US2134768A - Separating process and apparatus - Google Patents

Description

flvehforr flowardijlllf rellidd H. M. THRELKELD SEPKRATING. PROCESS AND APPARATUS Filed Jan. 15, 1935 Nov. 1, 1938 I Patented Nov 1, 1938 UNITED STATES PATENT OFFICE 2.1mm snrsns'rmo raocsss AND mm'ros Howard M 'l'hrelk mesne alsignmen tsf'to Benefits-act! My invention relates in general to the separation of material from fluids carrying the same tion, of a lubricant from a refrigerant in a re- 6 frigerating system.

The process and apparatus of my present invention are particularly adapted for application in refrigerating systems wherein "a fluid-refrigerating medium is circulated progressively to va- 10 riousparts of the systemin performing its heatexchanging function and wherein the refrigerating medium, in circulating in the system, may absorb or become mixed with a lubricating medium, employed in the system, to such a degree as to impair the heat-exchanging eillciency of the refrigerating medium and an important ob- Ject of the invention resides in providing a sim-' ple, yet thoroughly effective means for and method of continuously separating and removing, from a refrigerating medium, lubricant which may have become entrained or dissolved therein during the circulation of the medium in the refrigerating system.

Another important object is to provide a method of abstracting quantities of an evaporable liquid, such as a refrigerating medium, from a body of the same, such as may be contained in the evaporator of a refrigerating system, which consists in utilizing gaseous pressure developed by the evaporation of the liquid in order to fluctuate the liquid level, in at least a portion of the liquid body, above and below a point at which the liquid may be drawn oil, so that the removal of liquid may be accomplished only when the level-rises above the removal point and hence is accomplished at a restricted rate controlled by the evaporation of the liquid.

Another important object is to provide, for fluctuating the liquid level of the body, at the point of liquid removal, by utilizing the difl'erential action of the pressure of the gases evolved in the vicinity of the removal point and the hydraulic pressure of the liquid head in remote portions of said body.

Another important object isto apply the method in the extraction from the liquid body of liquid containing a non-evaporable constituent whereby the evaporable constituent, which otherwise will remain entrapped in said body, may be removed; a further object being to separate and reclaim the non-evaporable constituent from the circulating the refrigerating medium, and a lubricating medium for the fluid-forcing means and has more particular referenceto the separawhich dissolves in the refrigerating medium when the same is in liquid condition, the invention including the provision of means, located in the system at the'places-where the refrigerating medium changes its condition from liquid to gas and adapted to extract the lubricant from the liquid refrigerant and return the same to the fluid-forcing means. a

Another important object is to provide, in a refrigerating system including an evaporator and lubricated fluid-forcing means for circulating a fluid refrigerant to and from the evaporator, wherein the refrigerant is delivered to the evaporator as a liquid and discharged thence in gaseous form and wherein the lubricant, used to lubricate the fluid-forcing means, is soluble or miscible with or is of substantially the same speciiic gravity as the refrigerant so that the refrigerant and lubricant may not separate appreciably by stratification in the evaporator, and

means for extracting the lubricant from the refrigerant in the evaporator and returning the same to the fluid-forcing means. 7

Another object is to provide an evaporator, having an exhaust outlet for removing gaseous products of evaporation with a liquid outlet located in position to' withdraw an evaporable liquid, containing a non-evaporable medium, from a body of the same contained in the evaporator, and a conduit associated with said outlet and through which the withdrawn liquid is caused to flow, said conduit extending in heat-exchange relationship with respect to the'exhaust outlet so that the .evaporable constituent of the withdrawn liquid, traveling said conduit, may be evaporated by absorbing heat from the gaseous products of evaporation traveling said exhaust outlet "as well as from the surrounding atmosphere in order thus to separate the evaporable and non-evaporable constituents of the liquid flowing through said conduit. 1

Another object is to coil the conduit about the exhaust outlet inorder to effect heat-exchange relationship therebetween..

A further object is to provide for continuously removing from the evaporator, at a restricted rate, liquid refrigerant containing lubricant, evaporating the refrigerant constituent of the removed liquid by exposing it to the action of heat contained in gas previously evaporated in the evaporator and returning the residual liquid lubricant to the fluid-forcingmeans in condition to perform its lubricating function.

A further important object is to accomplish the return of the lubricating medium to the fluidforcing means by utilizing the pressure of the refrigerating medium in gasifled condition to enreturn the same to the fluid-forcing means.

A further object is to continuously remove, from the evaporator, liquid refrigerant containing dissolvedlubricant, evaporate the refrigerant constituent of the removed liquid in the vicinity of the evaporator in order to separate the constituents of the removed liquid without sacrificing the refrigerating ability of the refrigerant constituent and then return the separated constituents to the fluid-forcing means.

A further object is to return the liquid lubricant, the evaporated constituent of the removed liquid, as well as the gases evolved by evaporation of the refrigerant in the evaporator, to the fluid-forcing means through a common conduit.

Yet another object is to cause the refrigerant constituent of the liquid removed from the evaporator to evaporate as the same is returned to the fluid-forcing means in order to separate the lubricant by distillation of the refrigerant so that the separated lubricant may be delivered to the fiuid-forcing means.

Still another object is to utilize the expansive effect of evaporation of the refrigerant constituent of the liquid removed from the evaporator to force. the separated lubricant constituent on its way back to the fluid-forcing means.

A still further object is to form the evaporator with an evaporator space including an upwardly extending arm connected with the remaining portions of the evaporator space below the upper end of the arm so that the arm is or may be supplied with a column of liquid under pressure of the liquid head in the other portions of the evaporator space. an extractor conduit being connected in the I arm at a point below the level of the liquid head in the remaining portions of the evaporator space so that, as a result of the differential between the substantially constant pressure, applied on the column of liquid in the arm, by the head pressure of liquid in the remaining evaporator space, and the variable pressure applied on said column by gases evolved in the upper end of said arm by refrigerant evaporation therein, the liquid level in said arm may be caused to fall and uncover the end of the extractor tube and permit the evolved gases to be drawn out of said arm; thus permiting the liquid level in the arm to rise and cover the extractor conduit, so that said extractor conduit may alternately and successively receive liquid from said arm and gases evolved in said arm as a result of evaporation of refrigerant therein and thus permit the liquid to be withdrawn from the evaporator at a restricted or controlled rate.

Numerous other objects and advantages and inherent functions of-the invention will be apparent 'as the same is more fully understood from the following description, which, taken in connection with the accompanying drawing, discloses preferred embodiments of the invention.

Referring to the drawing:

Figure l is a diagrammatic .view of a refrigerating apparatus containing lubricant separating means embodying my present invention;

Figure 2 is a plan. view of a part of the refrigerating system shown in Figure l-and containing the lubricant separator;

Figure 3 is a sectional view taken substantially along the line 3-4 in Figure 2;

Figure 4 is a diagrammatic view showing' the elements of an evaporator having a lubricant .ex-

tractor in accordance with my present invention; and

rate from its entrapped position in the system and Figure 5 illustrates a modified arrangement of the separator shown in Figure 3.

To illustrate my invention, I have shown on the drawing, refrigerating mechanism comprising a circulating system, including an evaporator II,

a fluid-forcing device l3 connected with the evaporator and adapted to draw the refrigerating medium in gaseous condition from the evaporator, compress and deliver the same thence through a condenser I5, in which the compressed refrigerant is liquefied, a dehydrator I1, and a flow control B, back to the evaporator. The refrigerating medium is thus delivered in the evaporator in liquid condition, boils or evaporates therein and absorbs heat from the walls of and atmosphere surrounding the evaporator. The gases, evolved in the evaporator as a result of refrigerant evaporation therein, are drawn off by and returned to the fluid-forcing device l3 for a repetition of the refrigerating cycle.

The dehydrator is not an essential part of the system but may be used in order to ensure removal of any moisture which may be present in the refrigerating medium when intially loaded in the system. The dehydrator, if used in the system, and the flow control may have any suitable or convenient form, although I prefer to utilize a float controlled valve of the character illustrated.

The fluid-forcing device l3, also, may be of any suitable or convenient form and construction, although I prefer to utilize a compressor of the character shown in the application of Mahlon W. Kenney and Arthur R. Constantine for United States Letters Patent, Serial Number 724,894, filed the 10th day of May, 1934.

It is ordinarily desirable to lubricate the fluidforcing means and for this purpose a suitable lubricating medium, preferably a mineral oil, may be employed. The refrigerating medium, in traveling through the compressor, may dissolve,

entrain, or otherwise pick up a part of the lubricant and carry the same from the compressor into the condenser where the lubricant mixes intimately or dissolves with the refrigerating medium as the same liquefies in the condensers. The lubricant, thus mixed or dissolved with the refrigerant, will be carried into the evaporator and since the return connection from the evaporator to the compressor must necessarily be made in the evaporator above the level of the liquid refrigerant head therein to prevent return of the refrigerant to the compressor in liquid condition with consequent loss of refrigerating efficiency, and further, since lubricants do not evaporate at the temperatures prevailing in the evaporator, the lubricant, carried into the evaporator with the liquid refrigerant, will accumulate therein and eventually choke 'the evaporator.

While I may use any suitable refrigerating medium, I prefer, for various practical considerations, to employ dichloromethane, which is substantially odorless, non-explosive, and nonpoisonous.

Dichloromethane has a characteristic ability to dissolve ordinary lubricants and particularly mineral oils, such as I prefer to employ in lubricating the compressor. Consequently, the lubricant carried to the evaporator will not stratify therein by flotation. Other refrigerants, which make -no solution with the lubricating medium may, however, form so intimate a mixture as to prevent separation of the components as to be substantially inseparable by flotation in arcane the evaporator. This is particularly true where the lubricant and refrigerant when liquid are of approximately the same specific gravity. The liquid in the evaporator consequently will be a homogeneous solution or mixture of the refrlgerant and the lubricant and, if no provision is made for abstracting the lubricant constitucut, the liquid will contain an ever increasing proportion of lubricant approaching a condition in which all of the lubricant, contained in the system for the purpose of lubricating the com-' pressor, will become entrapped in the evaporator so thatits efilciency is seriously impaired, if not entirely destroyed, while the compressor, at the constituent together with the lubricant constitucut of the abstracted liquid to the compressor.

In accomplishing the return of the lubricant in this fashion from the evaporator to the compressor, I utilize not only the pressure of the liquid head in the evaporator but also the pressure generated by the evaporation of the refrigerant constituent of the liquid abstracted from the evaporator as well as the suction pro- I duced bythe compressor in drawing the evapm rated gases from the evaporator, in order to. causethe return of the lubricant.

The evaporator ll may, of course, be of any suitable form or construction and, as shown in the drawings, may comprise a hollow shell-like vessel, preferably comprising sheets 2| and 23 of heat-conducting material formed so that, when flttedand secured together, a refrigerant evaporating chamber is formed between the sheets. To this .end, the sheet 2| is preferably embossed with spaced header forming depressions 25 'near its opposite ends, and, at least, one of the sheets, preferably the sheet 2|, is embossed to provide a series of preferably parallel grooves 21, so that, when the sheets are fastened together in facing relationship. the depressions 28 and the grooves 21 form a chamber comprising spaced header portions 2! and ducts 3| interconnecting the header portions. The depressions 2i and the grooves 21 are preferably bothformed in the sheet II and the other sheet is assembled in position to overlie the depressions and grooves, the sheets being secured together as by curling the edges of one sheet about theedges of the other as shown at 33 and sealing the curled edges in any suitable fashion, as, for instance. bywelding or brazing.

The sheets may also be sealin'gly secured together around their peripheral edges and between the grooves 21 by welding, brazing, or by other suitable sealing'means. The sheet 23 may also be formed with depressions l! in position to register with the depressions 25 of the co-operating sheet in order to form elongated substantially cylindrical header chambers as shown in the drawing. One of the sheets, preferably the sheet 23, is also formed at intervals with depressions or grooves 31 forming ducts intersecting and communicating with the ducts 3|. The formed sheets II and 23, after having been secured together, may be bent to provide an evaporator having substantially U or channel shaped cross-sectional configuration substantially as shown in Figure l and having spaced apart side walls 39 and an interconnecting bottom wall 4i, the side walls containing the header chambers 29 near their upper edges and the refrigerant ducts 3i extending beneathv the header spaces in the side walls 39 and in the bottom wall 4|. embossed portions 21 project outwardly of the side and bottom walls and the ridges 31 project inwardly on the facing surfaces of the side walls and preferably form pairs of registering ridges upon and between which objects to be cooled may be supported. The opposite ends of the sheets 2i and 23 form the upper edges of the spaced walls of the evaporator and may be flanged as at 43 to provide means for hanging or otherwise mounting the evaporator in operative position as in the cooling chamber of a refrigerator.

The evaporator is provided with an inlet connection, which is preferably at or near the bottom wall 4i, and through which liquid refrigerant may be delivered into the evaporator. space at a point below the header chamber. To this end, I prefer to utilize one of the ridges 31 in order to form an inlet header. The ridge so employed is provided with an opening atone end, in which is mounted an inlet fitting 45 adapted for connection with a suitable pipe or conduit 46, through which the liquid refrigerant is delivered to the evaporator. The evaporator is also provided with an outlet for the vaporized refrigerating medium, which outlet preferably comprises a fitting 41 secured in an opening preferably formed in the sheet 23 opposite one of the header spaces 29. The fitting may have an extension comprising a pipe or conduit 49 extending within the header space and having an end opening above the normal liquid level in the .evaporator. The fitting 41 is also provided for connection with the suction side of the compressor l3 as by means of a suitable pipe or conduit 48. The outlet fitting 41 may, of course, be connected in either or both of the headers but I prefer to connect the fitting 41 in one header only and to interconnect the header chambers by means of a conduit fastened between the header forming portions 35 so that gaseous refrigerant evolved in one header chamber may escape through the conduit 5| into the other and then be withdrawn together with the gasified refrigerant evolved in said other chamber through the fitting 41 to the suction side of the compressor.

When the evaporator is in operation, the liquid level therein is normally maintained at an elevation substantially indicated by the dotted line 53 in Figures 4 and 5 of the drawing. The outlet pipe 49 opens substantially above said level. The refrigerating medium, which I prefer to use in the system, comprises dichloromethane and the system is preferably operated under conditions such that the liquid refrigerant will boil at the temperature prevailing in the vicinity of the evaporator.

In order to separate and extract the lubricant The,

entrapped in the evaporator and return the same I to the compressor, I provide the evaporating space in the evaporator II with an upwardly extending by blocking communication of an end of one of v the ducts 3i with the header space to which thecorresponding ends of the other ducts are connected. This blocked duct, forming the riser 51, is connected with the remaining portions of the evaporating space at a point substantially below its blocked upper end by means of the lateral ducts formed by the grooves 31. The blocked duct in effect comprises one arm of a manometer, the other arm of which comprises the remaining portions of the evaporator space between the plates 2| and 23. The rlsertl will consequently become filled with liquid refrigerant under the pressure of the liquid head maintained in the other portions of the evaporator, the refrigerant entering the riser 51 through the cross ducts 31. The refrigerant will evaporate in the riser 51 so. that a certain amount of gas will accumulate in the upper end of the closed riser ii.

A conduit lit, comprising a tube of relatively small internal size is connected with the riser 51 at a point below the level of the liquid head in the main portion of the evaporator, the conduit 58 being preferably sealed in an opening in one of the plates 1| or 23, preferably the latter, in position to communicate with the riser 51. This conduit is connected with the suction side of the compressor It, preferably by connecting the same in a lateral opening formed preferably in the upper side of the fitting l'l.

As shown in Figures 1, 2, 3, and 4, the conduit It may comprise a continuous piece of tubing connected at one end with the riser i1 and at the other end with the fitting 41, the tubing is also preferably coiled in order to increase the length of the same between the riser I1. and the fitting l9 and, in order to conserve space, the tube It may be'coiled about the fitting 41 as shown.

Since the conduit It is connected with the suction side of the compressor, the gases, collecting in the upper end of the riser II, will be drawn into the outlet fitting through the tube 5!, which, 111- m The surface tension of the lirmid in the tube II will retard the passage of the liquid through the restricted bore of the same. In the meantime,

the liquid refrigerant in the riser I'I continues 'to evaporate so that gases, accumulating in the upper ,end of said duct, will gradually force the liquid level in the duct below the opening of the conduit ll therein so that the gasified refrigerant may-be drawn into the conduit I! behind the slug of liquid. This cycle is repeated continuously asthe evolved gases in the upper end of the riser 51 are alternately withdrawn and permitted to accumulate. A succession of liquid slugs, separated by gasified refrigerant are thus caused to travel through the conduit ll, the slugs being drawn partly by the suction exerted in the line" and the fitting H by the compressor and partly being forced by the propulsion developed behind each'slug by- :the evaporatiorrof the refrigerant. As the slugs of liquid travel the conduit '0, the evaporable constituent thereof will be vaporized by absorbing heat through the conduit 5! from the surrounding atmosphere. The length of the conduit 50 and itsinternal size may be selected to ensure that all of the evaporable constituent of each slugdrawn successively into the conduit will have been evaporated by the time said slug reaches and enters the fitting 41. Consequently, the components of the liquid, forming the slugs, will have been separated entirely into the gaseous refrigerant and the liquid lubricant by the time said materials enter the suction line to the compressor. The lubricant, therefore, enters the fitting 4'! in substantially separated condition and is drawn through the suction line together with the gasified refrigerating medium, with which the lubricant will not mix or form a solution, and enters the compressor in condition to perform its lubricating function.

The evaporator, including the riser 51, and the lubricant extracting conduit 59 i may be formed to provide a regulating effect whereby to prevent the travel of liquid through the conduit 5! in a continuous stream and to ensure that liquid escapes from the evaporator only at a restricted rate. The length of the riser 51 from its upper end to its point of connection with the main portions of the evaporator space and the internal diameter or bore of the conduit 59 may be so selected that the resistance of the conduit to the flow of liquid therethrough will be such that if the conduit becomes choked with liquid, the pressure of the gases entrapped in the upper end of the riser I1, which pressure is determined by the head of liquid in the'main evaporator space above the level of liquid in the riser, will be.

insufiicient to force the liquid through the conduit in the conduit, broken up into a succession of slugs.

When the evaporator is initially placed in operation, or whenever the accumulation of gas in the upper end of the riser 51 takes place-too slowly, the liquid level in the riser may cover the attached end of the conduit is for a period sumcientto permit the conduit to become entirely or at least substantially full of liquid. It is desirable in such cases to provide means for preventing the liquid from continuing through the conduit 50 until such time as its evaporable constituent has at least become partially evaporated. This may be accomplished by properly selecting the conduit with respect to the size of its internal bore and by arranging the length of the riser 51, between its upper end and its point of connection with the main evaporator space, so that the maximum gas pressure in the riser, even when-the same is entirely filled with gas, is insufiicient to force the liquid column through, the conduit against the resistance to liquid flow provided by the restricted nature of the conduit channel. By properly. choosing the internal diameter of the conduit is and the length of the riser, it isthus possible to prevent liquid from entering the conduit as a continuous stream beyond a predetermined distance even when the end of the conduit, which is connected in the riser, remains cov- V ered by the liquid level in the riser.

I have discovered that the boiling point of a solution of oil in dichloromethane varies with the proportions of the media forming the solution.

' substantially uniform, though rapid rate, with increase in oil content, the boiling point of refrig-' posed in the receptacle slightly above the bottom thereof so that it will normally permit the evolved refrigerant to be drawn out through the ejector pipe but will draw the lubricating medium cumulates in the receptacle to a depth suflicient to cover the end of the pipe 63. a

The arrangement shown in Figure 5 thus per-l mits the lubricant to be delivered into the suc-' 5 erant free oil being approximately three huntion line in relatively larger quantities than is 5 dred and fifty degrees Fahrenheit, although thisthe case with the arrangements shown in the figure varies considerably for the different oils other figures of the drawing, in which the lubrithat may be employed as alubricating medium cant enters the suction line as a, succession of in refrigerating systems employing dic'hlororelatively small drops. methane asa refrigerant. v I prefer, however, to employ the coiled pipe It will be seen from the foregoing that greatarrangement shown in Figures 1, 2, 3, and 51, since est efficiency will be had by exposing the liquid, the same is of simple construction and inexpentraveling the conduit 59, to the boiling temperasive, and will remove as much lubricant from ture' of a solution containing from sixty to eightythe evaporator during an equivalent time interval live percent oil, since such a temperature will as will the arrangement shown in Figure 5. 5 ensure the evaporation of the refrigerant sub- It is thought thatthe invention and numerous stantially entirely from any solution containing of its attendant advantages will be understood less than sixty to eighty-five percent 011 to the from the foregoing description and itis obvious 'end that the liquid, discharged from the conthat numerous changes may be made in the form,

duit 59, will comprise between sixty and eightyconstruction, and arrangement ,of the several 0 five percent oil which is entirely satisfactory for parts of the illustrated apparatus without departlubricating purposes in the fluid-forcing device. ing from the spirit or scope of my invention or The additional refrigerant extractable from the sacrificing anywof its attendant advantages, the solution traveling the conduit 59 by heating the referred modes and forms herein described besame above the boiling point of an eighty-five ing merely for the ,purpose of illustrating the 25 percent 011 solution is not of sufficient importance invention. to. warrant the provision of means to apply the Having thus described my invention, what I additional heat particularly in view of the relaclaim as new and desire to secure by Letters Pattively rapid increase in boiling temperature with' cut is as follows:

increase in oil content above eighty-five percent. l. The process of abstracting a relatively non- 3 Of course, it is ordinarily not expected that the evaporable medium from a body of an evaporable evaporator itself will ever contain refrigerant liquid containing the same, which comprises having as much as seventy percent oil in solumaintaining the liquid-level in remote portions of tion therewith. In fact, the system when propsaid body at different altitudes, confining and erly operating, will rarelyifever permit as much utilizing the pressure of gases'evolved by the 35 as one percent of oil to remain entrapped in soluevaporation of the evaporable liquid in the portion in the refrigerant in. the evaporator. tion of lesser altitude differentially against the It will be seen from the foregoing that subhydraulic pressure exerted by the liquid head in stantlally all of the refrigerant, which enters the the other portion of said body in order to depress 4o fitting 41 and including that entering said fltthe altitude of the liquid level in the portion of ting through the conduit 59, is in gasified'condilesser altitude to permit removal of the evolved tion so that no loss in refrigerating eificiency is gases and liquid containing the non-evaporable entailed by withdrawing the refrigerant from medium alternately at a point intermediate the the evaporator in liquid condition into the conupper and lower altitude limits of the liquid level '45 duit 59. The arrangement, however, provides for in said portion of lesser altitude. 45 the'positive and continuous removal of the lub- 2. A refrigerating. apparatus comprising an ricant from the'evaporator as rapidly as the same evaporator and associated fluid-forcing means is drawn into the evaporator with the liquid readapted to deliver an evaporable liquid, containfrigerant delivered thereto so that the evaporaing a relatively non-evaporable lubricant, to said tor at no time contains enough lubricant to imevaporator, said evaporator being formed to pro- 50 pair its efilciency. vide a main evaporating chamber and a riser,

In Fi u I h v Sh wn n r n n connected below its upper end with the main wh rein th conduit 59 p e into 851111111 pevaporating chamber, whereby the presence of tacle 6 which may be mounted on the evaporaliquid in the main chamber will normally maini All le co t 53 extends from the tain'liquid at a predetermined level in said riser, 55 receptacle 6| and enters the'suction line. In an exhaust connection on the main evaporating this embodiment, it is unnecessary to extend the space of the evaporator, at a point above the norconduit 59 and coil the same in order to ensure mal liquid level therein, said connection leading the entire evaporation of the refrigerant conto said fluid-forcing means whereby gases, stituent of the liquid withdrawn from the duct evolved by the evaporation of liquid in the main 51, since the receptacle 6|, into which the liquid evaporator space, may be drawn to the fiuid-forcis delivered, is of a size to permit heat transfer, ing means, an outlet in said riser substantially to the liquid therein, with sufficient rapidity to at the liquid level normally maintained therein ensure the entire evaporation of the refrigerant whereby to; permit liquid, containing lubricant, w

constituent thereof while the same is in the to enter said outlet and whereby the evolution receptacle. Consequently, the receptacle will be of gases in said riser by the evaporation of the filled primarily with evaporated refrigerant with liquid therein will 'cause the liquid level in the a film of liquid in the lower portions of the recepriser to drop below said outlet at intervals where- I tacle. The end of the ejector pipe '63 is dis- .by to prevent escape of liquid continuously i through said outlet and to permit the evolved gases in said riser to escape through the outlet and" thuspermit the liquidto again rise above the same, and means connecting said outlet with through the pipe H as rapidly as the the exhaust connection whereby-the liquid and 15 the main evaporating chamber and adapted to receive liquid to a fluctuating level from the main evaporating chamber, an outlet in said riser substantially at the liquid level maintained in said riser, whereby said outlet may automatically be exposed above and submerged below said fluc- 'tuating liquid level and a conduit connecting said outlet with the fluid-forcing means whereby liquid, containing lubricant, may be withdrawn from said riser and delivered through the conduit to the fluid-forcing means whenever the outlet is submerged, said conduit extending in heat exchange relationship with a zone capable of supplying heat thereto to cause substantial evapora- =tion of the evaporable constituent of the liquid passing therethrough before the same reaches the fluid-forcing means in order that the lubricant may be separated from the evaporable liquid and delivered in separated condition to the fluidforcing means.

4. A refrigerating apparatus comprising an evaporator and associated fluid-forcing means adapted to deliver an evaporable liquid, contain- 'ing a relatively non-evaporable lubricant, to said evaporator and to withdraw, from the evaporator,

gases evolved by the evaporation of the liquid therein, said evaporator being formed to provide a main evaporating chamber connected with the fluid-forcing means above the liquid level therein,

, and a riser connected below its upper end with .end connected with the wh ereby liquid, containing lubricant. may be ,withdrawn from said riser and delivered through the conduit to the fluid-forcing means, said conthe main evaporating chamber and adapted to .receive liquid from the main evaporating chamber to a fluctuating level in said riser, an outlet in said riser substantially at the liquid level maintained in said riser, and a conduit connected at one end with said outlet and having a remote fluid-forcing. means duit being arranged in serpentine coils toincrease its efiective length, between said outlet the remoteend of said conduit, sufliciently to ensure the substantial evaporation of the evaporabie 'constituent of the liquid traveling the conduit before the same reaches 3- remote end thereof. ..5. A refrigerating atus comprising an evaporator and associated fluid-forcing means adapted to deliver an evaporable liquid, containing a relatively nonevaporable lubricant, to said evaporator and to withdraw, from-the evap- -'orator, gases evolved by the evaporation of the liquid therein, said evaporator being formed to provide a main evaporating chamber connected with the fluid-forcing means abowe' the liquid level therein and a riser connected below its upper en diwith the main evaporating chamber and adapted to receive liquid from the main craps crating chamber to a fluctuating levelin said risen an outlet in said riser substantially at the liquid level maintained in said riser, whereby said outlet may automatically be exposed above and submerged below said fluctuating liquid level, means forming a separator chamber, and means connecting said chamber with said outlet whereby liquid; containing lubricant, may be withdrawn from said riser, wherever the outlet is submerged, and delivered to the separator chamber, said chamber being arranged to permit evaporation of the evaporable constituent of the received liquid and the separation therefrom of the lubricant in said chamber, and means associated with said chamber for returning the separated lubricant and the evaporable constituent to the fluid-forcing means.

6. A refrigerating apparatus comprising an evaporator and associated fluid-forcing means adapted to deliver an evaporable liquid containing a relatively non-evaporable lubricant to said evaporator, said evaporator being formed to provide tin evaporating space, an exhaust connection communicating the fluid-forcing means with said evaporating. space above the liquid level therein whereby gases, evolved by the evaporation of liquid in said evaporating space, may be withdrawn therefrom and returned to the fluid-forcing means, a conduit connected with said evaporator in position to receive liquid, containing lubricant-and return the same to the fluid-forcing means, the intermediate portions of said conduit being disposed in heatexchange relationship with said exhaust connection whereby to utilize the heat in the gases traveling therethrough to cause evaporation of the evaporable constituent of the liquid traveling the conduit so that the lubricant may be separated and returned to the fluid-forcing means in separated condition.

'I. A refrigerating apparatus comprising an evaporator and associated fluid forcing means adapted todeliver an evaporable liquid containing a relatively non-evaporable lubricant to said evaporator, mid evaporator being formed to provide spaced evaporating chambers and a plurality of interconnected ducts between said chambers, one of said ducts being closed at one end to communication with one of said chambers but in communication with the other of said chambers, whereby the fluid pressure of the liquid in the other ducts and in said other chamber will normally maintain the liquid at a predetermined level'in said closed duct, an outlet in said' duct the liquid level normally maintained therein whereby to permit liquid containing a Iubricant'to enter said outlet, an exhaust connection between said fluid forcing means and the evaporating chambers at a point above the normal liquid level in the evaporator whereby gases evolved by the evaporation of the liquid inthe evaporating chambers may be drawn to the fluid forcing means and means connecting said outlet with said exhaust connection.

8. In the combination-of claim 7 wherein the means connecting the outlet with the exhaust connection comprises a coil of tubing encircling said exhaust connection.

9. In the combination of claim 7 wherein the means'connecting the outlet with the exhaust connection comprises a receptacle mounted on the evaporator, a. conduit connecting said rejceptacle to said outlet and a conduit connecting said receptacle to said exhaust connection.

v HOWARD M. 'lm- In :ou-l ,j,

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