US2198258A - Refrigeration system - Google Patents

Description

April 23, 1940.

R. MONEY REFRIGERATION SYSTEM Filed Jan. 21, 1937 lN\-ENTOR, H M0015).

ATTORNEYS.

Pa tentcdApr. 23, 1940 PATENT OFFICE.

nerarcsaarrou srs'rrm Roland 1]. Money, Cincinnati, Ohio, assignor to The Crosley Corporation, Cincinnati, Ohio, a

corporation of Ohio Application January 21 1937, Serial No. 121,631

' 2 Claims.

frigeration systems, such for example, as the systems of household refrigerators, whereinthere is used oil for lubricating a compressor and a refrigerant characterized by being miscible with or soluble in the oil. Most modern systems, which, of course,.comprise a compressor, a condenser and an evaporator are in the form of a closed system or circuit which containsboth the 10 refrigerant and the oil. The use of a refrigerant miscible with. the oil gives rise to a number of serious problems. In the first. place it is necessary to keep the oil in the place where its function is required. Oil in a condenser or evaporator 15 has no utility and may lead to trouble. The oil must be kept in suflicient volume in a crank-case or dome where it can perform its sole function, that of lubricating moving parts. It follows that the refrigerant elsewhere must be as free as posm sible from oil in order to do its work properly. It also follows that the oil mustbe kept as free from refrigerant as possible in order that its viscosity and therefore its lubricating quality be not reduced. T

Most modern refrigerators are of the so-called hermetically sealed type, that is to say, having a sealed dome or casing in which are located both the motor and the. compressor. For the purpose of an exemplary disclosure I shall describe my invention as applied to such a type.

So far as I am aware, hermetically sealed refrigerators employing oil-miscible refrigerant have always been arranged as follower-The inlet port of the compressor is connected directly by asuitable conduit to the evaporator; but the outlet port of the compressor opens into the dome or casing. The dome is connected with the condenser by a suitable conduit; and those skilled in v the art will understand that between the condenser and evaporator there is a connection including any of the known'means for controlling the supply of liquefied refrigerant to the evaporator.

In this construction the dome is subjected to a the highest working pressures encountered in the system. The dome contains the oil body, diluted of course with a large quantity of refrigerant.

It has been recognized that this dilution is a serious matter and tarious suggestions have been 50 made toward reducing it. One suggestion of which I am aware hasbeen to employ the heat a generated by the motor and the compressor for driving as much of the refrigerant out of the oil as possible. This suggestion does not perfectly solve the problem, however, for several reasons.

' z My invention relates to the operation of re- The great pressure to which the mixture of oil and refrigerant is subjected resiststhe boiling off of the refrigerant by heat. Moreover the amount of refrigerant so eliminated depends also, of course, upon the degree of heat which can be secured; and .this is subject in large measure to external temperature changes. Thus the operation is nonuniform. t

The fundamental object of my invention is to provide solutions for these problems as will hereinafter appear. In doing this I secure a number of :incidental but none-the-less important advantages which will later be pointed out or will be apparent to one skilled in the art upon reading these specifications. 16

I have found that as a mixture of oil and refrigerant is subjected to progressively lower pressure by the compressor in a refrigerator system,

this results in separating the gas from the oil,

and that this is not only effective in removing l0 from the oil very much more of the refrigerant gas than can be removed otherwise, but is also substantially independent o'fexternal conditions of temperature and the like. The place to subject the mixture of oil and refrigerant to the low a pressure is, of course, at the point where the oil is collected for lubricating purposes. In the socalled hermetically sealed refrigeration jobs, the oil is collected inside the dome which also houses the motor and the compressor. Therefore, in the practice of my invention as applied to such a system the dome, instead of being a high pressure dome, is made to be a low pressure dome andto this end is usually connected directly to'the evaporator. The oompressor inlet opens directly into the dome; whereas the compressor outlet by'suitable conduits is 'connected directly to the condenser of the refrigeration system. Thus the dome is progressively exhausted and its pressure reduced as thecompressor operates during each cycle of themachine. The oil in the dome during the operation of the compressor is subjected to progressive lower pressure which causes the refrigerant actively to boil out of the oil until at v the close of the cycle an equilibrium is reached 4,5 in the oil-refrigerant solution at the lowest pres sures which are obtained. It will be understood,

of course, that in normal operation a complete separation of oil and refrigerant is never obtained; but this is not necessary. .A working body of oilis, however, maintained very'much freer from the refrigerant than has been possible i l in refrigerating systems heretofore. Reliance 1s not had, therefore, on heat to remove refrigerant I from the oil; and because the reduced pressure 5 is so very much more effective in freeing the oil from the refrigerant, the system becomes quite independent of temperature conditions.

Moreover, my system gives to the refrigerant a much enhanced margin of safety. It is not economical to make a large dome a heavy one; yet where a dome is employed on the high side of the compressor it must for safetys sake be able to withstand extremely large pressures, generally much greater than those pressures which the refrigeration system must withstand as a whole, when it is out of operation, e. shipped or stored under conditions of relativ ly high external temperature. The reason for this is that if stoppage occurs in the line feeding the evaporator, i. e, if a float valve sticks, the compressor will continue to run and will build up an extremely high pressure which must be withstood by the dome, if the dome is on the high side of the system. This has been responsible for the bursting of many domes in service. Again, where the refrigerating system is subjected to very low external temperatures, the liquefied refrigerant will condense in a high side dome, and accumulate below the oil requiring expensive precautions for its removal. All of these incidental but important difliculties are avoided in my system.

For a better understanding of the system as such, reference is now made to the drawing where I have shown in a diagrammatic way a series of elements and a combination suitable for the practice of my invention in the aforesaid exemplary embodiment. In this drawing which, as indicated, is diagrammatic in character, dimensions have been disregarded and various operating Darts have been shown in operating relationship but displaced from their normal positions inorder that all of the parts could be shown in a single view.

In the drawing, (and first tracing through the elements of the closed system), i designates an evaporator adapted to be fed with liquid refrigerant from a condenser 2, through a high side float valve mechanism indicated generally at 3. Specific description of these elements is-notnecessary' because their form and function is well understood by the skilled worker in the art. It will further be understood that the high side float valve is merely exemplaryof the various means .which may be employed to control the level of .liquid refrigerant in the evaporator i, such for example, as a capillary tube or equivalent restricted flow device. 'My system is likewise operative in connection with flooded evaporators: having interior float valves to control the liquid level, and with evaporatorswhich are of the non-flooded type.

8 designates the dome of a hermetically sealed refrigeration unit. It contains the motor 5, which through appropriate operating mechanism drives the piston 6' of a compressor '3. 8 designates the outlet port including the valve of the compressor i and it will be noted that this outlet port is connected ,by means of conduits 9 and it) directly with the condenser 2. ii is a muffler connecting the conduits g and it, located within the dome 4 and making for silent operation. It will be .noticed that the elements 9, it) and H form a closed system, not opening into the dome. This system conducts the compressed refrigerant through the dome, .asindicated. Onthe other hamljthe evaporator l is connected by a low pressure conduit 92 directlywith the dome 4. 'The inlet port 93 of the compressor 1 effectively opens into the dome as shcwn. In. the exemplary embodiment there is a conduit I 4 connected with the inlet port l3 and. passing into a muflier I5; but this mufller opens into the .dome as will liquefied. It is then fed by suitable means to the evaporator i where it is subjected" to reduced pressure, vaporizes, and produces the desired lower temperature. The vaporized refrigerant passes through the conduit l2 to .the interior of the dome 4; and the inlet of the compressor opens into this dome as has previously been indicated.

The dome is designed to hold in its lower portion a body of lubricant indicated at Hi. The refrigeration system is one employing a refrigerant miscible with, this lubricant. The operation of the compressor will be such, in the system described, asto subject the interior of the dome 4, and therefore the lubricant 'body It contained therein, to progressively lower pressures. Under the influence of these low pressures the refrigerant mixed or dissolved in the body of the oil will boil off and be compressed and returned to the system. In this way the body of the oil at the end of each cycle is kept relatively free from refrigerant, and as the oil that passes through the system returns to the compressor housing or dome its contained gas is exhausted.

It will be understood that when oil returns with the refrigerant'throughi the conduit l2 and is subjected to the low pressure inside the dome, such oil will tend also to give upthe refrigerant mixed therewith as indicated; and oil particles relatively free of refrigerant will tend to collect on various parts of the apparatus in the dome l and on the walls of the dome, and will flow down and be collected in the oil body IQ. of course,

there will be at most times within the dome a fine such as that shown at n. This is a bell shaped fitting connected with the mufiler I5. The open end of the fitting is pointed downwardly. Thus oil collecting on the mufller and adjacent the enlarged opening of the fitting i! will tend to drip oil as at l8, rather than to be sucked into the compressor with the refrigerant gases. Another way of referring tothis function of the apparatus is that it operates as a separator to a certain extent. 7

My system thus operates not only to provide a body of oil at the point of service for lubricant which is as free as possible fromrefrigerant, but also operates to keep the refrigerant in the remainder of the parts of. the apparatus as free as possible from oil. v

It will be understood, of course, that the compressors of modern refrigerators do not operate continuously .but are designed to operate in cycles for-the saving of power; Thus there are extended periods when the compressor is not operating During such periods the pressure in the dome gradually rises and as it rises refrigerant in the dome gradually dissolves in the oil I! again, depending on the elapsed time. But when the system is in service, the pressure inside the dome 4 will always be less than pressure elsewhere in the system, and in these circumstances, the amount of refrigerant which becomes dissolved in the oil in the dome is less than it would ordinarily be. However, as soon as the next cycle starts and the dome is lowered in pressure by the compressor, the boiling of the refrigerant out of the 011 body l6 proceeds actively to the equilibrium point.

Therefore, as indicated, the body of oil I8 is maintained at the working point comparatively free of refrigerant at all times and quite free of refrigerant during theoperation of the condenser. Oil x'nay, therefore, be withdrawn from the body l6 and used within the dome for lubricating purposes where its effect would be greatly enhanced, because it is relatively undiluted by the refrigerant. In an exemplary refrigeration system, the oil initially introduced into it may have, say, a viscosity of 150. With the normal charge of a refrigerant which is miscible with the oil, say the common refrigerant freon, under conditions of shipment or storage, the viscosity of the oil will be reduced to around 100 due to dilution with the refrigerant. 'Ihis gives an indication of how essential it is to keep the oil for lubricating purposes as free of the refrigerant as' possible. With a body of oil IS in the dome 4 kept relatively free of refrigerant the lubrication problem is solved merely by delivering this oil to the parts to be lubricated and returning the oil to the lower part of the casing. I haveindicated at I! a pump for oil, connected as shown to the main drive of the compressor. This pump withdraws oil from the body I 6 by means of a conduit 20 connected to the inlet conduit II of the oil pump by a device which, in this instance, is a trap to maintain a body of oil continuously at the inlet of the oil pump IS. The pump, being constructed as shown, has no inlet valve. An outlet valve is shown at 22 and the oil from the pump I9 is delivered into a housing 23, from which a portion of the oil flows through a conduit 24 to those parts which require lubrication. Another portion of the oil flows, through an opening 25 in the housing 23, over the cylinder block of the compressor, so as to cool it. The

particular type of oil pump and the particular manner. of delivery of oil to the variousffparts to be lubricated, and the particular construction of these parts for eihcient lubrication by being bathed in oil, do not constitute limitations upon tion Serial No. 121,630, filed January 21, 1937,

which has matured into Patent No. 2,138,664, issued November 29, 1938.

It will be noted in my system that no gas can condense in the dome 4, for the reason that this dome is kept under reduced pressure. Therefore,

' different types of construction with the same force and efiect. It will further be understood that in the light of these teachings the skilled worker in the art can adapt my invention to varying types of constructionof refrigerating mechanism without departing from the spirit of it. Therefore, the appended claims are not to be taken as limited otherwise than as set forth in their terms.

. Having thus described my invention, what I claim as newand desire to secure by Letters Patent is:

1. In a refrigerating system of the type employing a lubricant, and a refrigerant which -is miscible with said lubricant, a dome,- a motor and a compressor located in said dome, an evaporator and condenser located outside said dome, a connection between said evaporator and said condenser, a connection between said condenser and the high side of said compressor, a connection between said evaporator and-said dome and a connection between the low side of said compressor and said dome,'whereby said dome is subjected to the lowest working pressures generated in said system by the action of said compressor and whereby oil in said system will tend to collect in said dome and be freed of refrigerant therein, said connection betweenthe low sideof said compressor and said dome comprising a muiller, and a down-turned bell-shaped entrance means therefor.

2. In a closed refrigerating system, a dome, a compressor in said dome having its inlet port connected to said dome, and its outlet port connected to conduit means passing through said dome, whereby said dome is a low pressure dome,

entrance means for refrigerant and entrained oil' to said dome, whereby said refrigerant may'be exhausted from said entrained oil by saidlow pressure and whereby said oil collects in said dome-and means for restricting entrance of said oili to said compressor comprising down-turned entrance means for the inlet port of said com-

Images