Heat exchanger and manufacturing method thereof

Abstract

1. A cross-flow heat exchanger constructed by an additive manufacturing process that defines a build direction, the heat exchanger having a core with fluid tubes extending in a first direction for carrying a first working fluid therethrough, the heat exchanger core having a plurality of heat exchange fins extending from the fluid tubes, the fins being substantially planar, parallel to one another and transverse to the first direction, and spaces between the fins allowing a second working fluid to flow therebetween, in use, in a second direction orthogonal to the first direction.

Description

[Technical Field]

[0001] The present invention relates to heat exchangers. In particular, a crossflow heat exchanger is disclosed herein. [Background technology]

[0002] The purpose of a heat exchanger is to transfer heat between two or more separate streams of working fluid. Depending on the relative flow direction of each working fluid, heat exchangers can be broadly categorized into several types. In a crossflow heat exchanger, the working fluids flow in directions perpendicular to each other. This contrasts with a counterflow heat exchanger, in which the working fluids flow in parallel, opposite directions to each other. The perpendicular flow directions in a crossflow heat exchanger allow for a simplified design of the ductwork and manifolds that direct the fluids to the heat exchanger core.

[0003] For a given application, a heat exchanger may be required to have a particular heat exchange capacity (or exchange rate) that meets the demands of that application. There are several other performance and design factors that may be optimized or taken into account when configuring a heat exchanger. For example, high performance applications may require the heat exchanger to be as compact as possible.

[0004] Fabricating a crossflow heat exchanger using conventional manufacturing techniques can be a labor-intensive process, requiring multiple stages of joining and brazing fins, tubes, end plates, and manifolds to form the final assembly. Conventional techniques also risk mechanical integrity issues in the joining / brazing areas and are limited in the core geometries that can be produced. Furthermore, the thermal performance of a heat exchanger is derived from its core geometry, and the shape and dimensions of the fins and tubes within a heat exchanger core significantly impact its ability to transfer heat. To optimize for minimum size, heat exchanger cores should have a high surface area density. As heat exchanger core features become smaller and more densely packed, they become more difficult to reliably manufacture using conventional manufacturing techniques.

[0005] Additive manufacturing techniques can be used to create more sophisticated geometries in heat exchanger cores than are feasible using traditional manufacturing methods. Because additive manufacturing can create high-resolution geometries, through careful design, it provides a means to manufacture heat exchanger cores with high compactness. However, additive manufacturing has its own unique considerations, including constraints and limitations that must be taken into account when designing and manufacturing heat exchanger cores. Summary of the Invention

[0006] According to one aspect of the invention there is provided a cross-flow heat exchanger constructed by an additive manufacturing process which defines a build direction, the heat exchanger having a core with fluid tubes extending in a first direction for carrying a first working fluid therethrough, the heat exchanger core having a plurality of heat exchange fins extending from the fluid tubes, the fins being substantially planar, parallel to one another and transverse to the first direction, the spaces between the fins allowing a second working fluid to flow therebetween, in use, in a second direction orthogonal to the first direction.

[0007] Embodiments of the present invention preferably have substantially all surfaces with an angle relative to the build direction axis that allows the heat exchanger to be constructed in an upright (vertical) orientation.

[0008] In some embodiments of the heat exchanger core, substantially all surfaces have a relatively small angle, for example, a predetermined angle or less, with respect to the build direction axis.

[0009] In an aspect of the invention, the fluid conduit has a cross-section with an elongated dimension parallel to the second direction, and the fluid conduit includes turbulence-inducing internal structures designed to disrupt or attenuate laminar flow of the first working fluid for better heat transfer.

[0010] In some embodiments of the present invention, the fluid conduits are arranged in multiple rows, with the positions of the fluid conduits in adjacent rows being staggered. Fins may extend between the fluid conduits within a row, with each row of fluid conduits having multiple rows of fins. The fins in adjacent rows are preferably staggered relative to one another in the first direction. Microfins may be provided extending between adjacent rows of fins, with the microfins having a planar dimension oriented transverse to the fins. The fins may be formed with a pattern or mesh of openings therethrough to increase surface area, reduce material, and promote mixing of the second working fluid. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view showing a heat exchanger according to one embodiment of the present invention. [Figure 2] FIG. 2 shows the heat exchanger in an orthogonal view. [Figure 3] FIG. 3 is a side view of the heat exchanger. [Figure 4] FIG. 4 shows a cross section taken along line AA in FIG. [Figure 5] FIG. 5 shows an enlarged view of region B in FIG. [Figure 6] FIG. 6 is an enlarged view of the fin structure of the heat exchanger core. [Figure 7] FIG. 7 is an end view of the heat exchanger. [Figure 8] FIG. 8 shows a cross section taken along line CC in FIG. [Figure 9] FIG. 9 shows an enlarged view of region D in FIG. [Figure 10] FIG. 10 is an end view of the heat exchanger. [Figure 11] FIG. 11 shows an E-E cross section of FIG. [Figure 12] FIG. 12 shows an enlarged view of region F in FIG. [Figure 13] FIG. 13 is a perspective view of a portion of a heat exchanger core showing the arrangement of fins and conduits therein. [Figure 14] FIG. 14 is a perspective view of a portion of a heat exchanger core showing the arrangement of fins and conduits therein. [Figure 15] FIG. 15 shows the internal structure of the heat exchanger conduits. [Figure 16] FIG. 16 illustrates schematically the inclusion of support structures for predetermined features in an additively manufactured item. [Figure 17] FIG. 17 is a plan view showing the region J in FIG. [Figure 18] FIG. 18 shows the cross section GG shown in FIG. [Figure 19] FIG. 19 shows the HH cross section shown in FIG. [Figure 20] FIG. 20 shows the KK cross section shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] The invention may be better understood from the following description of embodiments thereof, given by way of example only and made with reference to the accompanying drawings, in which: A crossflow heat exchanger according to one embodiment of the present invention is described herein. The detailed description uses numerical and letter references to designate features in the drawings. Like or similar references in the drawings and description are used to designate like or similar parts of the heat exchanger.

[0013] The terms "first," "second," and "third" may be used interchangeably herein to distinguish one component from another, without any intention to denote the location or importance of the individual components. The terms "upstream" and "downstream" refer to the relative direction of fluid flow in a fluid pathway. For example, "upstream" refers to the direction from which fluid flows, and "downstream" refers to the direction to which fluid flows.

[0014] As used herein, a "fluid" may be a gas or a liquid. Indeed, for heat exchangers designed to operate with first and second working fluids, the two fluids may be in different states during operation, such as one gas and the other liquid. For example, in one application, the cooling fluid is air (in its gaseous state) and the cooled fluid is water (in its liquid state). However, the underlying principles of the present invention may be used to create heat exchangers adapted for different types of liquid and gaseous fluids, where the cooled and cooling fluids are the same or different fluids. Other examples of cooled and cooling fluids include oil, fuel, hydraulic fluid, combustion gases, refrigerants, refrigerant mixtures, dielectric fluids for cooling avionics or other avionics systems, water, aqueous compounds, water mixed with antifreeze additives (e.g., alcohols or glycol compounds), and other organic or inorganic heat transfer fluids or fluid mixtures that enable sustained heat transfer at high or low temperatures.

[0015] A heat exchanger 10 ( FIG. 1 ) and a method for manufacturing the heat exchanger are disclosed. The heat exchanger core includes a plurality of fluid conduits and an array of heat transfer fins designed to be produced using additive manufacturing methods, but generally, the disclosed heat exchanger 10 can be manufactured or formed using any suitable process. However, in accordance with certain aspects of the present subject matter, the heat exchanger 10 can be formed using an additive manufacturing process, such as a 3D printing process. Using such a process, the heat exchanger 10 may be integrally formed as a single, unitary component, as described herein in accordance with exemplary embodiments. In particular, the manufacturing process may enable the heat exchanger 10 to be integrally formed and include various features not possible using previous manufacturing methods.

[0016] As used herein, the terms "additively manufactured" or "additive manufacturing technique or process" refer to a manufacturing process in which successive layers of material are typically applied to one another to "build up" a three-dimensional component layer by layer. The successive layers typically fuse to form a unified component that includes various integral subcomponents. Additive manufacturing techniques are described herein as enabling the production of complex objects by building the object, typically vertically, point by point, layer by layer, although other manufacturing methods are possible and within the scope of the present subject matter.

[0017] An exemplary additive manufacturing process is described herein. The additive manufacturing process uses three-dimensional (3D) information, such as a three-dimensional computer model, of the component to manufacture the component. Accordingly, a three-dimensional design model of the heat exchanger 10 may be defined prior to manufacturing. In this regard, a model of the heat exchanger 10 may be constructed by defining the three-dimensional design model of the heat exchanger 10 using an appropriate computer-aided design (CAD) program. As another example, a model or prototype of the heat exchanger may be scanned to determine the three-dimensional information of the heat exchanger 10.

[0018] The design model may include data such as 3D numerical coordinates of the overall configuration of the component, including both the exterior and interior surfaces of the heat exchanger 10. For example, the design model may define the exterior housing, heat exchange features, internal fluid flow paths or circulation conduits, fins, openings, support structures, etc. Depending on the additive manufacturing process utilized, the 3D design model may be converted into multiple slices or segments, for example, along the central (e.g., vertical) axis of the component or any other suitable axis. Each slice may define a two-dimensional (2D) cross-section of the component for a given height of the slice. Multiple consecutive 2D cross-sectional slices collectively form the 3D component. Thus, the component is "built up" slice-by-slice or layer-by-layer to completion.

[0019] In this manner, the heat exchanger 10 is manufactured using an additive process, i.e., more specifically, each layer is formed sequentially, for example, by using laser energy or heat to melt metal powders or by fusing or polymerizing plastics. For example, certain types of additive manufacturing processes may use an energy beam, e.g., an electron beam or electromagnetic radiation such as a laser beam, to sinter or melt powder materials. Appropriate lasers and laser parameters may be used, taking into consideration power, laser beam spot size, and scanning speed. The build material may be formed from appropriate powders or materials selected for increased strength, durability, and service life, especially at elevated temperatures.

[0020] According to current additive manufacturing capabilities, each successive layer may be, for example, between about 10 μm and 200 μm thick; however, the thickness may be selected or determined based on multiple parameters and may be an appropriate size according to other embodiments. Therefore, by utilizing the additive manufacturing methods described above, the minimum feature size in the "build direction" may be considered to be as small as the thickness of one of the associated powder layers used during the additive manufacturing process. In the dimension transverse to the build direction, the minimum feature size is determined, at least in part, by the spot size of the laser beam. According to the limitations of current additive manufacturing capabilities, laser beam spot sizes in the range of about 40 μm to 80 μm may be envisioned. Therefore, the minimum size of any three-dimensional feature that can be formed using additive manufacturing may typically depend on both the layer thickness and the laser spot size.

[0021] As previously mentioned, to optimize the heat exchanger for minimum size, the heat exchanger core should have a high surface area density. This typically means that the features of the heat exchanger core will be smaller and more closely packed together. Thus, the constraints on the minimum manufacturable feature size imposed by the process parameters discussed above are relevant to the heat exchanger design and inform the designer of how small and closely packed the core features can be within manufacturable limits.

[0022] In addition to the primary process-related feature size constraints of layer thickness and energy beam spot size, other factors can affect the final shape of additively manufactured heat exchangers with fine features and tolerances. Depending on the build direction of the additively manufactured product, surfaces at certain angles will be smoother than surfaces at other angles. In other words, the build direction used to additively manufacture a particular item can affect how faithful a particular feature in the manufactured item actually is to the computer model design from which it was manufactured. Furthermore, unless process limitations are addressed, not all features that can be designed in a computer model are necessarily manufacturable. An example of this is shown in Figure 16, which illustrates how certain features and surfaces may require support structures (the arrow labeled Z indicates the additive manufacturing build direction). While additive manufacturing rules (dfAM) typically dictate that support structures should be included to support overhanging features whose surface angle with respect to the build platform is less than approximately 45 degrees (the build platform is perpendicular to the build direction), certain additive manufacturing machines, processes, and / or materials may allow for the building of surfaces that are "flatter" than 45 degrees, albeit with a rougher downskin. After the additive manufacturing process is complete, the support structures must be removed (e.g., manually). While this is possible for the exterior surfaces of the product, removing the support structures may be infeasible if they are included in the internal structure of the product, which is inaccessible.

[0023] The embodiments of the invention disclosed herein are designed with these process constraints in mind. Printing the heat exchanger core geometry in a vertical (upright) orientation results in the most compact core and fin geometry with the highest dimensional accuracy, as vertical printing reduces downward-facing surfaces, allowing the lowest minimum feature distances to be achieved. However, there are other challenges associated with manufacturing crossflow heat exchanger cores in a vertical build orientation, which are addressed by the heat exchanger designs disclosed herein. To this end, as will be understood from the following description, substantially all surfaces of a heat exchanger core according to embodiments of the invention are angled relative to the build direction axis, allowing the heat exchanger to be built in a vertical orientation, thus eliminating the need for additional support structures.

[0024] As shown in the drawings, a heat exchanger 10 according to an exemplary embodiment of the invention has a generally rectangular prism-shaped exterior having three sets of opposing sides. Two sides are closed by shrouds 12. The heat exchanger 10 operates in a cross-flow configuration, with first and second working fluids passing through the heat exchanger core in intersecting, orthogonal directions. The first working fluid, which may be a liquid coolant, enters the heat exchanger 10 through an inlet opening 40 formed in one end face 30 in the direction indicated by arrow 16. Corresponding outlet openings are provided in the opposite end face 32, through which the coolant exits the heat exchanger in the direction indicated by arrow 17. The corresponding coolant inlet and outlet openings are interconnected by conduits extending through the heat exchanger core to carry the coolant fluid.

[0025] The upper and lower surfaces 52, 50 of the heat exchanger 10 are open to allow a second working fluid (e.g., air) to flow into and out of the heat exchanger core in the directions indicated by arrows 18, 19. The directions of bulk fluid flow of the first and second working fluids within the heat exchanger core are substantially perpendicular to one another.

[0026] The conduits 45 that carry the first working fluid through the heat exchanger core are thin-walled features that are elongated in the dimension parallel to the flow direction of the second working fluid and narrow in other transverse dimensions (FIG. 4). They are arranged in multiple rows (e.g., 46, 47), each row extending side-to-side and having multiple conduits 45. The positions of the conduits 45 in adjacent rows are offset from one another in a staggered arrangement.

[0027] The core of the heat exchanger 10 is provided with an array of fins 60, extending across the width of the core from one sidewall 12 to the other and interconnecting the conduits 45. The fins 60 are arranged parallel to one another with gaps between them to allow the flow of the second working fluid. The fins 60 are also arranged in a series of rows (e.g., 61, 62) extending side-to-side across the core of the heat exchanger 10. In the illustrated embodiment, there are two rows of fins for each row of conduits. The fins in adjacent rows are offset from one another in a staggered arrangement, with the fins in one row aligned with the gaps between the fins in the next row.

[0028] A close-up of the fins 60 and conduits 45 is shown in FIG. 6, revealing their detailed structure. A set of fins 60 extends between adjacent conduits 45, or, for fins at the ends of the heat exchanger core, between the conduits 45 and the heat exchanger sidewall. Two individual fins 60A and 60B are highlighted, from which it can be seen that each fin 60 is formed in a chevron shape, with a central peak at its top end and a complementary angled depression at its bottom end. The top and bottom ends of the fins 60 thus form a sawtooth pattern across the width of the heat exchanger core, and these ends are unsupported except for the inclusion of lateral gap microfins 75, which provide additional structure and support between the fins and the conduits across adjacent fins 60 in the core array. The support microfins 75 are positioned so that a set of fins 60 faces each other, but the microfins are oriented perpendicular to the orientation of the fins 60. The micro-fins 75 also have a substantially chevron-shaped structure.

[0029] The arrangement and structure of the fins 60 and conduits 45 are designed to promote mixing of the fluid flow through the heat exchanger core to increase heat transfer. As the second working fluid passes through the heat exchanger from its inlet (through the openings in face 50) to its outlet (through the openings in face 52), the staggered arrangement of the fins 60 forces the fluid to find new paths between each row of fins. The staggered arrangement of the conduits works in a similar way. The chevron shape of the fins is also designed to promote mixing of the fluid flow through vortex generation behind the leading and trailing ends of the fins. Furthermore, the fins 60 of the heat exchanger 10 are formed with a repeating pattern or mesh of diamond-shaped holes 69 therethrough, as shown in FIG. 6 . The holes 69 in the fins 60 increase the surface area of the fins while reducing the amount of material required to manufacture them. This allows for a reduction in the weight of the fins and also promotes mixing of the fluid flow as the second working fluid passes through the heat exchanger core.

[0030] Conduit 45 also includes internal structures 80 called "turbulators" (best seen in FIGS. 14 and 15) that are designed to improve heat transfer between the first working fluid and the fins by disrupting the laminar flow of the first working fluid within the conduit. Turbulators 80 include diamond-shaped partitions within conduit 45 that are staggered periodically along the length of the conduit to mix the first working fluid as it passes through the heat exchanger core. FIG. 15 shows two lengths of staggered turbulator partitions, excluding the outer wall of the conduit.

[0031] FIG. 17 is a plan view of the schematic portion 'J' of FIG. 13, and FIGS. 18-20 are cross-sectional views through the heat exchanger core, designated GG, HH, and KK, respectively, in FIG. 17. These figures show details of the internal structure of the heat exchanger core, including the cooling tubes (conduits) 45 with turbulators 80, the staggered air-side fins 60, the fin support fins 75A, and the tube support fins 75B. Notably, in this embodiment, the tube support fins 75B, which provide structural support between the air-side fins 60 and the walls of the conduits 45, are enlarged to potentially contribute to improved heat transfer and fluid flow within the heat exchanger core. In addition to providing structure, these enlarged micro-fins also function as heat transfer surfaces in the x-direction, whereas most heat transfer surfaces (e.g., fins 60) extend in the z-direction. The tube support fins 75B effectively function like fins oriented in the x-direction, promoting heat transfer from the hottest regions of the cooling tubes (conduits). Unlike z-oriented heat transfer surfaces which create localized accelerations of the flow, they are oriented in the flow direction, with little penalty in pressure drop. They also help prevent the formation of fluid wakes / separation regions behind the coolant tubes when in use.

[0032] Although the heat exchanger 10 is configured so that the coolant flows unidirectionally through the heat exchanger core, it is also possible to provide manifolds at one or both ends of the heat exchanger to redirect the coolant from one conduit to another, achieving a multi-pass configuration.

[0033] It is notable that, in the exemplary embodiment, some features of the heat exchanger 10 were previously not possible due to manufacturing constraints. However, the inventors have effectively utilized current advances in additive manufacturing technology to develop exemplary embodiments of the heat exchanger 10 generally in accordance with the present disclosure. While the present disclosure is not generally limited to the use of additive manufacturing to form the heat exchanger 10, additive manufacturing offers various manufacturing advantages, including ease of manufacture, reduced cost, greater accuracy, etc.

[0034] In this regard, by utilizing additive manufacturing, the heat exchanger 10 may be a single piece of continuous metal and, therefore, may include fewer components and / or joints than known heat exchangers. The integral formation of the heat exchanger 10 through additive manufacturing may advantageously improve the overall assembly process. For example, integral formation reduces the number of separate parts that must be assembled, thus reducing the associated time and overall assembly costs. Additionally, existing issues with, for example, leaks, joint quality between separate parts, and overall performance may be advantageously reduced.

[0035] The additive manufacturing methods described above also enable more complex and intricate shapes and contours for the heat exchanger 10. For example, the heat exchanger 10 may have thin walls, narrow passages, and novel heat exchange features. All of these features may be relatively complex and intricate to maximize heat transfer and minimize the size or footprint of the heat exchanger 10. Additionally, additive manufacturing processes enable the fabrication of structures having different materials, specific heat transfer coefficients, or desired surface textures that, for example, promote or restrict fluid flow through the passages. The continuous, additive nature of the manufacturing process enables the configuration of these passages and features. As a result, the performance of the heat exchanger 10 may be improved relative to other heat exchangers.

[0036] Suitable additive manufacturing techniques according to the present disclosure include, for example, laser powder bed fusion (LPBF), selective laser melting (SLM), and direct metal laser melting (DMLM).

[0037] The additive manufacturing processes described herein can be used to form components using suitable materials. For example, the materials can be plastic, metal, concrete, ceramic, polymer, epoxy, photopolymer resin, or other suitable materials that can be in a solid, liquid, powder, sheet material, wire, or other suitable form. More specifically, according to exemplary embodiments of the present subject matter, the heat exchanger 10 can be formed from some, all, or some combination of materials, including, but not limited to, pure metals, nickel alloys, chromium alloys, titanium, titanium alloys, magnesium, magnesium alloys, aluminum, aluminum alloys, and austenitic alloys such as nickel-chromium based superalloys.

[0038] Additionally, those skilled in the art will understand that a variety of materials and methods for joining those materials may be used and are contemplated within the scope of the present disclosure. As used herein, references to "fusing" may refer to any suitable process for forming a bonded layer of any of the above materials. For example, if the object is made of polymers, fusing may refer to creating a thermosetting bond between the polymeric materials. If the object is an epoxy, the bond may be formed by a crosslinking process. If the material is a ceramic, the bond may be formed by a sintering process. If the material is a powder metal, the bond may be formed by a melting process. Those skilled in the art will understand that other methods of fusing materials to produce components by additive manufacturing are possible and the presently disclosed subject matter may be practiced with those methods.

[0039] Additionally, the additive manufacturing processes disclosed herein enable the formation of a single component from multiple materials. Thus, the heat exchanger 10 may be formed from an appropriate mixture of the above materials. For example, a component may include multiple layers, segments, or portions formed with different materials, processes, and / or different additive manufacturing equipment. In this manner, components with different materials and material properties may be constructed to meet the needs of a particular application. Additionally, while the heat exchanger 10 is described above as being constructed entirely by an additive manufacturing process, it should be understood that in alternative embodiments, portions of the heat exchanger 10 may be formed via casting, machining, and / or other suitable manufacturing processes. Indeed, any appropriate combination of materials and manufacturing methods may be used to form the heat exchanger 10.

[0040] While various embodiments of the present invention have been described above, it should be understood that these are provided by way of example, not by way of limitation. It will be apparent to those skilled in the art that various changes in form and detail can be made herein without departing from the spirit and scope of the invention. Therefore, the present invention should not be limited by any of the exemplary embodiments described above.

[0041] Any reference in this specification to any prior publication (or information derived therefrom) or to any prior art should not be treated as an admission or acknowledgement, or as a form of suggestion, that the prior publication (or information derived therefrom) or prior art forms part of the common general knowledge in the field of endeavor to which this specification pertains.

[0042] 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.

Claims

1. 1. A cross-flow heat exchanger constructed by an additive manufacturing process that defines a build direction, the heat exchanger having a core with fluid tubes extending in a first direction for carrying a first working fluid therethrough, the heat exchanger core having a plurality of heat exchange fins extending from the fluid tubes, the fins being substantially planar, parallel to one another and transverse to the first direction, and spaces between the fins allowing a second working fluid to flow therebetween, in use, in a second direction orthogonal to the first direction.

2. 10. The heat exchanger of claim 1, wherein substantially all surfaces are angled relative to a build direction axis to allow the heat exchanger to be constructed in an upright (vertical) orientation.

3. 3. The heat exchanger of claim 1, wherein substantially all surfaces of the heat exchanger core form a relatively small angle with respect to the build direction axis.

4. The heat exchanger of claim 3 , wherein substantially all surfaces of the heat exchanger core are angled relative to the build direction axis at an angle less than or equal to the predetermined angle.

5. 5. A heat exchanger according to any preceding claim, wherein the fluid conduit has a cross section with an elongated dimension parallel to the second direction.

6. 8. A heat exchanger according to any one of claims 1 to 7, wherein the fins are narrow and closely spaced relative to the limitations of additive manufacturing processes.

7. 7. A heat exchanger according to any one of claims 1 to 6, wherein the fins have a chevron shape.

8. 8. The heat exchanger according to claim 1, wherein the fluid tubes are arranged in a plurality of rows, and the positions of the fluid tubes in adjacent rows are staggered.

9. The heat exchanger of claim 8 , wherein the fins extend between the fluid tubes in the row.

10. 10. The heat exchanger of claim 9, wherein each row of fluid tubes has a plurality of rows of fins.

11. 11. A heat exchanger according to claim 9 or claim 10, wherein the fins extending between the fluid tubes of adjacent rows are staggered relative to one another in the first direction.

12. The heat exchanger of claim 11 , wherein adjacent rows of fins are staggered relative to each other in the first direction.

13. 12. A heat exchanger according to any one of claims 9 to 11, wherein micro-fins are provided extending between adjacent rows of fins, the micro-fins having planar dimensions oriented transverse to the fins.

14. 14. A heat exchanger according to any preceding claim, wherein the fluid conduit comprises an internal structure that induces turbulence.

15. 15. A heat exchanger according to any preceding claim, wherein the fins are formed with a pattern or mesh of openings therethrough.

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