Refrigeration system with fluid defrost

Abstract

A refrigeration system having a refrigerant circuit including a condenser, a flow control device, an evaporator, and a compressor connected in series. The compressor is configured to circulate a cooling fluid through the refrigerant circuit. The refrigerant circuit has an inlet line fluidly connecting the condenser to the evaporator and a suction line fluidly connecting the evaporator to the compressor. A heater is positioned to heat the cooling fluid during a defrost mode, and a pressure control is coupled to the refrigerant circuit downstream of the evaporator. In the defrost mode, the pressure control apparatus is configured to increase system pressure during the defrost mode to maintain flow of refrigerant into the evaporator and to control flow of cooling fluid to the compressor.

1 . A refrigeration system comprising:
 a refrigerant circuit including a condenser, a flow control device, an evaporator, and a compressor connected in series, the compressor configured to circulate a cooling fluid through the refrigerant circuit, and the refrigerant circuit having an inlet line fluidly connecting the condenser to the evaporator and a suction line fluidly connecting the evaporator to the compressor;   a heater positioned to heat the cooling fluid during a defrost mode; and   pressure control apparatus coupled to the refrigerant circuit downstream of the evaporator,   wherein, in the defrost mode, the pressure control apparatus is configured to increase system pressure during the defrost mode to maintain flow of refrigerant into the evaporator and to control flow of cooling fluid to the compressor.   
     
     
         2 . The refrigeration system of  claim 1 , wherein the heater is positioned downstream of the flow control device. 
     
     
         3 . The refrigeration system of  claim 1 , wherein the pressure control apparatus includes a solenoid valve or a pressure regulator. 
     
     
         4 . The refrigeration system of  claim 1 , wherein the pressure control apparatus includes a first pressure regulator coupled to the suction line, the refrigerant circuit further including a bypass line that bypasses the first pressure regulator and that has a second pressure regulator, and wherein the first pressure regulator has a first pressure setpoint and the second pressure regulator has a second pressure setpoint that is higher than the first pressure setpoint. 
     
     
         5 . The refrigeration system of  claim 4 , wherein the first pressure regulator includes an evaporator pressure regulator valve and the second pressure regulator includes a solenoid valve. 
     
     
         6 . The refrigeration system of  claim 1 , wherein the heater includes a first heater, the refrigeration system further comprising a second heater in communication with the flow control device, wherein the second heater is configured to control the flow control apparatus to selectively permit or restrict flow of cooling fluid to the evaporator during the defrost mode. 
     
     
         7 . The refrigeration system of  claim 1 , further comprising a sensor coupled to the evaporator and configured to detect a temperature of the evaporator, and a controller in communication with the heater to activate the heater in response to buildup of frost on the evaporator, wherein the controller is configured to terminate the defrost mode by deactivating the heater in response to the sensor detecting a cooling fluid temperature at or above a predetermined temperature threshold. 
     
     
         8 . The refrigeration system of  claim 7 , wherein the temperature of the evaporator detected by the sensor includes a temperature of the cooling fluid in or exiting the evaporator. 
     
     
         9 . The refrigeration system of  claim 7 , wherein the controller is further in communication with the pressure control apparatus to regulate a position of the pressure control apparatus between an open position and a closed position. 
     
     
         10 . The refrigeration system of  claim 1 , wherein the refrigeration circuit further includes a recirculation line fluidly connected between the suction line and the inlet line, wherein the recirculation line is configured to recirculate cooling fluid exiting the evaporator to the inlet line upstream of the heater. 
     
     
         11 . The refrigeration system of  claim 1 , wherein the heater is positioned in and coupled to the evaporator. 
     
     
         12 . The refrigeration system of  claim 1 , wherein the heater is positioned directly below the evaporator. 
     
     
         13 . A refrigeration system comprising:
 a refrigerant circuit including a condenser, a flow control device, an evaporator, and a compressor connected in series, the compressor configured to circulate a refrigerant through the refrigerant circuit, and the refrigerant circuit having an inlet line fluidly connecting the condenser to the evaporator and a suction line fluidly connecting the evaporator to the compressor;   a refrigeration mode in which refrigerant is directed through the evaporator in a first direction via the inlet line;   a defrost mode in which refrigerant is directed through the evaporator in the first direction via the inlet line;   a first heater coupled to the inlet line and configured to heat the refrigerant during the defrost mode; and   a pressure control apparatus coupled to the refrigerant circuit downstream of the evaporator and configured to increase system pressure to maintain flow of refrigerant into the evaporator during the defrost mode.   
     
     
         14 . The refrigeration system of  claim 13 , wherein the heater is positioned downstream of the flow control device. 
     
     
         15 . The refrigeration system of  claim 11 , wherein the pressure control apparatus includes a solenoid valve or a pressure regulator. 
     
     
         16 . The refrigeration system of  claim 11 , wherein the pressure control apparatus includes a first pressure regulator coupled to the suction line, the refrigerant circuit further including a bypass line that bypasses the first pressure regulator and that has a second pressure regulator, and wherein the first pressure regulator has a first pressure setpoint and the second pressure regulator has a second pressure setpoint that is higher than the first pressure setpoint. 
     
     
         17 . The refrigeration system of  claim 14 , wherein the first pressure regulator includes an evaporator pressure regulator valve and the second pressure regulator includes a solenoid valve. 
     
     
         18 . The refrigeration system of  claim 11 , wherein the heater includes a first heater, the refrigeration system further comprising a second heater in communication with the flow control device, wherein the second heater is configured to control the flow control apparatus to permit flow of cooling fluid to the evaporator during the defrost mode. 
     
     
         19 . The refrigeration system of  claim 11 , further comprising a sensor coupled to the evaporator and configured to detect a temperature of the evaporator, and a controller in communication with the heater to activate the heater in response to buildup of frost on the evaporator, wherein the controller is configured to terminate the defrost mode by deactivating the heater in response to the sensor detecting a cooling fluid temperature at or above a predetermined temperature threshold. 
     
     
         20 . The refrigeration system of  claim 17 , wherein the controller is further in communication with the pressure control apparatus to regulate a position of the pressure control apparatus between an open position and a closed position. 
     
     
         21 . The refrigeration system of  claim 11 , wherein the refrigeration circuit further includes a recirculation line fluidly connected between the suction line and the inlet line, wherein the recirculation line is configured to recirculate cooling fluid exiting the evaporator to the inlet line upstream of the heater. 
     
     
         22 . A method of defrosting a refrigeration system having a refrigeration mode and a defrost mode, the method comprising:
 circulating refrigerant in the refrigeration mode through a condenser, a flow control device, an evaporator, and a compressor of the refrigeration system;   circulating refrigerant in the defrost mode through the evaporator in the same direction as the refrigeration mode;   heating the refrigerant in the defrost mode; and   increasing system pressure in the defrost mode to maintain flow of refrigerant into the evaporator during the defrost mode.   
     
     
         23 . The method of  claim 22 , further comprising deactivating the defrost mode based on a temperature of refrigerant exiting the evaporator meeting or exceeding a temperature threshold. 
     
     
         24 . The method of  claim 22 , further comprising heating the refrigerant upstream of the evaporator. 
     
     
         25 . The method of  claim 22 , further comprising heating the refrigerant within the evaporator.