Refrigeration – Refrigeration producer – Compressor-condenser-evaporator circuit
Reexamination Certificate
1999-05-19
2001-03-20
McDermott, Corrine (Department: 3744)
Refrigeration
Refrigeration producer
Compressor-condenser-evaporator circuit
C062S471000
Reexamination Certificate
active
06202437
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, refrigerant is normally present in the oil. 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. The accumulator is normally limited in size for reasons of cost, available space, or as a matter of design choice. These limitations allow only a certain maximum oil/refrigerant ratio where the amount of oil is determined by the size of compressor oil sump and the amount of refrigerant is set by the charge amount which optimizes system performance. 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, the liquid which has entered and collected in the suction accumulator 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. Normally, the liquid collecting in the accumulator in an inactive air conditioner will, primarily, be refrigerant and components relying on the normal oil content for lubrication may, instead, have lubricant washed away by refrigerant upon start up. Other than the initial liquid in the suction accumulator, gaseous and/or liquid 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 provides an accumulator with an increased volume and a pre-charge of oil which is retained in the accumulator as an oil/refrigerant mixture due to the affinity between refrigerants and lubricants. Since there is a residual charge of oil in the accumulator, when liquid refrigerant enters the accumulator, it mixes first with the oil in the accumulator, improving the quality of the oil/refrigerant mixture, before entering the compression chamber of the compressor. The oil viscosity, a determinant for lubrication, is determined by the proportion of refrigerant dissolved in the oil/refrigerant mixture and the pressure the mixture is exposed to. Thus, in order to maintain the minimum viscosity required for certain bearing designs derived from the minimum film thickness requirement, the oil/refrigerant ratio needs to be kept at a reasonably high level. To facilitate oil separation and its returning to the accumulator, the inlet to the suction feed pipe is preferably located at a point above the baffle screen/ports in the baffle through the use of a baffle 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.
Because it is necessary for the accumulator to store liquid refrigerant in the volume above the metering hole both when the system is active and when it is inactive, the volume of oil added according to the teachings of the present invention cannot reduce the available storage volume above the metering hole for liquid refrigerant. The present invention permits a greater residual liquid storage by extending the accumulator below the metering hole in the suction feed pipe and by providing a side discharge into the suction of the compressor such that the accumulator extends below the suction inlet of the compressor. By initially storing oil in the accumulator in the increased volume below the metering hole, there is a residual oil sump such that it is possible to dilute pure liquid refrigerant with oil before the mixture is drawn into the compressor though the metering port in the suction feed pipe or standpipe.
It is an object of this invention to improve the oil/refrigerant ratio in a an air conditioning or refrigeration system.
It is a further object of this invention to provide a circuitous gas flow path in an accumulator.
It is an additional object of this invention to provide a suction accumulator providing additional storage for oil. These objects, and others as will become apparent hereinafter, are accomplished by the present invention.
Basically, the volume of the suction accumulator is increased by providing a side discharge into the suction of a compressor and extending the accumulator below the suction inlet of the compressor so as to provide an increased volume. The suction accumulator is pre-charged with oil that is contained ordinarily in the accumulator body. This pre-charged oil amount is in addition to the amount of oil normally charged into the compressor oil sump, and makes the total amount of oil charge greater. This increased oil helps improve compressor lubrication under boundary lubrication conditions caused by liquid refrigerant. Without increasing the amount of oil in the oil sump of the compressor, the quality of the oil is improved with an accumulator with pre-charged oil. That is, additional oil is charged into the accumulator, and the oil return orifice is so located in elevation that a specified volume is contained below the orifice. In reality though, the volume does not necessarily contain pure oil because oil normally contains a certain amount of refrigerant.
REFERENCES:
patent: 1978463 (1934-10-01), Kettering
patent: 4429544 (1984-02-01), McCarty
patent: 5347817 (1994-09-01), Kim
patent: 5507159 (1996-04-01), Cooksey
patent: 5850743 (1998-12-01), Dreiman et al.
patent: 5868001 (1999-02-01), Shoulders
Carrier Corporation
McDermott Corrine
Norman Marc
LandOfFree
Suction accumulator pre-charged with oil does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Suction accumulator pre-charged with oil, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Suction accumulator pre-charged with oil will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2497210