Supercritical refrigeration cycle apparatus and method for controlling supercritical refrigeration cycle apparatus

Abstract

A supercritical refrigeration cycle apparatus and a method for controlling a supercritical refrigeration cycle apparatus are provided. The supercritical refrigeration cycle apparatus may include a compressor; a gas cooler configured to cool the compressed a refrigerant in a supercritical state; a pressure control electronic expansion valve connected to the gas cooler; a receiver configured to temporarily store the refrigerant; a flow control electronic expansion valve connected to an outlet side of the receiver to control a flow rate of the refrigerant; and a controller configured to control the flow control electronic expansion valve based on a suction superheat degree of refrigerant suctioned into the compressor and a target suction superheat degree, and control the pressure control electronic expansion valve based on a target operation high pressure and a current operation high pressure. In this way, flow control and pressure control of refrigerant may be respectively implemented in a separate manner, thereby enhancing reliability and operation efficiency of the compressor, respectively.

What is claimed is: 
     
         1 . A supercritical refrigeration cycle apparatus, comprising:
 a compressor configured to compress a refrigerant in a supercritical state;   a gas cooler configured to cool the compressed refrigerant;   a pressure control electronic expansion valve connected to the gas cooler to control a pressure of the refrigerant;   a receiver configured to temporarily store the refrigerant which has passed through the pressure control electronic expansion valve;   a flow control electronic expansion valve connected to an outlet side of the receiver to control a flow rate of the refrigerant; and   a controller configured to control the flow control electronic expansion valve based on a suction superheat degree of refrigerant suctioned into the compressor and a target suction superheat degree, and control the pressure control electronic expansion valve based on a target operation high pressure and a current operation high pressure.   
     
     
         2 . The supercritical refrigeration cycle apparatus of  claim 1 , wherein the controller decreases an opening degree of the flow control electronic expansion valve when the suction superheat degree of the refrigerant is less than the target suction superheat degree, and increases the opening degree of the flow control electronic expansion valve when the suction superheat degree of the refrigerant is greater than the target suction superheat degree. 
     
     
         3 . The supercritical refrigeration cycle apparatus of  claim 1 , wherein the controller increases an opening degree of the pressure control electronic expansion valve when the current operation high pressure is greater than the target operation high pressure, decreases the opening degree of the pressure control electronic expansion valve when the current operation high pressure is less than the target operation high pressure, and maintains the opening degree of the pressure control electronic expansion valve when they are the same. 
     
     
         4 . The supercritical refrigeration cycle apparatus of  claim 1 , further including:
 an intermediate heat exchanger in which refrigerant which has passed through the gas cooler and refrigerant which has passed through the evaporator exchange heat with each other.   
     
     
         5 . A supercritical refrigeration cycle apparatus, comprising:
 a compressor configured to compress a refrigerant in a supercritical state;   a gas cooler configured to cool the compressed refrigerant;   a pressure control electronic expansion valve connected to the gas cooler to control a pressure of the refrigerant;   a phase separator configured to accommodate refrigerant which has passed through the pressure control electronic expansion valve to perform phase separation;   a flow control electronic expansion valve connected to an outlet side of the phase separator to control a flow rate of the refrigerant;   an injection pipe, a first end of which is connected to the phase separator and a second end of which is connected to the compressor to provide gaseous refrigerant in the phase separator to the compressor;   a switching valve configured to open or close the injection pipe; and   a controller configured to control the flow control electronic expansion valve based on a suction superheat degree of refrigerant suctioned into the compressor and a target suction superheat degree, and control the pressure control electronic expansion valve based on a target operation high pressure and a current operation high pressure, and control the switching valve based on a compression ratio of the refrigerant and a refrigerant discharge temperature of the compressor.   
     
     
         6 . The supercritical refrigeration cycle apparatus of  claim 5 , wherein the controller decreases an opening degree of the flow control electronic expansion valve when the suction superheat degree of the refrigerant is less than the target suction superheat degree, and increases the opening degree of the flow control electronic expansion valve when the suction superheat degree of the refrigerant is greater than the target suction superheat degree. 
     
     
         7 . The supercritical refrigeration cycle apparatus of  claim 5 , wherein the controller increases an opening degree of the pressure control electronic expansion valve when the current operation high pressure is greater than the target operation high pressure, decreases the opening degree of the pressure control electronic expansion valve when the current operation high pressure is less than the target operation high pressure, and maintains the opening degree of the pressure control electronic expansion valve when the current operation high pressure is the same as the target operation high pressure. 
     
     
         8 . The supercritical refrigeration cycle apparatus of  claim 5 , further including:
 an intermediate heat exchanger in which refrigerant which has passed through the gas cooler and refrigerant which has passed through the evaporator exchange heat with each other.   
     
     
         9 . The supercritical refrigeration cycle apparatus of  claim 5 , wherein the controller controls the switching valve to open the injection pipe so as to provide refrigerant in the phase separator to the compressor when the compression ratio is above a predetermined value, and the discharge temperature of the compressor is above a predetermined temperature. 
     
     
         10 . A method for controlling a supercritical refrigeration cycle apparatus including a compressor configured to compress a refrigerant; a gas cooler configured to cool the compressed refrigerant in a supercritical state; a pressure control electronic expansion valve connected to the gas cooler to control a pressure of the refrigerant; a receiver configured to temporarily store the refrigerant which has passed through the pressure control electronic expansion valve; and a flow control electronic expansion valve connected to an outlet side of the receiver to control a flow rate of refrigerant, the method comprising:
 controlling an opening degree of the flow control electronic expansion valve based on a suction superheat degree of refrigerant in the compressor; and   controlling an opening degree of the pressure control electronic expansion valve based on an operation high pressure of the refrigerant.   
     
     
         11 . The method of  claim 10 , wherein the controlling of the opening degree of the flow control electronic expansion valve includes:
 checking a suction superheat degree of the refrigerant in the compressor;   comparing the suction superheat degree of the compressor with a target suction superheat degree; and   maintaining a current opening degree of the flow control electronic expansion valve when the suction superheat degree of the compressor is the same as the target suction superheat degree.   
     
     
         12 . The method of  claim 11 , further including:
 increasing the opening degree of the flow control electronic expansion valve when the suction superheat degree of the compressor is greater than the target suction superheat degree and decreasing the opening degree of the flow control electronic expansion valve when the suction superheat degree is less than the target suction superheat degree.   
     
     
         13 . The method of  claim 11 , wherein when the suction superheat degree of the compressor is the same as the target suction superheat degree, maintaining a current opening degree of the flow control electronic expansion valve, and then controlling the opening degree of the pressure control electronic expansion valve. 
     
     
         14 . The method of  claim 11 , wherein the controlling of the opening degree of the pressure control electronic expansion valve includes:
 sensing an outlet temperature of the gas cooler and an evaporation temperature of the evaporator, respectively;   calculating a target operation high pressure using the outlet temperature of the gas cooler and the evaporation temperature of the evaporator, and calculating a current operation high pressure corresponding to the outlet temperature of the gas cooler;   comparing the target operation high pressure with the current operation high pressure; and   maintaining a current opening degree of the pressure control electronic expansion valve when the current operation high pressure is the same as the target operation high pressure.   
     
     
         15 . The method of  claim 14 , further including:
 increasing the opening degree of the pressure control electronic expansion valve when the current operation high pressure is greater than the target operation high pressure; and   decreasing the opening degree of the pressure control electronic expansion valve when the current operation high pressure is less than the target operation high pressure.   
     
     
         16 . A method for controlling a supercritical refrigeration cycle apparatus including a compressor configured to compress a refrigerant; a gas cooler configured to cool the compressed refrigerant in a supercritical state; a pressure control electronic expansion valve connected to the gas cooler to control a pressure of the refrigerant; a phase separator configured to accommodate refrigerant which has passed through the pressure control electronic expansion valve to perform phase separation; a flow control electronic expansion valve connected to an outlet side of the phase separator to control a flow rate of the refrigerant; an injection pipe, a first end of which is connected to the phase separator and a second end of which is connected to the compressor to provide gaseous refrigerant in the phase separator to the compressor; and a switching valve configured to open or close the injection pipe, the method comprising:
 controlling an opening degree of the flow control electronic expansion valve based on a suction superheat degree of the compressor;   controlling an opening degree of the pressure control electronic expansion valve based on an operation high pressure of the refrigerant; and   controlling the switching valve based on a compression ratio of the refrigerant and a refrigerant discharge temperature of the compressor.   
     
     
         17 . The method of  claim 16 , wherein the controlling of the switching valve controls the switching valve to open the injection pipe so as to provide the refrigerant in the phase separator to the compressor when the compression ratio is above a predetermined value, and the discharge temperature of the compressor is above a predetermined temperature. 
     
     
         18 . The method of  claim 16 , wherein when the suction superheat degree of the compressor is the same as the target suction superheat degree, maintaining a current opening degree of the flow control electronic expansion valve, and controlling an opening degree of the pressure control electronic expansion valve. 
     
     
         19 . The method of  claim 18 , wherein the controlling of the opening degree of the flow control electronic expansion valve includes:
 checking a suction superheat degree of the refrigerant in the compressor;   comparing the suction superheat degree of the compressor with a target suction superheat degree;   maintaining a current opening degree of the flow control electronic expansion valve when the suction superheat degree of the compressor is the same as the target suction superheat degree, increasing the opening degree of the flow control electronic expansion valve when the suction superheat degree of the compressor is greater than the target suction superheat degree, and decreasing the opening degree of the flow control electronic expansion valve when the suction superheat degree of the compressor is less than the target suction superheat degree.   
     
     
         20 . The method of  claim 18 , wherein the controlling of the opening degree of the pressure control electronic expansion valve includes:
 checking an outlet temperature of the gas cooler and an evaporation temperature of the evaporator, respectively;   calculating a target operation high pressure using the outlet temperature of the gas cooler and the evaporation temperature of the evaporator, and calculating a current operation high pressure corresponding to the outlet temperature of the gas cooler;   comparing the target operation high pressure with the current operation high pressure; and   maintaining a current opening degree of the pressure control electronic expansion valve when the current operation high pressure is the same as the target operation high pressure, increasing an the opening degree of the pressure control electronic expansion valve when the current operation high pressure is greater than the target operation high pressure, and decreasing the opening degree of the pressure control electronic expansion valve when the current operation high pressure is less than the target operation high pressure.