Temperature control system with a directly-controlled purge cycle

Abstract

A temperature control system includes a compressor, a condenser, an evaporator, and an accumulator. A liquid level sensor is associated with the accumulator tank generates a signal indicative of the level of the liquid heat transfer fluid inside the accumulator. A valve is in fluid communication with the condenser, the compressor, and the evaporator and is operable in a first position and a second position. The first position directs the heat transfer fluid from the compressor to the condenser, and the second position directs the heat transfer fluid from the compressor to the evaporator without passing through the first heat exchanger. A controller is in electrical communication with the liquid level sensor and the valve and is operable to receive the signal and move the valve from the first position to the second position based on the signal.

1 . A temperature control system comprising:
 a compressor configured to compress a heat transfer fluid;   a first heat exchanger in fluid communication with the compressor and configured to receive the heat transfer fluid from the compressor and to cool and condense the heat transfer fluid;   a second heat exchanger in fluid communication with the first heat exchanger and the compressor and configured to exchange heat with a temperature-controlled space;   an accumulator in fluid communication with the second heat exchanger and the compressor and configured to receive a mixture of liquid and vapor heat transfer fluid from the second heat exchanger and direct a vapor portion of the heat transfer fluid to the compressor;   a liquid level sensor associated with the accumulator tank and operable to generate a signal indicative of the level of the liquid heat transfer fluid inside the accumulator;   a valve in fluid communication with the first heat exchanger, the compressor, and the second heat exchanger, the valve operable in a first position and a second position, wherein the first position is operable to direct the heat transfer fluid from the compressor to the first heat exchanger and the second position is operable to direct the heat transfer fluid from the compressor to the second heat exchanger without passing through the first heat exchanger; and   a controller in electrical communication with the liquid level sensor and the valve, the controller operable to receive the signal and move the valve from the first position to the second position based on the signal.   
   
   
       2 . The temperature control system of  claim 1 , wherein the first position corresponds to a cooling mode of the temperature control system and the second position corresponds to a heating mode of the temperature control system. 
   
   
       3 . The temperature control system of  claim 2 , wherein the cooling mode defines a cooling circuit for cooling the temperature-controlled space, wherein the cooling circuit includes the compressor, the first heat exchanger, the second heat exchanger, and the accumulator fluidly connected in series. 
   
   
       4 . The temperature control system of  claim 3 , wherein the heating mode defines a heating circuit for at least one of defrosting the second heat exchanger and heating and the temperature-controlled space, wherein the heating circuit bypasses the first heat exchanger and includes the compressor, the second heat exchanger, and accumulator fluidly connected in series. 
   
   
       5 . The temperature control system of  claim 4 , wherein the liquid level sensor is operable to generate a signal indicative of an optimal level of liquid heat transfer fluid inside the accumulator, and wherein the controller is operable to receive the signal indicative of the optimal level and to move the valve to the second position. 
   
   
       6 . The temperature control system of  claim 5 , wherein the optimum level includes a level of refrigerant that provides heating capacity during the heating mode, and wherein liquid heat transfer fluid at or below the optimum level does not enter the compressor. 
   
   
       7 . The temperature control system of  claim 4 , further comprising a second valve in fluid communication with the first heat exchanger and the accumulator, the valve operable in an open position and a closed position, wherein the open position is operable to direct at least a portion of the condensed heat transfer fluid from the first heat exchanger to the accumulator without passing through the second heat exchanger, and wherein the controller is in electrical communication with the second valve and operable to move the valve between open and closed positions. 
   
   
       8 . The temperature control system of  claim 7 , wherein the open position corresponding to a condenser evacuation mode of the temperature control system. 
   
   
       9 . The temperature control system of  claim 8 , wherein the condenser evacuation mode defines an evacuation circuit configured to allow at least a portion of the condensed heat transfer fluid to enter the accumulator from the first heat exchanger, bypassing the second heat exchanger, wherein the evacuation circuit includes the compressor, the condenser, and the accumulator fluidly connected in series. 
   
   
       10 . The temperature control system of  claim 9 , wherein the temperature control system enters the condenser evacuation mode after the temperature control system exits the cooling mode and before the temperature control system enters the heating mode. 
   
   
       11 . A method of operating a temperature control system, the method comprising:
 compressing a heat transfer fluid with a compressor;   directing the heat transfer fluid from the compressor to a first heat exchanger with a valve in a first position;   cooling and condensing the heat transfer fluid from the compressor in a first heat exchanger;   exchanging heat with a temperature-controlled space with the second heat exchanger;   receiving a mixture of liquid and vapor heat transfer fluid from the second heat exchanger into an accumulator;   directing a vapor portion of the heat transfer fluid in the accumulator to the compressor;   generating with a liquid level sensor associated with the accumulator a signal indicative of the level of the liquid heat transfer fluid inside the accumulator;   receiving the signal with a controller;   moving the valve with the controller from the first position to a second position based on the signal; and   directing the heat transfer fluid from the compressor to the second heat exchanger without passing through the first heat exchanger with the valve in the second position.   
   
   
       12 . The method of  claim 11 , further comprising:
 operating the temperature control system in a cooling mode when the valve is in the first position; and   operating the temperature control system in a heating mode when the valve is in the second position.   
   
   
       13 . The method of  claim 12 , further comprising:
 fluidly connecting in series a cooling circuit including the compressor, the first heat exchanger, the second heat exchanger, and the accumulator when operating in the cooling mode; and   cooling the temperature-controlled space when operating in the cooling mode.   
   
   
       14 . The method of  claim 13 , further comprising:
 fluidly connecting in series a heating circuit including the compressor, the second heat exchanger, and accumulator when operating in the heating mode;   bypassing the first heat exchanger when operating in the heating mode; and   at least one of defrosting the second heat exchanger and heating and the temperature-controlled space when operating in the heating mode.   
   
   
       15 . The method of  claim 14 , further comprising
 generating a signal indicative of an optimal level of liquid heat transfer fluid inside the accumulator,   receiving the signal indicative of the optimal level with the controller;   moving the valve from the first position to the second position with the controller based on the signal indicative of the optimal level.   
   
   
       16 . The method of  claim 15 , further comprising:
 initiating the heating mode;   providing heating capacity in the heating mode when the heating mode is initiated with the optimum level of refrigerant in the accumulator; and   inhibiting liquid heat transfer fluid from entering the compressor in the heating mode when the heating mode is initiated with the optimal level of refrigerant.   
   
   
       17 . The method of  claim 14 , further comprising
 directing at least a portion of the condensed heat transfer fluid from the first heat exchanger to the accumulator without passing through the second heat exchanger with a second valve in an open position.   
   
   
       18 . The method of  claim 17 , further comprising
 operating the temperature control system in a condenser evacuation mode when the second valve is in the open position.   
   
   
       19 . The method of  claim 18 , further comprising
 moving the second valve with the controller from the closed position to the open position;   fluidly connecting in series an evacuation circuit including the compressor, the first heat exchanger, and the accumulator when operating in the condenser evacuation mode;   allowing at least a portion of the condensed heat transfer fluid to enter the accumulator from the first heat exchanger when operating in the condenser evacuation mode; and   bypassing the second heat exchanger when operating in the condenser evacuation mode.   
   
   
       20 . The method of  claim 19 , further comprising
 entering the condenser evacuation mode after the temperature control system exits the cooling mode and before the temperature control system enters the heating mode.