Method of reducing liquid flooding in a transport refrigeration unit

Abstract

A method to reduce/prevent liquid refrigerant flooding in the compressor is disclosed herein. The method may include closing down the ETV when there is a risk of compressor flooding. The method may include closing down the ETV to a desired value when there is a risk of the compressor flooding. A failure to provide the superheated refrigerant vapor in a desired superheat temperature by the compressor may indicate a risk of the compressor being flooded by liquid refrigerant. The method may include measuring a refrigerant discharge temperature of the compressor, and closing down the ETV when a difference between the refrigerant discharge temperature of the compressor and a refrigerant saturate temperature is below a desired temperature threshold.

1 . A method to control an electronic throttle valve (ETV) of a transport refrigeration unit comprising:
 determining whether there is a risk of a compressor of the transport refrigeration unit being flooded by liquid refrigerant;   closing down the ETV when there is a risk of the compressor being flooded by liquid refrigerant; and   opening up the ETV where there is no risk of the compressor being flooded by liquid refrigerant,   wherein the ETV is configured to regulate a refrigerant flow into the compressor of the transport refrigeration unit, and   wherein determining whether there is a risk of a compressor of the transport refrigeration unit being flooded by liquid refrigerant includes:
 measuring a refrigerant discharge temperature from the compressor; 
 comparing the refrigerant discharge temperature to a saturated discharge temperature of the refrigerant; 
 when a difference between the refrigerant discharge temperature and the saturated discharge temperature of the refrigerant is below or equal to a threshold value, determining that there is a risk of compressor being flooded; and 
 when the difference between the refrigerant discharge temperature and the saturated discharge temperature of the refrigerant is higher than the threshold value, determining that there is no risk of compressor being flooded. 
   
     
     
         2 . (canceled) 
     
     
         3 . The method of  claim 1 , wherein the saturated discharge temperature of the refrigerant is derived from a refrigerant discharge pressure of the compressor. 
     
     
         4 . The method of  claim 1 , wherein the threshold value is between 10 to 15° R superheat. 
     
     
         5 . A method to control an electronic throttle valve (ETV) of a transport refrigeration unit comprising:
 determining whether there is a risk of a compressor of the transport refrigeration unit being flooded by liquid refrigerant;   closing down the ETV when there is a risk of the compressor being flooded by liquid refrigerant; and   opening up the ETV where there is no risk of the compressor being flooded by liquid refrigerant,   wherein the ETV is configured to regulate a refrigerant flow into the compressor of the transport refrigeration unit, and   wherein determining whether there is a risk of a compressor of the transport refrigeration unit being flooded by liquid refrigerant includes:
 measuring a refrigerant discharge temperature from the compressor; 
 when the temperature of the refrigerant discharge temperature is below or equal to a temperature threshold value, determining that there is a risk of compressor being flooded; and 
 when the temperature of the refrigerant discharge temperature is higher than the temperature threshold value, determining that there is no risk of compressor being flooded. 
   
     
     
         6 . The method of  claim 5 , wherein the temperature threshold value is between 10 to 15° R superheat. 
     
     
         7 . A method to control an electronic throttle valve (ETV) of a transport refrigeration unit comprising:
 determining whether there is a risk of a compressor of the transport refrigeration unit being flooded by liquid refrigerant;   closing down the ETV when there is a risk of the compressor being flooded by liquid refrigerant;   opening up the ETV where there is no risk of the compressor being flooded by liquid refrigerant;   measuring a refrigerant discharge temperature from the compressor;   comparing the refrigerant discharge temperature to a saturated discharge temperature of the refrigerant; and   controlling the electronic throttle so that a difference between the refrigerant discharge temperature from the compressor and the saturated discharge temperature of the refrigerant is at least at a desired threshold value   wherein the ETV is configured to regulate a refrigerant flow into the compressor of the transport refrigeration unit.   
     
     
         8 . The method of  claim 7 , wherein
 controlling the electronic throttle so that a difference between the refrigerant discharge temperature from the compressor and the saturated discharge temperature of the refrigerant is at least at a desired threshold value includes:   when the difference between the refrigerant discharge temperature and the saturated discharge temperature of the refrigerant is lower than the desired threshold value, closing down the ETV; and   when the difference between the refrigerant discharge temperature and the saturated discharge temperature of the refrigerant is higher than the desired threshold value, opening up the ETV.   
     
     
         9 . The method of  claim 1 , wherein the ETV is controlled in a step-wise manner. 
     
     
         10 . The method of  claim 1 , wherein
 determining whether there is a risk of a compressor of the transport refrigeration unit being flooded by liquid refrigerant includes:
 when the transport refrigeration unit is in at least one of a heating/defrosting mode and a transition between a cooling mode and the heating/defrosting mode, determining there is a risk of the compressor of the transport refrigeration unit being flooded. 
   
     
     
         11 - 12 . (canceled) 
     
     
         13 . A method of controlling a transport refrigeration unit, comprising:
 determining whether there is a risk of the compressor being flooded; and   limiting a refrigerant flow into a compressor of the transport refrigeration unit when there is a risk of the compressor being flooded,   wherein determining whether there is a risk of a compressor of the transport refrigeration unit being flooded by liquid refrigerant includes:
 measuring a refrigerant discharge temperature from the compressor; 
 comparing the refrigerant discharge temperature to a saturated discharge temperature of the refrigerant; 
 when a difference between the refrigerant discharge temperature and the saturated discharge temperature of the refrigerant is below or equal to a threshold value, determining that there is a risk of compressor being flooded; and 
 when the difference between the refrigerant discharge temperature and the saturated discharge temperature of the refrigerant is higher than the threshold, determining that there is no risk of compressor being flooded. 
   
     
     
         14 . The method of  claim 13 , wherein limiting a refrigerant flow into a compressor of the transport refrigeration unit includes closing down an electronic throttle valve of the compressor. 
     
     
         15 . (canceled) 
     
     
         16 . The method of  claim 15 , wherein the saturated discharge temperature of the refrigerant is derived from a refrigerant discharge pressure of the compressor. 
     
     
         17 . The method of  claim 15 , wherein the threshold value is between 10 to 15° R superheat. 
     
     
         18 . A method of controlling a transport refrigeration unit, comprising:
 determining whether there is a risk of the compressor being flooded; and   limiting a refrigerant flow into a compressor of the transport refrigeration unit when there is a risk of the compressor being flooded,   wherein determining whether there is a risk of a compressor of the transport refrigeration unit being flooded by liquid refrigerant includes:
 measuring a refrigerant discharge temperature from the compressor; 
 when the temperature of the refrigerant discharge temperature is below or equal to a temperature threshold value, determining that there is a risk of compressor being flooded; and 
 when the temperature of the refrigerant discharge temperature is higher than the temperature threshold value, determining that there is no risk of compressor being flooded. 
   
     
     
         19 . The method of  claim 18 , wherein the temperature threshold value is between 10 to 15° R superheat. 
     
     
         20 . The method of  claim 13 , wherein determining whether there is a risk of the compressor being flooded includes:
 when the transport refrigeration unit is in at least one of a heating/defrosting mode and a transition between a cooling mode and the heating/defrosting mode, determining there is a risk of compressor being flooded.