Patent Application
20130056186
This invention is directed toward the field of heat exchangers, and more particularly to a heat exchanging device which can form complex, three dimensional geometrical configurations.
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.
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.
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.
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 to either temporary or permanently align the parts. In addition, the holes 42 and 44 may provide a point for optical inspection to ensure proper alignment of the structure elements.
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 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 76, or other voids within the structure.
To aid in the flow of fluid, the slots or channels 76 associated with each of the subunit elements that may contain such feature may be orientated in different directions as described for slots or channels 62. 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
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.
