US3494146A

US3494146A - Refrigerating system with refrigerant-oil separator

Info

Publication number: US3494146A
Application number: US724365A
Authority: US
Inventors: Knud V Valbjorn
Original assignee: Danfoss AS
Current assignee: Danfoss AS
Priority date: 1967-04-28
Filing date: 1968-04-26
Publication date: 1970-02-10
Anticipated expiration: 1987-02-10
Also published as: DE1551295A1; FR1560970A; ES353144A1; DE1551295B2; BR6898610D0; DE1551295C3; GB1205696A

Description

United States Patent Int. Cl. F2sb 43/02 US. Cl. 62473 2 Claims ABSTRACT OF THE DISCLOSURE A method of gravity separation of a refrigerant and the lubricating oil of a refrigerating compressor and return of the oil as a cooling medium for the compressor. A refrigerating system, in which an oil-refrigerant gravity separator is disposed downstream of the condenser and upstream of the expansion valve and the evaporator of the system. The separator has two communicating compartments, of substantially alike construction and volume, into a first of which extends a conduit having a perforated end length that discharges the liquified refrigerant principally out the end and the lighter lubricating oil is discharged above the level of the refrigerant. The refrigerant is discharged to the evaporator from the other at a level above the refrigerant in the first compartment and the oil separated is discharged from the first compartment at a level above the refrigerant and is returned in a cooled condition to the compressor and further cooled by an expansion or throttle valve in the oil return line to the compressor.

This invention relates generally to refrigerating systems and more particularly to method and apparatus for sepa ration of lubricating oil from a refrigerant in a refrigerating system.

It is impossible to avoid transfer of lubricating oil for a refrigerant compressor from being transported or carried by the refrigerant through a refrigerating circuit or system. In large refrigerating systems or plants it is possible to keep that portion of the oil carried from the compressor by the refrigerant small i.e. to a limit in the order of 2% to 4% by weight of the refrigerant. In large sytems it has been the practice to have an oil separator between the compressor and the condenser in which a major portion of the oil entrained by the refrigerant is removed from the refrigeration cycle or circuit. Separation is relatively simple in these systems since the refrigerant is still in a gaseous state whle the lubricating oil is liquid. Moreover, because refrigerant dissolved in oil can be driven off by heating, the various separation apparatus remain relatively simple.

In contrast to the larger operating units an oil separator is not used in smaller refrigerating systems in which piston compressors are used. The entrained oil is about 0.11% by weight of the refrigerant. Care has to be taken particularly, in the case of low temperatures, that the refrigerant and oil readily mix with each other so that the oil does not build up at the throttle or expansion point in the evaporator and thereby interfere with operation of the system.

Refrigerating machines having encapsulated or screw compressors are well sealed and circulate larger quantities of oil. The oil is, however, contained in a capsule or casing in which the compressor is disposed. The oil in the casing is fed under pressure so that the casing itself serves as a refrigerant-oil separator.

Another problem encountered in the operation of refrigerant compressors is that they have to be cooled. For example, the capsules or casings of hermetically encapsu- 3,494,146 Patented Feb. 10, 1970 lated small refrigerating compressors are cooled by convection currents as well as by forced-draught means employing a driven blower. This requires that sufiicient space be provided around the capsule or casing or the compressor to enable the cooling air to be supplied and be effective. The space required for such air-cooled compressors is, therefore, relatively large and this results in a reduction of the useful space. Moreover, there is a further disadvantage in such constructions in that undesired noise is radiated from the compressor and its capsule to the surrounding space for the cooling air and in this way the noise is transmitted to a great and undesired extent.

It is a principal object of the present invention to provide a refrigerating system in which heat removal from thecompressor is effected without the use of air-cooling.

Another object of the present invention is to provide method and apparatus for cooling a refrigerating system with the lubricating oil of the compressor.

Still another object of the present invention is to provide a new and improved, simple gravity refrigerant-oil separator.

The refrigeration system according to the present invention comprises a compressor, which may be for example hermetically enclosed in a capsule, for compressing the gaseous refrigerant and delivering it to a condenser and then in a liquid state to an expansion valve and evaporator system and returning gaseous refrigerant to the compressor. A refrigerant-oil separator is disposed downstream of the condenser and upstream of the expansion valve for separating the lubricating oil and refrigerant and transmitting, in a cooled condition, the separated oil directly to the compressor.

In the method and system according to the invention the oil is not separated from the refrigerant before reaching the condenser but together with the refrigerant is cooled in the condenser where the refrigerant is liquified. If, for example, the refrigerant-oil mixture discharged from the compressor has a temperature of C. and leaves the condenser at 50 C. then a temperature difference of 70 C. is available. Thus it is possible without difiiculty to arrange that a sufficient quantity of oil, necessary for removal of heat from the compressor, passes through the condenser where it is cooled and returned to the condenser as a lubricant and coolant before it enters the remainder of the refrigerant circuit. The removal of heat from the compressor is, therefore, very effective since the oil absorbing heat from the compressor is greatly cooled outside the compressor in a system specifically designed for cooling purposes, namely the condenser, and the cooled oil is returned to the condenser.

In carrying out the invention the oil preferably employed is one that does not readily mix with the refrigerant. The refrigerant-oil separator effects a gravity separation operation. Thus the system in accordance with the invention contrasts with systems where oil separation is intended to take place before the condenser is reached in which oil is separated from a gaseous refrigerant. Moreover, in the method and apparatus according to the invention is different from those systems in which oil circulates through the entire refrigerant circuit and wherein it is important that the two components of the mixture should be readily soluble.

It has been found that an advantageous combination of refrigerant and oil in accordance with the invention can be effected by using monochlorofluoroethane as the refrigerant together with a highly refined parafiin-based refrigerating machine oil, e.g. Shell Clavus 27.

Experience has shown that the quantity of oil carried through the condenser in order to properly cool it should be more than 10% by weight and preferably 20% to 30% by weight of the refrigerant passing through the Feb. 10, 1970 K. V; VALBJQRN 3,494,146

I REFRIGERATING SYSTEM WITHREFRIGERANT-OIL SEPARATOR Filed April 26. 1968 ,15 EVAPORATOR- 22 -C ONDENSER ,2? L "W 6- I I 50C 1/ V2 o,s% Q

designated as such in the diagram having 12.5% K and 87.5% 0. Thus almost a pure refrigerant passes through the evaporator 20. The extremely small proportion of oil entrained or dissolved in the refrigerant passing through the evaporator and expansion valve cannot cause any damage.

The mixture returned by the oil return line 23 to the sump 13 is principally oil. Any refrigerant contained therein is expanded at the throttle or expansion valve 22 so that an additional cooling effect is available for cooling the coolant lubricating oil.

As illustrated in FIG. 3 a refrigerating unit 27 defines a space 28 enclosed by insulation 29 useful for a refrigerating system. Within the insulation is embedded a capsule or housing 30 within which is housed a hermetically sealed compressor, not shown, delivering refrigerant to a system, not shown, of the type heretofore described. The completely embedded and enclosed cupsule 30 eliminates any transfer of compressor noise externally of the refrigeration unit 27. Moreover, the capsule requires no additional space for air cooling since the oil cooling principles of the present invention are applied thereto.

Thus those skilled in the art will understand that the method and apparatus of the present invention provides new and improved cooling of refrigerant compressors and a new and improved method and apparatus for separation of refrigerant and oil from a refrigerant-oil mixture.

While a preferred embodiment of the invention has been shown and described it will be understood that many modifications and changes can be made within the true spirit and scope of the invention.

What I claim and desire to be secured by Letters Patent is:

1. In a refrigeration system, a compressor lubricated with lubricating oil for compressing a gaseous refrigerant in the system and discharging the compressed refrigerant mixed with lubricating oil, a condenser receiving the compressed refrigerant and lubricating oil mixed therewith cooling the refrigerant to liquify it and the oil mixed therewith, an evaporator in series with said compressor and expansion valve upstream of said evaporator, an oil separator downstream of the condenser and upstream of the expansion valve and the evaporator for separating from said refrigerant lubricating oil entrained by and mixed with said refrigerant, means to return oil separated from said refrigerant in said separator in a cooled condition to said compressor, and means to deliver refrigerant from said separator to said expansion valve and evaporator, said oil separator comprising means for effecting gravity separation of said oil and said refrigerant, said oil separator further comprising means defining two communicating compartments, a conduit extending into a first compartment and having perforations in a length thereof within said compartment to allow liquid refrigerant to be discharged from said conduit and oil lighter in weight than said refrigerant to be discharged from said perforations above the level of said refrigerant, said means to deliver refrigerant from said separator to said expansion valve and said separator comprising a conduit to discharge refrigerant from the other compartment to said evaporator, and said means to return said oil to the compressor comprising an oil line in said first compartment extending into said first compartment a length shorter than the length of said conduit having said perforations.

2. In a refrigeration system according to claim 1, in which said compartments are of substantially equal voltime and in which said oil line terminates at about an upper level of the oil separated from said refrigerant, said conduit to discharge refrigerant extending into said other compartment a length shorter than said length of said conduit having perforations extending into said first compartment.

References Cited UNITED STATES PATENTS 320,308 6/ 1885 Surkert 62-84 1,635,058 7/1927 Potter 62473 2,102,391 12/ 1937 Steenstrup 62453 2,921,448 1/ 1960 Carraway 62473 3,283,532 11/1966 Koc-her 62473 3,324,680 6/1967 Cremer 6284 FOREIGN PATENTS 146,359 7/ 1931 Switzerland.

522,598 9/ 1953 Belgium.

WILLIAM J. WYE, Primary Examiner