This is a non-provisional application of U.S. Provisional Application Ser. No. 61/247,824, filed Oct. 1, 2009, the disclosure of which is incorporated herein by reference.
The present invention relates generally to cooling systems and more particularly to a hybrid integrated cooling system including an active thermoelectric cooling device and an ejector cooling device.
Thermoelectric cooling systems are useful in many applications because they can be relatively small (e.g., a plate) and have no moving parts. Thermoelectric coolers use the Peltier effect to create cooling on one side of a plate or the like. However, the efficiency of thermoelectric cooling systems is inadequate for many applications, particularly where it is required to have a large temperature differential across the plate. In that event heat transfer from the hot side of the plate back to the cold side reduces effectiveness of the cold side in absorbing heat from the object or space to be cooled. Ejector cooling devices enjoy some of the same advantages, including that they have or can have no moving parts and can be constructed on a small scale. However, ejector cooling devices also suffer from efficiency problems in certain applications.
In one aspect of the present invention, an active cooling system for transferring heat from a heat source to an external heat sink generally comprises an ejector cooling system having a high temperature evaporator and a low temperature evaporator, and a thermoelectric cooling device. The thermoelectric cooling device has a hot side in thermal communication with the high temperature evaporator for supplying heat used to vaporize a primary fluid and a cold side in thermal communication with the low temperature evaporator for removing heat from the low temperature evaporator.
In another aspect of the present invention, an active cooling system for transferring heat from a heat source to an external heat sink generally comprises a low temperature evaporator for removing heat from the heat source, a pump for drawing refrigerating fluid from the low temperature evaporator and increasing the pressure of the fluid, and a condenser downstream of the pump for use in condensing the refrigerating fluid. A wicking structure in the condenser extends generally to the low temperature evaporator for capturing at least a portion of the condensed refrigerating fluid in the condenser and moving the condensed refrigerating fluid by capillary action back to the low temperature evaporator.
In still another aspect of the present invention, an active cooling system for transferring heat from a heat source to an external heat sink generally comprises a low temperature evaporator adapted to receive a secondary fluid for evaporation of the secondary fluid to absorb heat from the heat source. A thermoelectric cooling module uses electrical input power to generate refrigeration or cooling. An ejector cooling module integrated with the thermoelectric module includes a high temperature evaporator adapted to contain a primary fluid. The thermoelectric cooling module is disposed for rejecting heat into the high temperature evaporator of the ejector cooling module. A converging-diverging nozzle connected to the high temperature evaporator accelerates primary fluid to a high velocity and produces low static pressure. A mixing chamber for receiving high velocity primary fluid from the converging-diverging nozzle aspirates secondary fluid vapor from the low temperature evaporator. A diffuser chamber receives mixed primary and secondary fluid vapor from the mixing chamber, and is adapted to transition the flow of mixed primary and secondary fluids from high speed to stagnation so that the mixed flow can gain static pressure. A condenser is adapted to receive the primary and secondary fluid vapor from the ejector's diffuser chamber and reject heat to a heat sink outside the cooling system so that the vaporous primary and secondary fluids lower their temperature to their saturation points and liquefy. A wick structure connecting the condenser to the high temperature evaporator so that the liquids in the condenser can travel from the condenser to the high temperature evaporator by way of capillary force. A micro/nano-structured surface within the high temperature evaporator distributes the liquid within the high temperature evaporator and enhances thin film evaporation heat transfer. A duct between the high temperature evaporator and the low temperature evaporator is constructed to pass fluid from the high temperature evaporator to the low temperature evaporator at a certain flow rate of liquid to provide sufficient flow to the low temperature evaporator but not so much flow that the high temperature evaporator lacks sufficient fluid for heat transfer from the thermoelectric cooling module or for powering the ejector. A micro/nano-structured surface within the low temperature evaporator distributes the liquid within the low temperature evaporator and enhances thin film evaporation heat transfer. Insulating material is located between at least one of the condenser and high temperature evaporator; and the ejector's diffuser and high temperature evaporator
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.
Referring now to the drawings, and in particular to
The low temperature evaporator module 3 includes a housing 11 having a bottom and sides. Referring now also to
The thermoelectric cooler module 5 is located immediately above the low temperature evaporator module 3. The thermoelectric cooler module 5 comprises a plate 15 to which an electric potential can be applied to produce a cold side facing the low temperature evaporator module 3 and a hot side facing away from the low temperature evaporator module. The plate 15 may use the Peltier effect conventional for thermoelectric cooling. The plate 15 has a central opening 17 for passing evaporated secondary fluid out of the low temperature evaporator module 3 and two return openings 19 for passing condensed secondary fluid back into the low temperature evaporator module (see
The hot side of the thermoelectric cooler module plate 15 faces into the ejector and high temperature evaporator module 7, which is located just above the thermoelectric cooler module 5. The temperature of the hot side of the plate 15 is greater than the temperature of the source of heat Qin to be cooled by the hybrid integrated cooling system 1 of the present invention. As will be described, this heat is used, and hence removed from the hot side of the thermoelectric plate 15, to drive an ejector cooler. More particularly, the heat generated from the hot side of the thermoelectric plate 15 is used to vaporize the primary fluid in the ejector and high temperature evaporator module 7. Referring to
The ejector 27 is fluidically isolated from the high temperature evaporator 25 except through a primary nozzle 33, which opens into a mixing chamber 35 of the ejector. Although a single primary nozzle 33 is illustrated, multiple nozzles may be used. In the illustrated embodiment, the primary nozzle 33 is a micronozzle, but other sizes may be used within the scope of the present invention to achieve even greater efficiency. The mixing chamber 35 communicates with the low temperature evaporator module 3 through an opening 37 in the ejector 27 and high temperature evaporator module 7 that is aligned with the central opening 17 in the thermoelectric plate 15. A throat member 39 communicates with both the primary nozzle 33 and the mixing chamber 35. The throat member 39 opens opposite the mixing chamber 35 into a subsonic diffuser chamber 41 that leads to the vapor passage opening 31 to the condenser module 9. The ejector 27 is thermally insulated from the hot side of the thermoelectric plate 15 by an insulating panel 43 disposed between the hot side of the thermoelectric plate and the ejector 27 (see,
The higher pressure in the subsonic diffuser chamber 41 downstream from the throat member 39 induces a normal shock of essentially zero thickness. The shock causes a compression effect and a sudden drop in the flow speed from supersonic to subsonic. Further compression of the flow is achieved as it is brought to stagnation through the subsonic diffuser chamber which discharges the medium pressure and medium temperature flow (i.e., a pressure and temperature above original stagnation properties of the secondary fluid and below the original stagnation properties of the primary fluid) to the condenser module 9. To minimize shock wave losses, the throat member 39 is preferably shaped according to a constant rate of momentum change (CRMC) method known in the art to reduce or eliminate the shock wave. The high temperature evaporator 25, primary nozzle 33 and converging and diverging throat member 39 may be broadly considered to be a “pump” in the illustrated embodiment. The primary fluid and the secondary fluid both flow through the converging and diverging throat member 39 where they lose momentum and gain static pressure so that they can condense into liquid at the condenser.
Referring now to
It will be understood that the hybrid integrated cooling system 1 of the illustrated embodiment achieves advantages. Because the high temperature evaporator 25 for the ejector 27 is attached to the hot side of the thermoelectric cooler module 5, the heat will be directly removed by the sensible and latent heat increase of the primary fluid. This can help to reduce heat conduction from the hot side to the cold side of the thermoelectric 15. By rapidly removing heat from the thermoelectric cooler plate's hot side and preventing conduction from the hot side to the cold side, the coefficient of performance (COP) of the thermoelectric cooler module 5 can be maximized. Applications for the cooling system include without limitation, electronics cooling, microelectronics cooling, laser diode cooling, space cooling and refrigeration and other general heat transfer applications.
The waste heat rejected from the hot side of the thermoelectric cooler module plate 15 is reused to operate the refrigeration cycle of the ejector 27, thus the hybrid integrated cooling system's overall thermal efficiency is much higher than if a standalone thermoelectric cooling solution were employed. This provides for a total COP greater than the sum of the COPs of the thermoelectric cooling module 5 and ejector refrigeration system (including the low temperature evaporator module 3, the ejector 27 and the condenser module 9) individually. For example, given 1 unit input power into the thermoelectric cooling module 5, the heat received by the cold side of the thermoelectric cooling plate 15 would be COPTEC×1; and the energy rejected by the hot side of the plate to drive the ejector refrigeration system would be COPTEC+1. Thus, the cooling received by the low temperature evaporator 3 of the ejector refrigeration system is COPEJ×(COPTEC+1); and therefore total COPTE-Ej-AC is COPEj+COPTEC COPEj×COPTEC. In addition, the hybrid integrated cooling system 1 will be able to operate at higher temperature differentials than standalone thermoelectric cooling devices
In the refrigeration cycle of the ejector 27, liquid flow from the condenser through the high temperature evaporator 25 to the low temperature evaporator is created first by drawing the condensate to the high temperature evaporator using wick structures 29, 49 and then by sucking additional condensate to the low temperature evaporator module 3 because of its relatively low pressure when compared to the high temperature evaporator. No pump or moving parts are needed. However, the use of a pump having moving parts, valves or other components having moving parts does not depart from the scope of the present invention.
Thin film evaporation is used for both high temperature evaporator 25 and low temperature evaporator module 3 which can result in an extra high heat transfer coefficient which will improve overall system thermodynamic efficiency by minimizing the superheat between the heating surfaces and the working fluids within the system.
Having described the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.
When introducing elements of the present invention or the preferred embodiments(s) thereof, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.
As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
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