinal direction 20. In some applications it may be desirable for the legs 17 of the baffles 7 to extend into the flow gaps along such an angle. In such an embodiment, the legs 17 would still extend into the flow gaps 6 to create a sinusoidal flow pattern, as they would still be extending in the transverse direction from one of the edges 15, 16. Furthermore, the dimple pattern can be adjusted to provide dimple rows at angles other than 45°.

[0075] 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.

[0076] 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.