Cooling systems with passive sub-coolers

Abstract

The present disclosure provides a cooling system comprising a primary refrigerant circuit wherein a primary refrigerant fluid is circulated through a heat exchanger and one or more of: an evaporator, a compressor, a metering device and a condenser; and a secondary refrigerant circuit wherein a secondary refrigerant fluid is circulated through the heat exchanger and a fluid cooler, wherein the secondary refrigerant circuit uses carbon dioxide as the secondary refrigerant fluid and does not include any compression components in order to provide passive subcooling to the primary refrigerant fluid.

1 . A cooling system comprising:
 a primary refrigerant circuit wherein a primary refrigerant fluid is circulated through a heat exchanger and one or more of: an evaporator, a compressor, a metering device and a condenser; and,   a secondary refrigerant circuit wherein a secondary refrigerant fluid is circulated through the heat exchanger and a fluid cooler, wherein the secondary refrigerant circuit uses carbon dioxide as the secondary refrigerant fluid and does not include any compression components in order to provide passive subcooling to the primary refrigerant fluid.   
     
     
         2 . The cooling system of  claim 1  wherein the secondary refrigerant circuit comprises a carbon dioxide reservoir connected to an outlet of the fluid cooler, and a metering device connected between an outlet of the carbon dioxide reservoir and the heat exchanger. 
     
     
         3 . The cooling system of  claim 1 or claim 2  wherein the primary refrigerant circuit comprises a primary refrigerant reservoir connected between the condenser and the evaporator, and a metering device connected between an outlet of the primary refrigerant reservoir and the evaporator. 
     
     
         4 . The cooling system of any one of  claims 1 to 3  wherein the primary refrigerant circuit comprises one or more valves and bypass lines configured to bypass the compressor when a temperature at an inlet of the condenser is lower than a temperature of return air to the evaporator such that the system is operable in a free cooling mode. 
     
     
         5 . The cooling system of  claim 4  wherein the one or more valves and bypass lines are configured to bypass both the compressor and the condenser in the free cooling mode. 
     
     
         6 . The cooling system of any one of  claims 1 to 5  wherein the fluid cooler of the secondary refrigerant circuit is installed in cascade with the condenser of the primary refrigerant circuit. 
     
     
         7 . The cooling system of  claim 6  comprising a cooling fan located to move a cooling medium across the fluid cooler and the condenser. 
     
     
         8 . The cooling system of any one of  claims 1 to 5  wherein the fluid cooler of the secondary refrigerant circuit is installed at a separate location from the condenser of the primary refrigerant circuit. 
     
     
         9 . The cooling system of  claim 6  comprising a first cooling fan located to a move cooling medium across the condenser and a second cooling fan located to move the cooling medium across the fluid cooler. 
     
     
         10 . The cooling system of  claim 7 or claim 9  wherein the cooling medium is air. 
     
     
         11 . A method comprising:
 circulating a primary refrigerant fluid through a a primary refrigerant circuit comprising a heat exchanger and one or more of: an evaporator, a compressor, a metering device and a condenser; and,   subcooling the primary refrigerant fluid in the heat exchanger by circulating a secondary refrigerant fluid through a secondary refrigerant circuit comprising the heat exchanger and a fluid cooler, wherein the secondary refrigerant circuit uses carbon dioxide as the secondary refrigerant fluid and does not include any compression components in order to provide passive subcooling to the primary refrigerant fluid.   
     
     
         12 . The method of  claim 11  wherein the primary refrigerant circuit comprises one or more valves and bypass lines configured to selectively bypass the compressor, the method comprising:
 monitoring a temperature at an inlet of the condenser and a temperature of return air to the evaporator; 
 activating the compressor and controlling the one or more valves such that the primary refrigerant fluid passes through the compressor when the temperature at the inlet of the condenser is at least as high as the temperature of return air to the evaporator; and 
 deactivating the compressor and controlling the one or more valves such that the primary refrigerant fluid bypasses the compressor when the temperature at the inlet of the condenser is lower than the temperature of return air to the evaporator.