Method of controlling multiple refrigeration devices

Abstract

A refrigeration system for use with a plurality of temperature controlled cases is disclosed. The refrigeration system includes a cooling system having at least one compressor and a condenser for supplying liquid refrigerant to a cooling element associated with each case. Each cooling element receives liquid refrigerant through a liquid refrigerant supply line and returns vapor refrigerant through a suction line. The refrigeration system further includes a control module having a stored reference temperature (T ref) for each case, a temperature sensor disposed in each case for generating a signal representative of the actual temperature within the case (T act), and an expansion device provided at the liquid refrigerant supply line side of each case. The control module compares T ref with T act and moves the expansion devices between an open position and a closed position accordingly to obtain or maintain the desired temperature in each temperature controlled case.

1 . In a refrigeration system having at least one compressor and a condenser for supplying liquid refrigerant to a plurality of cooling elements, the cooling element being associated with different temperature controlled cases for maintaining a desired temperature in each temperature controlled case, each cooling element receiving liquid refrigerant through a liquid refrigerant supply line and returning vapor refrigerant through a suction line, the improvement comprising:
 a control module having a case temperature monitoring function including a case temperature setpoint for each temperature controlled case, and a superheat monitoring function including a superheat temperature setpoint for each temperature controlled case;   a sensor disposed in each temperature controlled case and configured to provide the control module with a signal representative of the actual case temperature within each temperature controlled case;   at least one of a temperature sensor and a pressure sensor proximate an outlet of the cooling elements and configured to provide the control module with a signal representative of an actual superheat temperature of the refrigerant exiting the cooling element; and   an expansion device provided at the supply line of each temperature controlled case,   wherein the control module compares the signals received from the sensors with the temperature setpoints for the respective temperature controlled cases and moves the expansion devices between an open position and a closed position in response to the signals to obtain or maintain a desired case temperature and a desired superheat temperature.   
   
   
       2 . The system of  claim 1  wherein the case temperature monitoring function of the control module is further configured to modulate the position of each expansion device when in the open position so that a flow rate of refrigerant through the cooling device corresponds to the desired case temperature. 
   
   
       3 . The system of  claim 2  wherein the temperature controlled cases comprises a first temperature controlled case and a second temperature controlled case, the first temperature controlled case being configured to operate as a low temperature case and the second temperature controlled case being configured to operate as a medium temperature case. 
   
   
       4 . The system of  claim 3  wherein the first temperature controlled case is configured to be maintained at a temperature within a range of approximately negative 15 degrees F. to approximately 15 degrees F. 
   
   
       5 . The system of  claim 3  wherein the second temperature controlled case is configured to be maintained at a temperature within a range of approximately 20 degrees F. to approximately 40 degrees F. 
   
   
       6 . The system of  claim 2  wherein the superheat monitoring function of the control module is configured to limit an open position of the expansion device to maintain the desired superheat temperature and prevent liquid refrigerant carryover at the outlet of the cooling element. 
   
   
       7 . The system of  claim 6  wherein the sensing arrangement comprises a temperature sensor and a pressure sensor located at the suction line side of the cooling element. 
   
   
       8 . The system of  claim 6  wherein the sensing arrangement comprises a first temperature sensor located proximate an inlet of the cooling element and a second temperature sensor located proximate an outlet side of the cooling element. 
   
   
       9 . The system of  claim 1  wherein the expansion device is a superheat control valve. 
   
   
       10 . A refrigeration device comprising:
 a case having a space configured to receive products to be cooled;   a case temperature sensor located within the space;   at least one cooling element coupled to the case and configured to provide cooling to the space;   a refrigeration system having a supply line and a return line configured to circulate a refrigerant through the cooling element;   a superheat temperature sensor arrangement coupled to at least one of the supply line and the return line;   an expansion device coupled to the supply line; and   a control module operable to maintain a desired temperature within the space by moving the expansion device between an open position and a closed position based on a signal received from the case temperature sensor and by modulating the expansion device when in the open position based on a signal received from the superheat temperature sensor arrangement.   
   
   
       11 . The device of  claim 10  wherein the superheat temperature sensor arrangement is a temperature/pressure sensing arrangement comprising a temperature sensor and a pressure sensor located at the return line. 
   
   
       12 . The device of  claim 10  wherein the sensor arrangement is a temperature/temperature sensing arrangement comprising a second temperature sensor located proximate an inlet of the cooling element and a third temperature sensor located at the return line. 
   
   
       13 . The device of  claim 10  wherein the expansion device is a superheat control valve. 
   
   
       14 . The device of  claim 10  wherein the refrigeration device is coupled to a second refrigeration device and the two refrigeration devices are coupled in parallel and share a common refrigeration system. 
   
   
       15 . The device of  claim 14  wherein the refrigeration device operates as a low temperature refrigeration device and the second refrigeration device operates as a medium temperature refrigeration device. 
   
   
       16 . The device of  claim 15  wherein the refrigeration system provides liquid refrigerant to the supply line based on the cooling requirements of the first refrigeration device rather than the cooling requirements of the second refrigeration device. 
   
   
       17 . A method of controlling temperature within more than one temperature controlled case coupled to a shared refrigeration system and operating at different desired temperatures, the method comprising:
 providing a plurality of cases, each having a space configured to receive products to be cooled;   providing a case temperature sensor located within the space of each case;   providing at least one cooling element coupled to each case and configured to provide cooling to the space of the respective case;   providing a refrigeration system having refrigerant supply line and a refrigerant suction line;   coupling the cooling elements in parallel to the refrigeration system;   providing a superheat temperature sensor arrangement at one of the supply line and the suction line for each case;   providing a superheat valve for each case coupled at the supply line; and   providing a control module operable to maintain the desired temperatures within each space by moving the respective superheat valve between an open position and a closed position based on a signal received from the respective case temperature sensor and by modulating the respective superheat valve when in the open position based on a signal received from the respective superheat temperature sensor arrangement.   
   
   
       18 . The method of  claim 17  further comprising operating at least one of the plurality of cases as a low temperature case and operating at least another one of the plurality of cases as a medium temperature case. 
   
   
       19 . The method of  claim 17  further comprising utilizing the sensor arrangement and the control module to provide a defrost mode. 
   
   
       20 . A refrigeration system, comprising:
 a cooling system having at least one compressor and a condenser for supplying refrigerant to a plurality of parallel branch lines, each branch line having a supply line with a superheat valve and a return line coupled to a separate temperature controlled case, each temperature controlled case having a cooling element through which the refrigerant is configured to flow to provide cooling to a space within the temperature controlled space;   a control module having a case temperature setpoint representative of a desired storage temperature within the space for each temperature controlled case, where the temperature setpoint for at least one of the temperature controlled cases is different from the setpoint for the other temperature controlled cases, and a superheat temperature setpoint representative of a desired refrigerant superheat temperature proximate the outlet of the cooling element;   a case temperature sensor disposed in each temperature controlled case and configured to provide the control module with a signal representative of the actual case temperature within each temperature controlled case;   a superheat temperature sensor arrangement configured to provide a signal representative of an actual superheat temperature of the refrigerant proximate an outlet of the cooling element;   wherein the control module is operable to compare the signal representative of the actual case temperature with the case temperature setpoint for each temperature controlled case, and to compare the signal representative of the actual superheat temperature with the superheat temperature setpoint, and provide an output signal to each superheat valve to obtain or maintain the desired storage temperature in each temperature controlled case and to maintain the desired refrigerant superheat temperature, so that a single cooling system is operable to maintain different storage temperatures in a plurality of temperature controlled cases.   
   
   
       21 . The system of  claim 20  wherein the control module is a centralized control module operable for use with all of the temperature controlled case.