Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
1999-12-27
2001-07-03
Tanner, Harry B. (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C062S506000, C062S219000, C062S206000
Reexamination Certificate
active
06253562
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to vapor compression refrigeration systems and, more particularly, to a subcooler within such systems for subcooling refrigerant.
Subcoolers have heretofore been used in vapor compression refrigeration systems to subcool refrigerant flowing from the condenser to the evaporator. Hot liquid refrigerant from the condenser typically passes through one or more orifices or nozzles located in the subcooler. These orifices or nozzles define a pressure drop between the condenser and the chamber of the subcooler. This pressure drop causes a portion of the liquid refrigerant to flash to vapor as it leaves the orifices or nozzles. The vapor refrigerant absorbs heat from the remaining liquid refrigerant passing into the chamber of the subcooler. The subcooler chamber may also include a condensing coil which circulates fluid having a temperature that recondenses the flashed vapor refrigerant. The recondensed refrigerant and the subcooled refrigerant exit the subcooler chamber for circulation through the evaporator. The above vapor compressor system is disclosed in U.S. Pat. No. 4,207,749 issuing to William J. Lavigne, Jr., on Jun. 17, 1980.
The orifices or nozzles of the aforementioned system are sized for a specific refrigerant flow that will create a particular pressure drop from the condenser into the subcooler chamber. The refrigerant flow is usually assumed to be the flow occurring at a full load condition for the vapor compression refrigeration system. This full load condition also assumes a particular entering condenser water temperature for the water circulating through the coil within the subcooler. The refrigerant flow to the orifices or nozzles will however drop as the full load condition on the refrigeration system drops. This drop in refrigerant flow will reduce the ability of the orifice or nozzle to produce the pressure drop needed to flash the refrigerant vapor in the subcooler chamber. This reduces the amount of cooling of refrigerant that may be provided by the subcooler. This in turn affects the overall efficiency and operating range of the refrigeration system.
It is an object of this invention to provide the necessary pressure drop through an orifice or nozzle within a subcooler so as to introduce sufficient flashed refrigerant vapor into a subcooler under a variety of operating conditions.
SUMMARY OF THE INVENTION
The above and other objects of the invention are achieved by an electronically controlled flash subcooler system that automatically adjusts to varying amounts of refrigerant flow from the condenser. The flash subcooler system preferably includes a metering device in the form of a valve upstream of the orifices or nozzles. The variable metering device is adjusted by a microprocessor control, which receives temperature of water entering the condenser coil within the flash subcooler chamber as well as pressure from a pressure sensor within the flash subcooler. The temperature of the water entering the condenser coil is used to determine a desired pressure setpoint within the flash subcooler chamber. The sensed pressure from the pressure sensor within the subcooler is fed back to the microprocessor controller in order to determine if the pressure in the flash subcooler chamber is within a predefined range of the desired pressure setpoint. Any difference in the sensed pressure value with respect to the predefined range of pressure from the desired pressure setpoint is used by the controller to determine the magnitude and direction of change to the valve opening in the metering device.
REFERENCES:
patent: 4171623 (1979-10-01), Lavigne, Jr. et al.
patent: 4437322 (1984-03-01), Ertinger
patent: 5570583 (1996-11-01), Boehde et al.
patent: 5613368 (1997-03-01), Marohl et al.
Carrier Corporation
Tanner Harry B.
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