Dual temperature refrigeration system

Abstract

A refrigeration system includes one or more compressors, a gas cooler/condenser, a receiver tank, one or more evaporators, an expansion valve, a sensor, and a controller. The controller is coupled to the sensor and the expansion valve. The controller receives sensor feedback from the sensor and performs operations, including determining, as a function of the sensor feedback, that a discharge air temperature of an airflow circulated through the one or more evaporators satisfies a discharge air temperature threshold. The discharge air temperature is cooled by the working fluid in the one or more evaporators. The operations also includes controlling, as a function of determining that the discharge air temperature satisfies the discharge air temperature threshold, the expansion valve to maintain or switch a mode of operation of the one or more evaporators. The modes of operation include a first temperature mode and a second temperature mode.

What is claimed is: 
     
         1 . A refrigeration system, comprising:
 one or more compressors configured to compress a working fluid;   a gas cooler/condenser fluidly coupled to the one or more compressors;   a receiver tank fluidly coupled to the gas cooler/condenser;   one or more evaporators fluidly coupled to the receiver tank and the one or more compressors;   an expansion valve fluidly coupled to and disposed between the receiver tank and the one or more evaporators;   a sensor coupled to the one or more evaporators; and   a controller coupled to the sensor and the expansion valve, the controller configured to receive sensor feedback from the sensor and perform operations, comprising:
 determining, as a function of the sensor feedback, that a discharge air temperature of an airflow circulated through the one or more evaporators satisfies a discharge air temperature threshold, the discharge air temperature cooled by the working fluid in the one or more evaporators; and 
 controlling, as a function of determining that the discharge air temperature satisfies the discharge air temperature threshold, the expansion valve to maintain or switch a mode of operation of the one or more evaporators, the modes of operation comprising a first temperature mode and a second temperature mode. 
   
     
     
         2 . The refrigeration system of  claim 1 , wherein the controlling comprises controlling the expansion valve based only on the discharge air temperature while maintaining a superheat temperature of the working fluid within a superheat range. 
     
     
         3 . The refrigeration system of  claim 1 , wherein the one or more evaporators are one or more dual temperature evaporators and the first temperature mode is medium temperature mode and the second temperature is low temperature mode. 
     
     
         4 . The refrigeration system of  claim 1 , wherein the refrigeration system is void of pressure-regulating valves at an outlet of the one or more evaporators. 
     
     
         5 . The refrigeration system of  claim 1 , wherein the expansion valve comprises an electronic expansion valve (EEV) and controlling the expansion valve comprises controlling the expansion valve as a stepper valve or using pulse width modulation. 
     
     
         6 . The refrigeration system of  claim 5 , wherein the controller is configured to control the EEV to maintain, in the first temperature mode, a discharge air setpoint of between 30 and 38 degrees Fahrenheit while maintaining a superheat of the working fluid within a superheat range. 
     
     
         7 . The refrigeration system of  claim 6 , wherein the superheat range is between 2 and 9 degrees Fahrenheit. 
     
     
         8 . The refrigeration system of  claim 5 , wherein the controller is configured to control the EEV to maintain, in the second temperature mode, a discharge air setpoint of between −20 and 32 degrees Fahrenheit. 
     
     
         9 . The refrigeration system of  claim 1 , wherein the one or more evaporators comprise one or more display cases, each of the one or more display cases comprising a single dual temperature evaporator coil configured to operate in low temperature mode and medium temperature mode. 
     
     
         10 . The refrigeration system of  claim 1 , wherein the controller is configured to maintain, in a medium temperature defrost mode of the one or more evaporators and as a function of determining that the discharge air temperature satisfies a second discharge air temperature threshold, the expansion valve closed to passively de-ice the one or more evaporators. 
     
     
         11 . The refrigeration system of  claim 1 , wherein a suction line coupled to an outlet of the one or more evaporators is arranged to operate with the working fluid at temperatures of between −20 and 45 degrees Fahrenheit. 
     
     
         12 . The refrigeration system of  claim 1 , wherein the one or more compressors comprise at least one low-temperature compressor and at least one medium temperature compressor. 
     
     
         13 . A refrigeration system controller, comprising:
 one or more hardware processors; and   a computer storage medium communicatively coupled to the one or more hardware processors, the computer storage medium comprising instructions that, when executed by the one or more hardware processors, cause the one or more hardware processors to perform operations comprising:
 receiving sensor feedback that comprises a discharge air temperature of an airflow circulated within an evaporator case, through one or more evaporators, and cooled by working fluid in the one or more evaporators; 
 determining that the discharge air temperature satisfies a discharge air temperature threshold; and 
 changing, as a function of the determination, an operation parameter of one or more expansion valves to regulate an amount of the working fluid circulated into the one or more evaporators to change the one or more evaporators between a first temperature mode and a second temperature mode. 
   
     
     
         14 . The refrigeration system controller of  claim 13 , wherein the first temperature mode comprises medium temperature mode in which items stored within the evaporator case are at a temperature of between 30 and 40 degrees Fahrenheit, and the second temperature mode comprises low temperature mode in which the items stored within the evaporator case are at a temperature of between −20 and 32 degrees Fahrenheit. 
     
     
         15 . The refrigeration system controller of  claim 13 , wherein the changing comprises opening or closing the expansion valve based on the discharge air temperature using pulse width modulation, and while maintaining superheat of the working fluid within a superheat range to prevent the working fluid to exit the one or more evaporators in liquid form. 
     
     
         16 . The refrigeration system controller of  claim 13 , wherein the one or more evaporators comprises one or more dual temperature evaporators, the refrigeration system controller is part of a refrigeration system comprising one or more sensors, one or more compressors, and a gas cooler/condenser, and the receiving comprises receiving the sensor feedback from the one or more sensors. 
     
     
         17 . The refrigeration system controller of  claim 16 , wherein the refrigeration system is void of pressure-regulating valves between the one or more evaporators and the one or more compressors. 
     
     
         18 . The refrigeration system controller of  claim 16 , wherein the expansion valve comprises an electronic expansion valve (EEV) and controlling the expansion valve comprises controlling the expansion valve using pulse width modulation to maintain, in the first temperature mode, a discharge air setpoint of between 30 and 38 degrees Fahrenheit while maintaining a superheat of the working fluid within a superheat range. 
     
     
         19 . The refrigeration system controller of  claim 18 , wherein the superheat range is between 3 and 6 degrees Fahrenheit. 
     
     
         20 . A method, comprising:
 receiving, from one or more sensors of a refrigeration system and by a controller, sensor feedback, the refrigeration system comprising one or more evaporators, a working fluid configured to flow through the one or more evaporators, and one or more expansion valves each residing upstream of each of the one or more evaporators, the sensor feedback comprising a discharge air temperature of an airflow circulated through the one or more evaporators and cooled by the working fluid in the one or more evaporators;   determining, by the controller, that the discharge air temperature satisfies a discharge air temperature threshold; and   controlling, as a function of the determination and by the controller, an operation parameter of the one or more expansion valves, regulating an amount of the working fluid flowed into the one or more evaporators to change the one or more evaporators between a first temperature mode and a second temperature mode.