Apparatus for maximizing air conditioning and/or refrigeration system efficiency

A vapor-compression heat transfer system having fluid refrigerant, a compressor, a condenser, an expansion valve, an evaporator, a refrigerant conduit between the condenser and the expansion valve, and a refrigerant pump in the conduit adapted to increase the pressure of the refrigerant between the condenser and the expansion valve,

• the improvement comprising
• (a) the fact that the said pump is a positive displacement pump, and
• (b) a first bypass conduit is provided in parallel around the pump, said first bypass conduit including a differential pressure regulating valve which imposes an upper limit on the pressure increase caused by the pump, and
• (c) a second bypass conduit is provided in parallel around the pump, said second bypass conduit including a check valve adapted to stop flow of refrigerant through the said second bypass conduit from the expansion valve to the condenser, but to allow flow of refrigerant through the said second bypass conduit from the condenser to the expansion valve, and
• (d) said pump, and bypass conduits being adapted to increase the said pressure of the refrigerant sufficiently to avoid the formation of refrigerant flash gas on the said conduit between the pump and the expansion valve, while still allowing flow of refrigerant from the condenser to the expansion valve if the pump fails to operate,
• wherein a liquid injector conduit is provided between an output side of the pump to an output side of the compressor, and adapted to deliver pressurized liquid refrigerant from the output of the pump to the output of the compressor to de-superheat the refrigerant which exists the compressor, and
• wherein the liquid injector conduit includes a variable-speed injector pump, and a control system is provided and adapted to monitor the difference in temperature of the refrigerant going into the condenser and within the condenser and to adjust the speed of the injector pump to minimize the difference in temperature, which in turn minimizes superheat in the refrigerant going into the condenser and, in turn, maximizes the efficiency of the condenser.

A compression type refrigeration system, comprising:

• an evaporator, a compressor, a condenser, a refrigerant receiver and conduit means interconnecting the same in a single closed loop for circulating refrigerant therethrough, the conduit means including;
• a first conduit for circulating a flow of refrigerant from the receiver to the evaporator and;
• a second conduit for circulating a return flow of refrigerant gas from the evaporator to the receiver solely through the compressor and the condenser for condensation by the condenser at a first pressure directly related to the head pressure at the compressor;
• a variable flow expansion valve in the first conduit adjacent the evaporator for expanding the flow of refrigerant into the evaporator;
• a third conduit which provides a parallel path around a section of said first conduit adjacent an outlet port of the receiver;
• a positive displacement pump in the third conduit adjacent the receiver, the pump being adapted, continuously during operation of the compressor, to increase the pressure of the condensed refrigerant in the first conduit by a generally constant increment of pressure of at least five pounds per square inch to provide the refrigerant with a second pressure greater than the first pressure by the amount of said increment, the second pressure being sufficient to suppress flash gas and feed a completely condensed liquid refrigerant to the expansion valve, the first conduit circulating the refrigerant solely through the pump;
• motor means for the pump;
• and
• a magnetic pump drive connecting the motor means to the pump to drive the pump, and
• the system including a liquid injector conduit between the first conduit after said section, and a point in said second conduit between the compressor and the condenser, said liquid injector conduit including a variable speed pump, the speed of which is controlled by a first temperature sensor adapted to sense the temperature of the refrigerant in the condenser, and a second temperature sensor adapted to sense the temperature of the refrigerant going into the condenser, the speed of the variable speed pump being controlled by said temperature sensors so that just the proper amount of liquid refrigerant is injected into the second conduit at a point after the compressor to desuperheat the compressor discharge refrigerant for optimum heat transfer in the condenser regardless of the refrigerant flow rate through the condenser and regardless of the amount of superheat present in the compressor discharge refrigerant.