Method for determining optimal coefficient of performance in a transcritical vapor compression system

Abstract

The high side pressure of a vapor compression system is selected to optimize the coefficient of performance by measuring the gas cooler exit temperature with a temperature sensor. For any gas cooler exit temperature, a single optimal high side pressure optimizes the coefficient of performance. The optimal high side pressure for each gas cooler exit temperature is preset into a control and is based on data obtained by previous testing. A temperature sensor measures the gas cooler exit temperature. The control determines the optimal high side pressure based solely on the gas cooler exit temperature and the data preset into the control.

1 . A transcritical vapor compression system comprising: 
 a compression device to compress a refrigerant to a high pressure;    a gas cooler for cooling the refrigerant, and the refrigerant exits the gas cooler at a gas cooler exit temperature;    an expansion device for reducing the refrigerant to a low pressure;    an evaporator for evaporating the refrigerant; and    a control to determine a desired high pressure of the refrigerant based solely on a characteristic indicative of the gas cooler exit temperature of the refrigerant and to adjust the high pressure to the desired high pressure.    
   
   
       2 . The system as recited in  claim 1  wherein the gas cooler exit temperature is measured by a temperature sensor.  
   
   
       3 . The system as recited in  claim 1  wherein the control adjusts the high pressure to the desired high pressure by adjusting the expansion device.  
   
   
       4 . The system as recited in  claim 1  wherein the desired high pressure corresponds to an optimal coefficient of performance.  
   
   
       5 . The system as recited in  claim 1  wherein the refrigerant is carbon dioxide.  
   
   
       6 . The system as recited in  claim 1  wherein the characteristic indicative of the gas cooler exit temperature is the gas cooler exit temperature.  
   
   
       7 . The system as recited in  claim 1  wherein the desired high pressure is determined based on a preset data programmed in the control relating the desired high side pressure to the gas cooler exit temperature.  
   
   
       8 . The system as recited in  claim 1  wherein the desired high pressure is selected to optimize a capacity and an efficiency of the vapor compression system when operating in a heating mode.  
   
   
       9 . A transcritical vapor compression system comprising: 
 a compression device to compress a refrigerant to a high pressure;    a gas cooler for cooling the refrigerant, and the refrigerant exits the gas cooler at a gas cooler exit temperature;    an expansion device for reducing the refrigerant to a low pressure;    an evaporator for evaporating the refrigerant;    a temperature sensor for measuring the gas cooler exit temperature; and    a control to determine a desired high pressure of the refrigerant based solely on a characteristic indicative of the gas cooler exit temperature of the refrigerant and to adjust the high pressure to the desired high pressure by adjusting the expansion device, wherein the desired high pressure corresponds to an optimal coefficient of performance.    
   
   
       10 . The system as recited in  claim 9  wherein the refrigerant is carbon dioxide.  
   
   
       11 . The system as recited in  claim 9  wherein the desired high pressure is determined based on preset data programmed in the control relating the desired high side pressure to the gas cooler exit temperature.  
   
   
       12 . The system as recited in  claim 9  wherein the desired high pressure is selected to optimize a capacity and an efficiency of the vapor compression system when operating in a heating mode.  
   
   
       13 . A method of optimizing a coefficient of performance of a transcritical vapor compression system comprising the steps of: 
 compressing a refrigerant to a high pressure;    cooling the refrigerant in a gas cooler, and the refrigerant exits the gas cooler at a gas cooler exit temperature;    expanding the refrigerant to a low pressure;    evaporating the refrigerant;    measuring a characteristic indicative of the gas cooler exit temperature of the refrigerant;    determining a desired high pressure of the refrigerant based solely on the characteristic indicative of the gas cooler exit inlet temperature; and    adjusting the high pressure to the desired high pressure.    
   
   
       14 . The method as recited in  claim 13  wherein the step of adjusting the high pressure includes adjusting a degree of expansion of an expansion device.  
   
   
       15 . The method as recited in  claim 13  wherein the refrigerant is carbon dioxide.  
   
   
       16 . The method as recited in  claim 13  wherein the characteristic indicative of the gas cooler exit temperature is the gas cooler exit temperature.  
   
   
       17 . The method as recited in  claim 13  further including the step of programming data relating the gas cooler exit temperature to the desired high pressure.  
   
   
       18 . The method as recited in  claim 13  wherein the desired high pressure corresponds to an optimal coefficient of performance.  
   
   
       19 . The method as recited in  claim 13 , further including the step of optimizing a capacity and an efficiency of the vapor compression system when operating in a heating mode.