US1987591A

US1987591A - Oil return means for flooded evaporators

Info

Publication number: US1987591A
Application number: US637607A
Authority: US
Inventors: Askin Joseph
Original assignee: Fedders Manufacturing Co Inc
Current assignee: Fedders Manufacturing Co Inc
Priority date: 1932-10-13
Filing date: 1932-10-13
Publication date: 1935-01-15
Anticipated expiration: 1952-01-15

Description

Jan. 15, 1935, J. ASKlN OIL RETURN MEANS FOR FLOODED EVAPORATORS Filed Oct. 13, 1932 A w M 8? deaf/Ki Patented Jan. 15, 1935 1;. i

UNITED STATES PATENT OFFICE y on. RETURN Foe FL oonEn nvAPoRATons. n a

Joseph Askin, Buffalo, N. Y.', assignor'to readers J v Manufacturing Company, Inc., Buffalo,

Application October 13, 932, Serial 'Nafss'mm.

M 6 Claims. (01-. 62- 126) This inventionrelatesto refrigeration evaporaity of tubes 11, and which is closed at one end by tors of the flooded, type such as are employed in a'platejl2-provided with an inlet line 13 and a compressor-condenser-expander systems of mesuction line 14. The inlet'line 13 passesthrough chanical refrigeratiomandit has particularrefa-boss 15, formed on the plate,-in which is mounterence to the provision of means for effecting the ed, an inlet valve 16,.theopening of which is con- 5 copious return of oil from the evaporatorto the ptrolled by a'pivoted'float member 17, in the form compressor without concomitant return ofliquid .of an open cup or receptaclei -A suctiontube 18, refrigerant; V f dependingintothe cavity of the cup 17, leads to It is wellunderstoodin the art that,-inthe type the suction line 14,; 1 v a a y of refrigeration apparatus referred t o, oil tends The operation is that, asrefrigerant evaporates 10 to accumulate in the evaporator, and some DIQ- in thecylinder 10, and, tubes 11, toproduce re- ,vision must be made for its return tothe comfrigeratiomthe liberated gases, together with such pressor, together with gasified refrigerant. It is lubricant asthey may carry, fall into the cup '17 likewise desirable to'prevent the return of liquid and are returned to the compressor through the 515 refrigerant tothe compresson aslossesof operatsuction tube 18. Such evaporation lowers the 15 ing efficiency result if this condition occursl If liquid level in'the evaporator, thereby permitting the oil is returnedtoo-rapidly, however, the tenthe float 17, to drop open the valve 16, and admit dency to r urn refri r n is au m nted whil -mixedliquid refrigerantiand lubricant 'to the too slow an oil return rate is attempted the'reevaporator to reestablish the liquid level therein.

- a m y 106601116 il legg d, a d solesse ed As the oil is lighter than the refrigerant, it floats 20 -in its refrigerating capacity. Oil logging:,may on the surface thereof, and is carrie d into the take place in a system which operates satisfaccavity ofthe'float'during the evaporating action. -tori1y under certain conditions i 13 C As statedabove, a violent evaporating action .rtions be materiallychanged. IForeXampleQit'has may cause the injection ofglarge quantities of 2.25 been noted that a domestic refrigerator operating liquid r fri rant i t th cup 1 7, hi h. i t .25

season.

P p y pp a y full capa ity may desired, while a very quiet action may not cause becomeo l logged w it is j w b ry suificient disturbance todischarge the oil into the li ht du y, as might be th ease y'w cup, thereby leading .to oil logging of the system. absent from the residence .during'; avaCatiOn To avoid both of these defects, this invention prof' vides for guarding the cavity of the cup from the 30 Thelpresent invention provides for" thejreturn injectionof liquid refrigerant, and provides means of oil in such copious quantities as to prevent oil for the taking up, of 5 substantial volumes of the logging from thisor any other cause, whilellimit- I oil floating on the're'frigerant surface.

ing the return of refrigerant toanor'malamount, 0 this gend, ,the cup 17 is covered with a cover and thenin the form of gas, and it also provides plate 21, which shown as being in the form of I 35 a wick feed for oil return purposes which; exerts alid having,- turned under marginal portions 22,

a constanteffect on the, C Whiph it is'irnadapted-to engage outwardly-[turned'flanges 23 mersed,, irrespective [of variations they iq fid formed onthe cup itself. A s1ot 24, guarded by an level in t e evaporator! n Setting q b the p upwardly turned flange 25-, is formed at the rear 0 p s of t v ti a 'ap i to Pra tice, fportion of. the lid 21,-sothat the lid may be slid 4o erencewill be made to a typepf oil'return device I over the cup and 1 beyond the, tube 18. 'The in which an open cup iS adap QB lubriclearance between the flange; 25 and the tube cant and refrigerant for return to the'compressor 1'8 provi de s1 -an' input passage for directing the through a suctionlin e disposed inthe cup but it gases to the tube- 18 andit is additionally propor- 145 will be understood that the'invention maybe em-' tioned to permit the bucket 17*to rise and fall bodied. in otherforms within the, purview ,ofi the freely with the liquid level, so asnot to interfere following, claims. I i v with the action of the valve 16, but the gap is not In thedrawing, Fig. l is a-transverse section .wide enough to provide for the free passage. of through anevaporato-r header containing the inlarge amounts of liquid refrigerant which may vention; v r occasionally be splashed overthe rear portion 50 Fig; 2is a longitudin'al'section; and, of the cup and aroundlthe tube v18. 1

Fig. 3 is a perspective of a cupshown in Figs. v The plate 21 is: provided, at a number of point land 2. i 1 adjacent its margin, with narrow slots or open- The evaporator is illustrated as comprising a ings-t26, in which are disposed wicks 27, dipping ylind i l h 1l f -w i sd n d a P m att their outer ends into the region ;-ofv .the oil i3 layer in the evaporator, and terminating at their inner ends within the cavity of the float. These wicks may be made simply by folding fine mesh copper screen, say from eighty to two hundred mesh, on itself a number of times, and then flattening the folds by a hammer blow or the like.

The size of the wicks is of some importance, and is readily ascertainable'for any given evaporator. Anne wick, :such as enemadeiof two hundred mesh wire, does not feed oil from the supernatant layer into the cup as rapidly as an eighty mesh wick of the same length and width,

However, a coarse mesh wick maybe so active .as to carry into the float an appreciable amount of liquid refrigerant, and hence, in providing for a,

plurality of wicks, it is understood that mere "feeding capacity alone is not contemplated, but the major purpose of using a large number of wicks is to provide for high oil return capacitmwithout increasing the refrigerant return.

Inthe present device, it'has' been found that three or four wicks of one hundred mesh screen serve to return the oil as rapidly as it accumulates, with practically no liquid refrigerant return. Thus, the use of a number of slow feeding wicks is preferred to a s'ingle iast' feeding wick, since the former arrangement provides an enlarged evaporativ'e surface for the liquid refrigerant whichis occasionally carried with the oil.

The lengthofthe exterior 'leg of the wick is, of course, constant, and its depth of immersion is determined for normal operating conditions by the cup 17 :were fixed with respect to the shell 10. Such construction is advantageous in preventing the return of liquid refrigerant through the wicks. A I i The apertures 26, through which the wicks 27 pass, preferably engage the wicks snugly, so that any liquidrefrigerant which spreads out over the surface of the plate 21, and attempts to flow through the apertures, is taken up by the wicks, to be further retarded in its flow as liquid,--orto be taken up by the oil in the -wicks -and'sorendered ineil'ective to cause-backfrosting. fI'n operation, gasified refrigerant passes fromthe vapor space above the liquid levels into the cavity of the cup 17 and thence into thesuction tube 1-8,'-'flo wing through the apertures which. are always open to it. Liquid refrigerant, which maybe-splashed on the plate 21, is so impeded in itsprogress that an opportunity is given to it to evaporate, and

hence practically no liquidrefrigeiant isadmitted to thereturn line. wicks, which, due to their nature'take upthe oil preferentially to the liquid refrigerant; and at such rate that the oilis returned practically as fast as it, collects. Oil may also bereturned through the openings in the plate 21,"or with the .gasified refrigerant, which serves as a carrier for small oil particles.

The wicks 2'? may be of such size as to be automatically disengageable from the liquid in the header when the oil is drained therefrom, with the object of preventing the withdrawal of pure liquid refrigerant from the header. This is. provided "for by the'difierencesin' specific gravity ofthe oil and the refrigerant, wherein normally the relatively light oil floats on the refrigerant in a layer of approximately one half inch, and, inasmuch as it affects the buoyancy on is rem-medby the said top being above the liquid in the evaporator,

of the float, it also affects the liquid level in the header, which is dependent upon the valve-controlling action of the float. Under these conditions, which may be assumed to be normal, the float is deeply immersed in liquid, and, as a re- 5 sult the wicks enter the oil layer. However, in the absence of or during a substantial depletion of the layer, the relatively heavier liquid refrigerant alone .afiects the buoyancy of 'the float, which therefore floats more readily, and, through 10 its control of the valve, in effect lowers the liquid level in the header. The wicks under this ,honditlon are withdrawn from the liquid until a substantial quantity of oil enters the header.

Under alloperating conditions the return or 15 imcerilcgs of the'wicks serve an additional purpose to that described in conveying portions of the liquid occasionally splashed on the plate 21 to-theinterior of the float. Such a portion may form in a film on the plate and engage the top 20 of a wick 27, whereupon it drains slowly intothe float. Inthis case each wick acts as a tortuous return :d-uc-t wherein 'thegravitational flow of such liquid portion 'is sufliciently :slow to permit and improved herein, and it will therefore be "understood that I contemplate the application of the principles of the invention in forms in which such valve controlis not included, and that various other modifications may be resorted to as may suggest themselves to those skilled in the art.

1. In a refrigerating'apparatus comprising an i evaporator having inlet means for admitting 40 lubricant and refrigerant for separation by gravity therein, lubricant return means comprisinga closed cup in the evaporator having a top portion extending above the liquid, said top portionhaving an aperture therein, a wick entering 15 the cup through theaper'ture of the top' portion thereof and having a portion extending into'the flu'bricant, said top portion being adapted to re- .an outlet conduit extendingfrom the cavity of thecup toaportion exterior of the evaporator.

. '2. In a refrigerating apparatus comprising an evaporator having inlet means for admitting lubricant and refrigerant for separation by" gravitytherein, lubricant return meanscomprising a cup therein havingv an opening in its top,

means closing said. opening, said 'means comprising a labyrinth structure adapted to gravita- .tionally convey lubricant into said cup to permit gas to the outlet conduit, and means on thefioat 4 for conducting lubricant from the evaporator to the interior of the float.

4. In a refrigerating apparatus comprising an evaporator having an inlet for admitting lubricant and refrigerant for separation by gravity therein, a control valve for said inlet, lubricant return means comprising an open float positioned within the evaporator for operating said valve, an outlet conduit extending into the float, a cover for said float, passage means in the cover to admit gas to the outlet conduit, and wick means extending into the float and having a portion entering the lubricant, said wick means being maintained in the lubricant by the buoying movement of the float.

5. In a refrigerating apparatus comprising an evaporator having an inlet for admitting lubricant and refrigerant for separation by gravity therein, a control valve for said inlet, lubricant return means comprising an open float positioned within the evaporator for operating said'valve,

an outlet conduit extending into the float, a cover for said float, passage means in the cover to admit gas to the outlet conduit, cooperating flange means on the float and cover for retaining the cover in assembled relation, and means on the float for conducting lubricant from the evaporator to the interior of the float.

6. In a refrigerating apparatus comprising an evaporator provided with means for admitting refrigerant and lubricant admixed therewith, an open float for controlling the liquid admission means, an outlet conduit extending into the cavity of the float, lubricant return means comprising a cover for the float, and means for conveying liquid deposited on the cover to the interior of the float, comprising a labyrinth structure entering the float through the cover and adapted to slowly convey lubricant into said cup to permit the evaporation of refrigerant carried therewith during transit.

JOSEPH ASKIN.