Method and controller for controlling a vapour-compression system with thermodynamic constraints satisfaction

Abstract

A method of controlling a vapour-compression system for circulating a working fluid. The vapour-compression system comprises a compressor, an expansion device and an evaporator configured to facilitate heat transfer from a thermal source into the working fluid. The method comprises: determining or receiving a cooling demand, the cooling demand being associated with a demand to cool the thermal source; determining a preliminary thermofluidic property objective value based on the cooling demand; determining a final thermofluidic property objective value based on the preliminary thermofluidic property objective value and one or more thermofluidic property objective value thresholds, wherein the final thermofluidic property objective value relates to a target thermofluidic property of the working fluid at a control location within the vapour-compression system; and controlling at least one of the compressor and the expansion device based on the final thermofluidic property objective value.

What is claimed is: 
     
         1 . A method of controlling a vapour-compression system for circulating a working fluid, the vapour-compression system comprising a compressor, an expansion device and an evaporator configured to facilitate heat transfer from a thermal source into the working fluid, the method comprising:
 determining or receiving a cooling demand, the cooling demand being associated with a demand to cool the thermal source;   determining a preliminary thermofluidic property objective value based on the cooling demand;   determining a final thermofluidic property objective value based on the preliminary thermofluidic property objective value and one or more thermofluidic property objective value thresholds, wherein the final thermofluidic property objective value relates to a target thermofluidic property of the working fluid at a control location within the vapour-compression system; and   controlling at least one of the compressor and the expansion device based on the final thermofluidic property objective value.   
     
     
         2 . The method of  claim 1 , wherein the final thermofluidic property objective value relates to a target pressure of the working fluid at the control location. 
     
     
         3 . The method of  claim 1 , comprising:
 monitoring a thermofluidic property of the working fluid at the control location, and   determining the preliminary thermofluidic property objective value based on both the cooling demand and the monitored thermofluidic property of the working fluid at the control location.   
     
     
         4 . The method of  claim 1 , comprising:
 determining the cooling demand based on:
 a temperature setpoint for the thermal source; and 
 a monitored or predicted temperature of the thermal source. 
   
     
     
         5 . The method of  claim 1 , comprising:
 determining the or each thermofluidic property objective value threshold based on at least one of:
 a desired maximum temperature for working fluid in the vapour-compression system; 
 a critical pressure for working fluid in the vapour-compression system; 
 a superheat setpoint for the working fluid in the vapour-compression system; 
 a subcooling setpoint for the working fluid in the vapour-compression system; and 
 a monitored temperature of the working fluid in the vapour-compression system. 
   
     
     
         6 . The method of  claim 1 , wherein the control location is:
 at an outlet of the evaporator;   on a suction line of the vapour-compression system, the suction line extending from the evaporator to the compressor;   at an outlet of the compressor; or   on a discharge line of the vapour-compression system, the discharge line extending from the compressor to a condenser or a cooler of the vapour-compression system.   
     
     
         7 . The method of  claim 1 , wherein the control location is at the outlet of the evaporator or on the suction line of the vapour-compression system, and wherein the method comprises:
 controlling the expansion device based on the final thermofluidic property objective value.   
     
     
         8 . The method of  claim 1 , wherein the control location is at the outlet of the compressor or on the discharge line of the vapour-compression system, and wherein the method comprises:
 controlling the compressor based on the final thermofluidic property objective value.   
     
     
         9 . The method of  claim 1 , comprising:
 determining the final thermofluidic property objective value based on the preliminary thermofluidic property objective value, a lower thermofluidic property objective value threshold and an upper thermofluidic property objective value threshold.   
     
     
         10 . The method of  claim 9 , wherein determining the final thermofluidic property objective value includes:
 setting the final thermofluidic property objective value as being equal to the preliminary thermofluidic property objective value if the preliminary thermofluidic property objective value is in a range between the lower thermofluidic property objective value threshold and the upper thermofluidic property objective value threshold inclusive;   setting the final thermofluidic property objective value as being equal to the lower thermofluidic property objective value threshold if the preliminary thermofluidic property objective value is less than the lower thermofluidic property objective value threshold; and   setting the final thermofluidic property objective value as being equal to the upper thermofluidic property objective value threshold if the preliminary thermofluidic property objective value is greater than the upper thermofluidic property objective value threshold.   
     
     
         11 . The method of  claim 1 , comprising:
 determining an additional final thermofluidic property objective value, wherein the additional final thermofluidic property objective value relates to a target thermofluidic property of the working fluid at an additional control location within the vapour-compression system; and   controlling at least one of the compressor or the expansion device based on the final thermofluidic property objective value and the additional final thermofluidic property objective value.   
     
     
         12 . The method of  claim 11 , comprising:
 determining a compressor speed objective value based on both the final thermofluidic property objective value and the additional final thermofluidic property objective value; and   controlling a speed of the compressor based on the compressor speed objective value.   
     
     
         13 . The method of  claim 11 , comprising:
 determining an expansion device operating parameter objective value based on both the final thermofluidic property objective value and the additional final thermofluidic property objective value; and   controlling an operating parameter of the expansion device based on the expansion device operating parameter objective value.   
     
     
         14 . The method of  claim 11 , wherein the vapour-compression system further comprises an additional evaporator configured to facilitate heat transfer from an additional thermal source into the working fluid, and wherein the method comprises:
 determining or receiving an additional cooling demand, the additional cooling demand being associated with a demand to cool the additional thermal source;   determining an additional preliminary thermofluidic property objective value based on the additional cooling demand; and   determining the additional final thermofluidic property objective value based on the additional preliminary thermofluidic property objective value and one or more additional thermofluidic property objective value thresholds.   
     
     
         15 . The method of  claim 14 , wherein the method comprises:
 determining the preliminary thermofluidic property objective value based on both the cooling demand and the additional cooling demand; and   determining the additional preliminary thermofluidic property objective value based on both the additional cooling demand and the cooling demand.   
     
     
         16 . The method of  claim 1 , comprising:
 determining a preliminary compressor speed objective value based on the final thermofluidic property objective value;   determining a final compressor speed objective value based the preliminary compressor speed objective value and one or more compressor speed objective value thresholds; and   controlling a speed of the compressor based on the final compressor speed objective value.   
     
     
         17 . The method of  claim 1 , comprising:
 determining a preliminary expansion device operating parameter objective value based on the final thermofluidic property objective value;   determining a final expansion device operating parameter objective value based the preliminary expansion device operating parameter objective value and one or more expansion device operating parameter objective value thresholds; and   controlling an operating parameter of the expansion device based on the final expansion device operating parameter objective value.   
     
     
         18 . A vapour-compression system for circulating a working fluid, the vapour-compression system comprising a compressor, an expansion device, an evaporator configured to facilitate heat transfer from a thermal source into the working fluid, and a controller configured to carry out the method of  claim 1 .