This invention is directed toward the field of heat exchangers, to a heat exchanging device, and methods of making a heat exchanging device which can form complex, three dimensional geometrical configurations; and to a method of constructing a heat exchanging device formable into a predetermined configuration which allows for manifold attachment or manifold closure that minimizes damage to existing internal structure.
Often, an operating machine or electronic component or an industrial process system generates waste heat in the course of its normal operation. If this waste heat is not removed, degraded performance or damage to the system may result. Frequently, the operating temperature of a system needs to be precisely maintained in order to obtain optimal performance. For example, it is often desirable to cool the sensors used in thermal imaging cameras to improve the sensitivity of the imager. Further, analytical instruments may require that the sample to be analyzed be presented to the instrument at a precisely controlled temperature.
Heat exchangers permit heat to be removed or added to the sample as may be desired. A common type of heat exchanger is referred to as a “heat sink.” A heat sink typically transfers heat between a solid object and some fluid media, which may a liquid, air or other gasses. Computer microprocessors frequently employ heat sinks to draw heat from the processor to the surrounding air, thereby cooling the microprocessor. Fins are often provided to increase the surface area of the heat sink to the air thereby increasing the efficiency of the heat sink. Such a heat sink could also comprise a closed fluid system. For example, a recirculating liquid coolant might be used to transfer heat from that portion of the heat sink in contact with the heat-generating device to a remotely located radiator. The heat sink could be of a single or a two-phase fluid design.
Another type of heat exchanger employs at least two fluids. In this type of heat exchanger, heat is transferred from a first fluid to a second fluid without direct contact between the fluids. For example, a fluid-to-fluid heat exchanger for a blood processing machine may employ heated water to warm the blood to the proper temperature. The blood circulating path is completely separate from that of the water circulating path and dilution or contamination of the blood is thus avoided. Other types of heat exchangers include those designed to recover waste heat from systems that produce excess heat, for example, a passenger compartment heater that derives heat from an automobile engine. Regardless of the type of heat exchanger, it is desirable to obtain a high degree of heat transfer efficiency.
Several factors affect the efficiency of heat exchangers. To maximize efficiency it is desirable that the following situations occur:
1. The thermal-conductivity of the materials that must conduct heat should be high so as to permit maximum heat transfer.
2. Heat transfer surface areas should be large and have features that efficiently transfer heat from the fluid to solid members.
3. Heat transfer members should, in general, have large cross-section lateral to heat transfer path.
4. Fluid flow should be efficient with minimal pressure loss with fluid dynamics that provide efficient heat transfer. Other important criteria are known and will not be detailed here.
In dual-fluid heat exchangers, a variety of flow relationships may be employed relative to the two fluids. In a counter-flow relationship, the two fluids flow primarily in opposite directions to one another. In a cross-flow relationship the two fluids primarily flow at right angles to one another.
Some basic heat exchanger configurations include: shell and tube, plate, plate and fin, and pillow plate. The shell and plate exchangers are the most widely used, basic heat exchanger configuration. This configuration provides a comparatively large ratio of heat transfer area to volume and weight, and is relatively easy to construct. This type of heat exchanger consists of a shell with a bundle of tubes inside it. One fluid runs through the tubes, and another fluid flows over the tubes (through the shell) to transfer heat between the two fluids. The set of tubes may be composed by several types of tubes, such as plain or longitudinally finned. The instant invention is provides for a configuration with extremely large heat transfer capability and is an improvement over the existing art.
The plate heat exchanger uses metal plates to transfer heat between two fluids. This has a major advantage over a conventional heat exchanger in that the fluids are exposed to a much larger surface area because the fluids spread out over the plates.
A plate-fin heat exchanger is designed to use plates and finned chambers to transfer heat between fluids. It is often categorized as a compact heat exchanger to emphasize its relatively high heat transfer surface area to volume ratio. A plate-fin heat exchanger is made of layers of corrugated sheets separated by flat metal plates, typically aluminum, to create a series of finned chambers. Separate hot and cold fluid streams flow through alternating layers of the heat exchanger and are enclosed at the edges by side bars. Heat is transferred from one stream through the fin interface to the separator plate and through the next set of fins into the adjacent fluid. The fins also serve to increase the structural integrity of the heat exchanger and allow it to withstand high pressures while providing an extended surface area for heat transfer.
A pillow plate exchanger is typically constructed using a thin sheet of metal spot-welded to the surface of another thicker sheet of metal. The thin plate is welded in a regular pattern of dots or with a serpentine pattern of weld lines. After welding the enclosed space is pressurized with sufficient force to cause the thin metal to bulge out around the welds, providing a space for heat exchanger liquids to flow, and creating a characteristic appearance of a swelled pillow formed out of metal.
Regardless of the design, the basic function of a heat exchanger is to convey heat from one location to another. While some heat exchangers are relatively simple, such as that of a cast aluminum heat sink for a semiconductor, others are quite complex and require a variety of sophisticated manufacturing processes. The means and process of the instant invention overcome many of the shortcomings of previous designs particularly with respect to the handling and fixturing of heat exchanger components.
Diffusion bonding or brazing of a stack of planar members is a common technique to produce heat exchangers. These processes permit the construction of very intricate internal structures. In the case of a heat exchanger or chemical reactor produced by these means, it is necessary to provide ports so the heat exchanging fluids or reactant chemicals can be hermetically ported into and out of the device proper. Often these ports comprise a manifold that serves to effectively couple fluids and/or gases into and out of the heat exchanger or reactor. While these manifolds and/or ports may be constructed at the time the stack assembly is bonded, several problematic issues may arise during this process. Diffusion bonded, including the use of a transient liquid phase, or brazed assemblies can be damaged by the relatively high heat required to attach manifolds by welding. The advantage of this process is that heat generated during the welding process is not readily transmitted to the critical regions of the brazed or diffusion bonded assembly. Additionally, this process permits manifold inlets and outlets to be safely added to the heat exchanger after other processes are completed. Adding the manifold inlets and outlets after the brazing or bonding phase has been completed can offer several benefits.
When manifolds and/or ports are constructed at the time the stack assembly is bonded, issues relating to internal washing, for example a cleaning wash, or if the part is to be wash coated to impart a film of alumina or other materials to the inner surfaces of a heat exchanger or reactor, can arise. In a similar manner, another washing process, such as a nitric acid wash, may be carried out to passivate the interior wetted surfaces of the part. If the inlet and outlet manifolds are present at the time of this wash, the flow through the system can be greatly diminished. This results in inhibiting thorough washing. Additionally, there may be regions in the assembly that cannot be adequately washed due to occlusion by the manifold/port features. The manifolds may also comprise “dead volumes” that prevent a uniform application of wash material, thorough washing or thorough wash coating material removal. By attaching the inlet and outlet manifolds after other processes have been completed, the wash flow path through a heat exchanger or reactor may be shortened and restriction of the flow path minimized, thereby ensuring a more uniform and consistent distribution of the coating material on the inside surfaces of the component or more thorough washing of the internal structure of the part.
While it can be advantageous to attach the manifolds after the stack bonding process, great care must be taken when attaching manifolds to a previously brazed assembly. Heat involved in the welding or brazing process can damage the stack proper. One form of damage occurs when the attachment process re-melts the braze material holding the stack together. This can lead to discontinuities in the brazed joints resulting in leaks through the structure. Additionally, if the braze material of the stack reaches the liquidus temperature, it can flow into delicate passages and block flow paths. If this re-melt is severe, the planar members of the structure may migrate relative to one another and distort the structure. The migration may result in closing off passages or, alternatively, creating internal leaks between passages.
Another problem results from the potential formation of “virtual leaks,” or dead spaces into which fluid can slowly, and undesirably, ingress and egress from the main flow path(s). Even if the members of the structure do not migrate, the assembly can be damaged by excess heat. This damage may take the form of surface oxidation or chemical and/or metallurgical alteration. These oxides or other surface contaminants may block delicate passageways within the structure or render the structure chemically inconsistent with its intended use. The structure of the stack proper may also be damaged due to stresses induced by excess heating which can result in warping, distortion or even cracking. This problem can be particularly bothersome if the weld is situated at the mutual convergence of multiple planar members, which is often the case when welding a manifold closure plate onto a manifold, in which case the welds may be situated at the juncture of two or more typically mutually perpendicular planar elements. Sometimes referred to as a “triple point” in the case of three planar elements, welds made in these regions are prone to many of the issues previously cited. Since welding frequently occurs at the region where these planes intersect, substantial heat from manifold welding can introduce high stresses at these points. The heat affected zone of the weld is relatively small in comparison to the bulk of the material, causing large localized thermal expansion. Detrimentally high temperatures may be applied at this point while attempting to obtain good weld penetration that is necessary to assure an acceptable weld within the rest of the structure. If this situation occurs near the stack proper, portions of the stack can be severely damaged during the welding process.
In some situations, additional elements are added to the bonding or brazing materials. For example, phosphorus is sometimes added to braze and transient phase diffusion bonding alloys to depress their melting point. If phosphorus containing alloys are used in transient liquid phase bonding (TLP), or other brazing processes used to bond the stack, cracking can be an issue due to localized excess phosphorus content. In this case, it is common for cracks to appear in regions that have been subjected to the high heat of welding. The presence of boron or carbon can also cause similar cracking in some materials. “Time-at-temperature” will permit local concentrations of phosphorus or carbon to diffuse through the part to reach progressively lower levels, but this may still be insufficient to prevent cracking during traditional high temperature welding processes. The present invention includes a method of constructing a heat exchanging device to overcome such problems.
Devices for dissipating heat are known in the art. For example, U.S. Pat. No. 3,457,988 describes a heat sink member using fin members which are mounted and spaced apart from each other on the heat sink. U.S. Pat. No. 3,537,517 describes a heat dissipating assembly which uses a stack of parallel cooling fins which are spaced apart and mounted on a peripheral surface of a core member. U.S. Pat. No. 5,375,655 describes an improved heat sink apparatus that includes a base plate and a plurality of finned assembly units. The finned assembly units are described as being constructed and arranged in an abutting relationship and off-set from each other to provide a fluid pathway. U.S. Pat. Nos. 5,535,816, 5,794,684, 5,900,670, 6,712,128, 6,861,293, 7,597,13, 7,760,506, and U.S. Patent Application 2001/0037875 describe variations to heat sink and/or air flow generating devices that dissipate heat utilizing individual, stacked heat exchanging elements.
Devices which do not utilize individually formed stacked plates are also known in the prior art. For example, U.S. Pat. No. 6,199,624 describes a heat sink having heat exchanging sections defined by a thermally conductive sheet folded into alternating ridges and troughs to define generally parallel finned spaces. U.S. Pat. No. 6,698,511 describes a device which is described as improving the thermal efficiency for heat transfer from an electronic device. The device is described as containing a fin array having regions with fins having different density and some fins having a curvilinear shape. These devices, however, are configured in the same manner as the traditional stacked plate configurations, and accordingly cannot assume complex three dimensional shapes.
Non heat sink related devices using plate-like configurations are known in the art. For example, U.S. Pat. No. 6,537,506 describes a chemical reactor for forming products. The chemical reactor is described as including simple plate structures which are stacked together to form a plurality of layers. U.S. Pat. No. 6,192,596 describes a device designed for micro-channel fluid processing. U.S. Pat. No. 5,888,390 illustrates a multilayer integrated assembly for handling fluid functions. The device is described as containing complementary micro-fluid structures which are etched within the surface of a foldable substrate.
The present invention provides a heat exchanging device formable into a three dimensional configuration. The heat exchanger device may be of the heat sink type, a dual fluid type, or virtually any other as may be desired. The heat exchanger device comprises a main body which is formable into a three dimensional shape and has a plurality of individual subunit elements adapted to form a plurality of stacked heat exchanging units. The individual subunits have surface configurations which are adapted to allow fluid flow. The surface configurations may be formed, for example, by removing a portion of the surface, either completely or to a specified depth, thereby yielding a window, or removed region in which fluid may flow. The exact geometry of these regions may take any form desired. By preparing a plurality of these elements and stacking them, a complex, three-dimensional geometry may be obtained. Because of the modular nature of the instant invention, a great variety of heat exchanger types and variations may be produced with little or no tooling change.
In an illustrative embodiment, a method of constructing a heat exchanging device formable into a three dimensional configuration which allows for manifold attachment or manifold closure that does not damage any existing heat exchanging device internal structure is described. The present invention provides for a remote welding process that uses a series of thin wing walled potions and cantilevered plates that are formed, preferably during the initial bonding of the stack. These walls and plates are configured in a manner that permits the attachment of manifolds by brazing or welding, while protecting the stack proper from damage. The process avoids the necessity of making the weld immediately adjacent to the structurally and metallurgically sensitive stack, thereby protecting it from excessive heat.
Accordingly, it is an objective of the instant invention to provide a heat exchanging device which can form complex, three dimensional geometrical configurations.
It is a further objective of the instant invention to provide a heat exchanging device comprising a plurality of individual subunit elements which are adapted to fold onto adjacent subunit elements to form complex, three dimensional configurations.
It is yet another objective of the instant invention—to provide a heat exchanging device which is modular in nature.
It is a still further objective of the instant invention to provide a heat exchanging device which can form complex, three dimensional configurations with little or no tooling change.
It is a further objective of the instant invention to provide a heat exchanging device which can be easily and economically produced.
It is yet another objective of the instant invention to provide a three-dimensional heat exchanging structure from a plurality of simple laminar elements.
It is a further objective of the instant invention to provide a complex, three-dimensional heat exchanging device which incorporates functional gradient members.
It is yet another objective of the instant invention to provide a complex, three-dimensional heat exchanging device which incorporates enhanced surface area features.
It is a still further objective of the invention to provide a complex, three-dimensional heat exchanging device which incorporates heat transfer enhancement features.
It is a further objective of the instant invention to provide a heat exchanging device which is highly scalable, permitting the production of heat exchangers of any size.
It is yet another objective of the instant invention to provide a process that provides for high temperature welding or brazing of manifold attachment or manifold closure to a heat exchanging device that does not damage the internal structures of the device.
It is a further objective of the instant invention to provide a process that avoids the necessity of making a weld immediately adjacent to a structurally and metallurgically sensitive heat exchanging stack, thereby protecting it from excessive heat.
Other objectives and advantages of this invention will become apparent from the following description taken in conjunction with any accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. Any drawings contained herein constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.
While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred, albeit not limiting, embodiment with the understanding that the present disclosure is to be considered an exemplification of the present invention and is not intended to limit the invention to the specific embodiments illustrated.
Referring to
The main body 12 contains a first end 16, a second end 18, a first side edge 20, and a second, opposing side edge 22. Each of the subunit elements 14A, 14B, 14C, 14D, 14E, or 14F contains a first surface 26 and a second surface 28. Each of the first surfaces of the individual subunit elements together defines the first surface of the heat exchanging device. Each of the second surfaces of the individual subunit elements together defines the second surface of the heat exchanging device.
The main body 12 contains a plurality of individual subunit elements, which when folded form a plurality of stacked heat exchanging units. Each of the individual subunit elements may contain surface configurations adapted to allow fluid flow and exchange of heat. Adjacent subunits may or may not have identical feature patterns as each adjacent subunit need not be unique to its immediate neighbor. For example, 3-4 subunit elements having the same configuration may be adjacently positioned to form a particular height or passage.
Alternatively, adjacent subunits may have different feature patterns. For example, subunit element 14 may contain one or more slots 30 which extend through the first surface 26 to the second surface 28, and one or more apertures 32 which extend through the first surface 26 to the second surface 28. Alternatively, the slots 30 and apertures 32 may extend through the first surface 26 to a specified depth. If the subunit elements contain a plurality of slots 30, such slots can be arranged in a parallel fashion, at right angles, or any other arrangement. The apertures 32 are shown arranged at or near the first edge 20 or opposing edge 22 and arranged in a row. The apertures may, however, be arranged in any fashion along any portion of the first surface 26 and/or second surface 28. The slots 30 or apertures 32 may be formed by punching, machining, fine-blanking, laser cutting, water-jetting, grinding, photo-chemical machining, ion-milling, abrasive blasting or any other suitable process. Preferably, the slots 30 and apertures 32 are aligned in such a manner that promotes the flow of a fluid through the heat exchanging device 10 in an efficient manner.
The heat exchanging device 10 may contain a plurality of fold regions, illustrated herein as fold lines 34. Such fold lines 34 allow each of the subunits to bend or fold relative to an adjacent subunit element. The fold lines 34 may be formed through semi-perforations, coining processes, or through other known mechanisms. To aid in the folding or bending of the subunits, the heat exchanging device 10 may contain one or more fold initiators 36. The fold initiators 36 may be formed by punching, machining, fine-blanking, laser cutting, water-jetting, grinding, photo-chemical machining, ion-milling, abrasive blasting or any other suitable process may take a variety of forms, such as, but not limited to, notches, grooves, slits or other forms that serve to promote bending of one or more portion of the main body 12 and/or the individual subunit elements. If the fold initiator 36 is constructed of a grooved form such that only a portion of the depth of the main body 12 is removed, the fold initiator may transverse the entire width of the main body. If the fold initiator 36 is constructed as a slot, hole or notch design, the slots, holes or notches would typically be of a discontinuous nature but still would exist predominately along the desired fold line.
One of the unique aspects of the instant invention is the fact that the heat exchanging device 10 is designed as a single unit which is capable of folding to form unique three dimensional geometries or shapes. Such a device provides a mechanism to produce heat exchangers that can be shaped according to odd geometries and can be produced in a cheaper manner that other devices that need to have specific shapes. Not having to handle individual subunit elements in forming the overall shape provides a distinct advantage when compared to conventional construction using individual sheets. Handling individual sheets can be time consuming and labor intensive and often results in misaligned configurations. Because the individual subunits are part of a larger main body arranged in predetermined sequences, the subunits cannot be aligned out of sequence. Referring to
The first surface 26 of each subunit element may be a bondable surface so that the second surfaces 28 of adjacent subunit elements may be joined together over one or more portions of each of the surfaces. The bondable surface my take the form of a clean, smooth surface that may be bonded by diffusion bonding, including transient liquid-phase diffusion bonding. Alternatively, the bondable surface may comprise a brazing alloy that can be melted to join together adjacent sections of the subunit elements. The brazing alloy may comprise a thin sheet of alloy or other material that is interleaved between adjacent the first surfaces and/or the second surfaces of the subunit elements. The brazing alloy may also comprise a paste or powder that is applied to either one of both of the first faces to be bonded. Further, the brazing alloy may be in the form of cladding or a plated layer on the laminar material, which when heated, bonds the adjacent layers. Brazing may also be accomplished by “dip-brazing” or other suitable processes as long as the process does not significantly interfere with desirable fluid path geometries. In lieu of or in addition to bonding adjacent layers by diffusion bonding or brazing, any suitable welding process may be employed to bond adjacent layers without the use of a brazing alloy.
Alternately, successive layers of the subunits elements may be joined at their periphery, thereby defining fold edges 38 and laminate edge 40, by brazing or welding. The fold edges 38 preferably comprise a hermetic seal. Welding processes may include, but are not limited to, laser welding, electron-beam welding, ultrasonic welding, resistance welding, press welding, friction welding, any of the processes referred to as “arc-welding,” such as gas metal arc welding (GMAW), metal inert gas (MIG) welding, tungsten inert gas welding (TIG) or the like. The above laminar element bonding or welding processes assume that the heat exchanging device 10 is comprised of metal or a metal alloy. The structure could however be comprised, without being limiting, of other materials such as ceramics, polymers glasses or composites. Adhesives such as epoxies, cyanoacrylates, silicones or other materials may be employed to bond adjacent layers and/or seal the periphery of the heat exchanging device 10 instead of or in addition to brazing and/or welding.
Registration features, illustrated herein as holes 42 and 44 positioned on each of the subunit elements may be employed to aid in alignment of the subunit elements during and/or after the folding process. Registration feature 42 and may also be employed as a mechanism to fix or secure the device 10 during brazing, welding or any other process including mounting the finished product. Other elements, such as pins or other guides, may be employed as part of the securing process and designed to interact with registration features 42 and 44 (see
Depending on the intended application, a manifold 46 may be employed to provide a hydraulic connection to a plurality of passages that are formed by the slots 30, the apertures 32, or other voids within the structure, see
By changing the shape and/or the surface configurations of one or more of the individual subunit elements, the heat exchanging device 10 may assume a variety of shapes with the capability to exchange heat in a variety of fashions.
For subunit elements 14B and 14D, the solid portion or plate 60 is replaced with a plurality of slots or channels 62 which extend through the subunit element 14B and 14D. As illustrated, the heat exchanging device 10 comprises alternating subunit elements so that subunit element 14C has the same configuration as subunit element 14A and subunit element unit 14D has the same configuration as subunit element 14B. Although not illustrated, the top and/or bottom subunit element may contain a manifold to provide a hydraulic connection to a plurality of passages that are formed by the slots or channels 62, or other voids within the structure. To aid in the flow of fluid, the slots or channels 62 associated with each of the subunit elements that may contain such feature may be orientated in different directions. For example, the subunit element 14B is shown having the slots 62 orientated in a direction which is parallel to openings 52 and 56, i.e. northwesterly to southeasterly direction. The subunit element 14D contains the slots 62 orientated in a direction which is parallel to openings 54 and 58, i.e. northeasterly to southwesterly direction. The length of the slots or channels 62 may be larger than the length of the solid portion or plate 60 so that in the folded or stacked configuration, a portion of the slots or channels 62 extend into the cut-out portions 52, 54, 56 or 58 of the above and/or below positioned subunit element. To aid in alignment, each of the subunit elements may contain one or more openings 61.
Referring to
The subunit elements 14 may contain portions which are adapted to provide fluid flow. For example, subunit element 14A contains a plurality of inlet and or outlet manifolds 66, 68, 70 and 72 which surround a generally centrally positioned solid portion or plate 74. The adjacent subunit element 14B is designed in a similar manner having the same inlet and or outlet manifolds 66, 68, 70 and 72. The solid portion or plate 74 is replaced with a plurality of generally centrally located slots or channels 76. The channels may be constructed to be cut within the surfaces at a partial depth instead of being cut through the surface. As illustrated, the heat exchanging device comprises alternating subunit elements so that subunit element 14C has the same configuration as subunit element 14A and subunit element unit 14D has the same configuration as subunit element 14B. Although not illustrated, the top and/or bottom subunit element may contain a manifold to provide a hydraulic connection to a plurality of passages that are formed by the slots or channels 76, or other voids within the structure.
To produce a cross flow heat exchanger, the slots or channels associated with each of the subunit elements that may contain such feature may be orientated in different directions as described for slots or channels of an alternate layer. For example, the subunit element 14B is shown having the slots 76 orientated in a direction which is parallel to openings 66 and 70, i.e. northwesterly to southeasterly direction. The subunit element 14D contains the slots 76 orientated in a direction which is parallel to openings 68 and 72, i.e. northeasterly to southwesterly direction. To aid in alignment, inspection, or device mounting each of the subunit elements may contain one or more openings 78. Other features to aid alignment, inspection, or device mounting known to one of skill in the art may be used, including tabs.
Referring to
As an illustrative example, individual plate structures having different widths are used to create such a functional gradient. In the structure shown in
Alternatively, the finlet 89 can be sized so that each overhang positioned above and/or below another overhang may be larger, smaller, or combinations thereof. For example, finlet 89 associated with plate structure 88B may be smaller than the finlet associated with plate structure 88D. The finlet associated with the plate structure 88D is smaller than the finlet associated with plate structure 88F, which is smaller than the finlets associated with plate structures 88H or 88J. The fin formed by the stack of laminar, heat exchanging units as illustrated by the stack comprising plate structure 88A and plate structure 88J as well as the other elements sandwiched between plate structures 88A and 88J comprises a functional gradient member. In addition to being able to readily and economically form functional gradient fins, fins of enhanced surface area or other enhanced geometry may be realized. The finlets 89 formed provide increased surface area for greater fluid contact and greater heat transfer. This functional gradient promotes greater heat transfer than a stack of platelets of continuously decreasing width because such arrangement would provide less fluid contact surface area.
The process of the instant invention may also be used to construct heat exchanger cores comprising fins 88 and 90 that are not necessarily contained in a closed hydraulic reservoir. The cores need not contain for example, the outer walled portions (the sealed edges) that define the closed reservoir. The cores are preferably used in applications where heat is conducted to and/or radiated through the surrounding atmosphere. Additionally, these cores may be placed in a chamber or other hydraulic containment means which has been fabricated by a conventional manufacturing process such as deep-drawing, machining, hydroforming or similar suitable processes but which do not necessarily utilize a plurality of laminar elements in its construction.
Referring to
The heat exchanging device 200 contains a main body 212, preferably made of a laminar material and/or other materials that exchange heat such as aluminum or copper, comprising individual subunit elements 214A, 214B, 214C, 214D, 214E, and 214F, 214G, 214H, 2141, collectively 214, see
Secured to the upper most subunit element 214A is an upper plate 220. Secured to the lower most subunit element 2141 is a lower plate 222.
The upper plate cantilevered or overhang portion 224 and the lower plate cantilevered or overhang portion 236 form the upper end and lower end of a heat resistance zone 246, see
Referring to
Each appendage or finger-like structure 262 comprises a main body 264 comprising a top surface 266, a bottom surface 268 (not shown) and two opposing side walls 270 and 272. The appendage or finger-like structure 262 extends outwardly, away from side edges 254, 256, 258, and 260. At the distal portion, i.e. away from the side edges, is an end plate connecting surface 274. The subunit element 214 is shown comprising two appendages or finger-like structure 262 per each side edge 254, 256, 258, and 260. In this arrangement, the heat resistance zone 246 is formed by a plurality of wing walled sections, each extending away from the main body of the stack. While illustrated as having two appendages or finger-like structures 262 per each side edge, the use of two is illustrative only as each side edge may have additional structures or none. Moreover, each of the appendages or finger-like structures 262 is not limited to a rectangular shape and may take on any shape or configuration as can be designed and manufactured.
In certain embodiments, it is desirable to produce a heat resistance zone wall having tall, thin or long appendages 262. As the ratio of the height and/or the length of the heat resistance zone wall relative to the wall width increases, it becomes increasingly difficult to produce. In some cases, the wall may collapse during the bonding or brazing process, as the individual platelets become displaced laterally from each other. In other cases, the wall may warp or buckle due to thermally induced stresses or under loading applied to facilitate brazing. By proper application of the use of stringers previously described and/or by careful application of removable supports employed during the brazing process, high aspect ratio walls, e.g. ⅛″ wide and as high as 3″ tall can be produced. Walls with such high height to thickness ratio and shorter thin walls can be particularly beneficial in the construction of brazed stacks configured for remote welding.
A heat exchanging device 200 having thin heat resistance zone walls can be employed to produce a more gradual temperature gradient between the part and the weld, and can be employed to isolate the heat from the sensitive portion of the stack. This minimizes problems associated with thermal expansion stresses and chemical or metallurgical reactions in the stack that can result from high temperature, post-bond operations. Because the total heat required to achieve an acceptable weld is minimized in a thin wall section, the thin heat resistance zone wall develops less stress in welding than a thicker part and less heat and stress are transmitted to adjacent parts. A heat resistance zone wall with a remote weld can avoid the “triple point” issue of having to manage welding to three surfaces simultaneously, potentially reducing the number to two. This is particularly important in that the process of welding three joints that meet at a single point can generate extreme stresses at that point. Depending on the welding process, the point where the welds meet is essentially heated at least twice and potentially three times, each time introducing additional stresses and increasing the chance of a damaging metallurgical change.
While the surface 276 of the subunit element 214 is shown without any surface configurations, the lack of such configurations is for illustration purposes only. The heat exchanging device 200 further comprises one or more endplates 278, 280. The end plate 278 is situated away from the main body of the stack and is attached by welding or brazing to one or more portions of the upper plate cantilevered or overhang portion 224, one or more portions of the lower plate cantilevered or overhang portion 236, the first heat resistance zone wall 248 (defined by a plurality of appendages or finger like structure 262A-262I), and the opposing second heat resistance zone wall 250 (defined by a plurality of second appendages or finger like structure 262A-262I, not shown). The end plate 280 may be attached in a manner similar to the attachment means described for end plate 278.
Because the welding process required to attach the end plate 278, 280 to the stack is removed from the region near the main body 212 of the platelet stack, minimal heat is transmitted from the weld area to critical areas of the brazed or diffusion bonded stack thereby sparing the stack from damage modes as described previously. An inlet/outlet port 282 is provided to permit fluid entry/exit, see
Referring to
Referring to
The reduced cross-section permits welds to be made with the application of less heat than would be required for full-thickness members, thereby limiting the potential for heat-induced damage to the stack proper, i.e. the portion of individual subunit element 214 that form fluid flow channels and/or heat exchanging capability. This benefit comes in addition to the benefit of having removed the weld zone(s) from the stack proper and the delicate geometries that may be contained therein. A further benefit of the design shown in
The heat exchanging device 200 may be constructed using any techniques and include one or more features described herein, including those described for the various heat exchanging embodiments described throughout. In an illustrative embodiment, a method of constructing a heat exchanging device formable into a predetermined configuration adapted to minimizes damage to the internal structure when adding a manifold attachment or manifold port, comprising the steps of providing or manufacturing a plurality of individual components which when stacked together form a shape. The individual components can be formed to include surface configurations or are provided with pre-made surface configurations which determine a fluid flow pathway. Accordingly, at least one of the plurality of individual components contain one or more surface configurations adapted to allow one of fluid flow or exchange of heat and to provide at least a portion of a heat resistance zone. The surface configurations may be formed by various techniques known to one of skill in the art, including, but not limited to forming by punching, machining, fine-blanking, laser cutting, water-jetting, grinding, photo-chemical machining, ion-milling, or abrasive blasting.
Once the individual components contain the desired surface configurations, two or more individual components are stacked to form a heat exchanging unit having at least a main body and at least one side edge. The two or more individual components are arranged so that when adjacent units are joined, the surface configurations are aligned to form a pre-determined shape or structure. At least one heat resistance zone is formed, preferably by providing individual elements having, or being constructed to have, a second set of surface configurations, such as the individual subunit having appendages 262, as illustrated
In addition to the advantages enumerated previously, the issue of cracking in materials in which phosphorus is present can be minimized by application of the remote welding process described herein. Certain nickel based brazing alloys often contain a small percentage of phosphorus. It is not uncommon for phosphorus to be present in quantities of up to 11% in some braze alloys. The phosphorus serves as a melting point depressant and facilitates the brazing process. However, when these alloys are subjected to the high heat of the welding processes, cracking frequently occurs. The use of the remote welding process can alleviate this problem in many ways. First, the high heat of the welding process can be removed from the most sensitive and complex portion of the main body or stack proper. Second, most of the weld-induced cracking occurs as a result of the extreme heating and cooling rates involved during the process, which leads to severe thermal expansion differences within the part. The wing walls serve as compliant members accommodating thermally induced stresses. Finally, the main body or stack proper, exclusive of the wing walls, essentially serves as a reservoir of the melting point depressant more so than the wing walls. This is because the micro-channels are transient liquid phase coated and the wing walls do not contain micro-channels. As such, they have significantly less of the melting point depressant. Additionally, the wing walls heat more quickly than the balance of the stack and the melting point depressant that is present will have a longer time to diffuse to a lower concentration. In the instance where the joining process does not depend on transient liquid phase, this mechanism is not present.
Welding access points and manifold geometry are no longer defined by the edges of the stack proper but are designed as an integral part of the stack. This allows weld preparation features to be purposely incorporated into the stack prior to the actual welding process and avoids using a post-bond machining process that might introduce contaminants into the device being fabricated. These weld preparation features are removed from the vicinity of the stack body such that attachment of manifolds by welding or brazing will not introduce unacceptable stresses, chemical, or metallurgical reactions to the bonded stack. Specifically, incorporation of stack face sheets that extend beyond (overhang) the main stack body eliminate the necessity of making a weld immediately adjacent to the sensitive stack body. Additionally, any mechanical attachment such as a threaded fastener or rivet may be made remotely and safely away from the main stack.
Because the process of the instant invention permits the potentially damaging high heat process of welding to be removed from the sensitive portions of the stack, a great deal of freedom may be enjoyed in the stack design. This freedom can include finer geometries of members and fluid passages, more delicate overall structures, and the creation of structures that would otherwise be impossible to avoid damaging during the manifold welding process of previous designs. This allows the stack to be manufactured with a highly beneficial manifold created during the processing step used for the manufacture of the stack. This process can eliminate manufacturing steps, provide a stronger and more robust manifold, and result in more efficient operation of the device through improved hydrodynamic performance. Independent of whether transient liquid phase or bare-bonding or conventional brazing is used to join stack components, it is important in wash-coating operations that an open manifold be used to assure that uniform coatings are achieved. Uniform coatings are difficult to create with no manifold as is used as well as when a closed face manifold is used. The wing walls created as a part of the assembly reduce the need for a temporary wall structure/manifold.
Because the individual component or platelet and face sheet extension features can occupy less space than a traditionally applied manifold, especially complex devices and manifolds that would be impossible to produce without sacrificing device performance can be produced using the method of the invention. Additionally, access points and manifold geometries are no longer defined by the edges of the stack proper, but are instead purposefully and functionally designed as an integral part of the stack. Therefore, less access room will be required for welding, thereby enabling production of more compact and efficient devices.
All patents and publications mentioned in this specification are indicative of the levels of those skilled in the art to which the invention pertains. All patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference.
It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and any drawings/figures included herein.
One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments, methods, procedures and techniques described herein are presently representative of the preferred embodiments, are intended to be exemplary and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in the art are intended to be within the scope of the following claims.
In accordance with 37 C.F.R. 1.76, a claim of priority is included in an Application Data Sheet filed concurrently herewith. Accordingly, the present invention claims priority as a continuation-in-part of U.S. patent application Ser. No. 13/226,051, filed Sep. 6, 2011, entitled “HEAT EXCHANGER PRODUCED FROM LAMINAR ELEMENTS”. The content of which the above referenced application is herein incorporated by reference in its entirety.
Number | Date | Country | |
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Parent | 13226051 | Sep 2011 | US |
Child | 14273008 | US |