US2562652A - Evaporator for refrigeration system - Google Patents

Description

L. F. WHITNEY EVAPORATOR FOR REFRIGERATION SYSTEM July 31, 195] Filed July 5, 1948 8 Sheets-Sheet l July 31, 1951 L. F. WHITNEY 2,562,652

EVAPORATOR FOR REFRIGERATION SYSTEM Filed July 5, 1948 8 Sheets-Sheet 2 y 31, 1951 F. WHITNEY EVAPORATOR FOR REFRIGERATION SYSTEM 8 Sheets-Sheet 5 Filed July 5, 1948 July 31, 1951 wHlTNEY 2,562,652

EVAPORATOR FDR REFRIGERATION SYSTEM Filed July 5, 1948 8 Sheets-Sheet 4 III 1 m1? Wag;

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v L. F. WHITNEY 2,562,652

EVAPORATOR FOR REFRIGERATION SYSTEM .Fuly 31, 195] 8 Sheets-Sheet 5 Filed July 5, 1948 Maia,

July 31, 1951 L. F. WHITNEY 2,562,552

EVAPORATOR FOR REFRIGERATION SYSTEM Filed July 5, 1948 8 Sheets-Sheet 6 July 31, 195] n- 2,562,652

EVAPORATOR FOR REFRIGERATION SYSTEM Filed July 5, 1948 8 Sheets-Sheet 7 July 31, 1951 1.. F. WHITNEY EVAPORATOR FOR REFRIGERATION SYSTEM 8 Sheets-Sheet 8 Filed July 5, 1948 Patented. July 31,1951

UNITED STATES PATENT OFFICE EVAPORATOR FOR REFRIGERATION SYSTEM Lyman F. Whitney, Cambridge, Mass., asslgnor, by mesne assignments, to Stator Company, a corporation of Massachusetts Application July 3, 1948, Serial No. 36,932

8 Claims.

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 evaporator, condensed and then returned to the evaporator. Non-aqueous refrigerants having high vapor pressures evaporate freely throughout the liquid mass by boiling, 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 only really cold 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 at least two serious difliculties. First, the leveling must be quite precise or there will be excessive flow at one side of the cooler and little or none over the rest; and, second, it is diilicult to provide a reserve of refrigerant liquid to supply losses, in the course of time, in connection with the purging out of fixed gases, as may be seen by the following considerations. Such a reserve could not be placed above the trickling film and overflowing onto it since it would necessarily always remain full and could supply no losses while maintaining the overflow trickle; and if placed below the trickle, it would contain an undue proportion of the antifreeze (which being less volatile than the refrigerant proper would accumulate in the unvaporized residue), and when successive portions of this strong solution joined the circulating refrigerant to supply losses, the antifreeze concentration in the working refrigerant would be deleteriously raised.

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 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 greatly increased refrigerating capacity without permitting stray globules of propellant to lodge in the evaporator, thereby overcoming the danger of leaving the propellant circuit with insufficient fluid to function properly.

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;

Fig. 2 is an enlarged plan view with parts broken away of the evaporator shown in Fig. 1;

Fig. 3 is a vertical section on the line 3-3 of Fi 2;

Figs. 4 and 5 are enlarged fragmentary elevations at right angles to each other of the evaporator and associated wicks;

Figs. 6 and 7 are views similar to Figs. 4 and 5 but showing a modified arrangement;

Figs. 8 and 9 are views similar to Figs. 4 and 5 but showing a further modification;

Fig. 10 is a fragmentary bottom view of the parts shown in Figs. 8 and 9;

Fig. 11 is a diagrammatic view of a modified form of the refrigerating system embodying the present invention;

Fig. 12 is an enlarged plan view of the evaporator shown in Fig. 11, illustrating the wick arrangement for siphonic action;

Figs. 13 and 14 are front and side elevations of the evaporator shown in Fig. 12; and

Fig. 15 is an enlarged fragmentary view, with parts broken away and shown in section, illustrating the mode of operation of the wicks.

In accordance with the present invention, the aforementioned difliculties and others are avoided by making use of capillary attraction to 3 spread refrigerant in a thin evaporating film on the heat-transmitting walls of the evaporator, and to this end a thin wick is disposed so as to conduct the liquid from the reservoir and allow it to vaporize on one side, thereby to receive heat from the evaporator wall on the other side. Alternatively, or in addition, the wall surface itself may be so treated, as by comminution and/or chemical or physical modification, that it will carry by capillarity a creeping and evaporating film of refrigerant.

The action of these devices, of course, need not be particularly sensitive to leveling, as the motive power used is not gravitational. The reserve problem is also simplified, since a reserve refrigerant container, such as a trough, may receive the liquid from the condenser and communicate it to deeply dipping wicks; these will then draw their supply from it even when its contents have been largely depleted. Wicks having appreciable thickness interpose undesirable thermal resistance to the heat flow, and it is therefore desirable both to make them as thin as practicable and also to use the comminuted wall surface itself to perform the function of a wick wherever feasible. Hence, the term wick, as herein used, includes such comminuted, capillary-acting wall surfaces, as well as woven, knitted or felted fabrics.

Since the travel of liquids by capillarity alone is of limited extent, particularly in an upward direction, I prefer to use my capillary devices as siphons primarily to raise the refrigerant out of a reservoir (which may comprise the reserve referred to) and-to regulate its relative flow on different sides of the evaporator so that misleveling will not cause an objectionable unequal distribution. Preferably thereafter the unevaporated liquid flows downward by gravity over the major inner surfaces of the evaporator walls while it evaporates, cooling them, and through them absorbing heat from the refrigeration space.

The facility with which aqueous refrigerant travels in a textile or fabric wick or on a comminuted surface wick can be greatly enhanced by incorporating therein substances which not only act as wetting agents, but also as antifreeze agents. Such volatile wetting agents condense with the refrigerant and aid in spreading it throughout the wicks. Particularly desirable volatile antifreeze and wetting agents are the monomethyl and monoethyl ethers of ethylene glycol and the like substances which have very favorable properties as volatile wetting agents, particularly for ferrous metal surfaces. This is of great importance because iron is the only common metal proof against attack or amalgamation by mercury which is the preferred propellant.

In the ejector-operated type of refrigeration, globules of propellant frequently appear in the cooler (in fact, in all parts of the apparatus), and unless provision is made for their prompt return to the propellant circuit, trouble can arise from the latter retaining inadequate supply. Mercury, my preferred propellant, tends strongly to form such globules, which adhere rather tenaciously to nearly horizontal surfaces, so that a substantial slope must ordinarily be given to the bottom of the evaporator and any other nearly horizontal surfaces on which such globules might rest. Woven wicks particularly, if they presented nearly horizontal upward-exposed surfaces, would retain globules on the thread interspaces 4 and other depressions which might be present. For this reason I prefer to keep all exposed wick surfaces either nearly vertical or facing downwardly, keeping the upper surfaces close against the evaporator wall or other solid part.

Referring to Fig. 1. the embodiment shown therein comprises a boiler I having a suitable heating element 2, such as a gas burner, provided with a draft-inducing flue I through which exhaust gases are vented. Mercury vapor passes from the boiler I through a riser I to branches 5" and 5 which are connected respectively to the first and second stage aspirators. The first stage aspirator may comprise a nozzle 8 from which mercury vapor passes at relatively high velocity into a mixing chamber 1. The latter is connected by a sloping vapor duct 8 to the cooler or evaporator ll embodying the construction hereinafter described. The evaporator contains a body of liquid refrigerant, such as water and a suitable antifreeze ingredient, such as the mono-methyl ether of ethylene glycol. Vapor is drawn through the pipe 8 to the mixing chamber I, and the mixed propellant and refrigerant vapors pass into the duct or funnnel l2, where the refrigerant is compressed and mercury is condensed. The funnel preferably may have proportions of the order shown in Fig. 3 of U. 8. Patent No. 2,180,- 447. The condensed mercury fiows from the lower end of the funnel l2 into a drain ll, while the vapors pass into a pipe coil or loop it which is provided with cooling fins and forms an interstage cooler for condensing mercury and cooling the vapors.

The latter is connected to an interstage drum or chamber l9 which has a substantially larger cross-section than the interstage cooler pipe It. so that the velocity of the vapor flowing through the drum is reduced, thus enhancing the tendency of condensed mercury particles to settle and collect at the lower part of the drum. The drum l9 may conveniently be provided with a bottom wall which inclines upwardly from its opposite sides to an intermediate ridge. Part of the condensed mercury collecting on this lower wall of the drum is directed to the pipe 20, while the remainder of the condensed mercury flows into the duct 2| which receives the refrigerant vapor. The pipe 20 contains a suitable body of liquid mercury forming a trap to preclude the flow of vapor from the drum through this pipe, the end of the pipe being connected to the drain It so that mercury from this pipe may overflow into the drain and to parts of the system hereinafter described.

The compressed and cooled refrigerant vapor passes from the pipe 2| into the second-stage mixing chamber 22 into which a stream of mercury flows at high velocity from the nozzle 23. This propellant stream is effective in causing further compression of the refrigerant vapor in the second-stage funnel 25. A drain 2! receives condensed mercury from the funnel 2i and from the drain I.

The first-stage funnel i2 and the second-stage funnel 25 preferably are provided with cooling fins disposed in jackets i2 and 25 which are connected, respectively, by ducts 12 and 25 to condensers or heat dissipators l2 and 25. Each of the jackets may contain a body of liquid coolant, such as alcohol, which may be vaporized by the heat of the corresponding funnel, the vapor rising to the corresponding condenser l2 or 25 and the condensate draining back from eachcondenser to the corresponding jacket. Preferably the jackets and condensers may be evacuated before operation of the apparatus is started, so that the coolant vaporizes and condenses at a lower temperature than would be the case were these parts of the system at atmospheric pressure when the system was not in operation.

The compressed refrigerant vapor passes upwardly from the funnel through the duct 29 to the refrigerant condenser 30, the arrangement of the pipe 29 being such as substantially to prevent mercury from passing into the refrigerant condenser 30 and accordingly reducing the quan- 1 tity of sludge formed by the condensate passing from the condenser back to the cooler II. The condenser 30 may be of any suitable form, being either air cooled or water cooled, as desired. As shown herein for purposes of illustration, the condenser 30 comprises a conventional pipe assembly with cooling fins 3 I.

A chamber or drum 32 preferably is located at the end of condenser 30 which is remote from the pipe 29. A pipe 33 has an open end communicating with this chamber and receives noncondensable gases therefrom. The lower portion of the condenser chamber 32 is connected to a drain or return pipe 34 through which condensed refrigerant may pass on its way back to the cooler. Especially when an antifreeze agent is employed, which tends to collect in a stronger solution at the upper part of the body of liquid refrigerant in the cooler, I preferably provide means to introduce the freshly condensed weak refrigerant into the cooler so that it tends to break up or dilute the strong solution. For this purpose the pipe 34 may have its lower end connected to an upwardly extending duct 35, the upper end of which is connected to a tube 36 of small diameter communicating with the interior of the cooler II above the surface of the liquid contained therein.

The lower parts of the pipe 34 and of the duct 35 form a trap A containing mercury which, dur ing normal operation, stands higher in leg 35. As condensed refrigerant collects above the mercury in the pipe 34, it depresses the mercury sufficiently to permit the liquid refrigerant to rise through the mercury column in the other leg of trap A, i. e., to pass into the upper part of duct 35. Since the temperature of the returning refrigerant is high relative to the temperature of the cooler, and since the pressure in the cooler is low, some vaporization of the refrigerant occurs in duct 35. Accordingly, the refrigerant passes through the tube 36 in the form of separate slugs or separate bodies of liquid, which are propelled by bodies of vaporized refrigerant. Thus, the returning refrigerant may be sprayed onto the surface of the liquid refrigerant in cooler II. Accordingly, the stronger antifreeze solution, which tends to collect at the top of the liquid body, is diluted and agitated, so that vaporization can more readily take place at the surface of the liquid body.

Under certain conditions, particularly due to the restricted diameter of tube 36, the returning refrigerant may freeze in this tube so that the condensed refrigerant can not return to the evaporator I I in the manner which has been described. To provide for such an eventuality, I provide means which permits the by-passing of the refrigerant to the cooler. For this purpose, the lower end of pipe 34 is connected to an inclined tube 40, the upper end of which has a vertical continuation 42 that may extend above the liquid level in the cooler and have a connection with a downwardly extending pipe 43 which is connected to a duct 44, which also serves as a drain. The upper end of duct 44 communicates with the lower part of the cooler II, and stray propellant particles may drain from the cooler through this duct. When freezing occurs in tube 36, liquid refrigerant will depress the mercury at the juncture of pipes 34 and 40, so that the refrigerant may rise in the duct portion 42 and pass into the portion 43 flowing from the latter into the drain 44.

The lower part of duct 44 provides a shallow trap communicating with a. drum 50. The duct 44 preferably has a relatively large diameter. A trap 5I connects the second-stage mixing head 22 to a drain 55 while a drain 49 connects the first-stage mixing head to the upper part of drum 50.

The drain 55 extends from the bottom of the drum to a trap 56, the opposite leg of which is connected to a duct 51, while the lower end of the latter communicates with the boiler I. The drain pipe 21 for the second-stage funnel 25 is connected to a small chamber 60 into which the lower end of inclined pipe 40 extends, and an upwardly inclined duct 6| extends from the chamber 60 to the upper part 64 of the purger assembly 63 described more fully in U. S. Patent No. 2,180,447.

The duct 69 of the purger assembly 63 is connected to a return duct 51, and the construction and arrangement of parts are such that the mercury column in drain 55 and the ducts 51 and 69 are automatically maintained at heights which balance the boiler pressure.

Trap B is constantly receiving mercury from pipe 21 during normal operation of the system, and the spill-over connection between pipe 6| and upper part 64 of the purger definitely limits the height of the mercury in pipe 21. Thus, a mercury column of constant height is automatically maintained in leg 6| 0f trap B, while the total static pressure in this leg of this trap is provided by this mercury column and the condenser pres- Sure thereabove. Such a total static pressure is balanced on the opposite side of the trap by components afforded not only by the mercury in pipe 40 but by the liquid heads in the respective branches of this leg of the trap B and by the respective pressures thereabove. The liquid heads in the respective branches may be provided by columns of mercury or of mercury and liquid refrigerant.

Referring to Figs. 2 to 10, the evaporator II comprises an inverted generally rectangular pyramidal structure located within the refrigerator and having a top wall IOI adjoining the surrounding floor I02 of the freezing compartment C. The convergent side Walls I03 slope at an angle which prevents mercury droplets and sludge from accumulating thereon, and their lower ends provide an opening communicating with the pipe 44. One of the side walls I03 adjoins a small cubicle I04 to which the vapor duct 8 and tube 36 are connected, as shown in Figs. 2 and 3.

A series of spaced rods I05, arranged in pairs, are supported at their ends against the under side of the top wall I 0| by Z-bars I06 which are welded or otherwise secured to the wall II, as shown in Figs. 4 and 5. Each pair of rods I05 supports the central portion of awovenfabric wick I01 so that its free ends hang downwardly and are partially submerged in a body of aqueous refrigerant whose surface S is close enough to the top wall IOI so that capillarity readily raises the refrigerant in the wick to the horizontal central P rtion, but not so close as to impede the escape of vapor between th wicks to vapor outlet 8. The rods III are preferably slightly sprung or bowed upwardly so that their middle portions press against the top wall IM and thus hold the wick in close contact therewith. In order to maintain the direction of pressure, as well as for ease of assembly,each pair of rods may be formed from a single length of' steel into an elongate U-shaped form which prevents rotation ofeach leg portion.

If the wick is squeezed too tightly against the under surface of the top wall II, it does not permit a free flow of liquid, and for this reason the upper part of each rod is serrated to provide spacing teeth I08 (Fig. which penetrat the fabric wick I01 and contact the under surface of the wall IIII. The parts are thus arranged so that the horizontal run of each wick is firmly held in position against the under surface of the top wall IOI, and the teeth I08 thus prevent the rods I05 from compressing the fabric wick so as to impede capillary flow of refrigerant to all parts or the horizontal portion of the wick.

In order to insure close contact between the horizontal run of the wick and the adjacentunder surface of the top wall, it may be advisable to have the contacting under surface of the top wall IOI'- formed with a convex contour, as shown in Fig. 6, so that tension of the wick is effective to hold it in close contact with the convex portion. Such tension may be supplied by turning the "spring of the rods outwardly so that it has an outward component, rather than being directed vertically. Thus, the wick being held from slipping by the serrations or teeth can be stretched tight by the sprung rods so that it will hug the convex surface of the top plate. In this construction the ends of the rods are clamped or otherwise secured to the Z-bars so that they are firmly anchored in position.

In the modification shown in Figs. 8 to 10, the fabric wicks of the previous embodiments are replaced by metal wicks or webs IIO, the surfaces of which are roughened as by sand blasting, grooved, corrugated or otherwise formed with rugosities which define a plurality of capillary passages, and thus provide, in effect, a wick adapted to distribute refrigerant over the entire surfaces, particularly in the presence of a wetting agent. The ends of the webs IIO terminate short of one side wall so that all vapor spaces communicate with vapor duct 8. The under surface of the top wall III is formed with a plurality of spaced parallel grooves II2 (Fig. 10) which receive the upper ends of the wick fins IIO which are secured in place by welding or otherwise. The under surface of the top wall III is likewise roughened or formed with rugosities. as indicated in Fig. 9, and thus is effective to distribute, by capillary action, refrigerant from the wick fins I I0.

With this construction and arrangement of parts, the refrigerant with its dissolved wetting agent creeps up the web fins 28 and-along the rugose under surface of the top wall I0I o that it covers the entire under surface of the top wall. Evaporation may thus occur freely all over the entire surface of both the fins and the top wall, consequently cooling it, and, by conduction. absorbing heat from articles on the top wall or within the freezing compartment. Since the fins IIO are of metal and hence have a relatively high degree of conductivity as compared with fabric wicks, they are considerably more efiicient 8 in enhancing the refrigerating effect attributable to the evaporation of the refrigerant liquid.

The embodiment of Figs. 11 to 15 illustrates an alternative form of ejector-operated refrigerator having an evaporator or cooler adapted primarily to cool a refrigeration space rather than to freeze ice cubes. Except for the construction and specific mode of operation of the evaporator, this modified system is in principle the same as that above described and its construction is substantially identical to that shown and described in my prior Patent No. 2,174,302, granted September 26, 1939, to which the reference characters of Fig. 11 correspond.

The evaporator I4 comprises a U-shaped housing or enclosure I20 surrounding the space to be cooled and provided with a suitable fioor I2I (Fig. 12) and a pair of access doors I22. The intermediate or rear section of the outer wall I24 of the housing is formed with an opening I25 to which the sloping vapor duct I2 is connected and an opening I26 (Fig. 13) to which the condensate return pipe 4i is connected. The inner surface of the wall I28 is preferably roughened, grooved or otherwise formed with capillary rugosities and its marginal portions are bent rearwardly so as to join the edges of the outer wall I24 and thus provide a vapor-tight evaporation chamber. The lower edges of the side walls and adjoining bottom walls of the enclosure are shaped to provide a series of up and down portions I30, I3I sloped so as to prevent the accumulation of propellant globules. The valleys of the sloped parts are connected by pipes 48, 43 to the drum 42, the lower part of which has a connection with drain 46 and trap 41 through which condensed propellant is returned to the boiler I (F18. 11).

Within the evaporator and spaced from its lower wall is a trough I35, the bottom wall of which is shaped to provide a series of up and down portions I36, I31 similar to and aligned with those of the bottom of the enclosure. The inner vertical wall of the trough is spaced from the inner side wall I28, and is formed with a curved or beaded lip, as shown more clearly in Fig. 15. The valleys or low points of the trough III are connected with drain tubes I45, each of which is curved to form a trap so that condensed propellant will drain out after filling the trap while the lighter refrigerant liquid will be retained in the trough. As shown more clearly in Fig. 13. the opening I26 is above th low point or bottom wall of the trough so that condensed refrigerant is admitted therethrough and largely fills the trough, as indicated in Fig. 15.

A fabric wick I50 hangs over the curved edge of the trough so that one edge portion dips well into the trough and its opposite toothed edse portion extends downwardly against the inner face of wall I28, as shown in Figs. 13 to 15. Liquid refrigerant, preferably containing a volatile wetting agent, travels from the trough I" through wick I50, over the edge of the side wall I42 and trickles from the toothed edge of the wick onto the side wall I28 where it spreads out by gravity and the capillary action of the rugose surface of the wall I28, thereby to form a liquid film over substantially the entire inner surface of the wall. Thus, the wick I50 provides a capillary siphon for distributing refrigerant over the inner surface of the wall I28 from which it is evaporated by absorption of heat from the interior of the refrigerating compartment enclosed by the wall.

If desired, the inner face and curved upper edge of the trough may be grooved or otherwise formed with capillary rugosities and thus enhance the "wick action; and/or the curved edge of the trough may be extended downwardly in contact with the inner face of the wall I28, in which event the fabric wick r50 may be eliminated. In either case, there is provided a capillary siphon which distributes the refrigerant over the surface of the wall I28 and thus greatly increases the heat absorption or refrigeration capacity of the system.

In operation, refrigerant vapors are drawn from the enclosure through the duct l2 in accordance with the demand, and such vapors, after being condensed as explained in Patent No. 2,174,302, are returned through pipes 40 and 4| to the trough. Normally mercury seals pipes 43 and ta In the event that more refrigerant liquid is siphoned from the trough than is evaporated. such excess runs down the sloping walls together with any condensed propellant. The

propellant liquid is returned to the boiler throughthe drum 4! and associated piping, while the refrigerant liquid is held at the bottom of the evaporator and in the lines 43 and 43 above the mercury traps. In order to prevent more than a given quantity of propellant liquid from accumulating in the bottom of the evaporator, the traps 63 and 43 are arranged so that when the propellant liquid has reached a certain level, mercury in the traps is displaced sufficiently so that the excess refrigerant liquid can rise up through the mercury in the trap and pass to the drum 42, where it separates from the mercury, is vaporized, and the vapor pumped by the ejector system into the water vapor condenser 33 (Fig. 11) the vapor being condenser therein and returning as liquid into the trough I35. The drum 42 may be in a relatively warm location.

While I have shown and described different desirable embodiments of the invention, it is to be understood that this disclosure is for the pur pose 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 refrigerating system of the type having a pump for propelling an aqueous refrigerant vapor and a condenser for receiving the propelled vapor, an evaporator comprising an enclosure at least one wall of which is in thermal communication with a compartment to be refrigerated, said enclosure containing a body of aqueous refrigerant in which is dissolved a volatile antifreeze and wetting agent, said body of aqueous refrigerant being at a level to provide a space below the top wall of said enclosure, an inlet for conveying condensed refrigerant from said condenser to said enclosure, an outlet communicating with said space for conveying refrigerant vapor to said pump, and wick means within said enclosure, said wick means having a part in contact with said body of aqueous refrigerant and another part communicating with a portion of the wall of said enclosure out of contact with said body of equeous refrigerant so as to distribute by capillary action a film of refrigerant whereby vaporization of said refrigerant is promoted with consequent increased cooling of the wall portion in communication with said wick means.

2. In a refrigerating system of the type having a pump for propelling an aqueous refrigerant vapor and a condenser for receiving the propelled vapor, an evaporator comprising an enclosure having top and side walls. at least one of which is in thermal communication with a compartment to be refrigerated, said enclosure containing an aqueous refrigerant in which is dissolved a volatile antifreeze agent, said refrigerant being at a level to provide a space below the top wall of said structure, at least one of the side walls of said enclosure having a rugose interior surface, an inlet for conveying condensed refrigerant from said condenser to said enclosure, an outlet communicating with said space for conveying refrigerant vapor to said pump, and a fabric wick for distributing refrigerant over said rugose surface, whereby vaporization is promoted with consequent increased cooling of said side wall.

3. In a refrigerating system of the type having a pump for propelling an aqueous refrigerant vapor and a condenser for receiving the propelled vapor, an,.evaporator comprising an enclosure having top and side walls, at least one of which is in thermal communication with a compartment to be refrigerated, said enclosure containing an aqueous refrigerant in which is dissolved a volatile antifreeze agent, said refrigerant being at a level to provide a space below the top wall of said enclosure, at least one of the walls of said enclosure having a rugose interior surface, an inlet for conveying condensed refrigerant from said condenser to said enclosure, outlet communicating with said space for conveying refrigerant vapor to said pump, and capillary means for distributing refrigerant over said rugose surface, whereby vaporization is promoted with consequent increased cooling of said side wall.

4. In a refrigerating system of the type having a .pump for propelling an aqueous refrigerant vapor and a condenser for receiving the propelled vapor, an evaporator comprising an enclosure having top and side walls, at least one'of which is in thermal communication with a compartment to be refrigerated, said enclosure containing an aqueous refrigerant in which is dissolved a volatile antifreeze agent, said refrigerant being at a level to provide a space below the top wall of said enclosure. at least one of the side walls of said enclosure having a rugose interior surface, an' inlet for conveying condensed refrigerant from said condenser to said enclosure. an outlet communicating with said space for conveying refrigerant vapor to said pump, a wick member within said enclosure extending into said refrigerant and communicating with said rugose surface, whereby vaporization is promoted with consequent increased cooling of said side wall.

5. In a refrigerating system of the type having a pump for propelling an aqueous refrigerant vapor and a condenser for receiving the propelled vapor, an evaporator comprising an enclosure having top and side walls, at least one of which is in thermal communication with a compartment to be refrigerated, said enclosure containing an aqueous refrigerant in which is dissolved a volatile antifreeze agent, said refrigerant being at a level to provide a space below the top wall of said enclosure, a plurality of rods disposed in contiguous relation to one of said walls at points above the level of said refrigerant, a fabric wick having a part submerged in said refrigerant and another part extending over said rods in contact with the adjacent wall portion, said wick being effective to distribute by capillary action refrigerant over said adjacent wall portion, thereby to promote vaporization 11 and consequent increased cooling of said adjacent wall portion.

6. In a refrigerating system of the yp having a pump for propelling an aqueous refrigerant vapor and a condenser for receiving the propelled vapor, an evaporator comprising an enclosure having top and side walls in thermal communication with a compartment to be refrigerated, the under surface of said top wall being formed with convex portions, said enclosure containing an aqueous refrigerant in which is dissolved a volatile antifreeze agent, said refrigerant being at a level to provide a space below the top wall of said enclosure, a fabric wick having a portion submerged in said refrigerant and another portion extending above said level, supporting means for holding a .part of the latter portion in contact with said convex portions so as to distribute by capillary action a film of said refrigerant thereover,.an inlet for conveying condensed refrigerant from said condenser to said enclosure, and an outlet communicating with said space for conveying refrigerant vapor to said pump.

7. In a refrigerating system of the type having a pump for propelling an aqueous refrigerant vapor and a condenser for receiving the propelled vapor, an evaporator comprising an enclosure having top and side walls, at least one of which is in thermal communication with a compartment to be refrigerated, said enclosure containing an aqueous refrigerant in which is dissloved a volatile antifreeze agent, said refrigerant being at a level to provide a space below the top wall of said enclosure, a plurality of rods disposed in contiguous relation to one of said walls at points above the level of said refrigerant, a fabric wick having a part submerged in said refrigerant and another part extending over said rods in contact with the adjacent wall portion, the-upper parts of said rods being formed with pointed teeth penetrating said fabric wick so as to hold it against movement along said rods and in properly spaced relation to said adi 12 jacent wall portion, said wick being eflectivc to distribute by capillary action refrigerant over said adjacent wall portion, thereby to promote vaporization and consequent increased cooling of said adjacent wall portion.

8. In a refrigerating system of the type having a pump for propelling an aqueous refrigerant vapor and a condenser for receiving the .propelled vapor, an evaporator comprising an'enclosure having top and side walls in thermal communication with a compartment to be refrigerated, a trough within said enclosure containing an aqueous refrigerant in which is dissolved a volatile antifreeze agent, said refrigerant being at a level to provide a space below the top wall of said enclosure, a wick having a part submerged in the refrigerant in said trough said wick extending over the edge of said trough and against a side wall so as to carry by capillary siphonic action said refrigerant from saidtrough and distribute it over said side wall, an inlet for conveying condensed refrigerant from said condenser to said enclosure, and an outlet communicating with said space for conveying refrigerant vapor to said .pump.

LYMAN F. WHITNEY.

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

UNITED STATES PATENTS Number Name Date 1,761,551 Weaver June 3,- 1930 1,845,640 Wescott Feb. 16, 1932 1,913,468 Aitenkirch June 13, 1933 1,979,482 Kohler Nov, 6, 1934 2,057,408 Andersson et a1. Oct. 13, 1936 2,307,947 Payne Jan. 12, 1943 2,426,044 O'Brien Aug. 19, 1947 FOREIGN PATENTS Number Country Date 417,909 Great Britain Oct. 15. 1934

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