Thermal control system and method

Abstract

Improvements in systems and methods which employ a two-phase fluid, such as a refrigerant, as a saturable fluid in direct heat transfer relation to a thermal load, are realized by extraction of vapor from the saturated fluid before heat exchange. Moreover, automatic changing of the paths under command of a controller enables charges to be effected between different modes at higher rates than in other systems by employing the variety of modes available in the direct transfer system.

1 . A method for the efficient exchange of thermal energy between a source and a load in which a two-phase medium comprising a saturable fluid is utilized that has a controllable temperature, vapor and pressure state comprising the steps of: 
 providing a pressurized saturable fluid at a temperature that is pressure determined;    before delivery of the saturable fluid to the load, extracting vapor from the saturable fluid while maintaining the pressure;    exchanging thermal energy between the saturable fluid after vapor extraction and the load;    recombining the extracted vapor with the fluid after thermal energy exchange and,    restoring the fluid to a selected pressure and temperature status.    
     
     
         2 . The method as set forth in  claim 1  further including the steps of: 
 compressing the fluid to a high pressure state;    condensing a portion of the high pressure fluid to substantially ambient temperature;    expanding the condensed fluid to a controlled pressure-temperature state;    blocking return flow of extracted vapor into the expansion step;    mixing the expanded fluid with compressed uncondensed fluid in selected proportions to provide a final temperature state for thermal energy exchange with the load;    exchanging thermal energy between the mixture and the load thereafter;    recombining the extracted vapor with the fluid after thermal energy exchange with the load, and    recompressing the recombined fluid.    
     
     
         3 . The method as set forth in  claim 2  above, wherein the extraction of vapor reduces the mass flow of saturable fluid through the load, with more efficient thermal exchange, and the saturable fluid after extraction is more efficiently recompressed.  
     
     
         4 . The method as set forth in  claim 2  above, further including the steps of controlling the proportion of compressed uncondensed fluid relative to the expanded fluid to determine the temperature thereof, sensing the change of load temperature when full hot gas flow is employed, and stabilizing the load temperature by diverting a partial flow of compressed uncondensed fluid directly for recompression.  
     
     
         5 . The method of circulating a two-phase fluid through a thermal exchange procedure so as to maintain efficiency over a wide temperature range of operation comprising the steps of: 
 compressing the fluid to a high pressure hot gas state;    condensing a portion of the pressurized hot gas to a liquid;    selectively expanding at least some of the condensed liquid to a liquid/vapor phase;    extracting vapor from the liquid/vapor phase while maintaining the pressure thereof;    mixing a selected proportion of the pressurized hot gas with the expanded liquid/vapor phase after extraction of vapor to establish a chosen temperature/pressure status in the liquid/vapor mixture prior to the thermal load;    passing the mixture in thermal exchange relation with the load, and    recycling the fluid from the load for recompression.    
     
     
         6 . A method as set forth in  claim 5  above, further including the steps of accumulating refrigerant after thermal exchange with the thermal load, and heating the accumulated refrigerant to establish desired pressure and temperature balance for recompression, and diverting a flow of pressurized hot gas directly to recompression and redirecting the flow passed in thermal exchange with the load.  
     
     
         7 . A method as set forth in  claim 5  above, wherein the step of condensation comprises supplying a condensate in thermal exchange with the compressed fluid, sensing the temperature of the condensate after the thermal exchange and adjusting the flow rate of coolant to maintain the temperature of the condensate after thermal exchange at a selected level, and wherein the step of extracting vapor includes coalescing droplets of vapor, accumulating a reservoir of liquid refrigerant therefrom, and flowing refrigerant in excess of a given level to thermal exchange with the load.  
     
     
         8 . A method for improving the control stability of a system utilizing saturable fluid in compressed, controlled temperature phase in a vapor-compression cycle, for thermal exchange with a load, comprising the steps of: 
 compressing a saturable fluid to a pressurized hot gas;    condensing a flow of the pressurized hot gas;    expanding the condensed flow to a selected level;    reducing the vapor content of the expanded flow without changing the pressure;    mixing a selected proportion of pressurized hot gas with the expanded flow;    adding thermal energy to the mixture to reach a target temperature;    feeding the mixture to the load for thermal exchange prior to return for recompression, and    when the proportion of hot gas to be provided to the load is at a high level, shunting a selected fraction therefrom directly to compression to stabilize the functions of controlling the expansion and controlling the pressure.    
     
     
         9 . A device for isothermally separating vapor from a liquid/vapor fluid mixture at saturation to increase the proportion of liquid therein comprising; 
 a chamber having input and output ports for the saturable fluid;    a barrier section of selected porosity and high surface area disposed within the chamber between the input and output ports and intercepting the liquid/vapor mixture;    a liquid outlet at a lower region of the chamber for output of liquid collecting within the chamber, and    a valve including a surface float disposed on the surface of liquid in the chamber and including a closure member in operative relation to the liquid outlet that is disposed to allow liquid in excess of a predetermined level in the chamber to flow out of the chamber.    
     
     
         10 . A device as set forth in  claim 9  above, wherein the inlet port has a flow impedance selected such that flow occurs from within the chamber through the outlet vapor port and the outlet liquid port, and wherein the inlet vapor port provides the saturable fluid and the barrier is a fibrous structure substantially vertically intercepting the flow path between the input and output ports and further including a check valve coupled in the flow path to the inlet port.  
     
     
         11 . a system for controlling the temperature of at least one thermal load unit using a circulating two-phase refrigerant comprising: 
 a vapor cycle refrigeration system including at least one compressor and condenser series, and employing a two-phase refrigerant as a temperature control medium, and arranged such that the refrigerant is first compressed and then at least a portion thereof is separately liquefied to a state of pressure saturation;    a proportioning device receiving a flow of compressed refrigerant as a hot gas;    an expansion device receiving a flow of saturated liquid;    a gas processor receiving the saturated liquefied state, for extracting at least some vapor therefrom without substantially altering the pressure/temperature equilibrium thereof,    a mixing junction coupled to receive the hot gas flow from the proportioning device and the flow from the expansion device;    a thermal load comprising at least one heat exchange structure receiving the vapor-extracted saturated liquid, and    a controller system coupled to operate the proportioning device and the expansion device to control the temperature of the thermal load.    
     
     
         12 . A system as set forth in  claim 11  above, wherein the extracted vapor from the gas processor is circulated to the compressor as input and wherein the flow path to the compressor also includes an accumulator receiving output from the load, and a controller-operated coupling from the proportioning device to the flow path to the compressor.  
     
     
         13 . A system as set forth in  claim 12  above, wherein the gas processor comprises a vapor separator including a level-responsive liquid-enriched flow of saturated fluid to the load, and thereafter vapor to the compressor input, and where a check valve is coupled into the input path to the vapor separator.  
     
     
         14 . A system as set forth in  claim 13  above, further including controller operated shunt and bypass valves in circuit with the proportioning device to enable abrupt commencement and cessation of hot gas flow and controller operated shunt and bypass valves in circuit with the expansion device to enable abrupt commencement and cessation of flow of condensed fluid and a close on rise valve in circuit with the compressor input and responsive to the input pressure thereat.  
     
     
         15 . A system as set forth in  claim 13  above, wherein the system includes means to extend the high temperature range of operation comprising: 
 a countercurrent heat exchanger coupled in circuit with the load and exchanging thermal energy between input and output flow to and from the load and a heater under command of the controller for adding thermal energy to the input to the load.