Patent Publication Number: US-2015075754-A1

Title: Single-pass cold plate assembly

Description:
BACKGROUND OF THE INVENTION 
     Contemporary high power dissipating electronics produce heat that may result in thermal management problems. Heat must be removed from the electronic device to improve reliability and prevent premature failure of the electronics. Heat exchangers or heat sinks may be employed to dissipate the heat generated by the electronics; however, the beneficial functions may be contrary to maintaining or reducing the weight of the product or reducing its cost. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, an embodiment of the invention relates to a single-pass cold plate assembly having a base and a cover arranged in confronting relationship to define a cold plate, a spiral channel having at least a portion provided in one of the base and cover, with a channel inlet located in a central portion of the one of the base and cover, and a channel outlet located at a periphery of the one of the base and cover, and a manifold provided in the other of the base and cover, with the manifold having a manifold inlet located on a periphery of the other of the base and cover, and a manifold outlet located in a central portion of the other of the base and cover and in fluid communication with the channel inlet, wherein coolant introduced into the manifold inlet may travel through the manifold, out the manifold outlet, into the channel inlet, where it moves through the spiral channel and out the channel outlet to complete a single pass through the cold plate assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a perspective view of a single-pass cold plate assembly according to the embodiment of the invention; 
         FIG. 2  is an exploded perspective view of the single-pass cold plate assembly of  FIG. 1 ; 
         FIG. 3  is a perspective view of the single-pass cold plate assembly of  FIG. 1  with electronic devices and coolant lines attached thereto; 
         FIG. 4  is a side view illustrating the single-pass cold plate assembly of  FIG. 3 ; 
         FIG. 5  illustrates the flow path of a coolant within the single-pass cold plate assembly of  FIG. 1 ; 
         FIG. 6  is an exploded perspective view of a single-pass cold plate assembly according to another embodiment of the invention; 
         FIG. 7  is a perspective view of the single-pass cold plate assembly of  FIG. 6 ; 
         FIG. 8  is a top view of the single-pass cold plate assembly of  FIG. 6 ; and 
         FIG. 9  is a side view illustrating the single-pass cold plate assembly of  FIG. 6  with an electronics device and coolant lines attached thereto. 
     
    
    
     DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
       FIG. 1  illustrates a single-pass cold plate assembly  10  having a base  12  and a cover  14  that may be arranged in confronting relationship to define a cold plate, for example the base and cover may be mated to form the cold plate. A spiral channel  16  having a channel inlet  18  and a channel outlet  20 , a manifold  22  having a manifold inlet  24 , a manifold outlet  26 , and a reservoir  28  (more clearly seen in  FIG. 2 ) are also illustrated as being included in the single-pass cold plate assembly  10 . The base  12  and cover  14  may be fastened together in any suitable manner. In the illustrated example, the base  12  and cover  14  have been illustrated as including openings  30  in which screws, not illustrated, may be inserted to fasten the base  12  and cover  14 . Alternatively, other methods for fastening may also be used including the use of an adhesive or brazing. In the case of an adhesive, a thermally conductive compound may be used to bond the base  12  and the cover  14 . The use of such a thermally conductive compound may minimize any thermal stresses that would be induced during production of the single-pass cold plate assembly  10  as compared to other means of fastening. While the base  12  and cover  14  have been illustrated in a square configuration, it is understood that they may take alternative forms including circular, rectangular, etc. The single-pass cold plate assembly  10  may be formed in any suitable manner including machining it from a solid metal blank. For example, the single-pass cold plate assembly  10  may be machined from aluminum or another metal depending on the thermal requirements. 
     The spiral channel  16  may have at least a portion provided in one of the base  12  and cover  14  while the manifold  22  may be provided in the other of the base  12  and cover  14 . As may more clearly be seen in the exploded view of  FIG. 2 , the spiral channel  16  has been illustrated as being at least partially provided within the cover  14  and the manifold has been illustrated as being provided within the base  12 . Although this need not be the case. 
     In the illustrated example, the channel inlet  18  may be located in a central portion of the cover  14  and the channel outlet  20  may be off-set and located on the edge periphery of the cover  14 . It may be understood that the spiral channel  16  does not need to be a circular spiral or a perfect spiral. Instead, the spiral channel  16  may have any suitable shape including that the spiral channel  16  may be formed from a series of rectangular, squares, triangles, irregular shapes, etc. The spiral channel  16  may be formed in any suitable manner providing that it has a progressively increasing diameter from the channel inlet  18  to the channel outlet  20 . A progressively wider channel may reduce pressure drop and reduce pumping power. In the illustrated example, the spiral channel  16  formed in the cover  14  is shown as having a cylindrical cross-section. It is understood that this need not be the case and that the spiral channel  16  may be shaped in any suitable manner including that it may have a rectangular cross section. 
     The manifold  22  has been illustrated as having the manifold inlet  24  located on an edge periphery of the base  12  and the manifold outlet  26  located in a central portion of the base  12  and in fluid communication with the channel inlet  18 . More specifically, the reservoir  28  has been illustrated as being located between the manifold outlet  26  and the channel inlet  18  and providing fluid communication between them. The manifold inlet  24  is laterally spaced from the channel outlet  20 . In this manner, the base  12  and cover  14  enclose the inner contour geometry of the cold plate including the manifold  22  and the spiral channel  16 . 
     One or more O-rings  32  may be included between the base  12  and the cover  14  to prevent leakage of liquid coolant used in the single-pass cold plate assembly  10 . One or more grooves or seats  34  may be machined into the base  12  and/or the cover  14  to retain the O-rings  32 . In the illustrated example, two O-Rings  32  have been included. One O-ring  32  is illustrated at an outside edge of the spiral channel  16  and the second O-ring  32  is illustrated at an edge of the reservoir  28 . The O-ring around the spiral channel  16  has been illustrated as being circular while the other O-ring has been illustrated as being semi-circular. It is understood that the shape of each O-ring  32  may be configured in any suitable manner. Each may have a shape corresponding to other structures within the single-pass cold plate assembly  10  including those of the spiral channel  16  and reservoir  28 . 
     Referring now to  FIG. 3 , an inlet fluid line  40  and an outlet fluid line  42  have been illustrated as being fluidly coupled to the manifold inlet  24  and channel outlet  20 , respectively. When the single-pass cold plate assembly  10  is assembled, the manifold inlet  24  is constructed to receive the liquid coolant and the channel outlet  20  is configured to allow the coolant to exit. The inlet fluid line  40  and outlet fluid line  42  may be fluidly coupled to a source of liquid coolant  44  and a pumping mechanism  46 , both schematically illustrated, such that liquid coolant can be delivered to the manifold  22  and spiral channel  16 . The inlet fluid line  40 , outlet fluid line  42 , source of liquid coolant  44 , and pumping mechanism  46  may all be considered to be a part of the single-pass cold plate assembly  10 . 
     An electronic device  50  or a high-powered electronic device may be mechanically coupled to the single-pass cold plate assembly  10 . The single-pass cold plate assembly  10  may be utilized with any electronic dissipating component that requires a coolant module for thermal management such as electronic components that require a uniform temperature distribution due to sensitivity with thermal expansion effects. For example, the single-pass cold plate assembly  10  may be used with both airborne and ground based electronics. In the illustrated example, the electronic device  50  has been illustrated as a metal-oxide-semiconductor field-effect transistor (MOSFET) electronic package such as silicon carbide MOSFET. The electronic device  50  has been illustrated as being mounted on a top surface of the single-pass cold plate assembly  10 , which includes the spiral channel  16 , in this case the cover  14 , as shown in  FIG. 4 . The electronic device  50  may be mounted to the single-pass cold plate assembly  10  in any suitable manner including that a thermal conductive adhesive may be used to couple the single-pass cold plate assembly  10  to the electronic device to be cooled. 
       FIG. 5  illustrates the movement of the liquid coolant through the cold plate assembly  10 . First, the liquid coolant enters the manifold  22  from the manifold inlet  24  as illustrated by the arrow  60 . At this point, the liquid coolant has its lowest temperature and effectively removes heat from the concentrated centralized hot spot under an electronic device  50  ( FIG. 4 ). Next, the liquid coolant flows into the central reservoir  28  as illustrated with arrow  62 . The liquid coolant within the reservoir  28  maintains a low temperature at the center of the cold plate assembly  10 . The liquid coolant is introduced into the reservoir  28  to minimize concentrated hot spots that are generated at the center of electronic components. The liquid coolant then enters into the spiral channel  16  as illustrated by arrows  64 . The coolant within the spiral channel  16  produces an effective convection heat transfer rate while achieving a minimum pressure drop and high speed flow rate within the single-pass cold plate assembly  10 . Finally, the liquid coolant flows out through the channel outlet  20  as illustrated with arrow  66 . 
     In the above described example, within the single-pass cold plate assembly  10  fully developed turbulent flow is created because the flow path through the spiral channel  16  is long compared with the entrance diameter. In addition, there are no sharp corners within the spiral channel  16 , thereby ensuring no high thermal and structural stress risers. The small radius in the spiral channel  16  minimizes fouling accumulation and maximizes the convection heat transfer coefficient. Furthermore, convection heat transfer is achieved within the single-pass cold plate assembly  10  with minimum pressure drop, since there is only one entrance and one exit hydraulic. The liquid coolant flow velocity distribution at the inlet adjusts itself to the geometry along the distance of the passage length. 
       FIG. 6  illustrates an alternative single-pass cold plate assembly  110 . The single-pass cold plate assembly  110  is similar to the single-pass cold plate assembly  10  previously described. Therefore, like parts will be identified with like numerals increased by 100, and it is understood that the description of like parts of the single-pass cold plate assembly  10  applies to the single-pass cold plate assembly  110 , unless otherwise noted. One difference between them is that the single-pass cold plate assembly  110  includes miniature heat pipes  170  located at least partially within the spiral channel  116  to conduct heat away from hot spots located within the electronic device  150  ( FIG. 9 ). The miniature heat pipes  170  may act as thermal vias to conduct high dissipation heat loads into the liquid coolant within the single-pass cold plate assembly  110 . The miniature heat pipes  170  may be formed in any suitable manner including that a diameter of each miniature heat pipe  170  may be smaller than a length of each miniature heat pipe  170 . Furthermore, the miniature heat pipes  170  may contain a phase change liquid/vapor such as water, ammonia, etc. As shown more clearly in  FIGS. 7 and 8  the miniature heat pipes  170  extend through both the base  112  and cover  114 . 
     As with the earlier described embodiment, the single-pass cold plate assembly  110  provides a high convection heat transfer coefficient to cool the electronic device  150 , shown in  FIG. 9 . The single-pass cold plate assembly  110  may be machined of materials with the same mechanical properties as the electronic device  150 , therefore matching the coefficient of thermal expansion of the electronics device  150 . As with the earlier embodiment, the spiral channel  116  has a channel inlet  118  that is below the center of the electronic device  150 , which provides an effective means of cooling any centrally located hot spots. 
     Regardless of whether the single-pass cold plate assembly includes heat pipes or not it is contemplated that the spiral channel may include riblets  180  that may project into the spiral channel. Such riblets  180  have only been schematically illustrated in  FIG. 8  for illustrative purposes. The riblets  180  may be integrally formed with the spiral channel in the direction of flow of the liquid coolant. Further, such riblets  180  may project from any surface of the spiral channel including the bottom and/or sides of the spiral channel. The riblets  180  may be formed in any suitable manner to reduce pressure drop within the spiral channel including that the riblets  180  may be sized and shaped in any suitable manner. By way of non-limiting example, the riblets  180  may be on the order of 150 microns in size. Such riblets  180  may act to reduce the friction forces, reduce turbulence, and reduce the pressure drop within the single-pass cold plate assembly. By way of further alternative examples, the single-pass cold plate assembly may also be formed from additional pieces including that the single-pass cold plate assembly may include a base, cover, and a central manifold section there between. Regardless of the exact structure of the single-pass cold plate assembly, it may have a structure with a coefficient of thermal expansion that matches the electronic device that is being cooled. 
     The embodiments described above provide a variety of benefits including that the single-pass cold plate assemblies solve the thermal management problem of cooling electronic devices with high power dissipations. The above described embodiments provide relatively uniform cooling with an effective convection heat transfer coefficient and have a large area coupling the cooling medium to the electronic device being cooled. Compared with contemporary heat exchangers such as a milli-channel heat exchanger, the above described embodiments provide an order of magnitude lower manufacturing cost, a three times more effective cooling means, lower manufacturing and operational induced stresses and two times lower fluid flow pressure drop. The above described embodiments may be manufactured rapidly and at low cost. Further, during production, the simplicity of parts allows ease of assembly. The above described embodiments have a lower heat sink volume and have a lower required pump pressure when compared to a conventional heat exchanger with internal fins, which minimizes pump electrical draw. The above described embodiments are also light weight, have a high thermal efficiency, and improved component reliability. 
     To the extent not already described, the different features and structures of the various embodiments may be used in combination with each other as desired. Some features may not be illustrated in all of the embodiments, but may be implemented if desired. Thus, the various features of the different embodiments may be mixed and matched as desired to form new embodiments, whether or not the new embodiments are expressly described. All combinations or permutations of features described herein are covered by this disclosure. 
     This written description uses examples to disclose the invention, including the best implementation, to enable any person skilled in the art to practice the invention, including making and using the devices or systems described and performing any incorporated methods presented. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.