Abstract:
Heat transfer devices and methods for making the same that include a first enclosure having at least one inlet port; a second enclosure having a bottom plate and one or more dividing walls to establish channels, at least one internal surface of each channel having rib structures to create turbulence in a fluid flow; and a jet plate connecting the first enclosure and the second enclosure having impinging jets that convey fluid from the first enclosure to the channels, said impinging jets being set at an angular deviation from normal to cause local acceleration of fluid and to increase a local heat transfer rate.

Description:
RELATED APPLICATION INFORMATION 
       [0001]    This application is a Divisional of co-pending application Ser. No. 13/415,266, filed Mar. 8, 2012, incorporated herein by reference in its entirety. 
     
    
     GOVERNMENT RIGHTS 
       [0002]    This invention was made with Government support under Contract No.: DE-EE0002894 (Department of Energy). The government has certain rights in this invention. 
     
    
     BACKGROUND 
       [0003]    1. Technical Field 
         [0004]    The present invention relates to cooling and, more particularly, to cooling devices that use inclined impingement of coolant fluid into ribbed channels. 
         [0005]    2. Description of the Related Art 
         [0006]    The demand for increased power and performance in semiconductor devices grows constantly. Meeting that demand produces an increased amount of heat, and therefore also increases the need for effective heat dissipation. While conventional cooling solutions have worked on the devices of the past, no straightforward extension of those principles has been found for high heat fluxes in the smaller and more efficient electronic devices that present fabrication technologies are capable of producing. In particular, the air-cooled heatsinks of the past are ineffective in addressing the cooling needs of modern devices. 
         [0007]    A number of alternative cooling solutions have been proposed, including liquid-based systems that pump liquid coolant across a heat dissipation apparatus. However, there are practical limitations to the efficiency of such devices when implemented at small scale. Improved cooling would allow for the use of higher-power devices and would enable an increase in the practical computing capacity of devices in many fields of technology. 
       SUMMARY 
       [0008]    A heat transfer device is shown that includes a first enclosure that has at least one inlet port; a second enclosure that has a bottom plate and one or more dividing walls to establish a plurality of channels, at least one internal surface of each channel having a plurality of rib structures to create turbulence in a fluid flow; and a jet plate connecting the first enclosure and the second enclosure having a plurality of impinging jets that convey fluid from the first enclosure to the plurality of channels, said impinging jets being set at an angular deviation from normal to cause local acceleration of fluid and to increase a local heat transfer rate. 
         [0009]    A heat transfer device is shown that includes a first enclosure to accept and collect fluid input that has at least one inlet port to introduce a fluid flow; a second enclosure that has a bottom plate and one or more dividing walls to establish a plurality of channels, at least one internal surface of each channel having a plurality of rib structures to create turbulence in a fluid flow, wherein the second enclosure is disposed below the first enclosure and offset such that the inlet port is laterally displaced from the plurality of channels; and a jet plate connecting the first enclosure and the second enclosure having a plurality of impinging jets that convey fluid from the first enclosure to the plurality of channels, said impinging jets being set at an angular deviation from normal to cause local acceleration of fluid and to increase a local heat transfer rate. 
         [0010]    A heat transfer device is shown that includes a first enclosure to accept and collect fluid input that has at least one inlet port in the center of a top surface of the enclosure to introduce a fluid flow; a second enclosure that has a bottom plate and one or more dividing walls to establish a plurality of channels, at least one internal surface of each channel having a plurality of rib structures to create turbulence in a fluid flow, wherein the second enclosure is disposed below the first enclosure and centered below the inlet port; and a jet plate connecting the first enclosure and the second enclosure having a plurality of impinging jets that convey fluid from the first enclosure to the plurality of channels, said impinging jets being set at an angular deviation from normal to cause local acceleration of fluid and to increase a local heat transfer rate. 
         [0011]    A method for forming a cooling device is shown that includes forming a top cover plate with at least one inlet port; forming a jet plate with a plurality of inclined jets set at an angular deviation from normal; forming a bottom plate with channel wails that have ribs; attaching the top cover plate to the jet plate to form an inlet plenum; and attaching the jet plate to the bottom plate to form a plurality of ribbed channels. 
         [0012]    These and other features and advantages will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]    The disclosure will provide details in the following description of preferred embodiments with reference to the following figures wherein: 
           [0014]      FIG. 1  is an exploded view of an embodiment of a cooling device in accordance with the present principles; 
           [0015]      FIG. 2  is a cut-away view of an embodiment of a cooling device, providing a cross-sectional view of cooling channels, in accordance with the present principles; 
           [0016]      FIG. 3  is a diagram of an embodiment of a coolant channel having ribs in accordance with the present principles; 
           [0017]      FIG. 4  is a cut-away view of an embodiment of a cooling device, providing a view along the length of the cooling channels, in accordance with the present principles; 
           [0018]      FIG. 5  is an exploded view of an alternative embodiment of a cooling device in accordance with the present principles; 
           [0019]      FIG. 6  is a cut-away view of an alternative embodiment of a cooling device, providing a view along the length of the cooling channels, in accordance with the present principles; 
           [0020]      FIG. 7  is a block/flow diagram of a method for forming a cooling device according to the present principles; and 
           [0021]      FIG. 8  is a block/flow diagram of an alternative method for forming a cooling device according to the present principles. 
           [0022]      FIG. 9  is a diagram of an embodiment of a cooling in accordance with the present principles. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0023]    The present principles combine inclined impingement of coolant with ribbed cooling channels to produce a cold plate for high heat flux applications. The present embodiments use an array of impinging jets to provide high local heat transfer rates and, furthermore, provide an increased wetted surface area and increase flow turbulence along cooling channels with ribs, thereby increasing the overall heat transfer rates by exploiting efficiencies that result from particular kinds of coolant motion. When flow is turbulent, coolant particles exhibit additional transverse motion. This enhances the rate of energy and momentum exchange between coolant particles, thus increasing the heat transfer coefficient and increasing the cooling effect. This improves on conventional single-phase cooling systems, which do not concern themselves with coolant flow at such a minute level. 
         [0024]    Although it is specifically contemplated that the present principles may be applied to fields of technology such as cooling for microprocessors and other electronic/semiconductor devices, the present principles may be applied to a broad range of devices. In particular, coolers made according to the principles described herein may be used in, e.g., industrial, automotive, and home appliance applications to more effectively dissipate waste heat. Any application that uses “active” cooling, where coolant is pumped across a heat dissipating surface, can benefit from implementing the present principles. 
         [0025]    Referring now to the drawings in which like numerals represent the same or similar elements and initially to  FIG. 1 , an exemplary exploded diagram of a cold plate  100  according to the present principles is shown. A bottom channel plate  102  is shown having an inset border  103 . The bottom plate  102  has a set of channel walls  104 , said walls having ribs  105  along their length. Alternatively, the walls  104  may be formed on a separate plate and then joined to the bottom plate  102 . The bottom channel plate  102  can be fabricated using any appropriate method or combination of methods, including milling, electrical discharge machining, etching, stamping, extrusion, and skiving. The bottom channel plate  102  should be formed from a material having a high thermal conductivity, such as copper, to promote efficient heat transfer from the device to be cooled into the coolant fluid. 
         [0026]    A hollow side cover block  106  fits over the recessed border  103  of bottom channel plate  102 . The hollow side cover block  106  forms a tight seal with the bottom channel plate  102 , and may be joined using any appropriate method or combination of methods, including brazing, soldering, and direct-bonding. The hollow side cover block  106  may be formed from the same material as the bottom channel plate  102  or may be formed from another material. Because coolant will still come into contact with the hollow side cover block  106 , the thermal transfer properties of the hollow side cover block  106  are relevant. The hollow side cover block  106  may be formed from any appropriate method, for example extrusion. The hollow side cover block  106  includes inset portions  108  to receive a jet plate  110 . 
         [0027]    The jet plate  110  may be formed from any appropriate material. The jet plate  110  will not come into contact with the bottom channel plate  102 , but will contact channel walls  104 , such that its thermal properties will still be relevant. On the other hand, the jet plate  110  forms a border between input coolant and output coolant. A material with a lower thermal conductivity may therefore be selected, trading off heat transfer from the channel walls  104  for superior insulation between warm outlet coolant and cold input coolant. 
         [0028]    The jet plate  110  fits into hollow side cover block  106  and joins with the channel walls  104 , forming channels with rectangular cross sections. Alternative cross sections may be formed based on the disposition of the channel walls  104 . It is specifically contemplated that quadrilateral cross-sections will be used, but other shapes may also be employed, such as triangles. The bottom surface of jet plate  110  has rows of inclined jet ports  112 , which open into the channels formed by the jet plate  110  and the bottom channel plate  102 . 
         [0029]    A top cover plate  114  fits onto the hollow side cover block  106  and the jet plate  110 , forming an inlet plenum. The top plate  114  may be formed of any appropriate material. In particular, the top plate  114  may be formed from materials similar to those employed in other components, or may be formed from a material having less thermal conductivity. A material with lower thermal conductivity is advantageous in the top plate  114 , as such a material provides superior insulation between warm outlet coolant and cold input coolant, as well as inhibiting the infiltration of ambient heat from the environment. The top cover plate has outlet ports  116  and an inlet port  118 . The number and particular positioning of outlet and inlet ports  116  and  118  may be altered according to the needs of the particular application. 
         [0030]    Coolant may be introduced and removed from cold plate  100  using any appropriate form of pump. The coolant may then be run through a larger heat-dissipation unit, e.g., a heat sink (not shown), reducing the temperature. This allows coolant to be recycled through the cold plate  100  in a closed system. 
         [0031]    Referring now to  FIG. 2 , a cut-away view of an assembled cold plate  100  is shown, illustrating coolant circulation. The coolant may be any suitable material, including air, water, and oil. Exemplary coolants include deionized water, propylene glycol, and mineral oil. The coolant material should be chosen keeping in mind the constituent materials of cold plate  100 , to prevent chemical reactions or degradation from occurring. An advantageous coolant will have a high thermal conductivity, high thermal capacity, and low viscosity. Coolant, illustrated by arrows, enters plenum  202  through inlet hole  118 . The inclined jet holes  112  are shown in jet plate  110 , guiding coolant into channels  204  at an angle, causing coolant to circulate within the channels  204 . This angle is directed perpendicular to the flow of coolant through the channels  204 , producing circulatory turbulence. 
         [0032]    The entrance effect in the inclined jets  112  causes local acceleration of the coolant jets and increases thereby the local heat transfer rates as compared to a normally impinging jet  112  in a combined environment. This effect is partially due to an increased coolant velocity transverse to the channel direction, such that any given quantity of coolant will come into contact with more of the internal surface area of channel  204 . The vortex that results in the coolant is significantly more effective in transferring heat away from the surface of channels  204  than would result with a normally impinging jet  112 , and it is clear that additional turbulence increases the heat transfer rate further. 
         [0033]    The number of jets  112 , jet impingement angle, jet diameter, jet location, and jet orientation may be determined according to the needs of the particular application. Some exemplary impingement angles include 20, 30, and 45 degrees with respect to the normal. It should be recognized that any impingement angle may be used, although too large of an angle will impede coolant flow. An exemplary diameter for jets  112  could be about 1 mm, and the jet  112  could be oriented to impinge upon either of the channels&#39;  204  sidewalls or upon the channel&#39;s base. 
         [0034]    It should also be recognized that the jets  112  may have any appropriate cross-sectional shape. Although it is specifically contemplated that the jets  112  may have a circular cross-section, other shapes may also be employed, including square and triangular cross-sections. One advantageous spacing for jets  112  is three times the diameter of the jets  112 , although it is contemplated that other spacings may be employed within the present principles. Placement, orientation, and size of jets  112  should be selected to maximize coolant flow and turbulence, such that heat transfer in the channels  204  is maximized. 
         [0035]    It should be noted that channels  204  have ribs  105  on three of its four walls. Ribs  105  may be used on one, two, three, or all of the walls of channels  204 , depending on the intended application, but it should be noted that having ribs on the top wall of channels  204 , e.g., on the jet plate  110 , will not contribute substantially to heat transfer and will increase the pressure drop across the cold plate  100 . As such, having ribs  105  on the jet plate  110  may adversely affect the overall dissipative performance of the cold plate  100 . Ribs  105  keep the flow in the channels  204  turbulent and increase wetted surface area. As those having skill in the art will recognize, wetted surface area refers to the surface area of the solid bulk of the walls of channels  204  that is in contact with the coolant fluid. This increase of surface area increases the rate of heat transfer even if a “dry” coolant, such as air, is used. 
         [0036]    Ribs  105  may be formed by milling, electrical discharge machining, etching, stamping, machining, extrusion, or any other suitable technique. Although for simplicity it is specifically contemplated that the ribs will be formed from the same material as the walls of the channels  204 , the ribs  105  may be formed from any appropriate material and added to the channels  204  in any appropriate fashion. Furthermore, ribs may be formed in any shape. For example, the ribs may have a triangular, rectangular, or cylindrical cross section. Furthermore, rib spacing may be adapted to the needs of the particular application and coolant and may be consistent or may vary from rib to rib. 
         [0037]    The bottom channel plate  102  is placed into contact with a surface of a heat source (not shown). Heat is carried away from the heat source and into bottom channel plate  102  by conduction. Because imperfections in solid surfaces may decrease thermal contact and inhibit heat flow, heat transfer may be facilitated by using a substance to promote thermal contact, such as thermal paste, which conducts heat well and which makes contact between the heat source and bottom channel plate  102 . 
         [0038]    Referring now to  FIG. 3  is a cutaway view of a channel  204 . As can be seen, there are ribs  105  along the bottom and two sides of the channel  204 , but not along the top of the channel  204 . The ribs  105  are shown as being regularly spaced, though it is contemplated that the spacing between the ribs  105  may vary. One exemplary profile for the ribs  105  could have a rib height of about 10% of the channel width and a rib spacing of about 5-10 times the rib height. In addition, ribs on multiple walls of the channels  204  could be arranged in an inline or in a staggered manner. 
         [0039]    Ribs  105  may be formed with any appropriate cross-sectional shape. In particular, rectangular cross-sections are shown in  FIG. 3 , but it is contemplated that other shapes, including triangles and semicircles, may be used. The ribs  105  increase coolant turbulence, and “rougher” surfaces will cause greater increases in turbulence. As such, cross-sections with sharp edges or irregularities are better suited to being used in ribs  105 . It is also contemplated that ribs  105  may be formed in such a way as to produce random imperfections on the rib surface, such as machining marks, that further increase coolant flow turbulence. 
         [0040]    Referring now to  FIG. 4 , a cutaway view of an assembled cold plate  100  is shown, viewing the length of one of the channels  204 . Coolant enters by way of coolant input  118  into plenum  202 . Coolant then passes through inclined impingement jets  112  into the channel  204 , creating turbulent flow. The ribs  105  are not shown in this figure for the sake of simplicity. The coolant then passes through side cavities  402  and exits by the coolant outputs  116 . 
         [0041]      FIG. 4  illustrates the fit between the bottom channel plate  102  and the hollow side cover block  106 . 
         [0042]    Referring now to  FIG. 5 , an alternative embodiment of a cold plate  500  is shown. A channel plate  502  includes channel walls  504  with ribs. The channel wails Ply be milled, electrical discharge machined, etched, stamped, skived, machined, or formed through some other appropriate process. Alternatively, the channel walls  504  may be separately formed and attached to channel plate  502 . Channel plate  502  includes a coolant output port  506 . Although the coolant output port  506  is depicted as being disposed within a side wall of the channel plate  506 , the coolant output port  506  may alternatively be disposed in a bottom surface of the channel plate  506 . 
         [0043]    A jet plate  508  is attached to the top of channel plate  502  and has a set of jets  510 . As above, the jets  510  may be inclined to increase coolant turbulence and heat transfer. A cover plate  512  is placed on top of the jet plate  508  and has a coolant intake port  514 . The parts can be joined to one another by any appropriate process, including brazing, soldering, and direct-bonding. 
         [0044]    Referring now to  FIG. 6 , a cut-away view of cold plate  500  is shown, illustrating coolant flow. Coolant enters through intake port  514  into a plenum  602 . Plenum  602  circulates coolant to the jets  510 , which provide the coolant to channels  604 . The channels  604  may extend along the entire length of the plenum  602  or may be shorter. In the present embodiment, the channels  604  are shorter than the full length of plenum  602 , so that there are no jets  510  directly beneath the coolant intake  514 . This provides greater distribution of coolant across the jets  510  along the channel. This improves the uniformity of cooling. If the coolant enters predominately at certain jets  510 , the cold plate  500  directly beneath those jets  510  will receive a disproportionate amount of cooling. By placing the intake  514  over a section that does not have jets  510 , the coolant is forced to circulate more uniformly through the plenum  602 . 
         [0045]    Referring now to  FIG. 7 , a block/flow diagram is shown for forming a cooling device according to the present principles. Block  702  forms a top cover plate  114  that has at least one inlet port  118  and at least one outlet port  116 . The top cover plate  114  may be formed by any appropriate process, including for example milling, electrical discharge machining, etching, stamping, and extrusion. Block  704  forms the jet plate  110  including jets  112 . The jets  112  may be formed with the jet plate by the above processes, or they may be drilled into the jet plate  110 . Block  706  forms side cover block  106 , having guides  108  of such a size as to accommodate the jet plate  110 . Block  708  forms the cooling plate  102  having channel walls  104 . The channel walls  104  may be formed integrally with the cooling plate  102  by, e.g., skiving, or may be formed on a separate surface and then attached to cooling plate  102  by any appropriate method or combination of methods, including brazing, soldering, and direct-bonding. 
         [0046]    Block  710  fits the side cover block  106  onto the cooling plate  102 . The cooling plate  102  may be designed with a recessed border  103  to accommodate the side cover block  106 , such that the side cover block  106  and the cooling plate  102  form a tight seal to prevent coolant leakage. Block  712  fits the jet plate  110  into the guides  108  in the side cover block  106 , and block  714  first the top plate onto the side cover plate  106  and jet plate  110 , forming plenum  202 . The points of contact between the various pieces are joined in such a way as to prevent coolant leakage along the edges, which would diminish cooling efficiency. 
         [0047]    Referring now to  FIG. 8 , a block/flow diagram is shown for an alternative method of forming a cooling device according to the present principles. Block  802  forms a top cover plate  512  that has at least one inlet port  514 . Again, the elements of this embodiment may be formed by any appropriate process, including for example milling, electrical discharge machining, etching, stamping, and extrusion. Block  804  forms jet plate  508  with jets  510  being formed integrally with the jet plate  508  or added afterward by machining or drilling. Block  806  forms a cooling plate  502  with channel walls  504  and sidewalls. As above, the channel walls  504  may be formed integrally with the cooling plate  502  or may be formed separately and then attached to the cooling plate  502  by, e.g., brazing, soldering, and direct-bonding. 
         [0048]    Block  808  forms one or more outlet ports  506  in the sidewalls of cooling plate  502 . The outlet port  506  may optionally also be formed integrally with the cooling plate  502  in block  806 . Block  810  fits the jet plate  508  onto the cooling plate  502 , and block  812  fits the top plate  512  onto the jet plate. The points of contact between the various pieces are joined in such a way as to prevent coolant leakage along the edges, which would diminish cooling efficiency. 
         [0049]    Referring now to  FIG. 9 , a diagram of an exemplary cooling system is shown. Chips  904  are shown, which generate heat during operation that must be removed. Each chip  904  has a cold plate  902  attached to it. The cold plate  902  may be attached using a thermal interface material to promote heat transfer away from the chip  904 . Coolant fluid is then pumped through the cold plate  902  and circulated to a heat rejection unit  906  which removes heat from the coolant and releases it into, e.g., the environment. The coolant then returns to the cold plates  902  to be used again. 
         [0050]    Having described preferred embodiments of a cold plate with combined inclined impingement and ribbed channels (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments disclosed which are within the scope of the invention as outlined by the appended claims. Having thus described aspects of the invention, with the details and particularity required by the patent laws, what is claimed and desired protected by Letters Patent is set forth in the appended claims.