Refrigeration system with variable speed compressor

Abstract

A temperature control system for a controlled environment room comprises a room evaporator, a variable speed compressor, and a condenser. A fluid return loop connects an outlet of the room evaporator refrigerant through the compressor, the condenser and back to an inlet of the room evaporator. A metering valve is interposed in the fluid return loop between the condenser and the room evaporator. Return air from the room is cycled through the room evaporator and back into the room. A room temperature sensor inside the room communicates with a control unit adapted to use input from the room temperature sensor to adjust the compressor speed and control the metering valve to meter mass flow to the room evaporator whereby the metering valve and the compressor cooperate to maintain the mass flow at a level required to maintain a temperature setpoint of the room while limiting compressor frequency.

What is claimed is: 
     
         1 . A temperature control system for refrigeration of a controlled environment room, comprising:
 a room evaporator having a room evaporator refrigerant inlet and a room evaporator refrigerant outlet;   at least one room impeller adapted to cycle return air from the controlled environment room through the room evaporator and back into the controlled environment room;   a control unit;   a variable speed compressor having a compressor refrigerant inlet and a compressor refrigerant outlet;   a room temperature sensor adapted to be positioned inside of the room to detect an internal temperature of the room, wherein the room temperature sensor is in communication with the control unit;   a condenser having a condenser refrigerant inlet and a condenser refrigerant outlet; and   a fluid return loop wherein:
 the room evaporator refrigerant outlet is in valve-controlled one-way fluid communication with the compressor refrigerant inlet; 
 the compressor refrigerant outlet is in one-way fluid communication with the condenser refrigerant inlet; 
 the condenser refrigerant outlet is in valve-controlled one-way fluid communication with the room evaporator refrigerant inlet; and 
 a metering valve is interposed in the fluid return loop between the condenser refrigerant outlet and the room evaporator refrigerant inlet; 
   wherein the control unit is adapted to use input from the room temperature sensor to adjust a speed of the compressor and control the metering valve to meter a mass flow through the metering valve to the room evaporator refrigerant inlet to cause the metering valve and the compressor to cooperate to maintain the mass flow at a level required to maintain a temperature setpoint of the room while limiting compressor frequency.   
     
     
         2 . The temperature control system of  claim 1 , further comprising:
 a valve-controlled hot gas bypass link interposed between the compressor refrigerant outlet and the condenser refrigerant inlet;   the hot gas bypass link having a bypass control valve interposed therein; and   the hot gas bypass link adapted to, under control of the bypass control valve, selectively flow uncooled refrigerant from the compressor refrigerant outlet, upstream of the condenser, to the room evaporator refrigerant inlet, downstream of the metering valve.   
     
     
         3 . The temperature control system of  claim 2 , wherein a muffler is interposed in the hot gas bypass link. 
     
     
         4 . The temperature control system of  claim 1 , further comprising:
 a fresh air evaporator having a fresh air evaporator refrigerant inlet and a fresh air evaporator refrigerant outlet;   wherein fresh air moves through the fresh air evaporator and toward the room evaporator whereby the fresh air moves through the room evaporator and into the controlled environment room;   the condenser refrigerant outlet being in valve-controlled one-way fluid communication with the fresh air evaporator refrigerant inlet, upstream of the metering valve; and   the fresh air evaporator refrigerant outlet being in valve-controlled one-way fluid communication with the compressor refrigerant inlet.   
     
     
         5 . The temperature control system of  claim 4 , wherein:
 a temperature-controlled modulating valve is interposed between the condenser refrigerant outlet and the fresh air evaporator refrigerant inlet; and   the temperature-controlled modulating valve being controlled by an outlet temperature sensor disposed downstream of the fresh air evaporator refrigerant outlet and adapted to detect a temperature of refrigerant exiting the fresh air evaporator refrigerant outlet.   
     
     
         6 . The temperature control system of  claim 1 , further comprising:
 a desuperheating temperature controller;   a desuperheating fluid loop wherein the condenser refrigerant outlet is in one-way valve-governed fluid communication with the compressor refrigerant inlet; and   a compressor inlet temperature sensor disposed on the desuperheating fluid loop upstream of the compressor refrigerant inlet, wherein the compressor inlet temperature sensor is in communication with the desuperheating temperature controller;   wherein a desuperheating control valve is interposed in the desuperheating fluid loop between the condenser refrigerant outlet and the compressor refrigerant inlet;   the desuperheating temperature controller being adapted to control the desuperheating control valve in response to the compressor inlet temperature sensor to mix cooled refrigerant from the condenser refrigerant outlet with uncooled uncompressed refrigerant from the room evaporator refrigerant outlet upstream of the compressor refrigerant inlet to inhibit superheating of the compressor.   
     
     
         7 . The temperature control system of  claim 6 , wherein a capillary is interposed in the desuperheating fluid loop downstream of the desuperheating control valve. 
     
     
         8 . The temperature control system of  claim 1 , further comprising a suction accumulator interposed in the fluid return loop between the room evaporator refrigerant outlet and the compressor refrigerant inlet. 
     
     
         9 . The temperature control system of  claim 1 , further comprising a receiver interposed in the fluid return loop between the condenser refrigerant outlet and the metering valve, wherein the receiver is adapted to provide a reservoir of pressurized liquid refrigerant. 
     
     
         10 . The temperature control system of  claim 9 , further comprising a dryer interposed in the fluid return loop between the receiver and the metering valve. 
     
     
         11 . The temperature control system of  claim 2 , further comprising boil-off condensate piping interposed in the fluid return loop between the compressor refrigerant outlet and the condenser refrigerant inlet, downstream of the hot gas bypass. 
     
     
         12 . The temperature control system of  claim 1 , wherein the temperature control system is mounted atop the controlled environment room in a penthouse arrangement. 
     
     
         13 . The temperature control system of  claim 1 , wherein:
 the at least one room impeller has variable speed; and   the control unit is adapted to use the input from the room temperature sensor to control the speed of the at least one room impeller according to cooling demand.   
     
     
         14 . A temperature control system for refrigeration of a controlled environment room, comprising:
 a room evaporator having a room evaporator refrigerant inlet and a room evaporator refrigerant outlet;   at least one room impeller adapted to cycle return air from the room through the room evaporator and back into the room;   a fresh air evaporator having a fresh air evaporator refrigerant inlet and a fresh air evaporator refrigerant outlet;   wherein fresh air moves through the fresh air evaporator and toward the room evaporator whereby the fresh air moves through the room evaporator and into the controlled environment room;   a control unit;   a variable speed compressor having a compressor refrigerant inlet and a compressor refrigerant outlet;   a room temperature sensor adapted to be positioned inside of the room to detect an internal temperature of the room, wherein the room temperature sensor is in communication with the control unit;   a condenser having a condenser refrigerant inlet and a condenser refrigerant outlet;   a fluid return loop wherein:
 the room evaporator refrigerant outlet is in valve-controlled one-way fluid communication with the compressor refrigerant inlet through a suction accumulator interposed between the room evaporator refrigerant outlet and the compressor refrigerant inlet; 
 the compressor refrigerant outlet is in one-way fluid communication with the condenser refrigerant inlet; 
 the condenser refrigerant outlet is in valve-controlled one-way fluid communication with the room evaporator refrigerant inlet through:
 a metering valve interposed between the condenser refrigerant outlet and the room evaporator refrigerant inlet; 
 a receiver interposed between the condenser refrigerant outlet and the metering valve, wherein the receiver is adapted to provide a reservoir of pressurized liquid refrigerant; and 
 a dryer interposed between the receiver and the metering valve; 
 
 the condenser refrigerant outlet is in valve-controlled one-way fluid communication with the fresh air evaporator refrigerant inlet, upstream of the metering valve and downstream of the dryer; and 
 the fresh air evaporator refrigerant outlet is in valve-controlled one-way fluid communication with the compressor refrigerant inlet through the suction accumulator; 
   a valve-controlled hot gas bypass link interposed between the compressor refrigerant outlet and the condenser refrigerant inlet, wherein:
 the hot gas bypass link has a bypass control valve interposed therein; 
 the hot gas bypass link is adapted to, under control of the bypass control valve, selectively flow uncooled refrigerant from the compressor refrigerant outlet, upstream of the compressor, to the room evaporator refrigerant inlet, downstream of the metering valve; and 
   a desuperheating temperature controller; and   a desuperheating fluid loop wherein:
 the condenser refrigerant outlet is in one-way valve-governed fluid communication, through the receiver and the dryer, with the compressor refrigerant inlet through the suction accumulator; 
 wherein a desuperheating control valve is interposed in the desuperheating fluid loop between the dryer and the compressor refrigerant inlet; 
 a compressor inlet temperature sensor is disposed upstream of the compressor refrigerant inlet and downstream of the suction accumulator, wherein the compressor inlet temperature sensor is in communication with the desuperheating temperature controller; 
   the desuperheating temperature controller being adapted to control the desuperheating control valve in response to the compressor inlet temperature sensor to mix cooled refrigerant from the condenser refrigerant outlet with the uncooled refrigerant from the room evaporator refrigerant outlet, upstream of the suction accumulator, to inhibit superheating of the compressor;   wherein the control unit is adapted to use input from the room temperature sensor to:
 adjust a speed of the compressor and to control the metering valve to meter a mass flow through the metering valve to the room evaporator refrigerant inlet to cause the metering valve and the compressor to cooperate to maintain the mass flow at a level required to maintain a temperature setpoint of the room while limiting compressor frequency; and 
 control the bypass control valve to flow the uncooled refrigerant from the compressor refrigerant outlet to the room evaporator refrigerant inlet downstream of the metering valve. 
   
     
     
         15 . The temperature control system of  claim 14 , wherein a muffler is interposed in the hot gas bypass link. 
     
     
         16 . The temperature control system of  claim 14 , wherein:
 the at least one room impeller has variable speed; and   the control unit is adapted to use the input from the room temperature sensor to control the speed of the at least one room impeller according to cooling demand.   
     
     
         17 . The temperature control system of  claim 14 , wherein:
 a temperature-controlled modulating valve is interposed between the condenser refrigerant outlet and the fresh air evaporator refrigerant inlet; and   the temperature-controlled modulating valve is controlled by an outlet temperature sensor disposed downstream of the fresh air evaporator refrigerant outlet and adapted to detect a temperature of refrigerant exiting the fresh air evaporator refrigerant outlet.   
     
     
         18 . The temperature control system of  claim 14 , wherein a capillary is interposed in the desuperheating fluid loop downstream of the desuperheating control valve and upstream of the suction accumulator. 
     
     
         19 . The temperature control system of  claim 14 , further comprising boil-off condensate piping interposed in the fluid return loop between the compressor refrigerant outlet and the condenser refrigerant inlet, downstream of the hot gas bypass. 
     
     
         20 . The temperature control system of  claim 14 , wherein the system is mounted atop the controlled environment room in a penthouse arrangement.