Apparatus for maximizing air conditioning and/or refrigeration system efficiency

• US 5,435,148 A
• Filed: 09/28/1993
• Issued: 07/25/1995
• Est. Priority Date: 09/28/1993
• Status: Expired due to Fees

• Current Assignee: JDM Limited
• Original Assignee: JDM Limited
• Inventors: Ward, David F., Sandofsky, Marc D.
• Primary Examiner(s): Wayner, William E.
• Application Number:
  US08/127,976
• Time in Patent Office: 665 Days
• Field of Search: 62/DIG. 2, 62/513, 62/DIG. 17, 62/527, 62/197, 62/498
• US Class Current: 62/197
• CPC Class Codes: F04C 14/08 characterised by varying the rotational speed
• CPC Class Codes: F04C 15/0069 Magnetic couplings
• CPC Class Codes: F25B 2339/041 of evaporative condensers
• CPC Class Codes: F25B 2400/22 Refrigeration systems for supermarkets
• CPC Class Codes: F25B 40/00 Subcoolers, desuperheaters or superheaters
• CPC Class Codes: F25B 41/00 Fluid-circulation arrangements
• CPC Class Codes: F25B 49/027 Condenser control arrangements
• CPC Class Codes: Y10S 62/02 Refrigerant pumps
• CPC Class Codes: Y10S 62/17 Condenser pressure control

Abstract

A compression-type refrigeration system is disclosed, in which "flash gas" formation is eliminated without artificially maintaining condenser temperature and pressure levels. Condenser temperatures and pressures are allowed to fluctuate with ambient operating conditions, resulting in reduced compressor load and increased refrigeration capacity. After condensation, liquified refrigerant in the conduit between the receiver and the expansion valve is pressurized without adding heat, by means of a combination of (a) a positive-displacement pump, in parallel with the conduit, (b) a bypass conduit pressure regulating controller, and (c) a check valve in the conduit, to a pressure sufficient to suppress flash gas in the conduit. A variable speed liquid injection pump is provided to inject liquid refrigerant from downstream of the positive-displacement pump to upstream of the condenser, at a controlled rate sufficient to desuperheat the refrigerant upstream of the condenser.

Claims

1. Any refrigeration, air conditioning or process cooling system using a reciprocating screw, scroll, centrifugal or other similar type of compressor and any type of refrigerant,

the improvement including

a first positive-displacement pump used in a parallel piping arrangement which arrangement is parallel to a conventional conduit between a condenser and an expansion valve, and parallel with a differential pressure regulating valve and a check valve, and

wherein the system includes

a second pump in a liquid injection line between the output of the first pump and the output of a compressor, used for desuperheating the compressor discharge vapor, and

a control mechanism that controls the speed of the second pump and thereby results in the desuperheating of the compressor discharge vapor to a saturated or near saturated condition at the inlet to the condenser, said control mechanism including a temperature sensor adapted to sense the temperature of the refrigerant at the condenser.

2. A system as recited in claim 1, wherein the system includes

a control system which sets the minimum condensing temperature setting of refrigerant exiting the condenser to a lower-than-conventional value when the first pump is functioning properly and reverts the air conditioning or refrigeration system back to the higher minimum condensing temperature setting in case of failure of the first pump.

3. 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.

4. 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.