Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
2000-01-28
2001-06-12
Tapolcal, William E. (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C062S468000
Reexamination Certificate
active
06244059
ABSTRACT:
BACKGROUND
1. Field of the Invention
This invention relates to refrigeration systems through which a volatile refrigerant is circulated along with oil and to eductor means for causing oil to return to its compressor source without the need for providing gas-flow risers having a high internal gas velocity with its accompanying high pressure drop.
2. Discussion of Prior Art
It is common for refrigerating systems employing one or more compressors for circulating a volatile refrigerant to experience oil transfer from the compressor to the flow stream of volatile refrigerant pumped by the compressor. In larger systems it is common to design vapor flow piping with internal vapor velocities high enough to ensure entrainment of such oil so that it can be reliably carried back to its source, the compressor. It is admitted that the smaller pipes needed to generate the higher vapor velocities have a reduced first cost. However, the higher internal vapor velocities required for this purpose generate vapor pressure drops which degrade system performance and efficiency, thereby imposing higher operating costs for the life of the equipment. The performance degradation is most pronounced where the oil flow is desired to occur in ‘suction lines’, those pipes carrying refrigerant vapor from a cooling coil or evaporator to a compressor. The portion of systems in which suction lines or pipes or conduits reside are frequently called “low-sides”, referring to the lower pressure existing in those pipes or conduits. Since any particular low-side may not be the region of lowest pressure within a given system, the term “lower pressure side” will be used interchangeably with the term lowside.
Compressors ordinarily are constructed with oil sumps or reservoirs. These are substantially always at the pressure of the suction line or conduit from which they pump. Therefore, such reservoirs or sumps are part of the low-side or lower pressure side as well as suctions lines and suction conduits.
While the use of eductors and venturis is well known for pumping waste water and slurries from one point to another, their application for oil return instead of through vertical risers in refrigeration systems is not known heretofore.
The term eductor as used herein applies to venturi-type devices having no moving parts. Eductors employ a higher pressure fluid to create an area of lower pressure into which a desired fluid at one location is attracted and conveyed to a second location.
Eductors are also known as venturis, jet-pumps, ejectors, syphons, injectors and aspirators.
They are manufactured by several companies one of which is the Fox Valve Development Corp. located at Hamilton Business Park, Unit 6A, Franklin Road, Dover N.J. 07801.
SUMMARY OF THE INVENTION
In a refrigeration system having at least one evaporator and at least one compressor having a suction side for receiving refrigerant vapor at a lower pressure and a discharge side for discharging refrigerant vapor at a higher pressure; first suction flow means positioned at a lower level for receiving refrigerant vapor and oil from an evaporator and second suction flow means positioned at a higher level for receiving refrigerant vapor from said first refrigerant flow means. The first suction flow means has oil collected therein. Means for transferring the oil collected in the first suction flow means to the second suction flow means. The transferring means comprises: venturi means having a high pressure inlet for receiving higher pressure refrigerant vapor, the venturi means further having a suction inlet including conduit means connected thereto for receiving oil from the first suction flow means; and flow means for conveying oil and higher pressure refrigerant to said second suction flow means.
OBJECTS AND ADVANTAGES
The following objects and advantages pertain to the use of the invention within a compression type refrigerating system or the like:
It is an object of the invention to provide non-mechanical means for moving oil from one location to another location within the suction side of the system.
It is a further object to provide such oil movement with suction mains and risers sized for minimum pressure drop and minimum vapor velocity.
It is a further object to provide such movement by the use of a venturi device.
It is a further object to use vapor from the discharge side of a compressor to activate the venturi.
It is a further object to control the pressure differential between the high pressure venturi inlet and the suction side of the system.
It is a further object to minimize flow of discharge vapor for the purpose by limiting the periods during which the flow occurs.
It is a further object to minimize discharge vapor flow to the lowside by limiting the pressure differential across the venturi.
It is a further object to provide a timer to allow and prevent discharge vapor flow to the venturi according to a predetermined cycle.
It is a further object to limit the periods of discharge vapor flow by sensing the presence and absence of oil and by allowing discharge vapor flow in the presence of oil and stop said flow in the absence of oil.
It is a further object to employ an oil level detector for detecting the presence and absence of oil.
It is a further object to employ a float type level detector for the purpose.
It is a further object to employ a non-float detector for the purpose.
In multistage refrigeration systems it is an object to employ inter-stage pressure to actuate the venturi.
In systems employing screw-type compressors, it is an object to employ pressure from the compressor, selected at a position between the suction inlet and discharge outlet, to actuate the venturi.
It is a further object to provide satisfactory oil return in systems employing higher viscosity oil.
It is a further object to provide satisfactory oil return in system where the lubricant and the refrigerant are not highly soluble in each other.
Further objects and advantages will become apparent as the invention is explained and disclosed in more detail in subsequent sections of this specification.
REFERENCES:
patent: 4404812 (1983-09-01), Zinsmeyer
patent: 5894740 (1999-04-01), Renz
Ali Mohammad M
Kramer Daniel
Tapolcal William E.
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