Heat transfer system and method

Abstract

A heat transfer system including a first heat exchange assembly, a second heat exchange assembly, and a heat transfer circuit interconnecting the first and second heat exchange assemblies, the circuit incorporating a working fluid to transfer heat between the first and second heat exchange assemblies. The heat transfer circuit preferably takes the form of a closed loop heat-pipe system. The heat transfer system is operative in a first mode where the working fluid is at or below a threshold pressure and in a second mode where the working fluid is at a higher pressure than the threshold pressure. A pressure regulating device is also provided to increase the pressure of the working fluid above the threshold pressure to effect change of operation of the heat transfer system from the first mode to the second mode. Optionally the pressure regulating device is a pressure vessel having at least one heat transfer surface. An air-conditioning system for conditioning air in a region, including the heat transfer system wherein the first heat exchange assembly is operative to moderate air temperature in the region and wherein the second heat exchange assembly is disposed adjacent a source/sink of substantially constant temperature.

1 . A heat transfer system comprising:
 a first heat exchange assembly;   a second heat exchange assembly;   a heat transfer circuit interconnecting the first and second heat exchange assemblies, the circuit incorporating a working fluid to transfer heat between the first and second heat exchange assemblies;   the heat transfer system being operative in a first mode where the working fluid is at or below a threshold pressure and a second mode where the working fluid is at a higher pressure than the threshold pressure; and   a pressure regulating device operative to increase the pressure of the working fluid above the threshold pressure to effect change of the heat transfer system from the first mode to the second mode.   
     
     
         2 . The heat transfer system of  claim 1  wherein the heat transfer circuit comprises a closed loop heat-pipe system. 
     
     
         3 . The heat transfer system of any preceding claim wherein the first and second heat transfer assemblies each include a wicking material. 
     
     
         4 . The heat transfer system of any preceding claim wherein the first and second heat transfer assemblies are operative mutually alternatively as evaporators and condensers. 
     
     
         5 . The heat transfer system of any preceding claim wherein the working fluid is arranged to transfer heat to the first heat exchange assembly from the second heat exchange assembly in the first mode. 
     
     
         6 . The heat transfer system of any preceding claims wherein the working fluid is arranged to transfer heat to the second heat exchange assembly from the first heat exchange assembly in the second mode. 
     
     
         7 . The heat transfer system of any preceding claim wherein the pressure regulating device comprises a pressure vessel having at least one heat transfer surface. 
     
     
         8 . The heat transfer system of  claim 7  wherein the pressure vessel is coupled to the heat transfer circuit via a fluid flow control valve. 
     
     
         9 . The heat transfer system of any preceding claim wherein the working fluid is selected from the group including demineralised water, ammonia, acetaldehyde, ether, pentane, ethyl chloride, and refrigerants R-245fa (1,1,1,3,3 Pentafluoropropane). 
     
     
         10 . An air-conditioning system for conditioning air in a region, comprising the heat transfer system of any one of  claims 1  to  9  wherein the first heat exchange assembly is operative to moderate air temperature in the region and wherein the second heat exchange assembly is disposed adjacent a source/sink of substantially constant temperature. 
     
     
         11 . The air-conditioning system of  claim 10  wherein the pressure regulating device uses a pressure source based on temperature of a separate region. 
     
     
         12 . An air-conditioning system for conditioning air in a habitable internal space, comprising the heat transfer system of either  claim 7  or  claim 8  wherein:
 the first heat exchange assembly is operative to moderate the temperature of air in the habitable internal space; 
 the second heat exchange assembly is disposed adjacent a source of substantially constant temperature; and 
 the at least one heat transfer surface of the pressure vessel is exposed to ambient temperature conditions. 
 
     
     
         13 . The air-conditioning system of either  claim 10  or  claim 11  wherein the source/sink of substantially constant temperature is a subterranean location below the habitable internal space. 
     
     
         14 . The air-conditioning system of  claim 12  wherein the subterranean location is in the range of 1 to 5 metres below ground surface, preferably 2 to 3 metres below the surface. 
     
     
         15 . The air-conditioning system of either  claim 12  or  claim 13  wherein the second heat exchange assembly is ground-coupled at the subterranean location. 
     
     
         16 . The air-conditioning system of any one of  claims 12  to  15 , wherein the first threshold pressure is established so that in the first mode the second heat exchange assembly is capable of acting as an evaporator at the substantially constant temperature to allow heat transfer from the second heat exchange assembly to the first heat exchange assembly. 
     
     
         17 . The air-conditioning system of any one of  claims 12  to  15 , wherein, when in the second mode, the pressure of the working fluid is at a level above the threshold pressure such that the second heat exchanger is capable of acting as a condenser at the substantially constant temperature to allow heat transfer from the first heat exchange assembly to the second heat exchange assembly. 
     
     
         18 . A pressure regulating device for a heat transfer system comprising a pressure vessel with at least one heat transfer surface. 
     
     
         19 . The pressure regulating device of  claim 18  further comprising a valve for coupling the pressure vessel to a working fluid circuit of the heat transfer system. 
     
     
         20 . A method of controlling a heat transfer system, the system being operative in a first mode where the working fluid is at or below a threshold pressure and a second mode where the working fluid is at a higher pressure than the threshold pressure, the method comprising:
 regulating working fluid pressure in a heat transfer circuit containing the working fluid by increasing the pressure of the working fluid above the threshold pressure to effect change of the heat transfer system from the first mode to the second mode.   
     
     
         21 . The method of  claim 20  further comprising selectively reducing the pressure of the working fluid to at or below the threshold pressure to revert the operation of the heat transfer system from the second mode to the first mode. 
     
     
         22 . The method of either  claim 20  or  claim 21  wherein a pressure regulating device is provided to regulate working fluid pressure. 
     
     
         23 . The method of  claim 22  wherein a pressure regulating device is provided to regulate working fluid pressure and is coupled to a working fluid circuit via a valve to enable the selective pressure regulation of the working fluid.