One or more aspects of the invention relate generally to heat transfer and, more particularly, to a fluid-operated heat transfer device for use in a thermal control system.
A continuing trend in the electronics, automobile, avionics, and spacecraft industries, among other industries, is to create more and more compact apparatuses leading to an increase in the power density of such apparatuses. Accordingly, as the power density of such apparatuses increases, there may be a corresponding increase in thermal energy to be dissipated for operability of such apparatuses. Notably, the size of such apparatuses, as well as the systems in which they are implemented, may impose additional constraints on the size of heat transfer devices used to transport such heat away.
Thus, the increase in power density of high-heat flux devices can make demands on heat transfer devices more acute. This additional demand on the ability to transport heat is further exacerbated by generally smaller dimensions utilizable for such heat transfer devices. Some examples of high-heat flux devices include microprocessors, graphics processing units, power handling semiconductors, lasers, programmable logic devices, motherboards, and digital signal processors, among other known high-heat flux devices.
Conventional heat transfer devices include passage ways by which a media, such as fluid, is flowed to transport heat. As a result of an increase in the amount of thermal energy to be transported, complexity associated with heat transfer devices has increased. This increase in complexity has generally led to an increase in hydrodynamic losses associated with fluid passing through such heat transfer devices. The increase in hydrodynamic losses has generally resulted in an increase in the consumption of energy for operation of the heat transfer devices themselves.
Accordingly, it would be desirable and useful to provide means for enhancing heat transfer but without the degree of hydrodynamic losses associated with prior heat transfer devices.
One or more aspects of the invention generally relate to heat transfer and, more particularly, to a fluid-operated heat transfer device for use in a thermal control system.
An aspect of the invention is a heat transfer device including a chambered heat exchanger having interior surfaces defining an interior volume, where the chambered heat exchanger has an inlet and an outlet for passage of liquid into and out of the interior volume. The chambered heat exchanger further includes: first pins extending from a first interior surface of the interior surfaces; first contours of a second interior surface of the interior surfaces being spaced apart from and at least substantially vertically aligned with ends of the first pins; a portion of the first contours having first orifices extending from the second interior surface through to a third interior surface of the interior surfaces; and the third interior surface having a network of micro-channels intersecting the orifices. The network of micro-channels has micro-channel passages with a hydraulic diameter in a range of approximately 0.2 mm to 3.5 mm.
Another aspect of the invention is heat transfer device including a housing having input and output ports for ingress and egress of a medium. The housing defines an interior volume. A first portion of the interior volume has pins extending therein, and a second portion of the interior volume is defined in part by a network of micro-channels. An interface between the first portion of the interior volume and the second portion of the interior volume has orifices for providing passageways for flow of the medium between the first portion and the second portion. A first portion of the pins are spaced apart from the interface to promote generation of vortices of the medium in the first portion of the interior volume.
Yet another aspect of the invention is a method of heat transfer. A medium is pumped into a heat transfer device. The medium is provided with a first set of parameters. The heat transfer device has an interior pin region coupled to an interior micro-channel region via orifices defined by a member of the heat transfer device. The member has a first side for defining in part the interior pin region and a second side for defining in part the interior micro-channel region. A flow of the medium occurs in the heat transfer device responsive to the pumping of the medium therein. The flow includes horizontal flow between pins of the heat transfer device in the interior pin region; vertical flow between the pins of the heat transfer device in the interior pin region; and swirling flow at least proximal to the orifices. In-micro-channel flow of the medium in the interior micro-channel region is affected by vortices associated with the swirling flow in the interior pin region to assist flow rate of the in-micro-channel flow. The medium exits the heat transfer device with a second set of parameters.
Accompanying drawing(s) show exemplary embodiment(s) in accordance with one or more aspects of the invention; however, the accompanying drawing(s) should not be taken to limit the invention to the embodiment(s) shown, but are for explanation and understanding only.
A relatively high-efficiency heat transfer device is described having a pin-dimple and dimple-micro-channel configuration of a heat sink structure. In the following description, numerous specific details are set forth to provide a more thorough description of the specific embodiments of the invention. It should be apparent, however, to one skilled in the art, that the invention may be practiced without all the specific details given below. In other instances, well known features have not been described in detail so as not to obscure the invention. For ease of illustration, the same number labels are used in different diagrams to refer to the same items; however, in alternative embodiments the items may be different.
Upper plate 101 includes pins 103. Pins 103 generally extend from upper plate 101 in a downward direction toward lower plate 102. Lower plate 102 includes pins 104. Pins 104 generally extend from lower plate 102 in an upward direction toward upper plate 101. It should be understood that pins 103 and 104 extend toward plates 102 and 101, respectively, but are spaced apart from such plates. This spacing with reference to pins 103 and lower plate 102 is generally indicated as distance 105. Additionally, the separation of pins 104 from upper plate 101 is generally indicated as distance 106. Distance 105 is generally measured from end surfaces (“ends”) 114 of pins 103 to an interior surface 109 of lower plate 102. Distance 106 is generally measured from ends 115 of pins 104 to an interior surface 108 of upper plate 101. More particularly, distances 105 and 106 are bounded by ends of pins 103 and 104, respectively, and interior surfaces 109 and 108, respectively, as associated with respective dimples. Additionally, pins 104 have a length 161 and pins 103 have a length 162.
Notably, heat transfer device 100 may have one set of pins and one set of corresponding dimples. Dimples 112 are formed to provide concave or recess contours (“dimples”) as part of the contour of interior surface 108. For example, a top plate may have pins extending therefrom and a bottom plate may have dimples, at least a portion of which correspond to ends of the pins. Such bottom plate need not have pins in this implementation. However, for purposes of clarity by way of example and not limitation, overlapping and spaced apart pins extending from both upper and lower plates is described.
In this example, upper plate 101 and lower plate 102 are machined from respective solid pieces of material, such as copper, aluminum, or other known material for use in heat transfer. Thus, interior surface 109 of lower plate 102 may be contiguous with side surfaces 110 of pins 104. Moreover, interior surface 108 of upper plate 101 may be contiguous with side surfaces 111 of pins 103. However, machining from solid pieces of material need not be used, and other manufacturing techniques, such as molding, stamping, or coining, may be used with or without machining. This may further facilitate using other types of materials, such as carbon fiber for example.
Dimples 112 and 113 are part of interior surfaces 108 and 109 of upper plate 101 and lower plate 102, respectively. These dimples 112 and 113 may be formed, in whole or in part, as a byproduct of the formation of pins, such as pins 103 and 104, respectively, or vice versa. Dimples 113 are formed to provide part of the contour of interior surface 109. Notably, ends 114 of pins 103 are generally centered with respect to dimples 113. Moreover, ends 115 of pins 104 are generally centered with respect to dimples 112. Thus, it should be appreciated that ends and dimples are spaced apart and are at least substantially coaxially aligned with respect to vertical orientation.
Formed in lower plate 102, or in a sealing plate 122 coupled to bottom plate 102, or in a combination thereof, may be a network of micro-channels as generally indicated in
The network of micro-channels bounded on at least two sides by sealing plate 122 and lower plate 102 defines a portion of an interior volume of heat transfer device 100. Another portion (“interior region”) 130 of an interior volume of heat transfer device 100 is bounded on at least two sides by upper plate 101 and lower plate 102. Fluid 121 may flow in an inlet (not shown in
Fluid 121, as generally indicated by arrows of
Fluid 121 may flow between pins 103 and 104 in interior region 130, for example in a substantially horizontal direction as indicated by arrows 123. In other words, fluid 121 may weave in and out between pins 103 and 104 in a direction generally transverse to orientation of pins 103 and 104. Additionally, fluid 121 may flow up and down between pins 103 and 104 as generally indicated by arrows 166. In other words, fluid 121 may weave in and out between pins 103 and 104 in a direction generally axial to orientation of pins 103 and 104.
The location of ends 114 with respect to dimples 113 and of ends 115 with respect to dimples 112 promotes the creation of vortices in flow of fluid 121 as indicated by circled regions (“vortices”) 124. Thus, swirling movement of fluid between ends 114 and interior surface 109 and between ends 115 and interior surface 108 is generated by pumping fluid 121 into interior region 130. It should be understood that vortices 124 may extend away from dimples 112 and 113 to be along part of the length of associated pins 103 and 104 proximal to associated ends 114 and 115, respectively.
While not wishing to be bound by theory, it is believed that vortices 124 at least proximate to, which may include extending into, orifices 116 influence the flow of fluid 121 in micro-channel 120. By creating vortices 124 affecting fluid flow in micro-channel 120 via orifices 116, flow rate of fluid 121 in micro-channel 120 may be accelerated by such swirling movements without having to correspondingly increase pressure provided by an external pump. While not wishing to be bound by theory, it is believed that this relationship between fluid flow in micro-channels 120 and fluid flow in interior region 130 is in effect a coupling of the two fluid flows via orifices 116, where fluid flow associated with vortices 124 proximal to orifices 116 propels or otherwise accelerated fluid flow in micro-channels 120. Notably, although generally uniform arrows are illustratively shown, it should be appreciated that fluid 121 flow in micro-channel 120, as well as in interior region 130, may generally be turbulent flow for purposes of removing heat. However, there may be some laminar flow too.
Heat transfer device 110 of
Orifices 146 may be formed like orifices 116, namely responsive to the formation of micro-channel 145 such that interior surface 148 of upper plate 140 are perforated. Orifices 146 provide passageways from interior region 130 through to the interior of micro-channel 145. Again, while not wishing to be bound by theory, it is believed that fluid flow associated with vortices 124 affects fluid flow in micro-channel 145 via orifices 146, where swirling motion of fluid flow may accelerate flow rate of fluid 121 in micro-channel 145 by such swirling movements without having to correspondingly increase pressure provided by an external pump.
As illustratively shown, pins 103 and 104 may be at least partially interposed with respect to one another. A portion of the vertical length of pins 103 may extend into a cavity region of lower plate 102 as defined in part by sidewalls 206 thereof. A portion of the vertical length of pins 104 may extend into a cavity region of upper plate 101 defined in part by sidewalls 205 thereof.
A block 210 has been put in contact with lower plate 102, and such block 210 may be coupled to lower plate 102, such as via a thermally conductive medium. Examples of thermally conductive media that may be used include thermal paste, solder, and other metals, among other known thermally conductive media. Block 210 is used to generally indicate an association with high heat flux device, such as an integrated circuit chip (“chip”), multi-chip module, or a heat sink for example. Thus, heat transfer assembly 200 of
Notably, either or both of heat transfer assemblies 200 and 220 may be implemented. However, it shall be apparent to one of ordinary skill in the art from the following description of an implementation of heat transfer assembly 200 that heat transfer assembly 220 may be implemented in a like manner.
Pump 301 may be coupled to heat transfer assembly 200 via conduit 305. Conduit 305 may be composed of tubing or piping which may or may not be circular in cross section. Pump 301 pumps fluid to an inlet of heat transfer assembly 200. Notably, although it has been assumed that a single inlet is used, as well as a single outlet, it should be appreciated that multiple inlets, and outlets, may be used for heat transfer assembly 200.
Pump 301 may provide fluid into heat transfer assembly 200 with a wide range of pressure and flow rate. Notably, the dimensions of a heat transfer assembly may vary from application to application, and the amount of heat removal may vary from application to application. Thus, these ranges are merely illustrative of the exemplary implementations described below, which implementations are generally directed at cooling microprocessors. It should be appreciated that other integrated circuits, multi-chip modules, heat sinks, or other devices associated with high heat flux may have different thermal characteristics than microprocessors, and thus variation of the exemplary embodiments herein may be used to accommodate such differences in such other applications.
Fluid flow characteristics in heat transfer assembly 200 may generally be characterized by flow rate, pressure gradient, and Reynolds number (“Re”). While not wishing to be bound by theory, it is believed that vortices 124 of
Outlet 202 of heat transfer device 100 is coupled to conduit 306. Conduit 306 is used to couple fluid flow from heat transfer assembly 200 to heat exchanger 302. Notably, heat exchanger 302 in this example is shown having an output which is coupled to pump 301. However, a less direct coupling may be used. In fact, even though heat exchange system 300 is shown as a closed loop system, an open loop system may be used. Such an open loop system may be more common where heat exchanger 302 is part of an HVAC system of a building. Use with an HVAC system may be more prevalent in applications where multiple high heat flux blocks are used simultaneously, such as computer server system applications. Additionally, it should be appreciated that to promote energy conservation, heat transported from heat transfer assembly may be used for heating, such as providing hot water for example. However, for purposes of clarity, it shall be assumed that heat exchange system 300 is a closed loop system such as for cooling a microprocessor or other integrated circuit(s) of a personal computer.
Fluid output from heat exchanger 302 is provided to pump 301 via conduit 307. Thus, it should be appreciated that conduits 305 and 307 are associated with a cold side of heat exchange system 300, and conduit 306 is associated with a hot side of heat exchange system 300. Notably, conduits 305 through 307 may be the same or different from one another with respect to their composition or hydraulic diameter or any combination thereof.
As shall be appreciated from description of the example implementations below, micro-channels and orifices of heat transfer device 100 may be such that filter 303 is optional. Even though heat exchange system 300 may employ water, it should be appreciated that other types of fluids may be used, such as water/anti-freeze mixture, oil, or a dielectric fluid for example.
Instead of dimples 112 associated with an upper plate, an upper plate 401 includes pimple contours (“pimples”) 412. Pimples 412 may extend further into fluid passageways of interior region 130 than dimples 113 of lower plate 102. Notably, pimples may not be as effective as dimples for effecting transfer of heat via fluid flow. Furthermore, it should be appreciated that some or all associated interior surface areas may formed with neither pimples 412 nor dimples 113, as such interior surface areas may be generally flat with orifices, like orifices 116, to provide fluid passageways between an interior region 130 and a network of micro-channels.
Distance between ends 115 of pins 104 and interior surface 408 of upper plate 401 as associated with pimples 412, namely distance 406, may be less than distance 106 of
Lower plate 402 includes pimples 413. Pimples 413 of
With reference to
Lower plate 502 includes dimples 113, pins 104, and fluid flow dams 583. Notably, some dimples 113 include orifices 116, while other dimples 113 do not include orifices 116. It should be appreciated that vortices, such as vortices 124 as described elsewhere herein, may be generated in both forms of dimples; however, dimples 113 having orifices 116 provide passageways for some confluence of fluid flow in an interior region, such as interior region 130 of
Notably, fluid may flow, for example, from left to right across lower plate 502. It should be understood that this fluid flow may start generally at a bottom left corner of lower plate 502 and proceed to an upper right corner of lower plate 502. Furthermore, it should be understood that as fluid flows across lower plate 502, such fluid when entering lower plate 502 has a significantly lower temperature than when exiting lower plate 502 when in use with a high heat flux device. In order to provide for a more uniform temperature gradient surficially across lower plate 502, fluid flow dams 583, which may have counterparts as part of an upper plate, may be used to direct fluid flow within lower plate 502. More particularly with respect to an interior region associated with lower plate 502, such as interior region 130 as previously described for example with reference to
Notably, the transverse spacing between a right interior surface of a left sidewall 206 and a left interior surface of a left fluid flow dam 583, generally indicated by arrow 507, is wider than the transverse spacing between fluid flow dams 583, generally indicated by arrow 508. This is because the cooler fluid entering lower plate 502 may be more widely dispersed for providing uniform cooling when generally initially received and less widely dispersed as such fluid moves through an interior region associated with lower plate 502 and becomes hotter. Furthermore, the transverse spacing between a left interior surface of right side fluid flow dam 583 and a left interior surface of a right sidewall 206 of lower plate 502, generally indicated by arrow 509, is narrower than the transverse spacing 508 between fluid flow dams 583. Thus, it should be appreciated that fluid flow dams 583 may be sufficiently tall that the interior region of a heat transfer device may be chambered such as for providing a more uniform temperature gradient surficially across a heat transfer device in connection with cooling a high heat flux device.
In this particular example, a serpentine fluid flow is used as generally indicated by arrow 500. However, other types of fluid flow may be used. Furthermore, depending on the application, it may be determined that more cooling is needed in one area than in another area of a high heat flux block, and accordingly, fluid flow dams may be positioned to accommodate different cooling needs associated with a high heat flux block.
In this example, a peninsula region 581 is provided and may be used as part of fluid flow dam 583. However, it should be appreciated that holes (not shown) may be formed in peninsula region 581 for coupling monitoring wires to monitor temperature.
For a microprocessor application, dimples 113 may be spaced apart by approximately 0.2 to 10 mm on center. Additionally, diameter of dimples 113 may be approximately 0.5 to 5.0 mm, and depth of dimples 113 may be approximately 0.25 to 2.50 mm. Furthermore, distance from the bottom of an interior surface of a dimple 113 to an end 115 of a pin 104, not shown in
It should be appreciated that surface 560 is an upper interior surface of lower plate 502. Bottom interior surface 109 of
Additionally, it should be appreciated that pressure may drop as a fluid moves from an inlet to an outlet. Additionally, it should be appreciated that fluid velocity may vary as fluid moves from an inlet to an outlet. Thus, to provide effective heat transfer from a heat source having a non-uniform temperature field, there may be generally more micro-channels closer to an outlet in comparison to the number of micro-channels closer to an inlet or vice versa. Thus, it should be appreciated that micro-channel distribution may be uniform, non-uniform, or any combination thereof, and thus may be adapted to the temperature field of target heat source application.
Accordingly, by tailoring a network of micro-channels 120, namely “network of micro-channels 598,” to a target device to be cooled, a heat transfer device, such as heat transfer device 100 of
It should be appreciated that hydraulic resistance may be adjusted by chambering an interior volume with fluid flow dams. For example, suppose an inlet is defined by an upper surface of an upper plate and positioned proximal to a corner thereof, with an outlet being on a diagonally opposite corner. In this configuration, fluid may first flow into a first chamber 575 generally entering at location 578. Such fluid may then flow into a second chamber 576, and then into a third chamber 577 and exit the third chamber generally at a location 579. Because chamber 575 has more pins than chambers 576 and 577, it is capable of transferring more heat than chambers 576 and 577. However, because chamber 575 is wider than chambers 576 and 577, fluid flow velocity may be less in chamber 575 than in chambers 576 and 577. It should be further understood that fluid temperature may be lower when entering chamber 575 than when exiting chamber 577, and may progressively increase until exiting chamber 577. Fluid flow velocity increases in chamber 576 over fluid flow velocity in chamber 575, as chamber 576 is narrower than chamber 575. Furthermore, fluid flow velocity increases in chamber 577 over fluid flow velocity in chamber 576, as chamber 577 is narrower than chamber 576. A more rapid fluid flow facilitates heat transfer. Thus, chambering fluid flow out, such to provide a serpentine flow as indicated by arrow 500 of
Lower plate 602 differs at least in part from lower plate 502 of
In contrast to the generally horizontally and vertically aligned cross-like orifices 116 of
Network of micro-channels 698 may be oriented to provide more uniform cooling across a surface. Accordingly, micro-channels 120 may be positioned relative to an inlet and an outlet for ingress and egress of fluid. In this example embodiment, horizontal distance 681 from end to end of an oblong orifice 116 is in a range of approximately 0.2 to 5.5 mm. Horizontal distance 682 from nearest ends of neighboring oblong orifices 116 is in a range of approximately 0.2 to 4.5 mm. Horizontal, as well as vertical, distance 683 of an X-like orifice 116 is in a range of approximately 0.2 to 4.5 mm. Lastly, distance 684, namely micro-channel width of a micro-channel 120, is in a range of approximately 0.2 to 5.5 mm.
Excess material associated with sealing plate 701 may be removed after soldering to lower plate 502. It should be appreciated that by having a thin sealing plate 701, heat conduction, and thus heat transfer, may be facilitated for removal of heat from a high heat flux block. Thus, lower portion of assembly 700 of a heat transfer device 100 of
It should be appreciated that a heat transfer device has been described where heat associated with a high-heat flux device may be transported away using a fluid as a thermal energy carrier. Notably, the degree of hydrodynamic losses associated with such heat transfer device is sufficiently low, such that complexity associated with pumping fluid is reduced. Furthermore, this reduction in hydrodynamic losses facilitates using less powerful pumps. Additional information regarding hydrodynamic losses may be found in M. Spokoiny et al., “Enhanced Heat Transfer in a Channel with Combined Structure of Pin and Dimples”, Proceedings of 9th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, 5-8 June (2006), San Francisco, Calif.
As previously indicated, numerical examples associated with a heat transfer device for an integrated circuit, and in particular a microprocessor, have been described. However, it should be understood that a heat transfer device may be decreased or increased in size to accommodate applications smaller or larger than an integrated circuit. So although specific numerical examples of dimensions have been provided, other dimensions may be used, as well as other known geometric shapes, other than those specifically described herein. Thus, in general, the following ratios may be used: the ratio of the cross-sectional area of a micro-channel to the cross-sectional area of a main channel may be in a range of approximately 5×10−6 to 2×10−1; the ratio of the depth of a dimple to the diameter of a dimple may be in a range of approximately 0.1 to 0.5; the ratio of the diameter of a dimple to the hydraulic diameter of a micro-channel may be in a range of approximately 0.1 to 50.0; the ratio of the distance from the end surface of a pin to surface of a dimple, for example distance 105 in
While the foregoing describes exemplary embodiment(s) in accordance with one or more aspects of the invention, other and further embodiment(s) in accordance with the one or more aspects of the invention may be devised without departing from the scope thereof, which is determined by the claim(s) that follow and equivalents thereof. For example, known materials other than those specifically listed herein may be used.
Claim(s) listing steps do not imply any order of the steps. Trademarks are the property of their respective owners.
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