heat exchanger

Abstract

1. A heat exchanger for transferring heat between a first fluid and a second fluid, the heat exchanger comprising: a housing having a passageway for the first fluid; and an internal member disposed within the passageway, extending along the length of the passageway, and carrying a second fluid in a direction substantially parallel to the direction of the first fluid, the internal member being formed from a thermally conductive material and having an active area that spreads the second fluid flow substantially evenly across the width of the passageway.

Description

[Technical Field]

[0001] The present invention is broadly directed to heat exchangers. In particular, a heat exchanger is provided having a passageway and an internal member within the passageway for transferring heat between a first fluid flow and a substantially parallel second fluid flow. [Background technology]

[0002] A heat exchanger is a system used to transfer heat between two or more working fluids. Heat exchangers are broadly categorized into several types depending on the relative flow direction of each working fluid. In a counterflow heat exchanger, the working fluids flow parallel to each other in opposite directions. This contrasts with a crossflow heat exchanger, in which the working fluids flow perpendicular to each other. In general terms, counterflow heat exchangers (also known as counterflow heat exchangers) are considered preferable to crossflow alternatives in certain applications because they offer better overall performance.

[0003] Existing counterflow heat exchangers typically come in one of two types. Tube-type heat exchangers have multiple inner tubes or channels surrounded by a single outer tube or jacket, through which a first fluid flows and a second fluid flows in a direction opposite to the first fluid flow through the outer tube. While tube-type heat exchangers are simple to manufacture and reliable, their relatively small surface area for heat transfer limits their overall performance. Plate-type heat exchangers, on the other hand, have a series of plates staggered along the length of the part, with narrow spaces between adjacent plates defining channels through which fluid flows across the height of the part. Machined grooves or gaskets in the plates allow fluid to flow in only one direction, and the plates are arranged so that hot and cold fluids flow between every alternating set of plates. While plate-type heat exchangers offer a greater potential heat transfer capacity per part of the same size compared to tube-type heat exchangers, the gaskets or seals between the plates are prone to leaks, resulting in contamination of the fluid flow.

[0004] In both types of counterflow heat exchangers, the overall heat transfer performance depends on the total heat exchange surface area provided between adjacent fluid streams. Conventional manufacturing techniques impose limitations on the surface geometries that can be machined. Furthermore, a typical heat exchanger involves the interconnection of multiple components and sub-components, and it is important to ensure adequate seals to prevent contamination or mixing of the different fluid streams. Conventional assembly methods are laborious and susceptible to poor connections, which can result in system failure.

[0005] In this context, there is a need for improved heat exchangers, or at least to provide the public with a useful choice. It is with these shortcomings in mind that the present invention was conceived. Summary of the Invention

[0006] In a first aspect, the present invention provides a heat exchanger for transferring heat between a first fluid and a second fluid, the heat exchanger comprising: a housing having a passageway for the first fluid; and an internal member disposed within the passageway, extending along the length of the passageway and carrying a second fluid in a direction substantially parallel to the direction of the first fluid, the internal member being formed from a thermally conductive material and having an active area that spreads the second fluid flow substantially evenly across the width of the passageway.

[0007] Preferably, the heat exchanger is a counter-flow heat exchanger in which the first and second fluids pass through it in substantially opposite directions.

[0008] In some forms, the housing may further include an inlet and an outlet in fluid communication with the internal member, where one of the inlet and the outlet may be disposed at a first end of the internal member and the other of the inlet and the outlet may be disposed at an opposing second end of the internal member. The internal member may extend laterally between a first side and a second side, where the inlet may be disposed at the first side and the outlet may be disposed at the opposing second side. Additionally or alternatively, the housing may extend in height between an upper side and a lower side, where the inlet may extend away from the lower side and the outlet may extend away from the upper side.

[0009] The inner member may include a passive region, which may be disposed in front of the active region in the direction of the second fluid flow, and which may have reduced surface friction compared to the active region. The passive region of the inner member may have a length that varies across its width. The length of the passive region may decrease from the first side to the second side across the width of the inner member. The length of the passive region may vary linearly across the width of the inner member.

[0010] Optionally, the plate may have a second passive area, which may be positioned after the active area in the direction of the second fluid flow.

[0011] In some embodiments, the internal member may have a plurality of internal turbulators defining the active area. The plurality of turbulators may be provided in an array. The array may be an array of separated turbulators.

[0012] The inner member may have a plurality of exterior projections extending into the passageway.

[0013] In some aspects, the internal member may have a plurality of plates disposed within the passageway, each plate having an internal flow path along which a portion of the second fluid flow may pass in the second direction. The plurality of plates may divide the passageway into a plurality of substantially equally sized separated passageways and may be spaced apart in a stacked arrangement within the passageway so that a portion of the first fluid flow passes along them. The internal member may further include a manifold that distributes respective portions of the second fluid flow across the flow paths of the plurality of plates.

[0014] The first fluid flow may be a gas flow. Additionally or alternatively, the second fluid flow may be a liquid flow.

[0015] Preferably, the housing and inner member are integrally formed with one another.

[0016] In a second aspect, the invention is a method of manufacturing a heat exchanger as described herein, the method simultaneously forming the housing and the internal member through an additive manufacturing process. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view of a heat exchanger according to one embodiment of the present invention, the heat exchanger having a generally rectangular housing whose interior volume defines a core for heat exchange between a first fluid stream and a second fluid stream. [Figure 2] FIG. 2 is a side view of the heat exchanger of FIG. 1 showing the inlet and outlet ports extending from the housing. [Figure 3] FIG. 3 is a bottom view of the heat exchanger of FIG. [Figure 4] FIG. 4 is a front view of the heat exchanger of FIG. [Figure 5] FIG. 5 is a cross-sectional view of the plate taken through line AA of FIG. 4, showing the internal flow channels of the plate through which the second fluid stream passes. [Figure 6] FIG. 6 is a perspective view of the cross-sectional plate of FIG. 5, showing the active and passive areas of the plate. [Figure 7] FIG. 7 is an enlarged view of boxed area B of FIG. 6, showing the arrangement of protrusions that define the active area. [Figure 8] FIG. 8 is a schematic end view of the heat exchanger of FIG. 1 illustrating the path of a first fluid flow through the internal flow passages from the inlet to the outlet. [Figure 9] FIG. 9 is a schematic plan view of the heat exchanger of FIG. 1 showing the spread of the first fluid flow across the width of the active area of ​​the plate. [Figure 10] FIG. 10 is a perspective view of a heat exchanger according to a preferred embodiment of the present invention, the heat exchanger including external protrusions extending from its plates. [Figure 11] FIG. 11 is an enlarged view of the external projection of FIG. 10, showing the arrangement of interlocking fins. [Figure 12] FIG. 12 is a side cross-sectional view along the length of the heat exchanger of FIG. 10, showing the fins extending between adjacent plates. [Figure 13] FIG. 13 is an enlarged view of boxed area C in FIG. 12, showing the fins and internal structure of the plate. DETAILED DESCRIPTION OF THE INVENTION

[0018] The invention is herein described, by way of non-limiting example only, with reference to the accompanying drawings, in which: In the following detailed description, reference is made to the accompanying drawings, which form a part of the detailed description. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the drawings, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are contemplated by the present disclosure.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, a limited number of exemplary methods and materials are described herein.

[0020] In general terms, the illustrated heat exchanger unit 100 includes a shell-like housing 102 with an interior volume, at least a portion of which defines a core 101 of the heat exchanger unit 100. The core 101 defines the heat transfer zone of the unit 100. A passage 104 extends axially along the housing 102. The passage 104 provides a path for a first fluid to flow along the core 101 in a first direction. An internal member 106 is disposed within the passage 104 and extends across its width. The internal member 106 functions as a baffle, providing a path for a second fluid to flow along the core 101 substantially parallel to the first fluid. The internal member 106 is formed from a thermally conductive material to allow heat to be transferred between the respective fluids. The internal member 106 has an active area 110 that spreads the second fluid flow substantially evenly across the width of the passage 104, thereby optimizing heat transfer efficiency between the fluids within the core 101.

[0021] As used herein, the term "fluid" is intended to encompass both gases, such as air, and liquids, such as water. In particular, it is understood that the heat exchanger unit 100 described herein is suitable for use as a liquid-to-liquid heat exchanger, in addition to a liquid-to-gas heat exchanger.

[0022] 1-3 , the housing 102 of the heat exchanger unit 100 is a box-like shell extending axially in length between a first or front end wall 112 and a second or rear end wall 114 and laterally in width between a first or near side wall 116 and a second or far side wall 118. Opposing bottom and top walls 120 and 122 enclose the volume of the housing 102. However, it is understood that the housing 102 need not be rectangular or box-like. In other examples, the housing 102 (and thus the core 101 housed therein) may have a different shape, such as a body with a circular profile, a triangular profile, other geometric profile, or other non-geometric or freeform profile. As a further example, the housing 102 may be substantially cylindrical, spherical, or have other volumetric shapes with vertical faces or with curved, freeform surface shapes. It should be noted that while the housing 102 in the illustrated embodiment has a constant cross-sectional area and profile, it is understood that this is merely a preference and not a requirement of the present invention.

[0023] The passageway 104 extends linearly along the housing 102 from the first end 112 to the second end 114. The passageway 104 has a rectangular cross-section. The passageway 104 provides a passageway for a first fluid flow through the unit 100 in a first substantially axial direction, indicated by F1 in the figures. The passageway 104 completely surrounds the plate 106 disposed therein, and the first fluid flow may be considered an external fluid flow, while the second fluid flow (within the internal passageway 108 of the plate 106, indicated by F2 in the figures) may be considered an internal fluid flow. In the illustrated embodiment, the passageway 104 is shown as encompassing substantially the entire internal volume of the housing 102, although it will be understood that this need not be the case. For example, the passageway 104 may be provided as a tubular pipe extending through the housing 102, for example.

[0024] Openings in the end walls 112, 114 provide an inlet 124 and an outlet 126, respectively, for the first fluid stream. As shown, the inlet 124 and outlet 126 are open, allowing the first fluid stream to exit the heat exchanger. Such an embodiment is suitable for gas-based fluids such as air. In other embodiments, the inlet 124 and outlet 126 may take the form of pipes or other enclosures suitable for the passage of liquids. It is understood that the heat exchanger unit 100 is a single-pass heat exchanger, meaning that the first fluid stream passes through the core 101 in a single pass, thereby maximizing the rate of heat transfer between the first and second fluid streams.

[0025] A second fluid flow enters the heat exchanger unit 100 via the inlet 128 and exits via the outlet 130. As best shown in FIG. 3 , the inlet 128 and the outlet 130 have circular cross-sections suitable for coupling with conventional tubular pipes. The inlet 128 and the outlet 130 are in fluid communication with the inner member 106. In the illustrated embodiment, the inlet 128 is disposed at the second end 114 of the housing 102, and the outlet 130 is disposed at the first end 112. It is understood that the direction of the second fluid flow along the core 101 is opposite or counter to the direction of the first fluid flow, from the second end 114 to the first end 112. It is understood that in other embodiments, the respective locations of the inlet 128 and the outlet 130 can be reversed so that the first and second fluids flow in the same direction along the core 101.

[0026] The inlets 128 extend downward from the first side wall 116, away from the bottom wall or base 120, while the outlets 130 extend upward from the opposing second side wall 118, away from the top wall or apex 122. Locating the inlets 128 and outlets 130 toward opposite sides of the interior member 106 imparts a lateral component to the direction of the second fluid flow, encouraging the flow to spread across the width of the plate 106 and minimizing the effects of thermal polarization.

[0027] 4, it can be seen that the internal member 106 includes a plurality of flat plates 106 extending along a substantial length of the passages 104. As shown, eight plates 106 are disposed within and extend along the passages 104; however, it is understood that there may be more or fewer plates 106 depending on the overall size of the heat transfer unit 100 and / or the nature and characteristics of the respective working fluids. For example, some embodiments may include only a single plate 106, while other embodiments may include 10, 15, or 20 or more plates. It is also contemplated that the internal member 106 need not extend along the entire length of the housing 102; for example, multiple heat exchanger units 100 may be arranged to share a common housing 102. It is further understood that in other embodiments (not shown), the internal member 106 may not be flat or otherwise plate-like. For example, the inner member 106 may alternatively be provided as a curved plate, or in other embodiments, as a tubular pipe or multiple tubular pipes.

[0028] The plates 106 are arranged in a stacked arrangement about the height of the passage 104. The spaces or gaps between adjacent plates 106 provide passages 132 for the flow of the first fluid. Preferably, the plates 106 are evenly and regularly distributed about the height of the passage 104 so that the portion of the first fluid in each passage 132 is approximately the same. As clearly shown in the figure, the plates 106 extend along a substantial length of the entire width of the passage 104, and no mixing occurs between the portions of the first fluid until the respective passages 132 are sealed from one another and the portions recombine toward the exhaust port 126.

[0029] As shown in FIGS. 5-7 , each of the plates 106 includes at least one internal flow channel 108. In the preferred embodiment shown in the figures, the internal flow channel 108 is provided as a slot extending substantially across the entire width of each plate 106. The internal flow channel 108 provides a passage for a second fluid stream. The internal flow channel 108 is a closed or sealed channel to prevent the fluid streams from mixing. The surface area of ​​the flow channel 108 is divided into an active region 110 and at least one passive region 136. The passive region 136 has a lower coefficient of surface friction than the active region 110. In this manner, the active region 110 can be considered the “roughened” region of the flow channel 108, and the passive region 136 the “smooth” region. The regions 108 are shaped such that, for a given flow rate, the active region 110 promotes turbulent flow conditions, while the passive region 136 promotes more laminar flow. Turbulent flow conditions within the active region 110 of the flow passage 108 are beneficial in promoting mixing of the second fluid and promoting heat transfer between the first and second fluids.

[0030] The active region 110 is the working region of the internal flow channel 108, covering the entire width of the flow channel 108 and extending along substantially its length. The passive region 136 is positioned before the active region 110 in the direction of travel of the second fluid. In this manner, fluid entering the flow channel 108 through the inlet 128 passes through the passive region 136 before reaching the active region 110, where the roughened surface of the active region 110 acts to create turbulence in the second fluid flow. The second passive region 136a is positioned after the active region 110, where the second fluid passes over the second passive region 136a, which substantially stabilizes the flow before exiting the flow channel 108 through the outlet 130.

[0031] 5 , the boundary or transition 138 between the passive region 136 and the active region 110 extends across the width of the flow channel 108 at an angle relative to the end walls 112, 114. As such, the passive region 110 has a length that varies across the width of the flow channel 108, with its greatest length along its end adjacent the inlet 128. Similarly, the second passive region 136a also has a length that varies across the width of the flow channel 108, with its greatest length along its end adjacent the outlet 130. As shown, the boundary or transition 138 extends linearly across the width of the flow channel 108. However, it will be understood that the boundary or transition 138 may follow other contours, such as a sinusoidal contour, to achieve different flow / boundary characteristics for the second fluid.

[0032] 6 and 7, the geometry of the active area 110 will be described. As shown in most detail in FIG. 7, the active area 110 is characterized by a plurality of upstanding protrusions 140 extending from the interior flow channel wall of the plate 106 into the flow channel 108. The protrusions 140 embody the active area with a roughened surface contour. The protrusions 140 function as turbulators, imparting a turbulent flow condition to the second fluid flow, encouraging the flow to span or cover the entire width of the flow channel 108, thereby enhancing heat transfer with the first fluid flow in the adjacent passage 104. The height of the protrusions 140 is selected based on the flow characteristics of the second fluid to ensure optimal spreading and promote heat transfer. For example, the protrusions 140 may extend substantially the entire height of the flow channel 108. As shown, the protrusions 140 are provided as an array of discrete turbulators. In other embodiments (not shown), it is also contemplated that the protrusions 140 are provided in a grid-like configuration. Optionally, the passive area 136 may also have protrusions 140. However, it is understood that such protrusions in the passive area may be reduced in height and / or density compared to the protrusions in the active area 110. Thus, the active area 110 has an increased or roughened surface structure compared to that of the passive area 136, resulting in higher surface friction.

[0033] As shown, the protrusions 140 extend between the interior channel walls of the plate 106. The protrusions 140 may also function to increase the structural strength of the plate 106. This is particularly beneficial in that it allows the plate 106 to have relatively thin walls (compared to existing / conventional plates) that promote increased heat transfer rates. In other embodiments, the protrusions 140 may take other forms, such as raised depressions, and / or may not extend the entire height of the channel 108. The protrusions 140 act as scaffolding during the additive manufacturing process of the plate 106, allowing the upper and lower interior channel walls of the plate 106 that define the channel 108 to be held apart and formed.

[0034] 8 and 9, the path of the second fluid flow will now be described. As shown in FIG. 8, the second fluid enters the core 101 through the inlet 128. A manifold or splitter 142 then splits the second fluid flow into several substreams, each of which is directed into a channel 108 in a respective plate 106. Each substream of the second fluid flow then travels axially along the channel 108 (in the opposite direction to the first fluid flow) and laterally across the channel 108 to the outlet 130, where the substreams recombine to form a combined outflow stream.

[0035] 9, it should be noted that the varying lengths of the passive areas 136 (or, in other words, the shape of the active areas 110 when considered from a plan view of the plate) facilitates spreading the second fluid flow substantially evenly across the entire width of the flow passage 108. The spreading of the second fluid flow increases the surface area for heat transfer between the first and second fluids.

[0036] Preferably, the plates 106 may have external protrusions 134 extending from their outer surfaces into respective passages 132 of the passages 104. Figures 10-13 show an exemplary embodiment of the invention in the form of a heat exchanger unit 100' having plates 106 with external protrusions 134. It will be appreciated that the heat exchanger unit 100' is otherwise similar to the heat exchanger unit 100, except for the provision of external protrusions between the internal members 106 within the passages. The external protrusions 134 affect the first fluid flow within the passages 104 by increasing the surface area of ​​the plates 106 through which the first fluid flow passes, promoting improved mixing and heat transfer.

[0037] As best shown in FIG. 12 , the external protrusions 134 are provided as an array of chevron-shaped interconnected fins, each fin extending laterally across the width of the passage 104. Each fin has a porous structure that permits fluid flow therethrough, with the first fluid flow in the passage passing through the porous structure of the fins 134. The porous structure may be in a honeycomb configuration. The porous structure of the fins 134 occupies a substantial volume of the passage 104, providing a labyrinthine flow path for the first fluid, promoting mixing and heat transfer with the second fluid. The height of the protrusions 134 is selected based on the flow characteristics of the first fluid to promote heat transfer. For example, as shown, the protrusions 134 extend substantially between adjacent plates 106. It is further understood that the length of each fin may vary along the passage 104—for example, fins located near the inlet end 128 may be longer than fins located near the outlet end 130. Varying the fin length in this manner allows for tailoring to a particular fluid and optimizing heat transfer performance along the passage 104. Although not shown, it is also contemplated that, like the protrusions 140, the projections 134 may be provided as a single grid arrangement, as opposed to multiple, separate fins.

[0038] Similar to the protrusions 140, the projections 134 may also reinforce the plates 106, acting as scaffolding to hold the plates 106 in place during the additive manufacturing process, allowing the housing 102 to be additively manufactured without compromising the structural integrity of the plates 106. While the illustrated embodiment shows the projections 134 extending substantially completely between the inlet 124 and the outlet 126, it is envisioned that the projections 134 may extend only partially along the passages 104. Furthermore, although described herein as projections integrally formed with each plate 106, it is understood that separate thermally conductive spacers 134' (not shown) may instead be provided in the gaps between adjacent plates 106 to provide similar functionality.

[0039] Without limitation, it is contemplated that the heat exchanger unit 100 (and heat exchanger unit 100′) described herein is manufactured using an additive manufacturing process, with the housing 102 and the internal member 106 integrally formed with one another as a unitary structure. Preferably, the housing 102 and the internal member 106 are formed simultaneously. For example, the unit 100 may be formed using a laser powder bed fusion (LPBM) additive manufacturing process. Advantageously, the heat exchanger unit 100, when manufactured according to such a method, does not require a separate assembly for positioning the plates 106 within the passages 104, thus avoiding the potential failure modes associated with welding or bolting. The resulting unit 100 is thus a single, seamless component. Furthermore, minimal finishing is required on the completed part 100. It is contemplated that at least the internal member 106 is formed of a thermally conductive material. Preferably, the internal member 106 is formed from a metallic material such as steel, aluminum, or titanium. Such exemplary materials are known to be suitable for laser powder bed fusion processes.

[0040] Additionally, it will be appreciated that the additive manufacturing processes described herein enable the protrusions 140 and projections 134 to be formed with complex and tunable geometries. This means that the exact geometry of these flow surface features can be varied to achieve specific flow characteristics, depending on the properties of the fluid itself. For example, a highly viscous fluid flow will be associated with a higher density of flow surface features than a less viscous fluid flow. Furthermore, the flow channels 110 can be manufactured to tighter tolerances and within a smaller overall height than would be possible with traditional machining—thus providing the ability to allocate an increased number of plates (and therefore increased heat transfer surface area) within a given passage volume.

[0041] In summary, it will be appreciated that the heat exchanger unit 100 described herein offers several performance advantages and manufacturing improvements over typical existing designs. For example, the geometry of the active areas 110 within the internal flow passages 108 of the plates 106 and the features 140 that define those areas act to spread and encourage flow across the entire width of the flow passages 108, thus increasing heat transfer with the opposing external fluid flow.

[0042] The reference in this specification to any prior publication (or information derived therefrom) or public knowledge should not be taken as an admission or acknowledgement or suggestion that the prior publication (or information derived therefrom) or public knowledge forms part of the common general knowledge in the field of endeavor to which this specification pertains.

[0043] Throughout this specification and the claims that follow, unless the context requires otherwise, the word "comprise" and variations such as "comprises" and "comprising" will be understood to imply the inclusion of a stated integer or step or group of integers or steps, but not the exclusion of other integers or steps or groups of integers or steps. [Explanation of symbols]

[0044] 100...Heat exchanger unit 101...Core 102...Housing 104...Passage 106...plate 108...internal flow passage 110...active area 112...front end wall 114... rear end wall 116... near side wall 118... far side wall 120... lower wall 122... upper wall 124...intake port 126...exhaust port 128...inlet 130...outlet 132...passage 134...external protrusion portion 136...passive region 138...transition portion 140...internal protrusion portion 142...Manifold

Claims

1. 1. A heat exchanger for transferring heat between a first fluid and a second fluid, the heat exchanger comprising: a housing having a passageway for the first fluid; and an internal member disposed within the passageway, extending along the length of the passageway, and carrying a second fluid in a direction substantially parallel to the direction of the first fluid, the internal member being formed from a thermally conductive material and having an active area that spreads the second fluid flow substantially evenly across the width of the passageway.

2. 10. The heat exchanger of claim 1, wherein the heat exchanger is a counterflow heat exchanger in which the first and second fluids pass therethrough in substantially opposite directions.

3. 3. A heat exchanger according to claim 1 or 2, wherein the internal member comprises a plate with internal channels for carrying the second fluid.

4. 4. The heat exchanger of claim 1, further comprising an inlet and an outlet in fluid communication with the internal member, one of the inlet and the outlet being disposed at a first end of the internal member and the other of the inlet and the outlet being disposed at an opposing second end of the internal member.

5. 5. The heat exchanger of claim 4, wherein the internal member extends laterally between a first side and a second side, the inlet being located on the first side and the outlet being located on the opposing second side.

6. 6. A heat exchanger as claimed in claim 4 or 5, wherein the housing extends in height between an upper portion and a lower portion, the inlet extending away from the lower portion and the outlet extending away from the upper portion.

7. 7. The heat exchanger of claim 1, wherein the internal member includes a passive area disposed in front of the active area in the direction of the second fluid flow, the passive area having reduced surface friction compared to the active area.

8. The heat exchanger of claim 7 , wherein the passive region of the inner member has a length that varies across its width.

9. 9. The heat exchanger of claim 8 when dependent on claim 5, wherein the length of the passive region decreases across the width of the inner member from the first side to the second side.

10. 10. A heat exchanger according to any one of claims 7 to 9, wherein the internal member has a second passive area, the second passive area being disposed after the active area in the second fluid flow direction.

11. 11. A heat exchanger according to any preceding claim, wherein the internal member has a plurality of internal projections defining the active area.

12. 12. The heat exchanger of claim 11, wherein the plurality of protrusions are provided as an array of separated turbulators.

13. 13. A heat exchanger according to any preceding claim, wherein the internal member has a plurality of external projections extending into the passages.

14. 14. The heat exchanger of claim 1, wherein the internal member comprises a plurality of plates arranged in the passages, each plate having an internal flow path along which a portion of the second fluid flow passes in the second direction.

15. 15. The heat exchanger of claim 14, wherein the plurality of plates are spaced apart in a stacked arrangement within the passageway to divide the passageway into a plurality of substantially equally sized separated passageways and for a portion of the first fluid flow to pass therealong.

16. 16. A heat exchanger according to claim 14 or 15, further comprising a manifold for dividing respective portions of the second fluid flow across the flow paths of the plurality of plates.

17. 17. A heat exchanger according to any preceding claim, wherein the first fluid flow is a gas flow.

18. 18. A heat exchanger according to any preceding claim, wherein the second fluid flow is a liquid flow.

19. 19. A heat exchanger according to any preceding claim, wherein the housing and the internal member are integrally formed with one another.

20. 20. A method of manufacturing a heat exchanger according to any one of claims 1 to 19, the method comprising simultaneously forming the housing and the internal member through an additive manufacturing process.

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