Estimating refrigeration capacity by measuring air temperature difference and/or airflow

Abstract

A refrigeration system includes a compressor, condenser, separator, and evaporator. A condenser inlet is connected to an outlet of the compressor. A separator inlet is connected to an outlet of the condenser. An evaporator inlet is connected to a first outlet of the separator. An evaporator outlet is connected to the separator inlet. The refrigeration system includes a control unit having instructions stored thereon for executing a method comprising the steps of repetitively calculating a refrigeration load on the evaporator. and controlling a level target of refrigerant in the separator based on the calculation of the refrigeration load. In one configuration, the separator is positioned substantially laterally of the evaporator so that the refrigerant is gravity fed from the separator to the evaporator.

1 . A refrigeration system, comprising:
 a compressor, condenser, separator, and evaporator, wherein;   a condenser inlet is connected to an outlet of the compressor;   a separator inlet is connected to an outlet of the condenser;   an evaporator inlet is connected to a first outlet of the separator;   an evaporator outlet is connected to the separator inlet; and   a control unit having instructions stored thereon for executing a method comprising the following steps:
 repetitively calculating a refrigeration load on the evaporator; and 
 controlling a level target of refrigerant in the separator based on the calculation of the refrigeration load. 
   
     
     
         2 . The refrigeration system of  claim 1 , the control unit further comprising instructions for determining a minimum level target and a maximum level target of refrigerant in the separator; and
 calculating a level target of refrigerant in the separator as a function of the minimum and maximum level targets and refrigeration load.   
     
     
         3 . The refrigeration system of  claim 1 , the control unit further comprising instructions for calculating a level target based on the calculation of the refrigeration load, wherein the level target is calculated to maintain a constant refrigerant charge within the combined volume of the separator and evaporator. 
     
     
         4 . The refrigeration system of  claim 1 , wherein the separator includes at least one analog level meter, and the control unit further comprises instructions for receiving a level measurement from the analog level meter and a step for comparing the measured level to the calculated level target. 
     
     
         5 . The refrigeration system of  claim 1 , wherein the control unit further comprises instructions for opening or closing an expansion valve connected to the inlet of the separator to control the level of refrigerant in the separator at the calculated level target. 
     
     
         6 . The refrigeration system of  claim 1 , the control unit further comprising instructions for overriding controlling the level of refrigerant in the separator based on the refrigeration load when a measured level in the separator is above a predetermined high level limit or below a predetermined low level limit. 
     
     
         7 . The refrigeration system of  claim 1 , further comprising a suction valve between a second outlet of the separator and an inlet of the compressor, and the control unit further comprises instructions for closing the suction valve when a high level of refrigerant or a high rate of level change of refrigerant is detected in the separator. 
     
     
         8 . The refrigeration system of  claim 1 , the control unit further comprising instructions for, for each calculation of refrigeration load, re-calculating a level target for controlling the refrigerant in the separator. 
     
     
         9 . The refrigeration system of  claim 1 , wherein a calculation of refrigeration load is based on one or more measured variables including air temperature before and after the evaporator, air flow over the evaporator, refrigerant gas flowing out of the evaporator, refrigerant pressure in the evaporator, or any combination of variables. 
     
     
         10 . The refrigeration system of  claim 1 , wherein a calculation of refrigeration load is obtained from the compressor. 
     
     
         11 . The refrigeration system of  claim 1 , wherein a calculation of refrigeration load is derived from signals from the compressor, wherein the signals include one or more of refrigerant pressure, refrigerant temperature, compressor rpm, compressor displacement, compressor motor input power, or a combination thereof. 
     
     
         12 . The refrigeration system of  claim 1 , wherein the refrigerant is ammonia, propane, carbon dioxide, a chlorofluorocarbon, a hydrochlorofluorocarbon, or a hydrofluorocarbon. 
     
     
         13 . The refrigeration system of  claim 1 , wherein the separator is positioned substantially laterally of the evaporator. 
     
     
         14 . A method of controlling a separator and evaporator of a refrigeration system, wherein an evaporator inlet is connected to a first outlet of the separator, and an evaporator outlet is connected to a separator inlet, the method comprising:
 repetitively calculating a refrigeration load on the evaporator; and   controlling a level of refrigerant in the separator based on the calculation of the refrigeration load.