Low-cost control for carbon dioxide condensing unit

Abstract

A system may include a condenser unit including a compressor configured to receive a refrigerant from a condenser unit input port and provide a compressed refrigerant; a gas cooler configured to receive the compressed refrigerant and provide a first cooled refrigerant at a gas cooler discharge port; an expansion valve configured to receive the first cooled refrigerant and provide a second cooled refrigerant to a condenser unit discharge port; and a first controllable valve configured to receive the first cooled refrigerant and provide a first metered refrigerant combined with the second cooled refrigerant into a combined refrigerant provided to the condenser unit discharge port, the first controllable valve configured to selectively open when a first temperature at the gas cooler discharge port is below a first temperature threshold.

What is claimed is: 
     
         1 . A system, the system comprising:
 a condenser unit, the condenser unit comprising:
 a compressor configured to receive a refrigerant from a condenser unit input port and provide a compressed refrigerant; 
 a gas cooler configured to receive the compressed refrigerant and provide a first cooled refrigerant at a gas cooler discharge port; 
 an expansion valve configured to receive the first cooled refrigerant and provide a second cooled refrigerant to a condenser unit discharge port; and 
 a first controllable valve configured to receive the first cooled refrigerant and provide a first metered refrigerant combined with the second cooled refrigerant into a combined refrigerant provided to the condenser unit discharge port, the first controllable valve configured to selectively open when a first temperature at the gas cooler discharge port is below a first temperature threshold. 
   
     
     
         2 . The system of  claim 1 , wherein the expansion valve is a fixed differential expansion valve. 
     
     
         3 . The system of  claim 1 , wherein the first controllable valve is a shut off valve. 
     
     
         4 . The system of  claim 1 , further comprising:
 a first temperature sensor physically attached to the first controllable valve, the first temperature sensor configured to directly activate a first controllable valve actuator configured to operate the first controllable valve.   
     
     
         5 . The system of  claim 1 , wherein the first temperature threshold corresponds to a critical temperature of carbon dioxide. 
     
     
         6 . The system of  claim 1 , the system further comprising:
 an evaporator unit, the evaporator unit comprising:
 a second controllable valve configured to receive at least one of the first cooled refrigerant and the first metered refrigerant from the condenser unit discharge port and provide a second metered refrigerant; and 
 an evaporator configured to receive the second metered refrigerant and provide an evaporated refrigerant at an evaporator discharge port configured to be coupled to the condenser unit input port, wherein the second metered refrigerant in the evaporator is configured to cool an adjacent space, 
 wherein the second controllable valve is configured to selectively open when a second temperature at the evaporator discharge port is below a second temperature threshold. 
   
     
     
         7 . The system of  claim 6 , wherein the second controllable valve is a shut off valve. 
     
     
         8 . The system of  claim 6 , further comprising:
 a second temperature sensor physically attached to the second controllable valve, the second temperature sensor configured to directly activate a second controllable valve actuator configured to operate the second controllable valve.   
     
     
         9 . The system of  claim 6 , further comprising:
 a first temperature sensor physically separated from the first controllable valve, the first temperature sensor configured to provide a first temperature signal representative of the first temperature at the gas cooler discharge port;   a second temperature sensor physically separated from the second controllable valve, the second temperature sensor configured to provide a second temperature signal representative of the second temperature at the evaporator discharge port, the second temperature signal transmitted through a second temperature port as a transmitted second temperature signal; and   a controller configured to compare the first temperature signal with a first temperature threshold signal representative of the first temperature threshold, the controller configured to assert a first control signal to indirectly activate a first controllable valve actuator configured to open the first controllable valve when the first temperature is below the first temperature threshold, the controller configured to compare the transmitted second temperature signal with a second temperature threshold signal representative of the second temperature threshold, the controller configured to assert a second control signal, the second control signal transmitted through a second control port as a transmitted second control signal to indirectly activate a second controllable valve actuator configured to open the second controllable valve when the second temperature is below the second temperature threshold.   
     
     
         10 . The system of  claim 9 , wherein the controller is configured to selectively activate at least one of the first controllable valve actuator and the second controllable valve actuator with pulse width modulation. 
     
     
         11 . The system of  claim 9 , wherein the second controllable valve is one of a thermally controlled valve, an electronic expansion valve, and a pulse width modulated valve. 
     
     
         12 . A method, comprising:
 condensing a compressed refrigerant with a gas cooler having a gas cooler discharge port to provide a first cooled refrigerant;   expanding the first cooled refrigerant to provide a second cooled refrigerant to a condenser unit discharge port;   detecting a first temperature at the gas cooler discharge port; and   conducting at least a portion of the first cooled refrigerant to combine with the second cooled refrigerant into a combined refrigerant at the condenser unit discharge port when the first temperature is below a first temperature threshold.   
     
     
         13 . The method of  claim 12 , wherein conducting the portion of the first cooled refrigerant to combine with the second cooled refrigerant into the combined refrigerant at the condenser unit discharge port when the first temperature is below the first temperature threshold includes:
 controlling a first controllable valve configured to receive the first cooled refrigerant and provide a first metered refrigerant combined with the second cooled refrigerant into the combined refrigerant provided to the condenser unit discharge port.   
     
     
         14 . The method of  claim 13 , wherein controlling the first controllable valve configured to receive the first cooled refrigerant and provide the first metered refrigerant combined with the second cooled refrigerant into the combined refrigerant provided to the condenser unit discharge port includes:
 activating a first controllable valve actuator configured to open the first controllable valve.   
     
     
         15 . The method of  claim 14 , wherein activating the first controllable valve actuator includes one of directly activating through a physical connection and indirectly activating through an electronic connection. 
     
     
         16 . The method of  claim 12 , further comprising:
 compressing a refrigerant from a condenser unit input port to provide the compressed refrigerant.   
     
     
         17 . The method of  claim 12 , further comprising:
 absorbing heat from an adjacent space with an evaporator having an evaporator discharge port;   detecting a second temperature at the evaporator discharge port; and   conducting the combined refrigerant to the evaporator when the second temperature is below a second temperature threshold, the evaporator providing an evaporated refrigerant to a condenser unit input port.   
     
     
         18 . The method of  claim 17 , wherein conducting the combined refrigerant to the evaporator when the second temperature is below the second temperature threshold includes:
 controlling a second controllable valve configured to receive the combined refrigerant and provide a second metered refrigerant to the evaporator.   
     
     
         19 . The method of  claim 18 , wherein controlling the second controllable valve configured to receive the combined refrigerant and provide the second metered refrigerant to the evaporator includes:
 activating a second controllable valve actuator configured to open the second controllable valve.   
     
     
         20 . The method of  claim 19 , wherein activating the second controllable valve actuator includes one of directly activating through a physical connection and indirectly activating through an electronic connection.