Energy-optimized cycle control of time-variant loads for thermal management of vapor compression systems

Abstract

Control methods for vapor compression systems and multiple-load vapor compression systems having one or more refrigeration loops include selecting a desired set-point temperature range for a load temperature at one or more load locations. The vapor compression system is then operated to transfer heat from the one or more load locations to a rejection location. While the vapor compression system is operating, a control apparatus continually adjusts various parameters. A capacity of an adjustable-capacity compressor is adjusted to maintain with respect to an evaporator load a maximum low-side pressure of the refrigeration loop as measured by a first sensor. An adjustable rejection capacity of a rejection apparatus is adjusted to maintain a minimum high-side pressure of the refrigeration loop as measured by a second sensor. An adjustable opening of an expansion valve is adjusted to maintain a load temperature measured by the third sensor within the desired set-point temperature range.

What is claimed is: 
     
         1 . A method for controlling a vapor compression system, wherein the vapor compression system comprises:
 a refrigeration loop configured to transfer heat from a load location to a rejection location, the load location having a load temperature resulting from a heat load at the load location, the heat load defining an evaporator load, the refrigeration loop having a plurality of components in fluidic communication through refrigeration lines containing a refrigerant, the plurality of components comprising:
 an adjustable-capacity compressor that compresses the refrigerant from a low-pressure side of the refrigeration loop and delivers the refrigerant to a high-pressure side of the refrigeration loop; 
 a condenser that condenses at least a portion the refrigerant from the adjustable-capacity compressor to produce chilled refrigerant, the condenser being in thermal communication with the rejection location via a rejection apparatus having an adjustable rejection capacity; 
 an expansion valve having an adjustable opening through which the chilled refrigerant from the condenser expands and is delivered back to the low-pressure side; 
 an evaporator at the load location that transfers heat from the heat load to the refrigerant arriving from the expansion valve and delivers the refrigerant back to the adjustable-capacity compressor; 
   a first sensor that measures a low-side pressure of the low-pressure side of the refrigeration loop;   a second sensor that measures a high-side pressure of the high-pressure side of the refrigeration loop;   a third sensor that measures the load temperature;   a control apparatus electronically coupled to the adjustable-capacity compressor, the expansion valve, the first sensor, the second sensor, the third sensor, and the rejection apparatus,   
       the method comprising:
 selecting a desired set-point temperature range for the load temperature at the load location; 
 operating the vapor compression system to transfer heat from the load location to the rejection location; and 
 adjusting continually with the control apparatus while the vapor compression system is operating one or more of:
 a capacity of the adjustable-capacity compressor so as to maintain with respect to the evaporator load a maximum low-side pressure as measured by the first sensor; and 
 the adjustable rejection capacity of the rejection apparatus so as to maintain a minimum high-side pressure as measured by the second sensor; and 
 the adjustable opening of the expansion valve so as to maintain the load temperature measured by the third sensor within the desired set-point temperature range. 
 
 
     
     
         2 . The method of  claim 1 , wherein the first sensor is between the evaporator and the adjustable-capacity compressor. 
     
     
         3 . The method of  claim 1 , wherein the second sensor is between the condenser and the expansion valve. 
     
     
         4 . The method of  claim 1 , wherein the expansion valve is an electronic expansion valve. 
     
     
         5 . The method of  claim 1 , wherein:
 the high-side pressure is a saturated discharge pressure; and   the low-side pressure is a saturated suction pressure.   
     
     
         6 . The method of  claim 1 , wherein the rejection apparatus is selected from the group consisting of fans, vents, variable bypass paths, and closed cooling loops. 
     
     
         7 . The method of  claim 6 , wherein adjusting the adjustable rejection capacity comprises adjusting a fan speed of a fan, modifying a vent opening of a vent, modifying refrigerant flow bypassing the condenser through a variable bypass path, or modifying a circulation speed of a coolant medium in a closed cooling loop. 
     
     
         8 . The method of  claim 1 , wherein the adjusting continually with the control apparatus comprises:
 continually adjusting the capacity of the adjustable-capacity compressor;   continually adjusting the adjustable rejection capacity of the rejection apparatus; and   setting the adjustable opening of the expansion valve to a maximum opening width.   
     
     
         9 . The method of  claim 1 , wherein the load location is an enclosed space that is cooled by the vapor compression system. 
     
     
         10 . The method of  claim 1 , wherein the load location is chosen from a radar apparatus, an aircraft, an electronic apparatus, a cabin environment, a cockpit environment, a weapon, a galley, a fluidic apparatus containing lubrication fluids, and a fuel compartment containing a fuel. 
     
     
         11 . The method of  claim 1 , wherein the rejection location is the environment. 
     
     
         12 . The method of  claim 1 , wherein the rejection location is an intermediate rejection location from which additional heat is removable to an ultimate rejection location, the intermediate rejection location being chosen from chilled water, a fuel tank, an air stream, and a body of water. 
     
     
         13 . The method of  claim 12 , wherein the ultimate rejection location is the environment. 
     
     
         14 . A method for controlling a multiple-load vapor compression system, wherein the multiple-load vapor compression system comprises:
 a refrigeration loop configured to transfer heat from multiple load locations to at least one rejection location, each load location having a load temperature resulting from a heat load at the load location, the heat load at a particular load location defining an evaporator load for the particular load location, the refrigeration loop having a plurality of components in fluidic communication through refrigeration lines containing a refrigerant, the plurality of components comprising:
 an adjustable-capacity compressor that compresses refrigerant vapor from a low-pressure side of the refrigeration loop and delivers compressed refrigerant vapor to a high-pressure side of the refrigeration loop; 
 a condenser that condenses at least a portion of the refrigerant from the adjustable-capacity compressor to produce chilled refrigerant, the condenser being in thermal communication with the rejection location via a rejection apparatus having an adjustable rejection capacity; 
 an expansion valve associated with each load location, each expansion valve having an adjustable opening through which the chilled refrigerant from the condenser expands and is delivered back to the low-pressure side; 
 an evaporator at each load location that transfers heat from the load location of the evaporator to the refrigerant arriving at the evaporator from the expansion valve associated with the load location and delivers the refrigerant back to the adjustable-capacity compressor; 
   a first sensor that measures a low-side pressure of the low-pressure side of the refrigeration loop;   a second sensor that measures a high-side pressure of the high-pressure side of the refrigeration loop;   multiple third sensors, each third sensor being associated with an individual evaporator and measuring the load temperature at the load location of the individual evaporator;   a control apparatus coupled to the adjustable-capacity compressor, each expansion valve, the first sensor, the second sensor, each of the third sensors, and the rejection apparatus,   
       the method comprising:
 selecting desired set-point temperature ranges for the load temperatures at each individual load location of the multiple load locations; and 
 operating the multiple-load vapor compression system to transfer heat from the multiple load locations to at the least one rejection location; 
 adjusting continually with the control apparatus while the multiple-load vapor compression system is operating one or more of:
 a capacity of the adjustable-capacity compressor so as to maintain a maximum low-side pressure, as measured by the first sensor, with respect to the evaporator load at an individual load location having a coldest desired set-point temperature range of the multiple load locations; and 
 the adjustable rejection capacity of the rejection apparatus so as to maintain a minimum high-side pressure as measured by the second sensor; and 
 each adjustable opening of each expansion valve independently from other expansion valves in the multi-load vapor compression system, so as to maintain the load temperatures measured by the third sensors associated with each evaporator within the desired set-point temperature range for each load temperature. 
 
 
     
     
         15 . The method of  claim 14 , wherein:
 the saturated discharge condition is a saturated discharge pressure, a saturated discharge temperature, or both; and   the saturated suction condition is a saturated suction pressure, a saturated suction temperature, or both.   
     
     
         16 . The method of  claim 14 , wherein the rejection apparatus is chosen from fans, vents, a condenser bypass, and closed cooling loops. 
     
     
         17 . The method of  claim 16 , wherein adjusting the adjustable rejection capacity comprises adjusting a fan speed of a fan, modifying a vent opening of a vent, modifying refrigerant flow bypassing the condenser through a variable bypass path, or modifying a circulation speed of a coolant medium in a closed cooling loop. 
     
     
         18 . The method of  claim 14 , wherein the adjusting continually with the control apparatus comprises:
 continually adjusting the capacity of the adjustable-capacity compressor;   continually adjusting the adjustable rejection capacity of the rejection apparatus; and   setting the adjustable opening of the expansion valve to a maximum opening width.   
     
     
         19 . The method of  claim 14 , wherein each load location is chosen from a radar apparatus, an aircraft, an electronic apparatus, a cabin environment, a cockpit environment, a weapon, a galley, a fluidic apparatus containing lubrication fluids, or a fuel compartment containing a fuel. 
     
     
         20 . The method of  claim 14 , wherein the at least one rejection location is an intermediate rejection location from which additional heat is removable an ultimate rejection location, the intermediate rejection location being chosen from chilled water, a fuel tank, an air stream, or a body of water.