The present disclosure is directed generally to heat exchangers and, more specifically, to heat exchangers formed via additive manufacturing.
Plate-fin heat exchangers use plates and fins to transfer heat between adjacent flows of fluids. Conventional plate-fin heat exchangers are formed of sheet metal with brazed joints. Stresses tend to be higher at joints between the fin and plate, which can induce cracks and result in failure. The design of plate-fin heat exchangers has been limited by traditional manufacturing methods and by build constraints when produced by additive manufacturing methods, specifically, powder bed fusion. Additively manufactured designs often include fillets at fin corners to reduce stress concentrations. The manufacture of fillets and numerous small features greatly increases CAD and build file size as well as build time, which directly correlates to component cost. Additionally, there are limitations to the minimum thickness of features that can be made with additive manufacturing methods.
A heat exchanger includes a first plate, a second plate separated from the first plate by a gap, and a first fin disposed across the gap, extending between and connected to each of the first and second plates. The first fin includes a stress concentration element disposed at a location separated from a first junction connecting the first fin to the first plate and a second junction connecting the first fin to the second plate.
The present summary is provided only by way of example, and not limitation. Other aspects of the present disclosure will be appreciated in view of the entirety of the present disclosure, including the entire text, claims, and accompanying figures.
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.
The present disclosure is directed a fin design for a plate-fin heat exchanger that incorporates additively formed stress concentrations designed to fail and relieve local stresses without causing a leak between interfacing fluids. Prior additively manufactured designs include fillets at fin corners to reduce stress concentrations. The manufacture of fillets greatly increases CAD and build file size as well as build time. Fillets can be eliminated when the disclosed stress concentrations are incorporated into the fin. There is a need for heat exchanger designs that can improve operational life and capability of the component, can reduce weight of the component, and can be efficiently manufactured using additive manufacturing methods.
Plates 112 and 114 are separated by gap 120. Fins 116 extend between and connect plates 112 and 114 to form flow channels 122 defined between plates 112 and 114 and adjacent fins 116. Fins 116 are joined to plates 112 and 114 at junctions 124 and 125, respectively. A first section 130 of fins 116 extends between junction 124 and stress concentration element 118. A second section 131 of fins 116 extends between junction 125 and stress concentration element 118. First and second sections 130 and 131 transition to region 128 of reduced thickness via chamfers 126 and 127. During operation, a first fluid flows through channels 122 between plates 112 and 114 and a second fluid flows across outer surfaces of plates 112 and 114 opposite channels 122. Plates 112 and 114 serve as the interface between first and second fluids. Heat is transferred between plates 112 and 114 from one of the first and second fluids to the other of the first and second fluids.
Plate 112 is separated from plate 114 by gap 120. Plate 112 extends parallel to plate 114. Fins 116 are disposed across gap 120, extending between and connected to plate 112 at one end and plate 114 at an opposite end. Fins 116 are disposed transverse to plates 112 and 114. Fins 116 extend a length of plates 112 and 114. Fins 116 are disposed in rows separated by flow channels 122. Adjacent fins 116 are spaced apart to form flow channels 122. The number of fins and spacing distance can be selected based on operational requirements, including static and dynamic loads. In some embodiments, fins 116 can be spaced apart 0.005-3.0 inches (0.127-76.2 millimeters) Fins 116 are joined to plates 112 at junction 124 and are joined to plate 114 at junction 125. Junctions 124 and 125 are free of fillets. Junctions 124 and 125 form right angles between fins 116 and plates 112 and 114. Fin thickness tf remains substantially uniform in first section 130 between junction 124 and stress concentration element 118 and in second section 131 between junction 125 and stress concentration element 118. Fin thickness tf can be selected to accommodate thermal and structural loading. Fin thickness tf can vary from one region of a heat exchanger to another to account for variations in thermal and structural loads. In some embodiments, fin thickness tf can range from 0.001-0.375 inches (0.025-9.53 millimeters).
Stress concentration element 118 is disposed on fin 116 between junctions 124 and 125. Stress concentration element 118 can be centrally located between junctions 124 and 125 or can be positioned closer to either of junctions 124 or 125. The location of stress concentration 118 can be selected to relieve local stresses without causing a leak between interfacing fluids. Stress concentration element 118 is located away from plates 112 and 114 where stresses could cause further crack propagation after failure.
Stress concentration element 118 includes region 128, which is a region of reduced fin thickness. Region 128 can extend parallel to plates 112 and 114 along a full length of fin 116. Fin 116 has thickness ts in region 128 of stress concentration element 118 which is less than fin thickness tf. Thickness ts in region 128 can be selected based on dynamic operational loads to fail or crack to relieve local stresses before failure occurs at junctions 124 and 125, which could cause a leak between interfacing fluids on opposite sides of plates 112 and 114. In some embodiments, thickness ts can be approximately half of fin thickness tf. In some embodiments, the ratio of fin thickness tf to thickness ts can range from 1.05-20. The size of reduced thickness ts can be selected based on local stresses, overall structural strength and stiffness, and material mechanical properties.
Region 128 can be formed by a recess extending from one or both sides 132, 134 of fins 116. Side 132 of fin 116 is disposed opposite of side 134. As illustrated in
First sections 130 and 131 can join region 128 by chamfers 126 and 127, respectively. Chamfers 126 and 127 provide a linear transition between each of first sections 130 and 131 having thickness tf and region 128 of reduced thickness ts. Chamfers 126 and 127 can reduce stress at junctions between fin sections 130, 131 and region 128 and localize stress concentration in region 128. Chamfers 126 and 127 do not have the same processing requirements as fillets and can be incorporated without significantly adding to build file size or build time. Stress concentration element 118 can be disposed over less than 70 percent of a height of fin 116 extending between plates 112 and 114 (i.e., size of gap 120). In some embodiments, a height h of region 128 is less than 50 percent of the height of fin 116. In some embodiments, a height h of region 128 is less than 20 percent of the height of fin 116. In some embodiments, region 128 has a height 0.003-4.5 inches and fins 116 have a height between 0.005-5 inches (0.127-127 millimeters).
Heat exchanger portion 100 can relieve local stresses without causing a leak between interfacing fluids. The fin design of heat exchanger portion 100 concentrates stress away from structural plates 112 and 114 and junctions 124 and 125 where stresses could cause further crack propagation after failure. Any failure caused by dynamic operational loads will occur at stress concentration element 118 and, particularly, at region 128. Cracks that form will have a tendency to propagate along region 128 where fin thickness is reduced thereby limiting risk of damage at junctions 124 and 125, which could result in leaks of interfacing fluids.
Apertures 220 are disposed in region 128 and extend through fins 116 from side 132 to side 134. Apertures 220 can be spaced along a length of region 128 with uniform or non-uniform spacing. Apertures 220 can be aligned in single row running parallel to plates 112 and 114 with region 128. Apertures 220 can be centrally located in region 128 between chamfers 126 and 127. Apertures 220 can be diamond-shaped. In other embodiments, apertures can be any of a variety of shapes including circles, rectangles, and polygons of various arrangements.
Stress concentration element 218 is designed to concentrate stress at apertures 220. The location, size, and geometric shape of apertures 220 can be selected based on dynamic operational loads to fail or initiate cracking to relieve local stresses before failure occurs at junctions 124 and 125, which could cause a leak between interfacing fluids on opposite sides of plates 112 and 114. Additionally, the location, size, and geometric shape of apertures 220 can be selected to arrest crack propagation initiated at adjacent apertures 220. Heat exchanger portion 200 is designed such that any failure caused by dynamic operational loads will occur at stress concentration element 218 and, particularly, at apertures 220. Cracks that form will have a tendency to propagate along region 128 where fin thickness is reduced thereby limiting risk of damage at junctions 124 and 125, which could result in leaks of interfacing fluids. Adjacent apertures 220 can serve as stop holes, which can arrest crack propagation initiated at an adjacent aperture 220.
Fins 316 are disposed in rows to form flow channels 122. Each fin 316 is split into fin segments 320 within each row. Fin segments 320 are separated by gaps 322. Fin segments 320 can be separated fully or partially between plates 112 and 114. As illustrated in
As discussed with respect to heat exchanger portion 200, heat exchanger portion 300 is designed such that any failure caused by dynamic operational loads will occur at stress concentration element 218 and, particularly, at apertures 220. Cracks that form will have a tendency to propagate along region 128 where fin thickness is reduced thereby limiting risk of damage at junctions 124 and 125, which could result in leaks of interfacing fluids. Adjacent apertures 220 can serve as stop holes, which can arrest crack propagation initiated at an adjacent aperture 220. Gaps 322 additionally serve to arrest crack propagation along fin 316 and confine crack growth to single fin segments 320.
Fins 416 are disposed across gap 120, extending between and connected to plate 112 at one end and plate 114 at an opposite end. Fins 416 are disposed transverse to plates 112 and 114. Fins 416 extend parallel to fins 316 along a length of plates 112 and 114. Fins 416 can be disposed between fins 316 to form flow channels 122 there between. Fins 416 can be solid along the length of plates 112 and 114 (e.g., free of gaps 322) such that a single fin 416 extends from a first end of plates 112, 114 to a second end of plates 112, 114. Fins 416 can be load bearing members, having a thickness tf greater than the thickness tf of fins 316 at sections 130, 131. Fins 416 can have a substantially uniform or constant thickness tf between plates 112 and 114. Fins 416 can be joined to plates 112 and 114 by fillets 418 and 419, respectively. Fillets 418, 419 can be located on each side of fins 416. Fillets 418 and 419 form junctions 424 and 425, respectively, where fins 416 meet plates 112 and 114. Fillets 418 extend from one end of fin 416 to plate 112; fillets 419 extend from the opposite end of fin 416 to plate 114. Fins 418 are substantially similar to fins 18 of the prior art as shown in
Fins 418 provide structural support to heat exchanger portion 400. Fins 416 are joined to plate 112 at junction 424 by fillet 418. Fins 416 are joined to plate 418 at junction 425 by fillet 419. Fillets 418 and 419 reduce the stress concentration at junctions 424 and 425 thereby limiting risk of damage at junctions 424 and 425, which could result in leaks of interfacing fluids. The number of fins 416 and spacing distance can be selected based on operational requirements, including static and dynamic loads. As illustrated in
Projecting elements 518 and 519 are disposed on either side of stress concentration element 218 between plates 112 and 114. Projecting element 518 is positioned between plate 112 and stress concentration element 218. Projecting element 519 is positioned between plate 114 and stress concentration element 218. Projecting element 518 is joined to section 530 of fins 316. Projecting element 519 is joined to section 531 of fins 316. Projecting elements 518 and 519 can project outward from each of sides 132 and 134 of fins 516 and have a combined thickness tp, which is greater than fin thickness tf. The extent to which each projecting element 518 and 519 extends from sides 132 and 134 can vary. The size and shape of projecting elements 518 and 518 can be selected based on the overall design goals, considering material properties, dynamic loading, thermal/fluid performance needs, and height, thickness, and build orientation of fins 516. In one embodiment, projecting element thickness tp can be approximately twice the fin thickness tf. Generally, a ratio of projecting element thickness tp to fin thickness tf is 1.125-5. A height hp of projecting members can also be varied to meet design goals. Generally, a ratio of projecting element height hp to fin height 120 is 0.005-0.3. As illustrated in
Projecting elements 518 and 519 can serve to arrest crack propagation initiated in region 128 of stress concentration element 218 and confine crack propagation to the location of stress concentration element 218. Projecting elements 518 and 519 thereby further limit risk of damage at junctions 124 and 125, which could result in leaks of interfacing fluids.
Heat exchanger portions 100, 200, 300, 400, and 500 can be made via powder bed fusion additive manufacturing processes. Powder bed fusion is an additive manufacturing process in which three-dimensional (3-D) objects are produced from powder in a layer-by-layer fashion directly from a digital model. All powder or selective regions of powder in a powder layer can be fused by melting or sintering with a laser or electron beam as the heat source. CAD and build file size and build time can be reduced by limiting the geometry of a component to that which can be defined by triangular points. As such, the elimination or reduction in number of fillets of the fin disclosed fin designs can reduce CAD and build file size and build time.
Fin designs disclosed in
Although particular fin design embodiments have been disclosed, it will be understood by one of ordinary skill in the art that any of the features disclosed in
Any relative terms or terms of degree used herein, such as “substantially”, “essentially”, “generally”, “approximately” and the like, should be interpreted in accordance with and subject to any applicable definitions or limits expressly stated herein. In all instances, any relative terms or terms of degree used herein should be interpreted to broadly encompass any relevant disclosed embodiments as well as such ranges or variations as would be understood by a person of ordinary skill in the art in view of the entirety of the present disclosure, such as to encompass ordinary manufacturing tolerance variations, incidental alignment variations, transient alignment or shape variations induced by thermal, rotational or vibrational operational conditions, and the like. Moreover, any relative terms or terms of degree used herein should be interpreted to encompass a range that expressly includes the designated quality, characteristic, parameter or value, without variation, as if no qualifying relative term or term of degree were utilized in the given disclosure or recitation.
The following are non-exclusive descriptions of possible embodiments of the present invention.
A heat exchanger includes a first plate, a second plate separated from the first plate by a gap, and a first fin disposed across the gap, extending between and connected to each of the first and second plates. The first fin includes a stress concentration element disposed at a location separated from a first junction connecting the first fin to the first plate and a second junction connecting the first fin to the second plate.
The heat exchanger of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features and/or configurations:
A further embodiment of the foregoing heat exchanger, wherein the stress concentration element comprises a region of reduced first fin thickness.
A further embodiment of any of the foregoing heat exchangers, wherein the stress concentration element is disposed over less than 50 percent of a height of the first fin extending between the first and second plates.
A further embodiment of any of the foregoing heat exchangers, wherein the stress concentration element is centrally located between the first junction and the second junction.
A further embodiment of any of the foregoing heat exchangers, wherein the stress concentration element is offset from a center location between the first junction and the second junction.
A further embodiment of any of the foregoing heat exchangers, wherein the stress concentration element extends parallel to the first and second plates along a length of the first fin.
A further embodiment of any of the foregoing heat exchangers, wherein the stress concentration element includes a plurality of apertures extending through the first fin.
A further embodiment of any of the foregoing heat exchangers, wherein the apertures are spaced along the length of the first fin.
A further embodiment of any of the foregoing heat exchangers, wherein the first fin comprises a first section extending from the first plate to the stress concentration element and a second section extending from the second plate to the stress concentration element, wherein the first and second sections have a first thickness and the stress concentration element has a second thickness less than the first thickness.
A further embodiment of any of the foregoing heat exchangers, wherein each of the first and second sections joins the region of reduced first fin thickness with a chamfer.
A further embodiment of any of the foregoing heat exchangers, wherein the first fin has a first side and a second side disposed opposite the first side and wherein the first side is recessed to form the region of reduced fin thickness.
A further embodiment of any of the foregoing heat exchangers, wherein the second side is recessed to form the region of reduced first fin thickness.
A further embodiment of any of the foregoing heat exchangers, wherein the first fin further comprises a first projecting element and a second projecting element disposed on either side of the stress concentration element, and wherein the first fin has a first thickness at the first and second junctions, a second thickness at the stress concentration element, and a third thickness at the first and second projecting elements, wherein the third thickness is greater than the first thickness and the first thickness is greater than the second thickness.
A further embodiment of any of the foregoing heat exchangers, wherein each of the first and second projecting elements joins the stress concentration element with a chamfer.
A further embodiment of any of the foregoing heat exchangers, and further comprising a plurality of first fins, wherein the first fins are disposed in rows separated by a fluid flow channel and wherein each row comprises a plurality of first fin segments, wherein adjacent first fin segments are separated by a gap, wherein adjacent first fin segments are separated by a distance less than 0.75 inches
A further embodiment of any of the foregoing heat exchangers, and further comprising a second fin extending between and connected to each of the first and second plates, the second fin having a thickness greater than a thickness of the first fin to provide structural support.
A further embodiment of any of the foregoing heat exchangers, and further comprising a plurality of first fins and second fins, wherein second fins of the plurality of second fins are separated by a plurality of first fins.
A further embodiment of any of the foregoing heat exchangers, wherein the second fin is joined to each of the first and second plates by a fillet.
A further embodiment of any of the foregoing heat exchangers, wherein the first fin has a first thickness at locations adjacent the first and second plates and a second thickness at the location of the stress concentration element and wherein the second thickness is less than half of the first thickness.
A further embodiment of any of the foregoing heat exchangers, wherein first and second plates and the first fin are integrally formed and wherein the first and second junctions are formed without fillets.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
This application claims the benefit of U.S. Provisional Application No. 63/016,680 filed Apr. 28, 2020 for “STRESS RELIEVING ADDITIVELY MANUFACTURED HEAT EXCHANGER FIN DESIGN” by A. P. Colson, G. Ngatu, and J. Kowalski.
Number | Date | Country | |
---|---|---|---|
63016680 | Apr 2020 | US |