Heat transfer engine

Abstract

The invention provides a method for a thermally activated closed loop heat transfer system, and requires no other external power source other than the heat which it is transferring. The system is based on a two-phase (liquid/vapor) working fluid, with heat input through an evaporator and heat rejected through a condenser. All of the mechanical power produced by an engine, driven by the high vapor quality fluid leaving the evaporator, is consumed by the pump. The pump drives the low vapor quality fluid leaving the condenser back to the evaporator. Nearly isothermal heat transport can be achieved when using a pure or azeotropic working fluid, since the operation only requires the evaporator pressure to be marginally higher than the condensers pressure.

Description

PRIORITY STATEMENT UNDER 35 U.S.C. §119[0001]The present U.S. Patent Application claims priority pursuant to 35 U.S.C. §119(e) to U.S. Provisional Application Ser. No. 61 / 890,656, filed Oct. 14, 2013, in the name of Jeremy Rice, entitled “A TWO-PHASE (LIQUID / VAPOR), CLOSED LOOP HEAT TRANSFER SYSTEM WITH A PASSIVE VAPOR DRIVEN PUMP (VDP),” the disclosure of which is hereby incorporated by reference in its entirety.BACKGROUND OF THE INVENTION[0002]There are several existing closed loop heat transfer technologies, including both passive and active methods. The passive methods are generally limited by heat load, transport distance or orientation, while the active methods require an external power source.[0003]Heat pipes are a passive device relying on two-phase heat transfer (evaporation / condensation). The liquid is pumped by capillarity through a continuous wick, from the condenser, to the evaporator. This device is reversible (i.e., the condenser and evaporator can be switched). The h...

AI Technical Summary

Benefits of technology

[0008]The invention is a thermally activated closed loop heat transfer system that alleviates the need for an external power source other than the heat being transferred, thus eliminating the external power overhead associated with motor driven pumps. The system is based on circulating a working fluid with a pump, part of which changes state from liquid to vapor and back, that is driven by an engine. All of the engine's power output is utilized by the pump. The system allows for nearly isothermal heat transport from the heat input to the heat output when pure or azeotropic working fluids are chosen, since the power required to circulate a fluid is miniscule when compared to the heat being transported.

[0009]The system has moving mechanical parts, in the form of a positive displacement engine directly powering a positive displacement pump. The system automatically allows for nearly proportional fluid flow relative to the total heat transported under a set operating condition, since the proportions of fluid passing through the engine and pump are fixed by the displacement ratio of the two devices. The need for external control to adjust the pumping speed is thereby eliminated.

[0010]Varying heat transport distance can readily be accommodated by the present invention, for instance distances of less than lm or greater than 100 m can be accommodated by the same system and same power loads. Also the system can work against gravity, centrifugal forces or other body forces, giving the system flexibility in its applications. The transport distance and ability to work against body forces yields flexibility in operation when compared to passive devices that rely on capillarity or gravity to circulate fluid.

Problems solved by technology

The passive methods are generally limited by heat load, transport distance or orientation, while the active methods require an external power source.

The heat load and distance is most frequently limited by the capillarity of the wick, but can also be limited by the sonic limit, nucleation limit, and entrainment limit.

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