HEAT EXCHANGER CORE GEOMETRIES USED AS SUPPORT MATERIAL AND FLUID CONNECTIVITY PASSAGES FOR HEAT EXCHANGER HEADERING

A fluid circuit of a heat exchanger includes a core and a first header. The core is configured to receive a fluid and includes a plurality of conduits. Each of the plurality of conduits extends along a longitudinal axis from a first end portion to a second end portion. The first header is integrally formed with and fluidly connecting the plurality of conduits. Outer walls of the plurality of conduits taper outward relative to the longitudinal axes to join the first header.

BACKGROUND

The present disclosure is directed generally to heat exchangers and more particularly to wall structure for additively manufactured heat exchangers.

Heat exchangers are most efficient when their core length is maximized since the majority of heat transfer occurs in this region. Consequently, if header sections of a heat exchanger can be reduced in size while maintaining the overall footprint of the heat exchanger, the heat exchanger can have improved performance. Multipass heat exchangers are used to increase thermal length of the heat exchanger while maintaining a compact footprint. Multipass heat exchangers, for example, require turnaround tanks or headers to redirect flow from a first pass to a second pass. Turnaround headers are traditionally manufactured as separate components and welded or assembled onto a heat exchange core. Post processing steps such as machining, welding, and inspection are typically required when additional components are needed to complete an assembly. Weld joints and additional supporting and/or joining structures often increase the footprint of the heat exchanger and/or reduce the effective size or length of the core.

SUMMARY

In one embodiment, this disclosure presents a fluid circuit of a heat exchanger. This fluid circuit includes a core and a first header. The core is configured to receive a fluid and includes a plurality of conduits. Each of the plurality of conduits extends along a longitudinal axis from a first end portion to a second end portion. The first header is integrally formed with and fluidly connecting the plurality of conduits. Outer walls of the plurality of conduits taper outward relative to the longitudinal axes to join the first header.

While the above-identified figures set forth embodiments of the present invention, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the invention. The figures may not be drawn to scale, and applications and embodiments of the present invention may include features, steps and/or components not specifically shown in the drawings.

DETAILED DESCRIPTION

The present disclosure is directed to a heat exchanger geometry that includes integrally formed headers or turn-around tanks. As disclosed herein, a self-supporting turn-around tank or header can be integrally formed with a heat exchange core via additively manufacturing using heat exchanger core passages as support material in the header. The disclosed heat exchanger can provide efficient heat exchange in a smaller footprint than traditional heat exchangers formed by assembling separate core and header components. Furthermore, the disclosed method of manufacture can reduce or eliminate post processing steps such as machining, welding, and inspection required with traditional manufacturing methods.

FIG.1is front view of a multipass heat exchanger fluid circuit.FIG.2is an isometric view of the multipass heat exchanger fluid circuit ofFIG.1.FIG.3is side view of the multipass heat exchanger fluid circuit ofFIG.1.FIG.4is a cross-sectional view of the multipass heat exchanger fluid circuit taken along the4-4line ofFIG.1.FIG.5is a top view of the multipass heat exchanger fluid circuit ofFIG.1.FIG.6is a cross-sectional view of the multipass heat exchanger fluid circuit taken along the6-6line ofFIG.5.FIGS.1-6are discussed together herein.

Fluid circuit10, inlet12, outlet14, core16, first header18, second header20, inner walls22and24, outer walls26and28, conduits30(including first pass conduits30A, second pass conduits30B, and third pass conduits30C), first end portions32, second end portions34, tapered portions36A,36B, and46A, narrowed portions38and40, apertures42,44, fillets46A,46B, and46C, build platform50, build direction52, build angles θA, θB, and θC, lengths L1, L3of inner walls22and24, length L2of outer wall26, lengths LH of first and second headers18and20, and length LC of core16are shown. Fluid flow through inlet12, outlet14, core16, and first and second headers18and20is shown by arrows. Dashed arrows indicate flow through conduits30. Solid arrows indicate flow in first and second headers18and20.

Fluid circuit10forms a portion of a multipass heat exchanger in which a first fluid received in conduits30is made to flow multiple times through a second fluid that flows between conduits30in core16before exiting. Thermal energy is transferred between the first fluid and the second fluid in each pass. Fluid circuit10can be, for example, a fluid circuit in a shell and tube type heat exchanger in which a body surrounds fluid circuit10to define a second fluid circuit.

Fluid circuit10includes inlet12, outlet14, core16, first header18, and second header20. Inlet12is configured to receive a fluid and outlet14is configured to discharge the fluid from fluid circuit10. Core16is disposed in fluid communication with inlet12and outlet14. Core16receives fluid from inlet12and discharges fluid to outlet14. Core16includes a plurality of conduits30configured to conduct the fluid, for example, between inlet12and first header18, between first and second headers18and20, and between second header20and outlet14.

As illustrated inFIG.1, the plurality of conduits30can be arranged in first, second, and third passes. Each pass can include a subset of the total conduits30. First pass conduits30A are arranged to transfer the fluid from inlet12to first header18. Second pass conduits30B are arranged to transfer the fluid from first header18to second header20. Third pass conduits30C are arranged to transfer the fluid from second header20to outlet14. First and second headers18and20are turnaround tanks. First header18is configured to direct fluid received from first pass conduits30A to second pass conduits30B. Second header20is configured to direct fluid received from second pass conduits30B to third pass conduits30C.

In alternative embodiments, fluid circuit10can include less than three passes or more than three passes. Inlet12and outlet14can be located on the same end of conduits30or can be located on opposite ends of conduits30depending on the number of passes provided in fluid circuit10. Two-pass heat exchangers include a single header. Multipass heat exchangers having more than three passes include three or more headers for redirecting fluid flow.

Conduits30extend in a lengthwise direction indicated by core length LC and header lengths LH. Each conduit30extends along a longitudinal axis A (shown inFIGS.1and4) disposed perpendicular to build plate50. Conduits30are arranged parallel to each other.

First and second headers18and20include inner walls22and24, respectively, Inner walls22and24are innermost walls of first and second headers18and20relative to the longitudinal axes of conduits30. First and second headers18and20include outer walls26and28, respectively. Outer walls26and28form outermost walls of first and second headers18and20relative to the longitudinal axes of conduits30. Inner walls22and24are integrally formed with outer walls26and28, respectively, and with conduits30.

First pass conduits30A can be joined at inlet12. Third pass conduits30C can be joined at outlet14. Inlet12and outlet14can have a branching configuration, in which a fluid flow is divided among a plurality of first pass conduits30A and third pass conduits30C, respectively.

First and second pass conduits30A and30B extend fully to outer wall26of first header18. Second and third pass conduits30B and30C extend fully to outer wall28of second header20. As shown inFIGS.4and6, first and second pass conduits30A and30B are joined to inner wall22outside of first header18by tapered portions36A. First and second pass conduits30A and30B are joined to outer wall26inside first header18by tapered portions36B. First and second pass conduits30A and30B can be joined to inner wall22inside first header18by fillet46A as shown inFIG.4. Second and third pass conduits30B and30C can be joined to inner wall24outside of second header20by fillet46B. Second and third pass conduits30B and30C are joined to inner wall24inside second header20by tapered portions36C. Second and third pass conduits30B and30C can be joined to outer wall28inside second header20by fillets46C.

Joining portions of conduits30are referred to herein as end portions. First pass conduits30A include first end portions32. Second pass conduits30B include first end portions32and oppositely disposed second end portions34. Third pass conduits include second end portions34. As further described herein, first end portions32and second end portions34support the integral formation of first and second headers18and20, respectively, during a build process. First header18is integrally formed with a fluidly connecting first end portions32of first and second pass conduits30A and30B. First end portions32of first and second pass conduits30A and30B extend into first header18. First and second pass conduits30A and30B are open to first header18. First end portions32of first and second pass conduits30A and30B include a plurality of apertures42to transfer the fluid to and from first header18. Second header20is integrally formed with and fluidly connecting second end portions34of second and third pass conduits30B and30C. Second end portions34of second and third pass conduits30B and30C extend into second header20. Second and third pass conduits30B and30C are open to second header20. Second end portions34of second and third pass conduits30B and30C include a plurality of apertures44to transfer fluid to and from second header20.

Conduits30can include tubes of cylindrical shape as illustrated. In alternative embodiments, conduits30can have other shapes designed to optimize thermal energy transfer and/or fluid dynamics. For example, fluid circuit10can include conduits of rectangular shape. In alternative embodiments, conduits30may have a corrugated shape.

Conduits30can be arranged in multiple rows as illustrated inFIGS.2,3,4and6. Conduits30in one row can be offset relative to conduits30in an adjacent row to form a convoluted flow path for the second fluid circuit of the heat exchanger. Each pass includes a plurality of conduits30(i.e., first pass conduits30A, second pass conduits30B, and third pass conduits30C). The number of conduits30in each pass and/or in each row and the number of rows of conduits30is not limited to the embodiment shown. It will be understood by one of ordinary skill in the art that the number, shape, and arrangement of conduits30can vary based on the heat exchanger application.

First end portions32of first and second pass conduits30A and30B include tapered portions36A and36B. In some embodiments, first end portions32can additionally include tapered portions in place of fillet46A. Conduit walls in first end portions32taper outward from first and second pass conduits30A and30B in tapered portions36A to join core16to first header18. Conduit walls in tapered portions36A are angled relative to first and second pass conduits30A and30B (i.e., portion of conduits30extending between first end portions32and second end portions34). As described further herein, tapered portions36A extend at a build angle θA relative to build platform50. A minimum build angle θA can be determined by the capability of the additive manufacturing process. Build angle θA can be, for example, equal to or greater than 45 degrees. Build angle θA can be selected to reduce length L1of inner wall22such that inner wall22is supported by tapered portions36A during the build process and such that inner wall22does not require additional supports as described further herein.

Conduit walls in first end portions32taper outward to join inner wall22outside of first header18(within core16). Inner wall22is disposed substantially perpendicular to conduits30. Inner wall22can have a curved shape. Inner wall22separates core16from first header18. Tapered portions36A are disposed in core16and thereby in thermal communication with the second fluid provided to fluid circuit10. Tapered portions36A extend fully around conduits30. For cylindrical conduits, tapered portions36A can have a frustoconical shape. The shape of tapered portions36A can vary in alternative embodiments depending on the shape of conduits30.

Flow passages through conduits30can retain a cylindrical (or other) shape through tapered portions36A, such that conduit walls are thickened in tapered portions36A as shown inFIGS.4and6.

First and second pass conduits30A and30B can be arranged and tapered portions36A can be designed to minimize length L1of inner wall22. Length L1is distance measured between adjacent tapered portions36A. Length L1can be substantially uniform around each tapered portion36A or can vary. As described further herein, length L1can be up to a maximum length allowed by an additive manufacturing process without supporting material.

A thickness of inner wall22can be selected to provide structural integrity of first header18while minimizing a contribution to the overall weight of fluid circuit10.

First end portions32include narrowed portions38. Narrowed portions38are segments of or extensions of conduits first and second pass conduits30A and30B disposed in core16. Narrowed portions38can have a shape substantially the same as the shape of first and second pass conduits30A and30B in core16. In some embodiments, narrowed portions38can extend from inner wall22toward outer wall26of first header18. Narrowed portions38can be joined to inner wall22by fillets46A. In other embodiments, tapered portions can extend from inner wall22to narrowed portions38.

Narrowed portions38include apertures42. Each narrowed portion38can include a plurality of apertures42. Apertures42in first pass conduits30A can provide substantially radial discharge of the fluid from first pass conduits30A in first header18. Apertures42in second pass conduits30B are configured to receive fluid from first header18. Apertures42in second pass conduits30B can be substantially the same as apertures42in first pass conduits30A. Apertures42can be offset along a length of narrowed portions38and/or apertures42can be offset about a circumference or perimeter of narrowed portions38. Each narrowed portion38can include, for example, six apertures as shown inFIG.4. In alternative embodiments, more than six or fewer than six apertures can be provided in each narrowed portion38. Apertures42can have any shape. The shape of apertures42is not limited to the oval shape shown inFIGS.4and6. The number, size, location, and/or shape of apertures42can be selected to reduce pressure loss in transfer of the fluid from first pass conduits30A to first header18.

Tapered portions36B extend from narrowed portions38to outer wall26of first header18within first header18. Walls of tapered portions36B taper outward from narrowed portions38to outer wall26of first header18. As described further herein, tapered portions36B extend at build angle θB. A minimum build angle θB can be determined by the capability of the additive manufacturing process. Build angle θB can be, for example, equal to or greater than 45 degrees. Build angle θB can be minimized to reduce length LH of first header18and maximize length LC of core16for a given footprint. As shown inFIG.2, build angle θB of tapered portions36B can be less than build angle θA of tapered portions36A to reduce the length LH of header18. Tapered portions36B can be substantially solid as shown, for example, inFIGS.4and6or can include a flow passage or portion of a flow passages substantially matching a cylindrical (or other) shape of the flow passage through narrowed portions38.

For cylindrical conduits, tapered portions36B can have a frustoconical shape. The shape of tapered portions36B can vary in alternative embodiments depending on the shape of conduits30.

Tapered portions36B can be designed to minimize length L2of outer wall26, shown inFIGS.4and6. Length L2is distance measured between adjacent tapered portions36B. Length L2can be substantially uniform around each tapered portion36B or can be non-uniform as shown by comparingFIGS.4and6, depending, for example, on the arrangement of conduits30. As shown inFIG.4, tapered portions36B of adjacent conduits30arranged front-to-back can meet at an angle such that L2is equal to approximately zero. As shown inFIG.6, tapered portions36B of adjacent conduits30arranged side-to-side can meet at outer wall26having a length L2greater than zero. As described further herein, length L2can be up to a maximum length allowed by an additive manufacturing process. Length L2can be equal to length L1of inner wall22. L2can vary depending on build angle θB of tapered portions36B.

A thickness of outer wall26can be selected to provide structural integrity of first header18while minimizing a contribution to the overall weight of fluid circuit10. Outer wall26and inner wall22are integrally formed. As such, no welding joints or fastening mechanisms are needed to secure outer wall26to inner wall22or to secure first header18to core16. Together outer wall26and inner wall22can have a domed or rounded shape, curving in extension to envelop end portions32. As further described herein, outer wall26and inner wall22are integrally formed as a unitary structure with first end portions32.

Second end portions34of second and third pass conduits include fillets46C, narrowed portions40, and tapered portions36C. Second and third pass conduits30B and30C can join inner wall24of second header20outside of second header20via fillet46B. Second end portions34, including tapered portions36C, narrowed portions40, fillet46C, and apertures44, are fully disposed in second header20. Conduit walls in second end portions34can be joined to outer wall28of second header20by fillet46C. Narrowed portions40extend from outer wall28or fillet46C toward inner wall24. Tapered portions36C connect narrowed portions40to inner wall24. Walls of tapered portions36C taper outward from narrowed portions40or inward from inner wall24, such that walls of tapered portions36C are angled relative to narrowed portions40. As described further herein, tapered portions36C extend at build angle θC. A minimum build angle θC can be determined by the capability of the additive manufacturing process. Build angle θC can be, for example, equal to or greater than 45 degrees. As previously with respect to tapered portions36B in header18, build angle θC of tapered portions36C can be minimized to reduce length LH of second header20and maximize a length of core16for a given footprint.

For cylindrical conduits, tapered portions36C can have a frustoconical shape. The shape of tapered portions36C can vary in alternative embodiments depending on the shape of conduits30.

Flow passages through conduits30B and30C can retain a cylindrical (or other) shape through tapered portions36C, such that conduit walls are thickened in tapered portions36C as shown inFIGS.4and6.

Conduits30B and30C can be arranged and tapered portions36C can be designed to minimize length L3of inner wall24. Length L3is distance measured between adjacent tapered portions36C. Length L3can be substantially uniform around each tapered portion36C or can vary depending on the arrangement of conduits30B and30C. As described further herein, length L3can be up to a maximum length allowed by an additive manufacturing process.

A thickness of inner wall24can be selected to provide structural integrity of second header20while minimizing a contribution to the overall weight of fluid circuit10.

Narrowed portions40are segments or extensions of second and third pass conduits30B and30C and can have a shape substantially similar to the shape of second and third pass conduits30B and30C in core16. Narrowed portions40include apertures44. Each narrowed portion40can include a plurality of apertures44. Apertures44in second pass conduits30B can provide substantially radial discharge of the fluid from second pass conduits30B in second header20. Apertures44in third pass conduits30C are configured to receive fluid from second header20and can be substantially the same as apertures44in second pass conduits30B. Apertures44can be offset along a length of narrowed portions40and/or apertures44can be offset about a circumference or perimeter of narrowed portions40. Each narrowed portion40can include, for example, six apertures as shown inFIG.6. In alternative embodiments, more than six or fewer than six apertures can be provided in each narrowed portion40A. Apertures44can have any shape. The shape of apertures44is not limited to the oval shape shown inFIGS.4and6. The number, size, location, and/or shape of apertures44can be selected to reduce pressure loss in transfer of the fluid from second pass conduits30B to second header20. The number, shape, and size of apertures44can be substantially the same as the number, shape, and size of aperture42.

A thickness of outer wall28can be selected to provide structural integrity of second header20while minimizing a contribution to the overall weight of fluid circuit10. Together outer wall28and inner wall24can have a domed or rounded shape, curving in extension to envelop end portions34. As such, no welding joints or fastening mechanisms are needed to secure outer wall28to inner wall24or to secure second header20to core16. As further described herein, outer wall28and inner wall24are integrally formed as a unitary structure with second end portions34.

Fluid circuit10can be formed using a powder bed fusion additive manufacturing process. Additive manufacturing processes include the ability to produce highly complex parts quickly and efficiently, and to modify design specifications of the desired part, for example by modifying CAD specifications, without re-tooling casting or machining equipment used for traditional, subtractive manufacturing processes.

Although the present figures depict a multipass heat exchanger, the tapered wall geometry presented herein can more broadly be applied to single pass heat exchangers with headers having internally connected fluid support features (i.e., fluid from multiple radial tubes can be collected in a common header). A single pass heat exchanger can include inlet and outlet plenum headers—one or both of which could have the disclosed tapered wall features.

FIG.1shows build platform50and build direction52. Fluid circuit10is designed to allow first header18and second header20to be integrally formed with core16. The integral formation of first header18and second header20can reduce an overall footprint of fluid circuit10and/or can elongate a heat exchange core16as compared to conventional heat exchangers that require weld joints and/or fasteners to assemble separate header inner and outer walls to the core. The lengths LH over which first header18and second header20extend from conduits30in core16can be reduced with integral formation of first and second headers18and20. As such, a length LC of conduits30in core16can be increased to provide additional heat exchange capacity without increasing an overall length of fluid circuit10as compared to conventional single pass and multipass heat exchanger designs. First end portions32and second end portions34support inner and outer walls22,26of first header18and support inner and outer walls24,28of second header20. A position of conduits30in first and second headers18and20remains fixed during operation of fluid circuit10and first and second headers18and20are sealed from a second fluid passing through core16. No brazing, welding, or other fastening or sealing mechanisms are needed to secure conduits30in fluid communication with and in a sealed relationship with first and second headers18and20.

As shown inFIG.1, fluid circuit10is built from inlet12toward outlet14. Outer wall28of second header20extends parallel to build platform50. Outer wall28can be curved around second end portions34toward inner wall24. Together outer wall28and inner wall24can have a domed or rounded shape, curving in extension to envelop end portions34. Narrow portions40(shown inFIG.4) can be formed directly on an inner surface of outer wall28. Narrow portions40can be joined to outer wall28by fillet46C. Narrowed portions40extend perpendicular to build platform50. Tapered portions36C are formed as an extension from narrowed portions40. Tapered portions36C are formed at build angle θC. A minimum build angle θC can be determined by the capability of the additive manufacturing process. Build angle θC can be, for example, equal to or greater than 45 degrees. A length of tapered portions36C or build angle θC can be selected to minimize the length L3of inner wall24between adjacent tapered portions36C, such that inner wall24is supported by tapered portions36C during the build process and such that inner wall24does not require additional supports, and to minimize length LH of second header20.

Conduits30extend perpendicular to build platform50. First pass conduits30A are formed from inlet12toward first header18. Second pass conduits30B are formed from inner wall24toward first header18. Third pass conduits30C are formed from inner wall24toward outlet14. First pass conduits30A and second pass conduits30B are joined to inner wall22outside of first header18by tapered portions36A. Tapered portions36A can be substantially the same as or similar to tapered portions36C and can be formed in substantially the same or similar manner. A length of tapered portions36A or build angle θA can be selected to minimize the length L1of inner wall22between adjacent tapered portions36A as previously described. Narrowed portions38(shown inFIG.4) can be formed on inner wall22inside first header18. Narrowed portions38can be joined to inner wall22by fillets46A. Narrowed portions38extend perpendicular to build platform50. Narrowed portions38are connected to outer wall26inside first header18by tapered portions36B. Tapered portions36B can be substantially the same as tapered portions36C and formed in substantially the same manner. A length of tapered portions36B or build angle θB can be selected to minimize the length L2of outer wall26between adjacent tapered portions36B and to minimize length LH of first header18. Inner wall22can curve around end portions32to join outer wall26. Together outer wall26and inner wall22can have a domed or rounded shape, curving in extension to envelop end portions32.

Fluid circuit10can be formed of any thermally conductive material suitable for the desired heat exchanger application and suitable for use in a powder bed fusion additive manufacturing process. Powder bed additive manufacturing processes can include but are not limited to selective laser sintering, selective laser melting, electron beam melting, and direct metal laser sintering.

The disclosed fluid circuit for a multipass heat exchanger is designed to provide self-supporting headers allowing for integral formation with a fluid circuit core. The disclosed fluid circuit is designed to reduce and/or eliminate post-processing steps, including assembly and welding and to increase an effective heat transfer length of core conduits to improve heat exchange capacity over conventional fluid circuit designs.

The embodiments disclosed herein are intended to provide an explanation of the present invention and not a limitation of the invention. The disclosed self-supporting features (i.e., tapered portions36A,36B,36C) and methods can be applied to the manufacture of single pass heat exchanger fluid circuits having an inlet and outlet header, two-pass heat exchanger fluid circuits having a single header consistent with either first header18or second header20and disposed opposite both an inlet and outlet, or multi-pass heat exchanger fluid circuits having three or more headers.

Discussion of Possible Embodiments

A fluid circuit of a heat exchanger includes a core and a first header. The core is configured to receive a fluid and includes a plurality of conduits, each conduit of the plurality of conduits extending along a longitudinal axis from a first end portion to a second end portion. The first header is integrally formed with and fluidly connecting the plurality of conduits. Outer walls of the plurality of conduits taper outward relative to the longitudinal axes to join the first header.

In an embodiment of the preceding fluid circuit, the first header can include an outermost wall and an innermost wall relative to the longitudinal axes of the plurality of conduits. The plurality of conduits can be joined to each of the outermost wall and the inner most wall. The outer walls in the first end portions of the plurality of conduits can taper outward to join at least one of the outermost wall and the innermost wall.

In an embodiment of any of the preceding fluid circuits, the outer walls in the first end portions of the plurality of conduits can taper outward to join the other of the outermost wall and the innermost wall.

In an embodiment of any of the preceding fluid circuits, the outer walls in the first end portions of the plurality of conduits can taper outward to join the innermost wall of the first header outside of the first header.

In an embodiment of any of the preceding fluid circuits, tapered portions of the outer walls of the first end portions can have a frustoconical shape.

In an embodiment of any of the preceding fluid circuits, each first end portion of the plurality of conduits can include an aperture disposed between the outermost wall and the innermost wall.

In an embodiment of any of the preceding fluid circuits, each first end portion of the plurality of conduits can include a plurality of apertures disposed between the outermost wall and the innermost wall.

In an embodiment of any of the preceding fluid circuits, apertures of the plurality of apertures can be offset axially.

In an embodiment of any of the preceding fluid circuits, apertures of the plurality of apertures can be disposed on different sides of the conduit.

In an embodiment of any of the preceding fluid circuits, the innermost wall can extend substantially perpendicular to the plurality of conduits.

In an embodiment of any of the preceding fluid circuits, the first end portions of the plurality of conduits can join the innermost wall inside the first header with a fillet.

In an embodiment of any of the preceding fluid circuits, the plurality of conduits is a plurality of first pass conduits and a plurality of second pass conduits and wherein the fluid circuit further include a plurality of third pass conduits extending parallel to the first pass conduits and the second pass conduits between first end portions and second end portions, and a second header integrally formed with and fluidly connecting the plurality of second pass conduits and third pass conduits. Outer walls of the pluralities of second pass conduits and third pass conduits can taper outward relative to the longitudinal axes to join the second header.

In an embodiment of any of the preceding fluid circuits, the second header can include an outermost wall and an innermost wall. The second and third pass conduits can be joined to each of the outermost wall and the inner most wall. Outer walls of the second end portions of the second and third pass conduits can taper outward to join at least one of the outermost wall and the innermost wall.

In an embodiment of any of the preceding fluid circuits, outer walls of the second end portions of the second and third pass conduits can taper outward between the outermost wall and the innermost wall to join the innermost wall.

In an embodiment of any of the preceding fluid circuits, outer walls of the second end portions of the second and third conduits can join the outermost wall with a fillet.

In an embodiment of any of the preceding fluid circuits, the outermost walls of the first and second headers can be integrally formed with the innermost walls of the first and second headers, respectively.

In an embodiment of any of the preceding fluid circuits, each second end portion of the second and third pass conduits can include an aperture disposed between the outermost wall and the innermost wall.

In an embodiment of any of the preceding fluid circuits, each second end portion of the second and third pass conduits can include a plurality of apertures disposed between the outermost wall and the innermost wall.

In an embodiment of any of the preceding fluid circuits, the second end portions of the first pass conduits can be fluidly connected to one of an inlet and an outlet and wherein the first end portions of the third pass conduits are fluidly connected to the other of the inlet and the outlet.