WO2018045052A1 - Thermoelectric cooling systems for electronic devices - Google Patents

Abstract

High efficiency thermoelectric electronics or CPU cooler utilizing advanced liquid heat rejection systems and flexible heated shroud for cooling below dew point is disclosed. Thermoelectric heat pump CPU chillers have several advantages. They overcome the limitations of conduction resistance by lowering the temperature of the conductive medium that is adjacent to the CPU die, thus increasing the driving temperature differential. Both the hot and the cold side of the modules have access to highly effective heat transfer skived fin microchannel heat exchangers. Additionally they distribute the load over several modules, allowing improved COPs. In addition, thermoelectric CPU chillers can provide CPU cooling to below ambient temperatures and in a single stage heatpump to below dew point cooling and in two stage and three stage heat pump configurations below zero C approaching cryogenic temperatures where the CPU can operate more reliably and at a high clock speed.

Description

THERMOELECTRIC COOLING SYSTEMS FOR ELECTRONIC DEVICES

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority from U.S. Provisional Patent Application No. 62/381,475 filed on August 30, 2016 entitled HIGH EFFICIENCY THERMOELECTRIC ELECTRONICS OR CPU COOLER UTILIZING ADVANCED LIQUID HEAT REJECTION SYSTEMS AND FLEXIBLE HEATED HEAT SPREADER SHROUD FOR COOLING SIGNIFICANTLY BELOW DEW POINT, which is hereby incorporated by reference.

BACKGROUND

[0002] The present application relates generally to thermoelectric cooling systems for electronic devices, particularly central processing units (CPUs), graphics processing units (GPUs), and other processing units and computer chip components.

[0003] Interest in CPU cooling has heightened as CPU speed increases generate levels of heat that are becoming increasingly more difficult for thermal engineers to control. Moore's Law appears to be still holding, and as CPU speeds increase exponentially, so does the heat generated. Worse, feature sizes have recently shrunk from 0.25 microns to 0.1 microns, leading to a 6 times smaller area. Computer chip manufacturers have publicly called for wider efforts to address the thermal issues, which threaten to restrict computer performance in the future. Common CPU failure mechanisms tend to be mechanical (e.g., wire bond failure, die fracture, corrosion) and electrical (e.g., overstress, migration and diffusion, gate oxide breakdown). Based on the

Arrhenius equation (for die temperatures operating in the range of -20° C to 140° C), every 10° C decrease in temperature reduces the failure rate by approximately a factor of 2. We can, therefore, expect a reduction in chip failure rates with lower operating temperatures. For all of these reasons, it has become apparent that heat fluxes are reaching levels that air cooling techniques cannot handle, and there has been a consequent shift towards water cooling in the last 12 months. Initially, concentrated in the niche "overclockers" sector, water cooling has moved into the mainstream. Notable examples include the recently released Apple G5 and the Sony VAIO RA810G computers. CPU heat could increase several times over today's levels in the next 2-3 years. Up until recently, air-coolers have been able to meet the cooling needs of a CPU through increased size & air velocity. However, further increases in size offer diminishing returns as conductive resistance increases, and further increases in air-velocity are limited by noise considerations. Typical air coolers have a thermal resistance to a CPU die of 0.4° C/W, whereas state of the art heat pipe devices with high speed fans can get as low as 0.2° C/W.

[0004] Liquid-cooled systems have much higher heat transfer coefficients than air systems, typically 500-1,000 W/mK compared to 50-100 W/mK, significantly reducing the thermal resistance at the CPU die. The heat is efficiently transferred through a "waterblock" into a liquid, which is typically water-based. The liquid is then pumped to a radiator, where the heat is conducted to air-cooled fins and out to ambient air. Radiators alleviate the need for high air velocities by more effective use of the fins, and the availability of larger fin arrays. Thus, water- cooling solutions overcome both conduction resistance and airflow limitations, and have allowed another generation of die size decreases and CPU power increases. Unfortunately, watercooling is limited by the conduction and convection resistances in the waterblock and by the space available for the hot side radiators. Inevitably, these limitations will be reached, necessitating an active cooling solution to service higher CPU heat loads in the future.

BRIEF SUMMARY OF THE DISCLOSURE

[0005] In accordance with one or more embodiments, a thermoelectric cooling system is provided for cooling an electronic device such as a CPU, a GPU, and other computer processing units or computer chip components. The system includes a thermoelectric apparatus having a first cold side and an opposite second hot side, wherein the electronic device can be thermally coupled to the first cold side. A heat exchanger system is thermally coupled to a second hot side of the thermoelectric apparatus. The thermoelectric apparatus can be powered to pump heat from the electronic device to the heat exchanger system, and the heat exchanger system rejects the heat into ambient air.

[0006] In accordance with one or more embodiments, a thermoelectric cooling system is provided for cooling an electronic device such as a CPU, a GPU, and other computer processing units or computer chip components. The system includes a liquid heat exchanger block apparatus thermally coupled to the electronic device. The liquid heat exchanger block apparatus includes at least one passage for flow of a heat transfer liquid therethrough. The system also includes one or more stages of thermoelectric apparatus. Each thermoelectric apparatus has a first cold side and an opposite second hot side. The system also includes a radiator for rejecting heat from heat transfer fluid, a convective fan associated with the radiator for increasing the heat transfer coefficient of the radiator, and one or more conduit systems for coupling the liquid heat exchanger block apparatus to liquid heat exchanger blocks associated with the one or more stages of thermoelectric apparatus, and the radiator such that the thermoelectric apparatus can be powered to pump heat from the electronic device successively through the one or more stages of thermoelectric apparatus to the radiator for rejection into ambient air.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIGS. 1-12 illustrate various exemplary systems utilizing one or more

thermoelectric device for cooling CPUs in accordance with one or more embodiments.

[0008] FIGS. 13A-13C illustrate an exemplary liquid heat exchanger block usable in a thermoelectric heat pump system in accordance with one or more embodiments.

[0009] FIGS. 14A-14C illustrate an exemplary liquid heat exchanger block usable in a thermoelectric heat pump system in accordance with one or more embodiments.

[0010] FIG. 15 illustrates an exemplary system utilizing thermoelectric devices for cooling CPUs in accordance with one or more embodiments.

[0011] FIG. 16 is a schematic illustrating DT reduction through a counter-flow arrangement in accordance with one or more embodiments.

[0012] FIGS. 17-19 illustrate various exemplary systems utilizing thermoelectric devices for cooling CPUs in accordance with one or more embodiments.

[0013] Like reference numbers represent the same or similar elements in the figures. DETAILED DESCRIPTION

[0014] Various embodiments disclosed herein relate to cooling systems utilizing thermoelectric devices for cooling electronic devices, particularly CPUs. While the description below may refer to CPUs, the cooling systems disclosed herein are also applicable to GPUs and other processing units and computer chip and other components.

[0015] A TE device is a solid-state active heat pump, which transfers heat from one side of the device to the other with consumption of electrical energy, depending on the direction of the current. In general, heat is transported across the device by the flow of charge carriers through a matrix of p-type and n-type semi-conductor materials. Since the heat is moved electronically, the module's instantaneous heat-pumping capacity can be adjusted by changing the supplied electrical current. This enables real-time fine-adjustment of the thermal capacity to compensate for changing conditions. Additionally, TE modules, as their name implies, are modular in nature and thermal systems can quite easily be constructed that contain a multitude of smaller independent cooling units working in series, in parallel, or in multiple stages.

[0016] As discussed above, CPU heat could increase several times over today's levels in the next few years. Until recently, aircoolers have been able to meet the cooling needs of a CPU through increased size and air velocity. However, further increases in size offer diminishing returns as conductive resistance increases, and further increases in air-velocity are limited by noise considerations. Typical aircoolers have a thermal resistance to a CPU die of 0.4° C/W, whereas state of the art heat pipe devices with high speed fans can get as low as 0.2° C/W.

[0017] Liquid-cooled systems have much higher heat transfer coefficients than air systems, typically 500-1,000 W/mK compared to 50-100 W/mK, significantly reducing the thermal resistance at the CPU die. The heat is efficiently transferred through a "waterblock" into a liquid, which is typically water-based. It should be understood that heat transfer fluids other than water (such as, e.g., propylene glycol) can also be used, particularly when low temperature cooling is required. The liquid is then pumped to a radiator, where the heat is conducted to air- cooled fins and out to ambient air. Radiators alleviate the need for high air velocities by more effective use of the fins, and the availability of larger fin arrays. State of the art water blocks can have thermal resistances of ~0.08°C/W and a large radiator can have a resistance of ~0.02°C/W. This gives a total thermal resistance of ~0.1°C/W for cutting edge water cooling today. Thus water-cooling solutions overcome both conduction resistance and airflow limitations, and have allowed another generation of die size decreases and CPU power increases. Unfortunately, watercooling is limited by the conduction and convection resistances in the waterblock and by the space available for the hot side radiators. Importantly, passive water cooling is dependent on the ambient temperature and can only cool to 20°C above ambient temperature if there is a 150W heat load and conventional PC radiators are used since a delta temperature above ambient is required for heat rejection. Inevitably, these limitations will be reached, necessitating an active cooling solution to service higher CPU heat loads in the future. Various embodiments disclosed herein provide a thermoelectric-to-CPU cooling solution to this problem.

[0018] FIGS. 1 and 2 illustrate exemplary thermoelectric-to-air cooling systems for cooling a CPU 10 to potentially sub-ambient temperatures in accordance with one or more embodiments. In FIG. 1, a single thermoelectric module 12 (identified in the drawing as TECH (thermoelectric cooler/heater)) is bonded to or otherwise attached with a thermal interface to a plate of thermally conductive material 14 (heat spreader plate), which is adjacent to the CPU 10. The function of plate 14 is to spread the heat from the CPU 10 to the cold side of the TE module 12. In one or more alternate embodiments, the TE module 12 is mounted directly to the CPU without a heat spreader plate. The heat is then rejected from the TE module hot side into ambient air via a heat exchanger system. In accordance with one or more embodiments, the heat exchanger system comprises a Sandia Air-Bearing Heat Exchanger 16.

[0019] In one or more embodiments, insulation 18 is provided at portions of the TE device 12 and CPU 10, and/or the heat spreader 14 is heated by the TE device 12 or a resistive heater to inhibit condensation on the CPU 10.

[0020] FIG. 2 shows an exemplary thermoelectric-to-air cooling system with a 2 stage TE device 12' or TE cascade. [0021] The Sandia Air Bearing heat exchanger 16 has significant advantages over a traditional finned heat exchanger with fan (FFHS). Traditional FFHS heatsinks involve a large array of fins and a fan that blows air across them. Heat is transferred from fins to atmosphere by this moving air in a process called diffusion, and thus the hot component is cooled. But this traditional technique has been used for forty years with very few innovations, and is marred by one large problem - hot air 'sticks' to the fins, and creates a large barrier that prevents efficient heat exchange, even with high-RPM fans. In addition to inefficient heat exchange comes the problem of dust, referred to as 'heatsink fouling' by Sandia researchers, which accumulates within FFHS fins and reduces the effectiveness over time without constant maintenance. The fan remains relatively dust-free due to its constant motion. Sandia's Air-Bearing Heat Exchanger sidesteps the FFHS heat exchanger and dust problems by combining the two functions of heatsink and fan, creating in effect a spinning heatsink. A large base plate 22 mates with the heat load (in this case the TE device 12) and rests underneath the impeller platen 24, separated by a 0.03 mm layer of air, which forms a "hydrodynamic gas bearing" 26. It is similar to the effect used in an air hockey table, and is the main effect in keeping hard drive discs stable. Mounted to the impeller platen are the cooling fins and a brushless DC motor 28, which spins at several thousand RPM, drawing cool air through the center and then expelling it to the sides of the device. It uses centrifugal forces to reduce the air barrier over the fins by up to ten times, offering hugely increased cooling performance. The Air-Bearing Heat Exchanger has an exceptionally short path between base plate and cooling fins, resulting in increased efficiency per square inch. The Sandia device architecture circumvents the poor efficiency of small, high-speed fans by using the mechanical work provided by the motor to directly generate relative motion between the heat exchanger structure and the surrounding air. The air bearing heat exchanger has a thermal resistance of only 0.2C/W compared to a typical FFHS at 0.6-0.8C/W, a threefold decrease. Future air bearing heat exchangers are expected to achieve a thermal resistance of ~0.1 C/W in a device of the same size. It is also inexpensive to manufacture as the heat-sink-impeller is a monolithic structure that could be fabricated by die-casting. The presence of a shroud is believed to make no significant impact on cooling performance. [0022] The air bearing heat exchanger also includes one or more heat pipes 30 (two are shown in the figures), which transmit additional heat to set of stationary fins 32 positioned peripherally around the rotating components of the air bearing heat exchanger.

[0023] In accordance with one or more embodiments, each of the systems disclosed herein can include an electronic control system for controlling TE cooling power based on inputs of ambient temperature, dew point, CPU temperature, and computer user interface control panel software.

[0024] FIGS. 3 and 4 illustrate an exemplary thermoelectric-to-liquid cooling systems for cooling a CPU 10 in accordance with one or more further embodiments. In these embodiments, a thermoelectric module 12 is bonded or otherwise attached with a thermal interface to a plate 14 of thermally conductive material, which is adjacent to the CPU. The plate spreads the heat from the CPU to the cold side of the TE module 12. In one or more alternate embodiments, the TE module 12 is mounted without a heat spreader plate directly to the CPU. The heat is then rejected from the module hot side into a fluid stream or liquid block heat exchanger 36 and from there through conduit 38 into ambient air via a radiator 40, which can utilize a fan 42 for increasing air convective heat transfer from the fluid. The FIG. 3 embodiment utilizes a single TE device 12, and the FIG. 4 embodiment features a 2 stage TE device or TE cascade 12' . This TE cooling arrangement can achieve sub ambient temperature cooling of the CPU.

[0025] FIGS. 5 and 6 illustrates further alternative thermoelectric CPU cooler systems in accordance with one or more embodiments. The cooler systems comprise CPU-to-liquid-to- thermoelectric heat pump systems with dual counter flow liquid loops 50, 52 and either single or multiple TE devices 60 between a single cold/hot skived fin heat exchanger 54 (FIG. 5) or serial discrete TEC-heat exchanger array 56 (FIG. 6) for cooling the CPU to sub-ambient and sub-dew point temperatures.

[0026] In the various cooler systems described herein, the liquid block heat exchangers can comprise a skived fin microchannel heat exchanger waterblock (described in further detail in FIGS. 13A-13C and 14A-14C). In the skived fin microchannel block, the coolant is directed through the sides of the water block so it can exit out the sides thus increasing flow and heat absorption. The trade-offs between channel heights, channel widths and wall thickness can be optimized through computer modeling. This heat exchanger can achieve CPU temperatures significantly below ambient temperatures.

[0027] Liquid hoses for the liquid loops in the various embodiments can be provided with optional insulation and optional heating on the outside to avoid condensation when needed for below dew point cooling. Liquid pumps for the loops can also be provided with optional insulation and optional heating on the outside to avoid condensation.

[0028] The systems can include a bank of multiple thermoelectric modules run at or close to their maximum coefficient of performance (COP) bonded or interfaced to high efficiency microchannel heat exchangers. The heat pump can comprise a single TE device or multiple TE devices between a single hot and cold plate skived fin microchannel heat exchanger (as shown in FIG. 5) or serial discrete TEC-heat exchanger array of TE devices with individual hot and cold microchannel heat exchangers for each TE device (as shown in FIG. 6).

[0029] FIGS. 7 and 8 illustrate cooling systems similar to FIGS. 5 and 6, respectively, except that the systems of FIGS. 7 and 8 include a TE device 12 in thermal contact with the CPU 10, thereby comprising a direct CPU-to-thermoelectric-to-heat pump system.

[0030] FIGS. 9 and 10 illustrate cooling systems similar to FIGS. 5 and 6, respectively, except that the systems of FIGS. 9 and 10 comprise CPU-to-liquid-to-dual stage thermoelectric heat pump systems with triple counter flow liquid loops 60, 62, 64. The systems include either single or multiple TE device(s) 54 (FIG. 9) between a single cold/hot skived fin heat exchanger or serial discrete TEC-heat exchanger array 56 (FIG. 10) (or any combination thereof) for cooling the CPU to sub-dew point temperatures, below freezing temperatures approaching cryogenic temperatures.

[0031] FIGS. 11 and 12 illustrate cooling systems similar to FIGS. 9 and 10, respectively, except that the systems of FIGS. 11 and 12 include a TE device 12 in thermal contact with the CPU 10, thereby comprising a direct CPU-to-thermoelectric-to-heat pump system. [0032] FIGS. 13A-13C illustrate top, side, and bottom views, respectively, of an exemplary liquid heat exchanger block usable in a thermoelectric heat pump system in accordance with one or more embodiments. Heat transfer fluid flows between a series of skived microchannel fins through the block, increasing the thermal interface area. The block can be made out of copper or aluminum or be made out of high temperature plastic to lower the cost and weight of the system. The bottom of the plastic block includes a copper plate with skived microchannel fins for improved heat transfer coefficient to increase heat transfer between the liquid and the thermoelectric heat pump module.

[0033] FIGS. 14A-14C illustrates a modified heat exchanger block similar to the block of FIGS. 13A-13C, but with an integrated pump for pumping heat transfer fluid through the conduit system.

[0034] FIG. 15 illustrates an exemplary thermoelectric heat pump system for cooling a CPU 10, in which a plurality of TE devices 12 and heat exchanger blocks 70, 72 are in a stacked arrangement. Each device 12 has a block 70 coupled to the cold loop on one side and a block 72 coupled to the hot loop on the opposite side. The blocks 70 are connected in series in the cold loop, and the blocks 72 are connected in series in the hot loop. The heat transfer fluids in the hot and cold loops are in a counterflow configuration.

[0035] FIG. 16 is a schematic showing a way to reduce DT through a counter-flow arrangement. In this configuration, the total required TE module size (TEC "B") is divided into a larger number of proportionally smaller TE modules (TEC "A"). (Note that TEC "B" in this example is 33% the size of TEC "A" so that the total size is equal for each case.) The coolant is then passed from one TEC A module's heat exchanger to another in a serial fashion. The heat transfer fluids flow in opposite directions to each other on opposite sides of the TE device. The coolant changes temperature as it passes through each heat exchanger, becoming progressively warmer or cooler respectively. The counterflow arrangement allows the profiles to "nest" into each other and results in the reduction of each "segment's required DT over the monolithic (TEC "A") case. Note that the number of segments shown in is small to simplify the example. There is no limit on the number of segments outside of practical concerns. As the segment number increases, the DT decreases and approaches the value TH4 - TCI . For the HVAC case, the counter-flow configuration reduces the DT by >20°F (>11°C).

[0036] FIG. 17 illustrates an exemplary thermoelectric heat pump system for cooling a CPU 10, in which a plurality of TE devices 12 and heat exchanger blocks 70, 72 are in a serial arrangement. The heat transfer fluids in each loop are in a counterflow configuration.

[0037] FIG. 18 illustrates an exemplary thermoelectric heat pump system for cooling a CPU 10 having a serial counter flow discrete TE heat exchanger array arrangement.

[0038] FIG. 19 illustrates an exemplary thermoelectric heat pump system for cooling a CPU 10, having a serial discrete TE heat-exchanger array condensed arrangement. Heat insulation is provided between pairs of heat exchanger blocks due to the direction of heat flow.

[0039] The thermoelectric heat pump chiller systems with liquid loops can achieve below sub-ambient and below dew point cooling and in the 2 stage and 3 stage configurations, below zero °C approaching cryogenic temperatures. In accordance with one or more embodiments, insulation and heated flexible heat spreader materials can be utilized to inhibit condensation on the CPU at lower temperatures. Insulated hoses and insulated heat exchangers inhibit the condensation on the cold liquid loop(s) of the heat pump.

[0040] Thermoelectric heat pump CPU chillers In accordance with various embodiments have several implicit advantages. They overcome the limitations of conduction resistance by lowering the temperature of the conductive medium that is adjacent to the CPU die, thus increasing the driving temperature differential. Both the hot and the cold side of the modules have access to highly effective heat transfer devices. Additionally they utilize the entire heat transfer surface of the module and distribute the load over several modules, allowing improved COPs. In addition, thermoelectric heat pump CPU chillers can provide CPU cooling to below ambient temperatures and in a single stage heatpump to below dew point cooling in two stage and three stage heat pump configuration below zero C approaching cryogenic temperatures. Insulation and heated flexible heat spreader materials can be utilized in accordance with various embodiments to inhibit condensation on the CPU. Insulated hoses and heat exchangers inhibit the condensation in the cold liquid loop(s) of the heat pump. [0041] In various embodiments, thermoelectric device(s) pump heat from liquid heat exchanger block(s) (loop #1) to liquid heat exchanger block(s) (loop #2), raising the temperature in liquid loop #2 and lowering the temperature in liquid loop #1. The lower temperature in loop #1 cools the water block (with optional integrated TE device) located on top of the CPU. The heat from the CPU is removed by the liquid in the water block or is pumped by the optional TE device into the water block where it is removed by the liquid in the waterblock and circulated in loop 1 to the TE heat pump where it is rejected into loop #2. For a two stage heat pump, the loop #2 is cooled by loop #3 by TE heat pumps that move heat from loop #2 to loop #3 similar to the way it is move from loop #1 to loop #2. Since the delta temperature in each loop is additive, the overall delta temperature increases by a factor of two. 2, 3, or 4 (or more) stages can be used in conjunction with or without a TE device integrated with the CPU/water block to achieve below 0C freezing and colder approaching cryogenic temperature cooling. Insulation and heated flexible heat spreader materials may be utilized to inhibit condensation on the CPU. Insulated hoses and insulated heat exchangers address the condensation in the cold liquid loop(s) of the heat pump.

[0042] In various embodiments, a TE/water block with a skived fin microchannel block design can be used such that the coolant is directed down through the center of the water block so it can exit out the sides thus increasing flow and heat absorption. This is more thermally efficient than a TE/air heat exchanger for transferring heat. In addition, a TE/waterblock heat exchanger can transfer much higher heat densities then a TE/air heat exchanger. Also a serial discrete TE heat exchanger array can reduce the in and out loop #1 and #2 delta temperatures across the TE device resulting in a higher COP of the TE device for a given temperature differential between loop #1 and loop #2. Thermoelectric CPU chillers can provide CPU cooling to below ambient temperatures and in a single stage heatpump to below dew point cooling in two stage and three stage heat pump configuration below zero C approaching cryogenic

temperatures. Insulation and heated flexible heat spreader materials can be utilized to inhibit condensation on the CPU. Insulated hoses and insulated heat exchangers prevent the

condensation on the cold liquid loop(s) of the heat pump. [0043] In one or more embodiments, for small applications, only one TE device with a hot and cold liquid heat exchanger can be used. However, for larger heat loads, multiple isolated or discrete TE/heat exchanger units may be needed to effectively pump larger heat loads with a sufficient delta temperature between the two loops. Larger liquid to air heat exchangers can be used for larger heat loads. For larger delta temperatures, a two stage heat pump may be used. Thermoelectric CPU chillers can provide CPU cooling to below ambient temperatures and in a single stage heatpump to below dew point cooling in two stage and three stage heat pump configuration below zero C approaching cryogenic temperatures. Insulation and heated flexible heat spreader materials can be used to inhibit condensation on the CPU. Insulated hoses and heat exchangers solve the condensation in the cold liquid loop(s) of the heat pump. Tubing in the 1st and 2nd loop may be insulated to inhibit condensation.

[0044] Advances in higher COP TE devices will result in a higher COP heat pump system. Water condensation from the cold liquid is inhibited through use of a layer of insulation material in cases where below dew point cooling is desired. A heated flexible heat spreader can be put on top of the insulation to inhibit condensation even at very low CPU temperatures. The active heating of the heat spreader can be done through the use of a resistive heater or the TE heat pump. Water will not condense on a hot surface and any water that does condense will be evaporated away by the heated heat spreader.

[0045] Cooling systems in accordance with various embodiments can be installed on a CPU of a computer and provide cooling to below ambient temperatures. The single state heat pump can provide cooling to below dew point and below zero C temperatures while the two stage heat pump or three stage heat pump can cool to below zero °C approaching cryogenic temperatures. Insulation and a heated flexible heat spreader can protect the CPU or electronics from condensation at below dew point temperatures. The TE CPU chiller can cool to below ambient and further to below subzero approaching cryogenic temperatures where the CPU can operate more reliably and at a high clock speed. Following the Arrhenius equation, every 10°C decrease in temperature reduces the failure rate by approximately a factor of 2. Therefore, a reduction in chip failure rates can be expected with lower operating temperatures. [0046] Various embodiments disclosed herein can be used for cooling electronics other than CPUs and will be more efficient and cool faster than a conventional air heat exchanger or liquid loop heat exchanger. For instance, various embodiments disclosed herein can also be used to cool large arrays of processors in servers that support the cloud to increase clock speed and increase CPU reliability.

[0047] Having thus described several illustrative embodiments, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to form a part of this disclosure, and are intended to be within the spirit and scope of this disclosure. While some examples presented herein involve specific combinations of functions or structural elements, it should be understood that those functions and elements may be combined in other ways according to the present disclosure to accomplish the same or different objectives. In particular, acts, elements, and features discussed in connection with one embodiment are not intended to be excluded from similar or other roles in other embodiments. Additionally, elements and components described herein may be further divided into additional components or joined together to form fewer components for performing the same functions. Accordingly, the foregoing description and attached drawings are by way of example only, and are not intended to be limiting.

Claims

1. A thermoelectric cooling system for cooling an electronic device, comprising: a thermoelectric apparatus having a first cold side and an opposite second hot side, wherein the electronic device can be thermally coupled to the first cold side; and a heat exchanger system thermally coupled to a second hot side of the thermoelectric apparatus; wherein the thermoelectric apparatus can be powered to pump heat from the electronic device to the heat exchanger system, and the heat exchanger system rejects the heat into ambient air.

2. The system of claim 1, further comprising a thermally conductive heat spreader plate between the first cold side of the thermoelectric apparatus and the electronic device for spreading heat from the electronic device to the cold side of the thermoelectric apparatus.

3. The system of claim 2, wherein the heat spreader plate is heated to inhibit condensation on the electronic device.

4. The system of claim 1, further comprising insulation around a portion of the thermoelectric apparatus to inhibit condensation on the electronic device.

5. The system of claim 1, wherein the thermoelectric apparatus comprises two or more cascaded thermoelectric devices.

6. The system of claim 1, wherein the electronic device comprises a central processing unit (CPU), a graphics processing unit (GPU), a computer processing unit, or a computer chip component.

7. The system of claim 1, further comprising a control system for controlling power supplied to the thermoelectric apparatus based on ambient air temperature, dew point temperature, and/or electronic device temperature inputs.

8. The system of claim 1, wherein the heat exchanger system comprises an air- bearing heat exchanger having a base thermally coupled to the second hot side of the

thermoelectric apparatus, a finned structure rotatably supported on the base by a hydrodynamic air bearing, and a motor for spinning the finned structure.

9. The system of claim 1, wherein the heat exchanger system comprises: a liquid heat exchanger block apparatus thermally coupled to the second hot side of the thermoelectric apparatus, the liquid heat exchanger block apparatus including at least one passage for flow of a heat transfer liquid therethrough; a radiator for rejecting heat from the heat transfer fluid; a convective fan associated with the radiator for increasing the heat transfer coefficient of the radiator; and a conduit system coupling the liquid heat exchanger block apparatus and the radiator for circulating the heat transfer fluid between the liquid heat exchanger block apparatus and the radiator.

10. The system of claim 1, wherein the heat exchanger system comprises: a liquid heat exchanger block apparatus thermally coupled to the second hot side of the thermoelectric apparatus, the liquid heat exchanger block apparatus including at least one passage for flow of a heat transfer liquid therethrough; a radiator for rejecting heat from the heat transfer fluid; a convective fan associated with the radiator for increasing the heat transfer coefficient of the radiator; one or more additional stage thermoelectric apparatus; conduit systems for coupling the liquid heat exchanger block apparatus to the one or more additional stage thermoelectric apparatus and the radiator such that heat is moved from the thermoelectric apparatus successively through the one or more additional stage thermoelectric apparatus to the radiator.

11. The system of claim 10, wherein each additional stage thermoelectric apparatus comprises a plurality of thermoelectric devices spaced apart from one another, and having a liquid heat exchanger block apparatus on opposite sides thereof.

12. The system of claim 11, wherein each additional stage thermoelectric apparatus comprises a plurality of discrete thermoelectric devices spaced apart from one another, and having separate liquid heat exchanger block devices on opposite sides thereof arranged in series for flow of the heat transfer fluid sequentially therethrough.

13. The system of claim 10, wherein the liquid heat exchanger block apparatus includes a plurality of microchannel fins for enhanced heat transfer.

14. A thermoelectric cooling system for cooling an electronic device, comprising: a liquid heat exchanger block apparatus thermally coupled to the electronic device, the liquid heat exchanger block apparatus including at least one passage for flow of a heat transfer liquid therethrough; one or more stages of thermoelectric apparatus, each thermoelectric apparatus having a first cold side and an opposite second hot side, and one or more liquid heat exchanger blocks; a radiator for rejecting heat from heat transfer fluid; a convective fan associated with the radiator for increasing the heat transfer coefficient of the radiator; one or more conduit systems for coupling the liquid heat exchanger block apparatus to the liquid heat exchanger blocks of the one or more stages of thermoelectric apparatus and the radiator such that the thermoelectric apparatus can be powered to pump heat from the electronic device successively through the one or more stages of thermoelectric apparatus to the radiator for rejection into ambient air.

15. The system of claim 14, wherein each thermoelectric apparatus comprises a plurality of thermoelectric devices spaced apart from one another, and having a liquid heat exchanger block apparatus on opposite sides thereof.

16. The system of claim 14, wherein each thermoelectric apparatus comprises a plurality of discrete thermoelectric devices spaced apart from one another, and having separate liquid heat exchanger block devices on opposite sides thereof arranged in series for flow of the heat transfer fluid sequentially therethrough.

17. The system of claim 14, wherein the liquid heat exchanger block apparatus includes a plurality of microchannel fins for enhanced heat transfer.

18. The system of claim 14, wherein the heat transfer fluid comprises propylene glycol.

19. The system of claim 14, further comprising a thermally conductive heat spreader plate between the liquid heat exchanger block apparatus and the electronic device for spreading heat from the electronic device to the liquid heat exchanger block apparatus.

20. The system of claim 19, wherein the heat spreader plate is heated to inhibit condensation on the electronic device.

21. The system of claim 14, further comprising insulation around a portion of the liquid heat exchanger block apparatus to inhibit condensation on the electronic device.

22. The system of claim 14, wherein the electronic device comprises a central processing unit (CPU), a graphics processing unit (GPU), a computer processing unit, or a computer chip component.

23. The system of claim 14, further comprising a control system for controlling power supplied to the thermoelectric apparatus based on ambient air temperature, dew point

temperature, and/or electronic device temperature inputs.