US1985785A - Refrigerating apparatus - Google Patents

Description

Dec. 25, 1934. H. c. KELLOGG REFRIGERATING APPARATUS Original Filed June 10. 1929 2 Sheets-Sheet 1 ATTOE/VA-K 1366- 1934. H. c. KELLOGG REFRIGERATING APPARATUS Original Filed June 10. 1929 2 SheetsSheet 2 r h m w d W fivw-wrae: h (1. #2647 fir ATraeA/EK tors of the flooded type.

Patented I, Dec. 25, 1934 UNITED STATES REFRIGERATING APPARATUS Herbert G. Kellogg, Detroit, Mich., assignor to Temprite Products Corporation, a corporation of Michigan Application June 10, 1929, Serial No. 369,669.

Renewed January May 19, 1930 14 Claims.

The invention has to. do more particularly with refrigerating apparatus for cooling liquids, though in some of its aspects it is not limited to liquid cooling.

One of the objects of the invention is to lengthen the cycle of operation of refrigerating systems and particularly of the refrigerating system of liquid coolers of the direct or instantaneous type, such as is disclosed in my United States Letters Patent No. 1,675,108.

A further object of the invention is the provision of a liquid cooling unit of the direct or instantaneous type that is characterized by great compactness, highly efficient operation and low cost of production.

Another object of the invention is to minimize the amount of refrigerant required for the operation of direct or instantaneous liquid coolers.

Another object of the invention is the provision of an improved means for controlling the action of refrigerant evaporators.

Other objects more or less incidental or ancillary to the foregoing as well as the manner of attaining the various objects will be set forth in the following description, having reference to the accompanying drawings which illustrate preferred embodiments of the invention.

In the drawings, Fig. 1 is a diagrammatic view of a refrigerating system embodying my improvements and which is particularly designed for liquid cooling.

Fig. 2 is a vertical sectional view on an enlarged scale of one of the cooling units of the system illustrated by Fig. 1.

Fig. 3 is a fragmentary detached view of a detail of the construction shown in Fig. 2,

Fig. 4 is a section on the line 4--4, Fig. 2.

Fig. 5 is a vertical sectional view onan enlarged scale of the second cooling unit of the system illustrated in Fig. 1.

Referring in detail to the construction illustrated, and first to the apparatus illustrated in Figs. 1 to 5, 1 and 2 designate as entireties liquid cooling units of the direct or instantaneous type.

' 3 is a refrigerant compressor which may be of any suitable known form of construction and 4 is an electric motor by which the compressor is driven through a belt 5. 6 is a condenser which may be cooled by water circulation or in any other known manner. .A conduit 7 connects the discharge passage of the compressor with the condenser 6. As will later more fully appear, the liquid cooling units 1 and 2 are in effect evapora- A conduit 8 connects the condenser 6 with the liquid refrigerant inlet In Germany of each of the units or evaporators 1 and 2, and a conduit 9 connects the inlet or suction opening of the compressor 3 with the discharge passages of the units or evaporators 1 and 2. 10 is an equalizing tank or chamber which communicates through a conduit 11 with the suction conduit 9. This tank is designed to have a relatively large capacity in comparison with the capacity of the return or suction conduit 9 and this may be achieved either by making the tank 10 of adequate size or a tank of smaller size may be employed and the desired effective capacity secured by providing in the tank a solid adsorbent material adapted to adsorb the gaseous refrigerant. When the available space is limited I prefer to make use of such adsorbent material as the equalizing tank or chamber can then be made of quite moderate size, and in the construction illustrated the tank 10 is filled with a suitable adsorbent material 12 such, for example, as adsorbent carbon, silica gel, or the like. To give the gas ready access to the entire body of adsorbent material the tank 10 is provided with an axially arranged foraminous tube 13 with the lower end of which the conduit 11 is connected. The operation of the compressor, as is usual in apparatus of this character, is intermittent and in the construction illustrated it is controlled by an automatic switch 14 which may be of any suitable known construction and which is actuated by the pressure of the gaseous refrigerant in the suction conduit 9 with which the pressure chamber of the switch 14 communicates through a conduit 15. Such switches are well known and are commonly adjustable, as hereinafter indicated, to cut in and cut out at various refrigerant pressures or temperatures. 16 is the usual manual switch for throwing the entire apparatus into or out of operation. The conduits 8 and 9 are shown broken awaybetween the cooling units 1 and 2 to indicate that the cooling units may be installed at some distance from each other. Furthermore the system may include additional cooling units of the character of those illus-' trated, as is indicated by the extension of the conduits 8 and 9 beyond the unit 1. The showing of two of the cooling units is deemed sufficient to indicate the character of the system.

Referring now in further detail to the con struction of the cooling units, the cooling unit 1 comprises an evaporator casing structure 1'7 made up of a drawn steel shell 17 constituting the top" and the cylindrical side walls of the casing and a bottom wall 17, the lower end of the shell 1'7 and the wall 1'7 being formed with a folded and soldered gas tight joint of well known character.

The bottom wall 17 is formed with radial corrugations to stiffen andstrengthen it. A threaded bushing 18 is mounted in a central aperture in the top wall of the shell, the joint between the parts being soldered as indicated to form a gas tight joint. In the bushing 18 is mounted a liquid refrigerant fitting 19 which is threaded to engage the threads of the bushing 18 and is provided with a soft metal packing 20 to make the joint between the parts 18 and 19 gas tight. The lower part of the fitting 19 is in the form of a depending tube 19 which carries at its lower end an inlet valve mechanism consisting of a valve seat member 21 and a threaded cap 22, which engages the threads on the lower end of the tube 19, and a needle valve 23 which is arranged to engage the valve seat and has a depending stem 23* projecting through an aperture in the end wall of the cap 22. The cap serves to tightly secure the valve seat member in the end of the tube 19 and to limit the movement of the valve. A tubular wire gauze strainer 24 is secured to the end of the valve seat member 21 and projects upwardly in the tube 19 so as to prevent any foreign particles in the refrigerant entering the tube 19 from passing the needle valve. A manually operable cut-off valve device 25 is screwed into the threaded upper end of the fitting 19. As this cut-off valve is not essential to the present invention, its construction need not be described. The said fitting has its inlet 25 connected to the liquid refrigerant pipe 8, as shown in Fig. 1.

The inlet valve 23 is operated by an opentopped, cup-shape float 26 which has an upstanding tube 26 secured with a tight joint toa central aperture in the bottom wall of the float and thus serves as a tubular guide which loosely engages the depending tube 19. A strap 26 is secured to the under side of the fioat and serves to engage the lower end of the valve stem 23 so as to lift the valve and press it against its seat when the liquid level in the shell rises or to permit the. valve to move away from its seat when the said liquid level falls. The needle valve 23* is turned from triangular rod stock leaving flat sides on the valve which permit liquid refrigerant to pass the valve and enter the chamber of the shell through the aperture in the lower end of the cap 22.. The float 26 is designed to maintain a liquid level in the evaporator well below the top rimof the float as indicated by the line ab in Fig. 2.

A threaded bushing 27 is secured in the top wall of the shell adjacent the bushing 18 and carries a depending tube 28 which projects downward into the cavity of the fioat 26 and has its open lower end adjacent the bottom wall of the fioat. The tube 28 is designed to serve as an outlet for evaporated refrigerant and the bushing 27 is connectedto the compressor suction pipe 9 through the casing of an automatic cut-off valve device indicated in its entirety by 29.

The valve device 29 has a cylindrical main casing member 30 with a threaded inlet nipple 30 adapted to engage the shell fitting 2'7 and a threaded outlet nipple 30 adapted to connect with the suction pipe 9. The shoulder 31 at the inlet end of the discharge nipple 30 serves as a seat for a valve 32 having an elongated stem 32. A disk 33 is rigidly secured to the valve 32 with a gas tight joint. At the open end of the valve casing member 30 is arranged a disk 34' which is clamped between the member 30 and a. casing cover member 35 which is threaded on the member 30. The disk 34 should be secured in the casing with a gas tight joint and this may be accomplished with the soft metal gasket 36. A metallic bellows 37 is interposed between the disks 33 and 34 and has its ends hermetically secured to peripheral parts of said disks. A coiled spring 38 is interposed between the disk 33 and an adjustable abutment ring 39 which is mounted in a central aperture in the disk 34. The stem 32 of the valve slidably engages the aperture in the abutment 39 to guide the valve. The casing cover 35 is formed with a central threaded aperture to receive the threaded stem of a knurled screw 40 which is adapted to control the action of the valve 32. The inner end of the device 40 is formed with a socket 40 into which the adjacent end of the valve stem 32*- projects. By screwing in the device 40 the valve 32 can be forced against its seat and when the device 40 is retracted more or less it serves as a stop to limit the opening movement of the valve 32.

It will be seen that the space surrounding the disk 33 and the bellows 37 is open to the gas or vapor pressure within the evaporator shell 17 and when this pressure rises sufliciently .to overcome the pressure of the spring 38 it forces the valve 32 off its seat and on the other hand when the pressure in the evaporator falls below the point or value referred to, the valve 32 is closed by the action of the spring 38. The vapor pressure at which the valve will open and close can be varied by adjusting the abutment 39 to vary the tension of the spring 38. Obviously the movement of the screw 40 to positively close the valve 32 or vary its opening movement, does not affect the adjustment of the abutment 39 which determines the tension of the spring 38 and consequently also the pressure and temperature at which the valve 32 is automatically closed or opened.

The evaporator shell 17 has a top aperture in which is secured a threaded pipe fitting 41 which is adapted to connect with a water or other liquid supply pipe 42, the fitting having a gas tight connection with the shell and being mechanically secured by a sleeve 43 and a nut 44. The shell 1''! also has a top aperture in which is secured a threaded pipe fitting 45 adapted to connect with a liquid discharge pipe 46, the fitting 45 being mounted in the shell in the same manner as the fitting 41. Within the shell 17 are a pair of liquid cooling coils 47 and 47*, the inner coil 4'7 being connected at its upper'end at 41 to the inlet fitting 41 and being connected at its lower end to the lower end of the outer coil 47 while the upper end of the latter is connected to the outlet fitting 45 at 45. Except where the coils 4'7 and 4'7 are connected with the fittings 41 and 45 the coil tubing is drawn into an out-of-round shape approx imating in transverse section the figure 8, the object of this form of the tubing being to permit expansion of the walls of the tube in case the tem; perature of the liquid in the coils should accidentally be carried below the freezing point of said liquid.

Centrally arranged in the lower part of the chamber within the shell 17 is an inner shell 48 which is gas tight and made of relatively light sheet metal, this inner shell serving to occupy the major part of the space below the float .26 and within the inner coil 47 with the result that the cubical capacity of the shell 17 is considerably reduced and the amount of liquid refrigerant necessary to submerge the major part of the cooling coils. 47, 4'7 is minimized. A pressure equalizing tube 49 communicates at one end with the interior of the chamber within the inner shell of the tube 49 being preferably bent back upon I 48 and at its other end with the gas or vapor space in the upper part of the shell 17, the upper end itself as indicated in Fig. 3 so as to make it difiicult for liquid refrigerant to enter the .tube and find its way into the shell 48. By equalizing the pressure inside and outside of the shell 48 the walls of the latter can be made of considerably lighter metal than would otherwise be possible, thus reducing cost. At the same time, the space within the shell 48 is made a part of the effective vapor space of the evaporator.

Within the shell 48 'is a tube 50 which is bent at right angles with one part extending upward through the top wall of the shell 48 and its open end in communication with the liquid refrigerant space, while the other, horizontal part of the tube extends through the side wall of the shell 48 near the bottom of the latter to communicate with the liquid refrigerant space in the lower section thereof. The object of the tube 50 is to provide a conduit for the free flow of liquid refrigerant from the central region directly below the inlet valve to the lower part of the liquid refrigerant space. I have found that in refrigerant evaporators having passageways for the circulation of the liquid and gaseous refrigerant between the different levels, the efficiency of the evaporator may be greatly reduced by the lodging in such passageways of bubbles of refrigerant gas or vapor. The walls of these bubbles cling to the passage walls and by obstructing the passages bubbles prevent liquid refrigerant from passing either upward or downward with the result that substantial sections of the metallic walls through which heat should be conducted into the liquid refrigerant are rendered ineffective for that purpose because of the lodging of the bubbles of gas or vapor and the resultant failure of the liquid refrigerant to contact with the full surface of the metal walls through which the heat must pass to the said refrigerant. Such an action tends to occur in liquid cooling units of the character of those herein disclosed, the bubbles of gas or vapor lodging between the inner and outer coils and between said coils and the adjacent walls of the evaporator. In the construction illustrated this is prevented because, when vigorous evaporation occurs in the lower part of the liquid space of the evaporator, the bubbles that form and tend to rise in the liquid are not prevented from doing so, because the tube 50 serves to freely conduct liquid refrigerant from the higher level near the center of the evaporator where ebulli'tion is less active downward to the lower part of the liquid refrigerant space where it can replace liquid that tends to rise during the ebu'llition and also serves to provide a solid liquid column which more than counter-balances the columns of mixed gas and liquid in the passageways through which the gas seeks to escape upward, so that the bubbles are forced upward and cannot lodge in the said passageways. The result is that in the cooling units herein described the liquid refrigerant is kept in contact with the surfaces of the cooling coils to a maximum extent and the efficient action of said coils thereby insured. It is to be observed,

that the conduit or passage which is to. perform the function of the tube 50 must either be of such a large caliber that any bubbles incident to evaporation of liquid passing through the conduit cannot readily lodge on or cling to the inner surface of the conduit, or it must be sodisposed in the structure that it is not open to the absorption of heat so that formation of bubbles within it is obviated. In the construction illustrated the latter condition holds. V

The cooling unit 2, shownindetail in Fig. 5, is of the same general character as the cooling unit 1 already described but differs from it in some respects. It has an evaporator shell or casing 51 of the same character as the shell or casing of the first cooling unit, but the shell is of greater height in order to provide increased cooling capacity. mounted a liquid refrigerant inlet fitting 52 with which is connected a cut-off valve fitting 53 having an inlet 53 adapted to connect with the 'liquid refrigerant conduit 8. The fitting 52 com? prises a tubular depending portion 52 which is fitted with an inlet valve which is of thesame In the top wall of the shell 51 is' character as that shown and described in con nection with the cooling unit 1 and which there- 'fore is not shown and described in detail in con nection with the unit 2. An open-topped.,cup-,

shape float 54, which also is of the same characterli."

as the float of the cooling unit 1 is mounted upon the depending tube 52 and serves to actuatethe' valve therein.

The top wall of the shell 51 is provided with a gaseous refrigerant outlet fitting 55 which carries a depending tube 56 which projects downward into the cavity of the float and has its openlower end near the bottom of the float. l-.An automatic cut-off device 5'1 which is of exactly the same character as the cut-ofi device 29 of the first cooling unit, hasi'ts 7 connected with the fitting 55 and ha a on 57lfito which is connected one end'EO l? which-extends downward along the side shell 51 and is connected at itsiqwer' to a T-fitting 59, one branch of which's c n cted to the compressor suction pipe 11f" Within t e mai shell 51" is an inner shell 60 comprisingtopand sidewalls drawn from a single sheet of metal sufficiently heavy to withstand any pressures to be met in the evaporator, the side wall of the shell '60 being. connected at its lower open end to the bottom wall of the outer shell 51 by welding or the like so as to form a gas tight joint. This inner shell, as in the case of the inner shell 48 of the first described cool-v ing unit, forms in effect a reentrant section of through the side wall of the shell 60 to communicate with the liquid refrigerant space at thebottom of the shell 51. The bottom wall of the shell 51 has a central aperture which is provided with a thimble 62 in which is threaded a pipe fitting 63 which connects at its lower end with one branch of the T-fitting 59 and which carries an upwardly extending foraminous tube 64 which is preferably disposed on the axis of the inner shell 60 and extends nearly to the top wall of the latter. Within the inner shell 60 is disposed a mass of adsorbent material 65 such as adsorbent carbon, silica gel, or the like, which is of the same character as the adsorbent material 12 in the equalizer tank previously described and which thus serves to supplement the capacity of the latter. As shown in Fig. 5, the adsorbent material 65 is arranged in layers with interposed layers 66 of fibrous material such as mineral wool or the like.

An inlet fitting 67 for liquid to be cooled is secured to the top wall of the shell 51 by means of a header fitting 68 within the shell, the fitting 68 having a threaded nipple 68 on which thefittingfi'l is screwed so as to tightlysecure the two fittings to the shell. In the lower part of the shell'is a header 69 which projects through the sidewall of the shell and has a liquid outlet fitting'f'IO connected to it. Within the shell are three liquid cooling coils 71, 72 and 73 which are coaxially arranged and have their upper ends connected to the header 68 and their lower ends connected to the header 69, said coils thus being connected in parallel between the two headers. As in the first described cooling unit the coils '71, 72 and 73, except at the ends where they connect with the headers, are formed out-ofround in cross section in the manner and for the purpose above described.

Any one of various commonly used refrigerants, such as sulphur dioxide, methyl chloride and ethyl chloride, may be employed in my improved apparatus. Lubricating oils which are suitable for lubricating the compressor are more or less soluble in most if not all of the preferred and commonly used refrigerants such as those mentioned. Thus suitable mineral oil lubricants are partially soluble in sulphur dioxide and are completely soluble in methyl chloride and ethyl chloride, at least within the limits of the proportions of oil and refrigerant normally employed. On account of this solubility, the liquid lubricant which is scrubbed past the compressor piston and discharged into the condenser, dissolves in the refrigerant liquefied in the condenser and passes, in solution, with the latter into the evaporator. Then when the refrigerant is evaporated the oil is left and accumulated in the evaporator so that provision must be made for its return to the compressor. In the two cooling units above described this is accomplished in the manner disclosed in the copending application this applicant and Edward M. May, Serial No. 295,174 filed July 25, 1928, (Patent No. 1,885,836).

Assuming that the above described apparatus has been assembled and a suitable amount of refrigerant, such for example as sulphur dioxide, together with a suitable amount of lubricant, such for example as a suitable mineral oil, have been charged into the system; and assuming further that the liquid coolers are being employed for cooling drinking water, the operation of the apparatus is as follows. A commonly desired temperature for drinking water is 50 F. To secure an average temperature for the water of 50 F. the switch 14 may be set to start the compressor when the temperature of the refrigerant in the cooling unit rises to 53 F. and to stop the compressor when said temperature falls to 47 F. This will tend to keep the refrigerant in the cooling units at the average temperature of 50 F.; and if the length of the cooling coils are properly proportioned to the rate of draft of the water and to its entering temperature, the water issuing from the cooling coils will be at approximately the same temperature as the liquid refrigerant surrounding the coils. When, now, water is drawn from the discharge pipe of one or more of the cooling units, relatively warm water. say, for example, at 80 F., entering the cooling coils of such unit or units gives up its heat through the walls of the coils to the liquid refrigerant in contact with the coils with resultant evaporation of the refrigerant and a corresponding rise of the pressure in the evaporator and in the return or suction conduit 9. When the rise of pressure continues to a certain point corresponding to the temperature of 53 F. it causes the operation of the switch 14 to close the electric-circuit and start the operation of the compressor 3. The compressor draws the gaseous refrigerant from the evaporator or evaporators thus reducing the pressure therein and increasing the rate of evaporation of the liquid refrigerant in the evaporator and such evaporation is continued while water is being drawn through the cooling coils. When the draft of water ceases the compressor continues in operation until the pressure in the suction conduit 9 falls to the point corresponding to the temperature of 47 F. in the evaporator at which the switch 14 operates to stop the compressor motor. In liquid cooling systems such as that described in which there is a heat interchange between the liquid to be cooled and the liquid refrigerant directly through the single metal wall of a conduit, the interchange is rapid and the natural tendency is for the vapor pressure in the evaporator, and consequently in the suction line leading from the evaporator to the inlet of the compressor, to rise correspondingly rapidly with the resultant relatively prompt starting of the compressor as just described; then as soon as the draft of water or liquid being cooled ceases, the warm water which then remains in the cooling coils, tends to have its temperature lowered relatively rapidly so that the pressure in the evaporator falls and stops the compressor relatively promptly. In other words, as systems of this character have heretofore been constructed and operated they are more or less subject to what has been termed short cycling. In my present apparatus short cycling, with the attendant extra wear upon some parts of the apparatus incident to frequent starting and stopping, is effectively avoided by the provision, in connection with the suction conduit of the compressor, of one or more equalizing tanks or chambers and preferably, though not necessarily, these latter are provided in combination with automatic cutoffs such as those which are shown at 29 in Fig. 2 and at 57 in Fig. 5. Referring first to the effect of the equalizing tanks or chambers alone it will be seen that when there is a sufficient draft of water to cause starting of the compressor the operation of the compressor will continue after the draft of water has stopped for a considerably longer period of time because the greater capacity of the low side of the system which results from the provision of the equalizing chambers necessitates the removal of a considerably larger mass of refrigerant vapor in order to reduce the pressure and temperature in the evaporator chambers to the cut-out point of the switch 14. Furthermore, when the pressure and temperaturehave been so reduced and the compressor stopped, upon further draft of water the starting of the compressor again will be correspondingly delayed because an increased amount of evaporation corresponding to the increased capacity of the low side of the system must occur before the pressure and temperature rise to the cut-in point of the switch 14. Obviously the result is to cause operation of the compressor for longer but less frequent periods. This result can be secured to a higher degree by the addition of adsorbent material in the equalizing chambers because such material very greatly increases the effective capacity of said chambers or permits use of correspendingly smaller tanks. The action of the adsorbent material is to adsorb large amounts of the refrigerant gas or vapor during the first part of the period of evaporation and before the compressor has been started, and then, after evaporation has ceased and the operation of the compressor is continuing to reduce'the pressure in the low side of the system, the adsorbent material gives up the adsorbed gas or vapor under the suction effect of the compressor and is thus placed in condition to again adsorb large amounts of the gas or vapor when another period of evaporation follows.

The automatic cut-off devices 29 and 57 are provided primarily in order to prevent the freezing up and possible injury of the cooling coils in case an uninformed attendant should improperly adjust the switch 14 in a manner to carry the temperature in the cooling units below the freezing point of water. The automatic cut-off devices 29 and 57 are initially adjusted at the factory so that their valves effectively close the passage between the evaporators and the suction inlet of the compressor at evaporator pressures corresponding to temperatures safely above the freezing point of water and preferably slightly below the cut-out temperature of 47 F. at which the switch 14 should properly operate, say for example F. The cut-oil devices, having thus been adjusted, have their casings permanently sealed at the factory so that it is, practically speaking, impossible to tamper with them. If, now, an attendant improperly adjusts the control switch 14 in the manner stated, for example so as to keep the compressor running until the temperature would be lowered to say 25 F., the cut-off devices 29 and 57 operate, when the temperature has fallen to 45 F. to close the suction passage between the compressor and the evaporating chambers of the cooling units. The continued operation of the compressor then has no further effect upon the temperature of the cooling units. It does, however, continue to reduce the pressure in that portion of the low side of the system between the cutoff devices 29 and 57 end the compressor, including the equalizing chambers, until a pressure corresponding to the predetermined temperature of 25 F. is attained.

Thus by combining the automatic cut-oil devices with the equalizing chambers I not only prevent freezing up of the cooling coils by improper adjustment of the control switch but at the same time gain the advantage of increased refrigerant capacity in the low side corresponding to the relatively low cut-out temperature at which the switch 14 is set. Indeed, in some cases where it is not feasible or convenient to provide equalizing chambers of suflicient capacity to prevent the objectionable short cycling, the desired result can be secured with my improved system with equalizing chambers of very moderate capacity by intentionally setting the control switch 14 to cut out at a pressure well below the pressure corresponding to the temperature which it is desired to maintain in the evaporators, and relying upon the automatic cut-out devices to insure that the temperatures in the evaporators shall not be carried below the desired point. In such method of operating the apparatus the switch 14 may be set to cut in and start the compressor at any pressure which is not higher than the saturated vapor pressure corresponding to the maximum predetermined temperature of the evaporator and which at the same time is enough higher than the cut out pressure of said switch to sufficiently prolong the idle and working periods, respectively, of the compressor. And in such operation the cut- oil valves 29 and 57 may well be set to close and open more nearly at the predetermined minimum temperature of the evaporator. For example, if 50 F. water is desired from both evaporators and the switch is set to cut in at a pressure corresponding to 53 F., the valves may be set to close-and open at approximately 47 F. On the other hand, if 50 F. water is desired and the switch is set to cut in at some pressure below that corresponding to 50 F., the cut-off valves 29 and 57 should be set to close and open at approximately 50" F. The essential considerations in this method of operation or control are that the switch 14 shall be adapted to start the compressor when the pressure in the conduit 9 rises above a predetermined value within a range not extending higher than the vapor pressure corresponding to the maximum predetermined temperature of the evaporator and to stop the compressor when the pressure in the conduit 9 falls below a predetermined value which is within a range below the pressure (or pressures, in the event the evaporators are to operate at different temperatures) at which the cut-off valves 29 and 57 operate and which is also enough lower than the cut-in pressure of the switch to sufllciently prolong the idle and working periods of the compressor, as above noted.

It will be understood that the last described method of operating my improved apparatus is not limited to the use of equalizer chambers of moderate capacity, since obviously the advantage incident to this method of operation or control can be secured to a still higher degree by the use of equalizing chambers of larger size.

While the automatic cut-out devices 29 and 57 are adapted to prevent freezing of the cooling coils if the apparatus is handled in any manner within reason, to render the apparatus still further proof against unreasonable abuse, the cooling coils are made with the out-of-round section previously described and are thus adapted to safely withstand many freeze-ups.

It will be observed that the hand screw 40 with which the cut-off devices 29 and 57 are provided affords a very simple and inexpensive yet effective means for manually closing the suction outlet of the evaporators or cooling units in case it is necessary for purposes of inspection or repair or adjustment to break the connections between the evaporators and the compressor. The screw device 40 also serves, as has been stated, as a stop to limit the opening of the cut-off valves so that there is no possibility of injuring the metallic bellows 37.

The larger cooling unit 2 affords a construction that lends itself well to the requirements of many installations since it provides an equalizing chamber within a self-contained cooling unit structure. However, when the cooling units required in any particular installation are of too small a size to make it advantageous to include the equalizing chamber within the cooling unit, it is usually feasible to provide an equalizing chamber of a capacity adequate to serve all of the cooling units and such an equalizing chamber can usually conveniently be installed in conjunction with the compressor-condenser set, as in the case of the equalizing tank 10 shown in Fig. 1.

The construction and operation of the cooling units 1 and 2 present other novel aspects which will now be referred to, with reference first to the cooling unit 1. The float valve mechanism employed is similar to that which is fully set forth in the copending application of Kellogg and May, Serial No. 295,174, above referred to and for the purposes of the present application it will sufiice to describe the operation briefly. A relatively slight rising and falling movement of the float 26 serves to control admission of liquid refrigerant past the valve 23 in a manner to replace refrigerant evaporated and maintain a normal or quiescent liquid level as indicated by the line ab. The lubricant oil which is used to lubricate the compressor in the operation of the latter is scrubbed past the compressor piston and thus finds its way into the condenser where it dissolves more or less completely in the liquid refrigerant, depending upon the particular refrigerant used. In the case of sulphur dioxide, for example, the mineral oil employed is soluble to a limited extent therein. Hence lubricant enters the evaporator dissolved in the liquid refrigerant. When the latter evaporates the lubricant is left behind and being lighter than the lubricant rises and forms a distinct stratum at the top of the body of liquid. It is necessary'for obvious reasons to insure the return to the compressor of the lubricant thus accumulating. In the present apparatus this may be accomplished in either or both of two ways which will now be mentioned. In the operation of the system, when the evaporator is first started with the resultant relatively rapid lowering of the pressure in the evaporator, ebullition begins and bubbles of gaseous refrigerant start to rise through the body of the liquid refrigerant. These bubbles, by reason of the space occupied by them, raise the liquid level in the evaporator and this effect is especially marked at the beginning of the ebullition before any of the bubbles have had time to travel to the surface of the liquid and escape into the vapor space above the liquid. The resuit is a temporary marked rising of the liquid level with a subsequent partial subsidence of the level. By properly designing the height of the side walls of the float above the normal liquid level the temporary rise of the liquid at the beginning of ebullition can be taken advantage of to cause an overflow of some of the stratum of oil at the top of the liquid into the cavity of the float from whence it is drawn by the suction effeet in the tube 28 and carried back to the compressor where it again performs its lubricating function.

As the ebullition continues after the initial rise and subsidence of the liquid level, as above described, particularly if the ebullition is vigorous, the continued breaking of refrigerant vapor through the upper stratum of the liquid causes foam ng of the liquid to such an extent that a considerable mass of foam builds up around the sides of the float until some of it falls over into the float. This foam is made up of gaseous refrigerant and sufficient liquid to form the walls of the small bubbles constituting the foam, and this liquid consists almost entirely of lubricant. The result is that inthis additional manner lubricant is separated from the mass of liquid in the evaporator chamber and carried into the cavity of the float from whence it is drawn in the manner above stated back to the compressor. If desired this latter action may be relied upon entirely to return the lubricant from the evaporator o the compressor. That is to say, even if the top edge of the float is high enough above the normal liquid level at a.b to prevent the initial overflow of oil as first described above, the building up of the mass of foam in the manner stated will serve to separate the excess lubricant from memes the liquid refrigerant and bring about its return to the compressor.

When use is made of a refrigerant, such as methyl chloride, in which mineral oil is completely soluble, at least in the proportions in which lubricant and refrigerant are commonly employed in apparatus of the character in question, the lubricant of course does not separate from the liquid refrigerant by gravity and rise to the top of the liquid bath. Consequently it is not feasible in that case to rely upon the initial rise of the liquid level to cause liquid lubricant to spill over into the float, but reliance must be placed upon the foaming action which has been described. In the case of methyl chloride, as well as in the case of sulphur dioxide, the formation of the bubbles making up the mass of foam appears to have a selective action on the lubricant, doubtless because the surface tension of the lubricant adapts it to form the walls of the bubbles.

While the lubricant which is separated in either or both of the ways above described from the liquid refrigerant and carried over into the float is almost pure lubricant, it does carry in solution slight amounts of liquid refrigerant and one of the objects aimed at in the present invention is to more fully insure complete evaporation of any such liquid refrigerant carried in such solution before it can be drawn out of the evaporator chamber. This I have accomplished by disposing the inlet end of the section of the coil 4'7 of the cooling unit 1 immediately adjacent the upper part of the side wall of the float. Thus lubricant, either in the form of liquid only or in the form of foam, rising to the top edge of the float must pass over the adjacent surfaces of the coil 47 which are at a relatively high temperature because of the temperature of the entering water which has not yet had opportunity to give up its heat to the liquid refrigerant. Consequently any small amounts of liquid refrigerant dissolved in the lubricant is evaporated therefrom as the latter rises to flow over into the float and a correspondingly high evaporative efficiency is secured.

The cooler 2 presents the same features of construction and operation that have just been described in connection with the cooler 1. That is to say, the float valve mechanism of the cooler 2 operates in the same manner as that of the cooler 1 to maintain the liquid level and to return lubricant from the cooling unit back to the compressor; and the arrangement of the cooling coils 71, 72 and 73 with their inlet ends or sections adjacent the float 54 has the effect of insuring complete evaporation of the liquid refrigerant, in the manner described above. Also the circulating tube 61 of the larger cooling unit functions in the same manner as the tube 50 of the smaller cooling unit.

The provision of a plurality of cooling coils connected in parallel as previously described is especially adapted to provide a cooler of large capacity. The concentric arrangement of the various parts of the cooling units makes possible a highly effective use of space with resultant compactness of the device. The annular form of the space provided for the coils, or substantial parts of the coils, also minimizes the amount of'liquid refrigerant necessary to secure effective application of the refrigerant to the coils. The coaxial arrangement of the coils of the cooling unit 1 and the connection of said coils in series as d'ethe advantage of bringing the inlet and outlet ends of the conduit adjacent the same end of the casing, thus materially facilitating both the initial connection of the conduit with inlet and outlet fittings of the casing and subsequent servicing of the apparatus.

As has been previously indicated a system such as has been described may include a'considerable number of cooling units which may be distributed about a building at points more or less remote from each other and from the compressorcondenser unit which serves all of them.

It should be understood that the constructions illustrated and described are presented for purposes of explanation and illustration and that they may be widely varied' without departing from the invention as defined in the appended claims.

What I claim is:

1. In refrigerating apparatus, the combination of means for liquefying gaseous refrigerant comprising a compressor and a condenser; an evaporator having an inlet for liquid refrigerant and an outlet for gaseous refrigerant; a conduit connecting the said inlet to the discharge of the condenser; a second conduit connecting the said outlet of the evaporator to the inlet of the compressor; avalve for controlling the flow of gaseous refrigerant through the second conduit and adapted automatically to cut off said flow when the temperature in the evaporator falls below a predetermined point and to re-establish the flow when the temperature again rises above said point; a chamber for gaseous refrigerant communicating with the second conduit between the said valve and the compressor and having a capacity that is large in comparison with the capacity of the remainder of that part of the low pressure side of the system on the outlet side of the said valve; and automatic means adapted to start the compressor when the pressure in the second conduit rises above a predetermined value below the vapor pressure corresponding to the predetermined maximum temperature of the evaporator and to stop the compressor when the refrigerant pressure in the said second conduit between the said valve and the compressor falls below a predetermined value below the pressure at which said valve operates and substantially lower than the pressure at which the compressor starts.

2. In refrigerating apparatus, the combination of means for liquefying gaseous refrigerant comprising a compressor and a condenser; an evaporator having an inlet for liquid refrigerant and an outlet for gaseous refrigerant; a conduit connecting the said inlet to the discharge of the condenser; a second conduit connecting the said outlet of the evaporator to the inlet of the compressor; a container for liquid to be cooled comprising a metal section having its wall in contact on one side with liquid refrigerant in the evaporator, whereby heat flows directly from the liquid to be cooled through said wall into the liquid'refrigerant; a valve for controlling the flow of gaseous refrigerant through the second conduit and adapted automatically to cut off said flow when the temperature in the evaporator falls below a predetermined point and to re-establish the flow when the temperature again rises above said.

point; a chamber for gaseous refrigerant communicating with the second conduit between the said valve and the compressor and having a capacity that is large in comparison with the ca pacity of the remainderof that part of the low pressure side of the system on the outlet side of the said valve; and automatic means adapted to start the compressor when the pressure in the second conduit rises above a predetermined value below the vapor pressure corresponding to the predetermined maximum temperature of the evaporator and to stop the compressor when the refrigerant pressure in the second conduit benecting the said inlet to the discharge of the condenser; a second conduit connecting the said outlet of the evaporator to the inlet of the com pressor; a valve for controlling the flow of gaseous refrigerant through the second conduit and adapted automatically to cut off said flow when the temperature in the evaporator falls below a predetermined point and to re-establish the flow when the temperature again rises above said point; a chamber for gaseous refrigerant communicating with the second conduit between the said valve and the compressor and having a capacity that is large in comparison with the capacity of the remainder of that part of the low pressure side of the system on the outlet side of the said valve; and adjustable means adapted automatically to start the compressor when the pressure in the second conduit rises above some predetermined value within a range below the vapor pressure corresponding to the predetermined maximum temperature of the evaporator and to stop the compressor when the refrigerant pressure in the said second conduit between the said valve and the compressor falls below a predetermined value within a pressure range below the pressure at which the said valve operates.

4. In refrigerating apparatus, the combination of means for liquefying gaseous refrigerant comprising a compressor and a condenser; an evaporator having an inlet for liquid refrigerant and an outlet for gaseous refrigerant; a conduit connecting the said inlet to the discharge of the condenser; a second conduit connecting the said outlet of the evaporator to the inlet of the compressor; a container for liquid to be cooled comprising a metal section having its wall in contact on one side with liquid refrigerant in the evaporator, whereby heat flows directly from the liquid to be cooled through said wall into the liquid refrigerant; a valve for controlling the flow of gaseous refrigerant through the second conduit and adapted automatically to cut off said flow when the temperature in the evaporator falls below a predetermined point and to re-establish the flow when the temperature again rises above said point; a chamber for gaseous refrigerant communicating with the second conduit betweenthe said valve and the compressor and having a capacity that is large in comparison with the capacity of the remainder of that part of the low pressure side of the system On the outlet side of the said valve; and adjustable means adapted automatically to start the compressor when the pressure in the second conduit rises above some predetermined value within a range below the vapor pressure corresponding to the predetermined maximum temperature of the evaporator and to stop the compressor when the refrigerant pressure in the said second conduit between the said valve orator and liquefying it; a suction conduit for conducting the gaseous refrigerant from the evaporator to the last named means; a conduit for conducting the liquefied refrigerant from the liquefying means to the evaporator; means for controlling the operation of the refrigerant liquefying means and thereby controlling the temperature in the evaporator; adjustable auxiliary control means, operable when the temperature in the evaporator falls below a point predetermined by the adjustment of said control means, to close the said suction conduit and thereby limit the cooling action of the evaporator; and manual means operable at will to hold the auxiliary control means in'its closed position without modifying the said adjustment thereof.

6. In apparatus for cooling liquids, the combination of an evaporator of the :flooded type; a compressor having its inlet connected to the evaporator to withdraw refrigerant gas therefrom; a condenser connected to receive compressed refrigerant from the compressor and deliver the liquefied refrigerant to the evaporator; a body of refrigerant in the closed system; liquid lubricant in the closed system soluble to at least some extent in the liquid refrigerant; areceptacle in the evapora-, tor having atop opening; a discharge passage leading from the said receptacle into the suction posed within the evaporator and having the inlet end of said coil disposed adjacent the opening of the said receptacle in the evaporator.

7. In apparatus for cooling liquids, the combination of an evaporator of the flooded type; a compressor having its inlet connected to the evaporator to withdraw refrigerant gas therefrom; a condenser connected to receive compressed refrigerant from the compressor and deliver the liquefied refrigerant to the evaporator; a body of refrigerant in the closed system; liquid lubricant in the closed system soluble to at least some extent in the liquid refrigerant; a receptacle in the evaporator having a top opening; a discharge passage leading from the said receptacle into the suction conduit of the compressor; means associated withthe evaporator for controlling admission thereto of liquid refrigerant and adapted to maintain in the evaporator a normal liquid level at a distance below the top opening of the said receptacle such that lubricant lifted by ebullition from the body of liquid in the evaporator can fall into the said receptacle; and a coil for liquid to be cooled disposed within the evaporator with a portion of it adjacent the opening of the said receptacle in the evaporator.

8. In apparatus for cooling liquids, the combination of an evaporator casing having a substantially cylindrical side wall; an inlet tube for liquid refrigerant mounted in a central aperture of the top. wall of the casing and projecting into the chamber thereof; a valve for controlling the passage of liquid refrigerant through said tube into the casing; an open-topped cylindrical cupshape float guided for vertical movement on said tube and adapted to actuate said inlet valve to maintain a predetermined liquid level in the casing; an outlet conduit for gaseous refrigerant extending through an aperture in the casing and having its inlet end disposed within the chamber of the float near the bottom thereof; and a cylindrical coil of tubing for liquid to be cooled disposed within the evaporator casing between the side walls of said casing and of the cup-shape float, said coil being connected to supply and discharge conduits extending through the wall of the evaporator casing.

9. In apparatus for cooling liquids, the combination of an evaporator casing structure forming an evaporator chamber with an annular space and a second chamber surrounded by said annular space and having communication with the evaporator chamber to receive gaseous refrigerant therefrom; means for admitting liquid refrigerant into the evaporator chamber; means for discharging gaseous refrigerant from the two chambers; and a coil for liquid to be cooled disposed in the annular space of the evaporator chamber.

10. In apparatus for cooling liquids, the combination of an evaporator casing the interior chamber of which has a reentrant bottom wall forming with the side wall of the casing an interior space annular in form; means for admitting liquid refrigerant into the said chamber; means for discharging gaseous refrigerant therefrom; a coil for liquid to be cooled disposed in the annular portion of the evaporator chamber; a second bottom wall forming a gas tight closure for the space partially enclosed by the reentrant bottom wall; solid adsorbent material in the last named spaceadapted to adsorb the gaseous refrigerant; and means for placing the said space in communication with the refrigerant vapor space of the evaporator casing.

11. In apparatus for cooling liquids, the combination of an evaporator casing having an interior chamber with a lower portion which is annular and a higher portion which is cylindrical; means for maintaining a body of liquid refrigerant in the annular and cylindrical portions of the said chamber; a coil for liquid to be cooled disposed in the annular portion of the chamber; and a conduit connecting the cylindrical portion of the chamber with the lower part of the annular portion of the chamber, the said conduit being adapted to permit free flow therethrough of liquid refrigerant from the cylindrical portion to the annular portion of the chamber without interference by gas or vapor bubbles.

12. In apparatus for cooling liquids, the combination of a substantially cylindrical evaporator casing; a. cylindrical shell of smaller size disposed within the side walls of the evaporator casing so as to form an annular space within the lower part of the latter; means for admitting liquid refrigerant to the interior chamber of the evaporator casing; means for discharging refrigerant gas therefrom; a coil for liquid to be cooled disposed in the annular portion of the casing chamber and submerged in the liquid refrigerant therein; and a pressure equalizing tube communicating at one end with the interior of the cylindrical shell and at the other end with the vapor space in the upper part of the evaporator casing, whereby the walls of the said shell can be made of relatively light metal.

13. In apparatus for cooling liquids, the combination of an evaporator casing structure having upright wall sections arranged one within the other to form an annular evaporator space; a coil for liquid to be cooled disposed in said annular space and connected with inlet and outlet openings in the top wall of the casing; means for admitting liquid refrigerant through the top wall of the casing to contact with the said coil; and means for discharging gaseous refrigerant from the casing through the top wall thereof.

14. In apparatus for cooling liquids, the combination of an evaporator casing structure having upright wall sections arranged one within the other to form an annular evaporator space; a conduit for liquid to be cooled comprising substantially coaxial coils arranged one within the other and joined in series at their adjacent ends at the middle of the conduit and said conduit having its inlet and outlet ends connected with inlet and outlet openings in the top wall of the casing, the coils of said conduit being disposed in the said annular space of the casing; means 'for admitting liquid refrigerant through the top

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