US2633007A - Injector type refrigerating system - Google Patents

Description

March 31, 1953 E. A. WEAVER 5 9 INJECTOR TYPE REFRIGERATING SYSTEM Filed Nov. 19, 1948 5 Shasta-Sheet 1 March 31, 1953 E. A. WEAVER 2,633,007

INJECTOR TYPE REFRIGERATING SYSTEM Filed Nov. 19, 1948 5 Sheets-Sheet 2' .hlllllllllt ililll J I RHHHHHU lllllll ll 3 r llll |||i Ill IllllllC Fillllllll It ll ll lllll' Fl llllllllxc Rllll l||| It l J l l l l l I I l March 31, 1953 E. A. WEAVER 2,633,007

INJECTOR TYPE REFRIGERATING SYSTEM March 31, 1953 E. A. WEAVER INJECTOR TYPE REFRIGERATING SYSTEM 5 Sheets-Sheet 4 Filed Nov. 19, 1948 6 fmv'ezzior' asdmrzfl, e'wver All 6 March 31, 1953 E. A. WEAVER 2,633,007

INJECTOR TYPE REFRIGERATING SYSTEM Filed Nov. 19, 1948 I 5 Sheets-Sheet 5 I til 4/ i I l J 7f 1 Wm mun Patented Mar. 31, 1953 INJECTOR TYPE REFRIGERATING SYSTEM Eastman A. Weaver, Winchester, Mass., assignor, by mesne assignments, to Stator Company, a corporation of Massachusetts Application November 19, 1948, Serial No. 60,881

3 Claims. (01. 62-117.65)

This invention relates to refrigeration apparatus of the type shown in U. S. Patents Nos. 1,761,551 and 2,180,447, and more particularly to an improved evaporator for such systems.

Conventional refrigerating apparatus embodies an evaporator disposed in heat transfer relation to the cooling and/or freezing compartment and which contains a refrigerant, the vapors of which are pumped from the evaparator, condensed, and then returned to the evaporator. Non-aqueous refrigerants having high vapor pressures evaporate freely throughout the liquid mass byboiling, agitating the liquid mass and bringing it in contact with vapor. Thus any portion of the liquid mass located so as to receive heat from the space to be refrigerated can absorb that heat continuously by ebullition. The same is not true of aqueous and other refrigerants having low volatility, for at the low temperatures called for by present-day refrigeration their vapor-pressures are so low that in the absence of dissolved gases no bubbles will ordinarily form below the free surface of the liquid unless the latter becomes substantially superheated. Thus the mass is not agitated by boiling, and the free surface gets all the cooling, which is not readily communicated elsewhere due to the low heat-transmissivity of quiescent liquids. Hence, the coldest portion of the evaporator is that adjacent to the line of contact between liquid and vapor, which would afford very limited area for cooling an adequate refrigeration space. Enough copper or other good heat-conductor to distribute the cooling effect would be clumsy, expensive and generally impractical.

Although the trouble could theoretically be remedied by introducing the condensed refrigerant at a point close to the top of the evaporator so as to trickle down the evaporator walls in a thin film, as a practical matter this method encounters certain difliculties including a need for precise levelling to spread the flow to all sides of the evaporator. Relativelyslight misleveling tends to flood one portion of the wall-s and leave the rest dry.

volatile a substance would cause prohibitive difficulty by failure to condense fully with the water vapor, blocking the condenser with accumulated vapor and causing the pressure to rise too high for the ejector to pump against it. This leaves, as the lesser evil, a choice of antifreeze which vaporizes less readily than the water and accumulates at the evaporating surface, lowering the vapor pressure.

The principal objects of the present invention are to overcome the aforementioned difficulties and to provide a system effective to insure adequate evaporation with minimum superheating over a Wide region in order to control the temperature of a substantial portion of the space to be refrigerated, and to provide a system which affords an extended area of refrigerant surface in contact with its vapor phase and in good thermal communication with the space to be refrigerated. A more specific object is to provide a refrigerating system of the type shown in the aforementioned patents having increased refrigerating efficiency without permitting stray globules of propellant to lodge in the evaporator and thereby to overcome the danger of leaving the propellant circuit with insufiicient fluid to function properly.

A further object is to eliminate the steep slopes which have heretofore been given to the bottoms of such evaporators in order to drain stray propellant back to the propellant circuit after forcing the separate globules to coalesce. Such slopes were awkward to fit into rectangular refrigerator compartments, and caused much waste of space.

A further object is to accomplish all the above in the presence of a dissolved antifreeze which, being less volatile than the water, would accumulate at quiescent evaporating surfaces and impede vaporization if not redistributed.

A further object is to agitate and circulate the refrigerant, bringing less-cold portions to the surface for evaporation, and spreading the cooling effect over the heat-transfer walls.

Further objects will be apparent from a consideration of the following description and the accompanying drawings, wherein:

Fig. 1 is a diagrammatic view of a complete refrigeration system embodying the present invention;

Figs. 2 and 3 are enlarged elevations at right angles to each other, with parts broken away, of the evaporator shown in Fig. 1, with the associated lifting device;

Figs. 4. and 5 are a plan and elevation of the same evaporator;

Figs. 6 and 7 are an enlarged fragmentary plan and elevation of a corner of th same evaporator; and

Fig. 8 is an enlarged sectional view of the lifting device showing its mode of operation, its attachment to the evaporator, and its location within the refrigerator insulation.

In accordance with the present invention, the aforementioned difficulties are avoided and the evaporator construction is streamlined and rendered more economical by utilizing the thermal energy in the incoming warm condensate to lift, circulate, and agitate the refrigerant contained in the cooler and to spread it in a thin trickling film over the walls of the evaporator, particularly adjoining the food space. This is done by means of the air-lift principle, whereby vapor from said warm condensate expands into the low-pressure interior of the evaporator, carrying upward before it slugs of refrigerant drawn from the bottom of the cooler to be distributed over the upper part of its walls, keeping them wet with a down-trickling, evaporating film of liquid.

To this end the refrigerant or condensate return system comprises a vapor-lift pump with its liquid intake connected to the outlet of the evaporator or cooler, with its vapor intake connected to the return duct leading from the refrigerant condenser, and with its discharge connected to the inlet of the evaporator at a level above the liquid-vapor interface. In addition, there is interposed between the vapor intake of the lift pump and the outlet of this refrigerant condenser a pressure trap which may be in the form of a U-tube containing mercury, a restricted orifice, mechanical valve, or the like device capable of maintaining the necessary pressure difference between the condenser and evaporator.

The operation of such a lifter or vapor pump can develop sufficient power by its intermittent action so that the liquid being drawn to it, if confined in a narrow channel, can at times move with adequate speed and force to carry with it stray globules of mercury from the evaporator, even if the channel is not sloped. This enables me to dispense with the steeply sloping floors heretofore necessary in such evaporators.

Since vaporization of some of the incoming condensate is vitally necessary to operate this lifter, and since it might fail to vaporize if left out of contact with vapor (since it is quite free of dissolved gases and might therefore become superheated), I provide for bringing it into contact with refrigerant vapor on its arrival at the base of the lifter, so that the liquid will vaporize and furnish sufficient vapor to operate the lifter. To this end a vapor-generator may be associated with the vapor intake of the pump, or a vapordome, such as an enlargement may be formed in or connected with the vapor intake line.

This vaporization of course absorbs some heat, most of which is supplied by the sensible heat of the warm condensate. The release of pressure is sometimes such that freezing might occur with possible stoppage of the flow, since the condensate is weaker in antifreeze than is the evaporator contents. To prevent this I locate the tube in a sufliciently warm zone of the insulation. Too warm surroundings would of course lead to inefiiciency by carrying unnecessary heat into the evaporator. Keeping this tube small and placing it inside the insulation serve to restrict the amount of heat so absorbed.

Referring to Fig. 1, the system shown therein, except for the cooler or evaporator and exhaust return lines, is substantially identical to the system shown in U. S. Patent No. 2,174,302, granted September 26, 1939, and the same reference characters are applied to corresponding parts. In this system the boiler l contains mercury, is heated by a main burner M, and the mercury vapors flow upwardly from the boiler I through the riser pipe Hl. to the first and second stage aspirator assemblies 56 and 26, respectively. The first stage aspirator draws refrigerant vapor from the cooler i401, through the pipe l2, mercury being condensed in the first stage assembly it and the resulting condensate passing into the drain 28. Vapor from the first stage assembly passes through a vapor pipe l9 to an interstage cooler at, and thence through a duct 2! to the mixing chamber of the second stage assembly 25. The mercury vapor from the second stage nozzle 25 is here effective in further compressing the refrigerant vapor. Condensed mercury from the second stage assembly is received by the drain 311 which also receives mercury from the drain 28. The compressed refrigerant passes upwardly through the vapor duct 32 to the refrigerant condenser 33, whichv may be provided with fins and which located in the water tank T. Condensate from condenser 33 passes downwardly through a return pipe. 34 which communicates at its lower end with an inclined pipe 35 forming one leg of a trap, the opposite leg of which is provided by the lower part of drain 35.

A pipe 31 is connected to the drain 3D and affords a spill-over connection which determines the level of mercury in the trap provided by pipes 3G, 34, 35 and 40, through which condensed refrigerant standing in 3 passes the junction of lines at and Gil into the low pressure zone of pipes EB and ll. The junction between 49 and H extends above the level of the liquid refrigerant in the cooler M, as shown more clearly in Fig. 8.

The system thus far described is substantially identical with the aforesaid system, but the return line 4|, instead of being directly connected with the drain of the cooler or evaporator, is connected with a vapor pump 15 (Fig. 8) which comprises a vertically extending capillary tube 36 or the like duct formed with a narrow passage, the lower end or intake of which is connected with the drain 43 of the evaporator Ma. At a point just above the drain connection the tube 79 is connected with the condensate return M and just above this connection is a second connection with a vapor dome or contactor '18 which may be closed at its upper end and located in close proximity to the return line 34 so as to receive sufficient heat therefrom to remain full of vapor. This vapor affords a vapor-contact with the warm liquid rising in the tube '16, and insures against failure of this liquid to vaporize which might occur through retention of superheat by liquid out of contact with vapor. The drain 43 extends downwardly from the bottom of the cooler M to a mercury trap 44 which is connected to the mercury circuit through the head drain 46 and spill-over 41 which determines the mercury level. Excess mercury spills over into the line 33a and stands in boiler-feed tube 39 at a height sufficient to balance the boiler pressure. The upper end or discharge of the vapor pump 16 is connected to the upper end of the evaporator or cooler 14c which, in order to take full advantage of the operation of the vapor pump, is preferably of the construction shown in Figs. 2 to 7.

Apparatus Of this type must be kept well evacuated in order to function properly and the many welded joints and seams in its constructionjmust be. tested under high pressure to detect leaks. It'is therefore undesirable that the cooler comprise anylarge, fiat, unsupported surfaces such as would require intricate clamping devices'to prevent bulgingduring the pressure test. For this and other reasonsI make my evaporator walls of a flat sheet steel outer plate and a stamped, serrated inner plate, seam-welded together at frequent intervals to form vertical semidetached compartments, and welded airtight around the edges.

The evaporator is of generally rectangular shape having a bottom wall 80, side walls 8|, a rear wall 82 and a pair of access doors 84 constituting the front wall, these walls defining the space or freezing compartment to be cooled. The side and rear walls, as shown more clearly in Figs. to 7, consist of a continuous outer shell of flat steel plate 95 and a continuous inner shell 86 which is stamped or otherwise formed to provide an upper horizontally extending channel 88, a lower horizontally extending channel or capillary passage 99 and vertically extending compartments 92 formed by the serrations 93, the inner and outer shells being seam-welded at their edges to provide a vapor-tight closure.

The outer rear wall of the evaporator is formed with a vapor outlet to which the duct [2 is connected, and the discharge end of the vapor pump 16 is connected to a duct 94 which passes through an opening formed in the upper central part of the rear wall and is connected with branched feed tubes or distributing pipes 95 coextensive with the horizontal channel 88. The output tube or discharge of the vapor pump thus comes in at the top level and divides into the two horizontal feed tubes 95 which pass both ways inside the top portion of the vapor passage 98. The tubes 95 are provided with a series of small outlet holes 96 (Fig. '7), one to each vertical compartment 92, through which the liquid is ejected in such direction as to spread well over the wall surface. The holes 96 may have increased size with increasing distance from the inlet and the inner wall surface of the inner shell is preferably sand-blasted or otherwise corrugated so that the liquid (which contains a volatile wetting agent) will spread all over the heat-transfer walls and present a maximum of evaporating surface continually renewed with fresh liquid.

The unvaporized residue of refrigerant will collect at the lower portion of each compartment, together with any stray globules of mercury. Each bottom end narrows to a constricted outlet which communicates with the'horizontal capillary passage or conduit 99 in which mercury globules being more or less crowded together tend to coalesce until sufficiently large to be dragged along, spasmodically, with the refrigerant as it travels toward the vapor pump. This capillary passage 90, running horizontally along the lower edge of the evaporator just inside the bottom weld, is formed at its mid-point with an outlet which is connected with the drain tube 43 thus allowing mercury to drain via tube 44 to the mercury circuit and aqueous refrigerant to be fed to the vapor pump.

The operation of the lifter, best shown in Fig. 8, is as follows: As the refrigerant normally stands an inch deep or so in the evaporator compartments, as indicated in Fig. 8 the lifter 16 will be filled partly with liquid and largely with vapor, the total liquid head equalling the liquid head in the compartments. When fresh condensate accumulates in the line 34, raising the liquid head sufiiciently to push through into return lines 40 and 4|, part of the liquid vaporizes (due to warmth and release of pressure) there, and probably some more on contact with the vapor contained in vapor dome 19. This vapor will then push up in tube 16 and rise, carrying ahead of itat least one slug of liquid and ejecting it into the horizontal distributing tube in the evaporator. This lightens the contents of tube 16, so that further refrigerant (strong in antifreeze) will flow down drain 43 and up in tube 16 to replace the lifted liquid. The cycle is thereafter repeated, as continued vaporization displaces this new contents upward in tube 16.

The function of the vapor dome 18 can be performed by the upward loop between lines 40 and 4|, provided it is made too large to be cleared of vapor by a rush of liquid. The resulting agitation and circulation of the refrigerant increases the vapor pressure fed to the ejector, lowers the cooler-wall temperature, and increases the proportion of refrigerant (lowering the antifreeze content) in the vapor pumped each of these effects being beneficial.

If mercury should at any time accumulate sufficiently in the horizontal passage 92, say near the ends where the motive power is weakest, to throttle the flow of refrigerant, the latter will accumulate in the compartments involved, raising the pressure until the mercury stoppage is cleared. The intermittent action of the lifter seems to guard against a too gradual and partial clearing which would leave a partial stoppage and a partial segregation of refrigerant in the throttled-off compartments.

While I have shown and described certain desirable embodiments of the invention, it is to be understood that this disclosure is for the purpose of illustration and that various changes and modifications may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

I. claim:

1. In a refrigeration system of the type having an evaporator partially filled with an aqueous refrigerant, a pump for propelling refrigerant vapor from said evaporator, a condenser and return line for receiving the propelled vapor and returning the condensate to the lower part of the evaporator: means for withdrawing aqueous refrigerant from the lower part of said evaporator. mixing it with the condensate and delivering the mixture to the upper part of said evaporator, said means comprising an upright tube having a relatively narrow passage, the lower end of said tube being connected to said return line adjacent to its connection with said evaporator so as to receive both condensate and refrigerant from said evaporator, the upper end of said tube being connected with the upper part of said evaporator so as to discharge refrigerant therein, and a vapor dome having a closed upper part disposed in heat transfer relation to a relatively warm part of the system, and the lowerpart of said dome having an opening communicating with the lower end of said tube so as to discharge vapor therein, which conveys the refrigerant upwardly and discharges it into said evaporator, thereby agitating and circulating the refrigerant.

2. The refrigeration system set forth in claim 1, wherein the upper end of said tube is connected 7 with a discharge line extending into said evaporator at a point above the level of refrigerant therein.

3. The refrigeration system set forth in claim 1, wherein the upper end of said tube is connected with a discharge line extending into said evaporator and having a substantially horizontal portion of appreciable length within said evaporator and formed with a series of small outlet openings.

EASTMAN A. WEAVER.

REFERENCES CITED The following references are of record in the file of this patent:

Number UNITED STATES PATENTS Name Date Schliemann Aug. 4, 1914 Davenport Apr. 12, 1932 Phillips July 5, 1938 Phillip Nov. 29, 1938 Whitney Nov. 21, 1939 N. Erland A Kleen Oct. 19, 1943 Clancy May 14, 1946,

Images