Refrigeration – Refrigeration producer – Compressor-condenser-evaporator circuit
Reexamination Certificate
1999-03-29
2001-01-30
Doerrler, William (Department: 3744)
Refrigeration
Refrigeration producer
Compressor-condenser-evaporator circuit
C062S471000
Reexamination Certificate
active
06178771
ABSTRACT:
BACKGROUND OF THE INVENTION
In an inactive air conditioning or refrigeration system, refrigerant tends to condense and collect at low and/or cool locations in the system. Because of the affinity between refrigerants and the lubricants used therewith, oil is normally present in the refrigerant. If liquid refrigerant and/or oil is drawn into the compressor, a condition known as slugging occurs. Because liquids are essentially incompressible, the increased volume required to be discharged due to the incompressibility can cause damage to the compressor. This damage is due to the pressure build up caused by the higher than design volumetric flow due to the incompressibility of the liquid refrigerant and/or oil.
To avoid liquid slugging, a suction accumulator is commonly located immediately upstream of the suction of the compressor of an air conditioning or refrigeration system. An accumulator serves two major purposes in that it acts as a sump for storing liquid refrigerant and any associated oil as well as serving to meter the feeding of the liquid refrigerant/oil back to the compressor. The suction feed pipe extends into the accumulator to a height above the design level of liquid refrigerant/oil and has a metered opening in fluid communication with the interior of the accumulator in a lower portion of the accumulator corresponding to a minimum residual liquid refrigerant/oil level.
When the compressor is started after a sufficient time for liquid refrigerant and associated oil to collect in the accumulator, the liquid which has entered and collected in the suction feed pipe will tend to be drawn into the compressor with the liquid refrigerant tending to evaporate due to the reduced pressure associated with the suction stroke of the compressor. Other than the initial liquid in the suction feed pipe, gaseous refrigerant will be drawn from the evaporator into the accumulator and via the suction feed pipe into the compressor with the flow entering the suction feed pipe at a location in the upper portion of the accumulator. Additionally, any liquid in the accumulator at a level such as to be in fluid communication with the metered opening will be drawn into the suction flow on a metered basis with the liquid refrigerant tending to be evaporated in being aspirated into the suction flow. The metered flow into the suction feed pipe will continue until the liquid level is brought down to the level of the metered opening.
SUMMARY OF THE INVENTION
The present invention locates the inlet to the suction feed pipe at a higher location in the accumulator thereby permitting the storage of a larger volume of liquid in the accumulator without changing the dimensions of the accumulator. Specifically, for a given size/height of an accumulator, the factors limiting the storage volume are the location of the baffle and standpipe tip or inlet. Conventionally, the baffle is located where the straight body portion of the accumulator casing ends and the tip of the standpipe is located at a lower point than the baffle. The relocation of the inlet to the suction feed pipe to a point above the baffle screen/ports in the baffle is achieved through the use of a baffle which accommodates the increased height of the suction feed pipe and which coacts therewith to require two 180° turns in the flow entering the accumulator before it reaches the inlet of the suction feed pipe thereby tending to separate out any entrained liquid due to centrifugal action. As a result of the use of the present invention, more liquid can be stored for a given size of accumulator body as compared to a conventional accumulator which can only use 40-60% of its volume for liquid storage. Alternatively, a smaller accumulator can be used to store the same amount of liquid as compared to a conventional accumulator. Additionally, the more circuitous flow path has the unexpected benefit of quieter operation.
As noted, the present invention permits a greater liquid volume storage but, if desired, the original storage capacity can be maintained while reducing the size of the accumulator. Because the accumulator can be directly connected to and supported by the compressor, the full height of the compressor may be available for the accumulator. This extra height provides a unique opportunity in that it permits extending the accumulator to a lower level which is beneath the suction inlet of the compressor. Because the accumulator is located below the suction inlet, this lower portion may be initially charged with oil to avoid the alternative of providing excess oil within the compressor. Since oil is carried through the refrigeration system with the refrigerant, a portion of the oil disappears with respect to the compressor due to its coating and collecting in various parts of the system. Accordingly, this design permits providing the required excess oil without interfering with compressor operation since the excess oil is metered from the accumulator into the circulating refrigerant when the system is initially run.
It is an object of this invention to increase the liquid refrigerant storage capacity of an accumulator.
It is another object of this invention to provide a quieter accumulator.
It is a further object of this invention to provide a circuitous gas flow path in an accumulator. These objects, and others as will become apparent hereinafter, are accomplished by the present invention.
Basically, the suction feed pipe of an accumulator extends above the flow path through a baffle dividing the accumulator thereby permitting the storage of a larger amount of liquid in the accumulator. Where the accumulator has a portion located below the fluid connection going into the compressor, this portion can be used to store a charge of make-up oil to replace the oil distributed in the system during operation without initially overcharging the compressor or compromising the compressor oil charge.
REFERENCES:
patent: 4111005 (1978-09-01), Livesay
patent: 4194371 (1980-03-01), Morse
patent: 5347829 (1994-09-01), Newman
patent: 5377501 (1995-01-01), Muston
patent: 5507159 (1996-04-01), Cooksey
patent: 5660058 (1997-08-01), Harris et al.
patent: 5868001 (1999-02-01), Shoulders
Carrier Corporation
Doerrler William
Jiang Chen-Wen
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