US1829417A - Refrigerating apparatus - Google Patents

Description

Oct. 27, 1931. R. K. MILLER 11,829,417

REFRIGERATiNG APPARATUS Filed NOV. 30. 1927 STATES rant RALPH K. mm, OF DAYTON, OHIO, ASBIGNOB, BY MESNE ASSIGNMENTS, T FRIGID- AIBE CO BPOBATION, A. CORPORATION OF DELAWARE BEBRIGEBATING AEPABATUS Application filed November 30, 1927. Serial No. 286,717.

This invention relates to refrigerating apparatus and particularly to a novel method of lubricating such apparatus.

One of the objects of the invention is to provide positive and regular circulation of lubricant in refrigerating apparatus. More specifically it is an object of the invention to return lubricant from the evaporating or expander to the compressor of a refrigerating [0 system.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings,- wherein a preferred [5 form of the present invention is clearly shown. In the drawings;

Fig. 1 is a conventional or diagrammatic representation of a refrigerating system in go which my invention is embodied, and

Fig. 2 is a vertical longitudinal section thru a portion of the evaporator of such system.

Fig. 1 shows a compressor-condenser-expander type of refrigerating apparatus hav- 5 ing an evaporator and a condensing element including a compressor 11, a condenser 12, and a receiver, or liquid refrigerant tank 13. Refrigerant vapor is withdrawn from the evaporator thru the vapor or low pressure conduit 14 and is liquefied in the condenser 12 and returned to the evaporator thru the liquid or high pressure conduit 15. The compressor is operated by a motor 17 controlled by an automatic switch 18 which may be actuated in response to the refrigerating demand, for example by a pressure responsive device 19 connected to the low pressure conduit 14.

Referring to F 2, the evaporator comprises a header 20 forming a reservoir for liquid refrigerant, and a number of tubes or ducts 21 de ending from the header for circulating re rigerant. The liquid refrigerant is indicated by 22 and is kept at a constant level 23 by a valve 24 actuated by afloat 25. The liquid refrigerant is supplied by a connection 15 and the vapor is withdrawn thru a tube 14: connected to the vapor con duit 14.

All of the apparatus above described is Well known in the art and its particular form and arrangement is immaterial to the present invention. It has been customary to lubricate the compressor of suchsystems by placing a quantity of oil in the crank case and depending upon the splashing ofthe rotating parts to distribute the oil thruout the compressor. Some of the oil is dissolved in the refrigerant, and some of the oil is mechanically pumped by the compressor to the condenser and receiver and eventually to the evaporator. The refrigerant boils off in the evaporator, leaving the oil, which collects in a layer from inch to' 1% inches thick on top of the refrigerant.

A great deal of trouble has been experi;

enced in the past because this oil could not be effectively removed from the evaporator, Not only does the collection of oil in the evaporator exhaust the supply of lubricant in the compressor, but it also hinders evaporation of the refrigerant, causing the pressure and consequently the temperature of the refrigerant to increase. Various arrangements have been attempted for periodically or regularly extracting this oil from the evaporator and returning it to the compressor. One of those proposed and widely in use is the evaporator exhaust connection 14. shown in Fig. 2. This is a tube projecting into the evaporator and having its open end 25 above the level of the oil layer. One or more drain openings 26 are formed in the side of the tube below the level of the opening 25 and also below the estimated level of the oil but above the estimated level of the liquid refrigerant. The theory of this arrangement is that the refrigerant vapor will be withdrawn from the top of the header thru the opening 25 by the suction of the compressor and that whenever the oil level used for refrigerating apparatus lie on top reaches the opening 26, oil will drain out of drawn without removing this definite quan the evaporator. However, this arrangement tity of oil, consequently a positive and re'guhas proved unsatisfactory and unreliable in lar circulation of oil is effected.

service, and as far as I am aware, no plan I have also discovered that while the oil for removing oil has been completely sucpreviously used will form a very thick layer cessful. It is well known that evaporators on top of the refrigerant, sometimes as much of this character may collect oil until the as 1% inches, these foaming oils do not form compressor is completely dry, and that while such a thick layer. The maximum thickness oil may be returned to the compressor at inof the foaming oil layer which I have obtervals, the return-is extremely Irregular and served is about A, inch. This characetristic the apparatus will frequently operateas'much materially improves the operation of the as sixty days without returning any oil whatevaporator, because the boiling temperature ever to the compressor. of the refrigerant is not increased materially .I-havediscovered that the oils heretofore by this thin layer of oil. 7

, The oils which I have found particularly of the refrigerant in a thick layer which is suitable are certain paraffin base oils" from quite solid and is free from bubbles exceptthe Pennsylvania district, and it isjessential' as is disturbed y the boiling of h m g that these oils remain in a homogeneous erant beneath it and the escape of the refrigliquid state at all temperatures encountered erant thru it. When. boiling of the refrigin the refrigerating apparatus. By homoerant ceases, the few bubbles formed by the geneous liquid state I mean that the oil must ebullition rapidly disappear. I'have also disremain sufficiently fluid to flow readily and covered that there are certain oils, not heremust rem in fr fromsuspen-ded solid bodies tofore used for refrigerating apparatus, such as crystals or particles of paraflin at the which when used in such an evaporator form temperatures encountered in refrigerating a dee but light and fluify layer of sustalned practice, for example at temperatures as low bubb es. That is, the boiling of the refrigas 15 F. Attempts have previously been erant causes the oil to foam and form alaymade to use paraflin base oils in refrigerating er of bubbles which may even reach the top apparatus but it was found that solid paraffin of the evaporator. When boiling of the rewould separate out from such oils within the frigerant ceases, these bubbles do not immeordinary temperature range of refrigerating diately disappear but-retain their form for a t It a l f d th t t th a considerable period. The relative behav1or t ratures produced by ordinary refri 0f the tWO oils mentioned above may be rougherat ng apparatus such oils would congeal, 5 C p to boiling P Water and boll- Either the separation of paraffin or the coning soap solution respectively.

This discovery. has enabled me to devise a new method of lubricating refrigerating elation rendered the oil unfit for use in rerigerating apparatus, and for these reasons paraflin base oils have not been used.

apparatus. accordance with this method I Ordinary paraflin oils have a pour point use as lubricant in the apparatus one of the in the neighborhood of 30 F., whereas 1t has last-mentioned oils, which I term ffoamang been usual, in ordinary domestic mechanical By t term I mean ny 011 Whlch, refrigerating apparatus, to specify oil having when mixed with refrigerant, is capable of pour. i t f -3() F, B thi i meant forming sustained bubbles or foam 1n appre-th t th 11 in Pour readily f a ciable quantities- In so doing I Prefer to tainer at this temperature. I have discovcalibrate the float 25 so ha h re ig ered that in the case of foaming oils, oils of a level is CODSldGIabIy below the level 0f the considerably higher pour point may be used outlet, as indicatedin Fig- 2- That I successfully. For example one of the foamleave an apprecmble Space between t S111" ing oils which I have used successfully has a face of the q Whether 011 refmgemnt, pour point of 5 F. When this oil is mixed easily withdrawn without danger of splash ing liquid refrigerant into the outlet. When the refrigerant is boiling, the oil (because of its foaming characteristics) forms bubbles or bodies of. refrigerant vapor totally entwo liquid phases are formed which are generally called the sulphur dioxide phase and the oil phase. The sulphur dioxide phase appears to be and acts very much like sulphur dioxide but is reall. a solutionof a small closed b films of 011. The suctlon roduced y J by the dbmpressor withdraws thesd bubbles Rroportlon of 011 m sulphur dloxldeg 9 thru the exhaust tube and it will be 011 phase appears and acts very much hke Oll. evident that each time a bubble is drawn 0 i t th tl t, t i tit f ffi portlon of sulphur dioxide in 011. Inthe parerant vapor and a certain quantity of oil is tlcular case under dlscussion the 011 phase positively returned to the compressor. Since r ma ns in a homogeneous liquid state and the oil foams up over the end of the exhaust has a pour point as low as -27 F. The reconduit, refrigerant vapor can not be with? duction of the pour point from ,5 to 27 "11 and the Outlet so that 011 and Vapor may be with a refrigerant, such as sulphur dioxide,

but this is in fact a solution of a small pro-.

may possibly be due to the dissolving of the sulphur dioxide in the oil.

I hav found that a paraffin base oil made by the Kendall Refining Company, Bradford, Pennsylvania, and having the following physical characteristics is suitable for my purpose:

Specific gravity at F .8665 Viscosity (Saybolt) at 100 F 94 sec Viscosity (Saybolt) at 21 F 973 sec. Flash point 360 F. Fire point 425 F. Cold H SO absorption 2.48% Pour point 5 F.

While I have described my invention as ascribed to an evaporator of the flooded type it will be understood that the method of lubrication is equally applicable to other kinds of evaporators such as the dry expansion type. Also while I have described my method of lubrication as involving a paratfin base oil, I wish it to be understood that the invention is not limited to this type of oil, any oil having the above described foaming characteristics being. suitable. For example, I may add materials to asphalt base oils which will impart a foaming characteristic to such oils without detracting from their other characteristics which render them suitable for refrigeration.

What is claimed is as follows:

1. The method of operating refrigerating apparatus which consists in circulating through the apparatus a volatile refrigerant and oil capable of forming sustained bubbles in the presence of the refrigerant.

2. The method of removing both refrigerant and lubricant from a refrigerating evaporator which consists in evaporatin the liquid refrigerant, forming sustained ubbles of refrigerant vapor and liquid lubricant, and removing the bubbles from the evaporator.

3. The method of circulating refrigerant and lubricant in a refrigerating system which comprises introducing liquid refrigerant and liquid lubricant into an evaporator, evaporating the refrigerant, forming sustained bubbles of refrigerant vapor and lubricant and removing the bubbles from the evaporator.

4. The method of circulating refrigerant and lubricant in a refrigerating system which comprises introducin into an evaporator liquid refrigerant an oil capable of formsustained bubbles in the presence of the re r1 'gerant, evaporating the refrigerant,

forming sustained bubbles of refrigerant vapor and oil, and removing the bubbles from the evaporator.

5. Refrigerating apparatus comprising in combination a closed system including an evaporating element and a condensing element connected thereto, the system containing a volatile refrigerant and oil capable of forming sustained bubbles in the presence of the refrigerant.

6. The method of operating refrigerating.

apparatus which consists in circulating through the apparatus sulphur dioxide and oil capable of forming sustained bubbles in the presence of the refrigerant.

7. The method of removing sulphur dioxide and liquid lubricant from a refrigerating evaporator which consists in evaporating the sulphur dioxide, forming sustained bubbles of sulphur dioxide vapor and liquid lubricant, and removing the bubbles from the evaporator.

8. The method of circulating refrigerant and lubricant in a refrigerating system which comprises introducing liquid sulphur dioxide and liquid lubricant into an evaporator, evaporating the sulphur dioxide, forming sustained bubbles of sulphur dioxide and the lubricant and removing the bubbles from the evaporator.

9. The method of circulating refrigerant and lubricant in a refrigerating system which comprises introducing into an evaporator sulphur dioxide and oil capable of forming sustained bubbles in the presence of sulphur dioxide, evaporating the sulphur dioxide, forming sustained bubbles of sulphur dioxide vapor and the foaming oil, and removing the bubbles from the evaporator.

10. Refrigerating apparatus comprising in combination a closed system including an evaporating element and a condensing element connected thereto and sulphur dioxide and oil capable of forming sustained bubbles in the presence of the refrigerant in the systerm.

In testimony whereof I hereto afiix my signature.

RALPH K. MILLER.

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