US2526032A - Defrosting method and apparatus for refrigeration systems - Google Patents

Description

Patented Oct. 17, 1'9`5 OFFICE DEFROSTING METHOD AND APPARATUS FOR REFRIGERATION SYSTEMS Louis F. La Porte, Wellston, Mo., assigner to Francis L. La Porte, San Bernardino, Calif.

Application October 11, 1948, Serial No. 53,839

The present invention relates generally to the defrosting of cooling units, or evaporators, included in mechanical refrigeration systems, and is a continuation in part of my co-opending application, Serial No. 732,742, filed March 6, 1947.

A satisfactory solution of the defrosting problem has long been sought by refrigeration experts and engineers. Various automatic, semiautomatic, and manually controllable devices and methods have heretofore been devised, in a vain effort to provide simple, yet effective defrosting means.

Some of such methods and the apparatus associated therewith have been patented. However, for one reason or another, these have been found wanting in many respects, and fraught with so many disadvantages that it seems the refrigeration industry generally has seen fit to discard them.

The primary object of the present invention y therefore. is to provide a simple method, and

simple apparatus, whereby the disadvantages inherent in the herebefore methods are overcome.

In my said pending application there is disclosed a method and apparatus for defrosting cooling units and the drain pans associated therewith.

Broadly, the method of defrosting therein set forth, includes the provision of a closed, or airtight fluid system of heat-conducting metallic material, which system after having been first evacuated, and thereupon charged with apredetermined quantity of a Volatile liquid, is incorporated in the cooling' unit or units in such manner, that branches of the system propagate throughout the system the hot vapors generated by a vapor generator.

A vapor generator, in which the volatile liquid collects before and after defrosting operations, is included in the system. When defrosting becomes necessary, the external application of heat to said generator causes the therein collected refrigerant to vaporize. The hot vapors produced travel upwardly and onwardly along the interiorsurfaces of the system, give up their heat to those surfaces, and thereby having been liqueed, return by gravity to the generator.

The present invention, while including a vapor generator and a hermetically sealed system similar to that disclosed in said application, has features and advantages not found therein.

For example, in the apparatus of the pending application, heat is applied to the vapor generator when a defrosting operation is required. In the instant apparatus, the necessary heat is available at all times for instant use.

9 Claims. (Cl. (i2-115) In other words, the present vapor generator is submerged in a eutectic or heat-holding solution sealed within an insulated container. During compressor operations, this liquid is heated by means of the compressor discharge line passing through said tank.

During the defrosting cycle, when, in the present method, the compressor does not operate, the solution is continually heated by electrical means.

Thus, an accumulated or stored quantity of heat is at all times available for the vapor generator, so, that immediate defrosting may be had when desired, and the temperature of the stored or banked heat is not permitted to dissipate during defrosting.

Obviously, with an arrangement of this character, the invention includes means whereby the volatile liquid is prevented from returning to the vapor generator following a defrost operation.

The invention also provides a solenoid operated valve permitting immediate ingress of said uid into the generator with the shutting off of the compressor, and the simultaneous energization of the heating element.

yOne of the features of the invention is its adaptability to any refrigeration system wherein a compressor is included, provided a source of electrical energy for operating the solenoid valve and the heater is available.

Particularly, though not at all exclusively, the apparatus hereof is highly efficient in connection with 10W temperature refrigerated rooms, such as food lockers, ice cream hardening rooms, and perishable commodity storage rooms.

Further, the invention may be incorporated, with equal eiciencyof operation, in cooling units of the nned coil type as well as of the plate type.

Advantages and features not hereintofore set forth, should be apparent, or will be specifically noted in the description to follow, reference being had also to the accompanying drawing, in which the application of my method to a coil type, and also to a plate type evaporator unit, is illustrated.

In said drawing:

Fig. 1 is a diagrammatical illustration of a defrosting system incorporating the invention, shown in association with an evaporator installation of a refrigerated room;

Fig. 2 is a longitudinal central sectional view of a solenoid valve and elements adjacent thereto;

Fig. 3 is an end view, partly in vertical section,

of a header assembly which constitutes the preferable vapor generator construction;

Fig. 4 is a ver-tical sectional view of a cooling Fig. 5 is a similar view of a cooling unit of thev plate type;

Fig. 6 is an enlarged fragmentary view, partly in section, illustrating the closed end construction of certain tubes and conduits. f

With particular reference now to Fig. 1, numeral I0. indicates generally an evaporator or cooling unit which may be of the coil type provided with ns, or of the plate type. 'I'he evaporator I0 is shown suspended from the ceiling of a refrigerated room, fragmentarily indicated in broken lines and designated by the numeral I2.

Beneath the evaporator there is disposed the usual drain pan I4, provided with a drain pipe I6. A solenoid operated valve, generally designated I8, is interposed in a line generally indicated 20, which extends between the evaporator I0 and a vapor generator assembly generally designated 22.

A condenser and a compressor included in the refrigeration system are designated 24 and 26 respectively, and the compressor discharge line is identified by numeral 28.

The evaporator or cooling unit I0 may be of the type illustrated in Figs. 4 or 5. For the present, the Fig. 4 unit will be considered. It is seen to include a conventional refrigerant coil 30, provided with inlet and outlet lines 32 and 34 respectively, as is understood. The drain pan I4 therebeneath disposed may be supported in any well-known manner.

Brazed or welded to the coil 30 at spaced intervals, are the usual heat absorption plates or fins 36. In normal operations, frost forms and accumulates on the exterior of the coil and ns exposed to moisture in the refrigerated space, and it is this frost which requires removal from time to time for efficient operation of the refrigeration system, as is well understood.

The valve I8 is illustrated in detail in Fig. 2, wherein it is seen to include a housing or casing 38 provided with an upper chamber 40, and a lower` chamber 42. A wall 44 separates said chambers, and has formed therein a tapered seat 46 for a valve member 48.

Normally, this valve is closed. That is to say valve member 48 seats itself by gravity. However, as will appear, when the solenoid coil 50 is energized by the closing of manual switch 52, the valve member 48 will be elevated to establish fluid communication between chambers 40 and 42.

The solenoid valve I8 mai7 be of any well known design, it being requisite only that the opening 54 in the casing 38, through which the stem thereof extends, be hermeticallysealed.

The line generally designated 20, includes an upper conduit or tube 56, and a lower conduit or tube 58, each leading to and from the valve I8, tube 56 being in communication with upper chamber 40, tube 58 with lower chamber 42.

The invention also includes means for heating the drain pipe I6. Thus, for example, at-a region adjacent the drain pan I4, the tube 56 is coiled about said pipe as suggested at 60, whence said tube extends upwardly and then laterally, as at 62, to terminate in a closed end 84.

As shown in Fig. 4 the laterally extending portion 62 preferably passes through the upper portion of each of the fins 36, and a first branch line 66, extending laterally from tube 56, preferably passes through the lower portion of each of said iins.

2,526,032 I l l In addition, a second laterally extending branch line 68 is in contact with the drain pan I4. Each branch line terminates in a closed end 64.

As illustrated. in Fig.' 1, tube or conduit 58 terminates in a downwardly inclined portion 10 in communication with a horizontally disposed header 12 included in the vapor generator 13.

With reference also to Fig.` 3, it is seen that said generator may include one or more depending tubes 14, each having a closed end 16, and each preferably of a reversely curved conguration as shown. A series of plates, or heat-collecting ns 18, is provided for each tube 14, said fins being rigidly secured thereto at intervals as shown.

It should here be noted that the precise construction of the vapor generator may be varied from the form shown, although the illustrated embodiment is highly efficient.

As shown in Fig. 1, the vapor generator is submerged in a eutectic solution indicated a: which is contained within a hermetically sealed tank 80. The latter is enclosed in a layer or layers of insulating material 82, obviating loss of heat from within the tank.

The hot discharge line 28, leading from compressor 26 to condenser 24, passes through tank 80 and the liquid Withinysaid tank, a coil 84 is formed in said line, so that heat from the hot gases passing therethrough may be more completely transferred to the solution r.

Also submerged in said solution is a suitable electric heating device 86. Preferably, the heater 86 is in a circuit leading from a power source, and including lines 88 and 90, switch 52, lines 92 and 94, solenoid 50, and leads 96 and 98. Thus it should be manifest, that when switch 52 is closed, both the solenoid coil and the heating device 86 will simultaneously be energized.

That portion of line 20, namely tube 58 and its downwardly inclined terminal length 10, ex-

tending between valve I8 and the vapor generator assembly 22, is covered with suitable insulation .99, as shown.

In iiuid communication at its lower end with tube 58, and at its upper end with what m'ay be termed the uppermostzone of the defrost apparatus, is a vapor tube |00, the provision of which between valve I8 and generator 13 is important, as will appear.

It is noted that, though not requisite, the condenser, the compressor, and the generator assembly, are all preferably located exteriorly of the `refrigerated space.

The cooling unit, or evaporator I0, may be of the plate type, as hereinbefore stated. In that case, as portrayed in Fig. 5, the refrigerant coil 30 is located interiorly of a hermetically sealed metallic casing |02. Conduit 56 leads into said casing, but the lateral branches 62 and 66 are dispensed with. Branch line 68 for the 'drain pan is retained, as shown. c

From the foregoing it should be apparent that the invention includes a hermetically sealed system of hollow components comprising, in connection with a finned type evaporator, the generator 13, line 20, valve housing 38, vapor tube |00, and laternal branches 62, 66, and 68.

In connection with a plate type evaporator, the hermetically sealed system includes generator 13, line 20, valve housing 38, vapor tube |00, casing |02, and lateral* branch 68.

In each case, the integrated system thus provided, is first evacuated by the application of suction, and is thereafter charged with a predetermined quantity of refrigerant, which may be Freon, for example, or an analogous volatile liquid. Thereupon the opening, to which the suction had been applied and thereafter the charge had been introduced, is sealed.

As will appear, in accordance with the present method, this entire charge is contained within that portion of the system to the left of solenoid valve I8 during normal refrigeration operations, and flows by gravity into the vapor generator during defrosting operations. Therefore, the quantity of volatile liquid in the system is predicated upon the aggregate volume of header 12 and tubes 14. In the drawing, the approximate level of this liquid, designated y, when to the left of the valve, is suggested in Figr5.

Assuming that the refrigeration system is in normal operation, hot discharge gases passing from the compressor to the condenser via line 28 give up their heat to the liquid The coil 84 in said line is provided for increased heat transfer, as is understood. Dissipation of the heat thus obtained is obviated by the insulation 82 surrounding the tank 80, and the insulation 99 about conduit B. In other words, the arrangement is such that the heat accumulates and is stored in the tank.

At this time switch 52 is open, so that heater 86 is non-operative, and valve 48 is seated by gravity against valve seat 44. Vapor generator 13, submerged in the eutectic solution x, ob-

viously is also hot. Therefore, any of the volatile liquid y which had been trapped within the system to the right of valve I8 at the close of a previous defrosting operation, will have vaporized and passed through vapor line |00 into the uppermost portion of the system.

That is to say, shortly after normal operation is resumed, all of the refrigerant yvwithin the system will be confined to the left of valve I6, as will be more clearly explained.

Assuming now that the evaporator requires defrosting, the compressor is turned off and switch 52 is closed. Energization of the solenoid coil 50 elevates valve 48 from its seat,v whereupon the liquid y in chamber 40 and in the system to the left thereof, quickly i'lows into the vapor generator 13. Simultaneously, heating device 86 is energized so that additional heat is supplied duringv the entire defrosting cycle.

As the refrigerant y now collects in the already hot generator 13, it quickly vaporizes. The hot vapors under pressure rise and travel along the inner surfaces of the system, give up their heat to the evaporator and drain pan to defrost the same, and having thereby become condensed, or liquefied, return by gravity to the generator.

It is noted that the present system does not operate on the thermo-syphon principle, since the remote ends of the various tubes are closed as shown particularly in Fig. 6 at 64.

In other Words, thehotvapors do not circulate in the thermo-syphon sense, but rather do they permeate the system and then in reliquef'led form, return to the generator by gravity along the same passages they previously traveled in vapor form. This action is diagrammatically il. lustrated in connection with Fig. 6, wherein the arrows indicate vapors, and the letter y the condensed refrigerant returning to the generator.

The defrosting cycle continues as long as switch 52 remains closed. Most of the vapors generated iiow upwardly through line 20 into the branches 62, 66, and 68. Some vapors also ow through tube I 00 into the uppermost region of the system.

Since branches 62 and 66 are in intimate contact with each of the iins 36, diffusion of heat throughout the evaporator parts is rapid.

At the same time, since branch 68 is in intimate contact with drain pan I4, quick heat conduction to the latter is had. Coils 66 about drain pipe I6 obviate the necessity of any separate or special device to pervent drippings from freezing.

Obviously, a defrostingoperation continues until all of the accumulated frost on the evaporator assembly has been melted. The fins 18 are provided on the generator tubes 14 to more quickly transfer the heat from the liquid a: to the liquid y. Device 86 continuously replaces the heat withdrawn by the generator.

Should the cooling unit be of the plate type, the defrosting cycle operates in identical fashion. In such case, the casing |02 performs the function of branches 62 and 66, so that the accumulated frost on the exterior surfaces of said casing are caused to melt.

Assuming now that defrosting is complete, switch 52 is thrown open, the compressor is turned on, and normal refrigeration resumes. Simultaneously with the opening of switch 52, valve 48 drops into its seat, thereby preventing all the liquid yin the system to the left of the valve from returning again to the generator.

However, it is apparent that concurrently some of the liquid y will be on its way to lche generator in conduit 58. Since the accumulated heat in tank has been continually replenished by the heating device 86, all the liquid in the system to the right of the valve will continue to vaporize and pass through tube I 0I) into the uppermost region of the system, whence it joins the body of liquid already trapped to the left of the valve.

From the foregoing, it is manifest that a novel method, and apparatus for performing the method, has been provided. A defrosting operation may be initiated quickly, since an ever present quantity of heat is available. In addition, because of this arrangement, complete defrosting requires only a short time, so that no appreciable temperature rise in the refrigerated space will result.

Although not illustrated, it should be evident that a single vapor generator assembly 22 of proper proportion may serve to defrost a plurality of evaporators. Also that the solenoid valve, the heating device, and the compressor may all be in the same, or in separate circuits.

The particular embodiment illustrated and described is obviously susceptible of modification without departing from the principles of the invention.

For example, the eutectic solution may be heated by a hot Water coil immersed therein, instead of by the compressor discharge line, if desired. Further, instead of said eutectic solution, the tank 80 may contain water or other liquid maintained at a high temperature by any suitable means. Thus, for example, assuming that the tank 80 does contain water, it should be apparent that a constant or an intermittent iiow of hot water into and out of said tank would produce the same result as that produced by the compressor discharge line, the hot water coil, and so on. I

Therefore, it is to be understood that the invention is not to be limited to the precise details illustrated and described.

What I claim is:

` l. The method of defrosting an evaporator which consists in transferring the heat from the compressor discharge line to a eutectic solution contained in a hermetically sealed tank and preventing the dissipation of said heat during normal refrigerating operations, subjecting a predetermined quantity of volatile liquid to the action of said heat during a defrost operation, providing means for transmitting the hot vapors thus generated to the evaporator for condensation and return to the heat supply, and providing electrical means for continuously replenishing the heat withdrawn from said supply during each defrosting cycle.

2. Apparatus for defrosting an'evaporator and its associated drain pan, said apparatus including an integrated system of hollow components which after having rst been evacuated has thereafter been charged with a predetermined quantity of volatile liquid sealed therein, a vapor generator remote from the evaporator and in fluid communication with said system, a hermetically sealed heat storage tank containing a supply of eutectic in which said generator is submerged, a coil formed in the discharge line of a compressor and submerged in the eutectic to heat the same, and a covering of insulation about said tank to prevent the escape of accumulated heat therefrom.

3. Apparatus for defrosting an evaporator and its associated drain pan, including an integrated system of hollow components which after having rst been evacuated has thereafter been charged with a predetermined quantity of volatile liquid sealed therein, a vapor generator remote from the evaporator and in fluid communication with said system, a hermetically sealed heat storage tank containing a supply of eutectic in which said generator is submerged, a coil formed in the discharge line of a compressor and submerged in the eutectic to heat the same, a covering of insulation about said tank to prevent the escape of accumulated heat therefrom, a normally nonoperating heating element also submerged in said eutectic, a solenoid operable valve for normally coniining the secondary refrigerant within a portion of the system remote from said generator, and .means for energizing said heating element and solenoid during a defrost operation.

4. The apparatus of claim 3 in which the integrated system of hollow components includes said vapor generator, said solenoid operable valve, a rst conduit leading from the valveV to the generator, a second conduit leading from the valve to the evaporator and terminating in a laterally extending portion in intimate contact with elements of said evaporator, a rst laterally extending branch also in intimate contact with elementspf said evaporator, a second laterally extending branch in intimate contact with said drain pan, said laterally extending portion and said branches being provided with closed ends, coils formed in the second conduit about the drain pipe associated with said drain span, and a vapor line the lower end of which is in fluid cornmunication with the rst conduit, and the upper end of which is in communication with a portion of said system in the uppermost zone thereof.

5. The apparatus of claim 3 in which the integrated system of hollow components includes said vapor generator, said solenoid operable valve, a first conduit leading from the valve to the generator, a second conduit leading from the valve to the casing of a plate type evaporator, a laterally extending branch in intimate contact with said drain pan and being provided with a closed end, coils formed in the second conduit and about the drain fpipe associated with said drainpan, and a vapor line the lower end of which is in fluid communication with the first conduit, and the upper end of which is in communication with said casing at the top thereof.

6. In a defrosting apparatus of the character described. a vapor generator assembly including a hermetically sealed tank, a quantity of eutectic therein, a covering of insulation enclosing the tank, a generator submerged in the eutectic, an electrically operable heating device submerged in the eutectic, means for controlling the operation of said heating device, and means for heating said eutectic during normal refrigeration operations.

7 In a defrosting apparatus of the character described, a vapor generator assembly including a hermetically sealed tank, a quantity of eutectic therein, a covering of insulation enclosing the tank, a generator submerged in the eutectic, an electrically operable heating device submerged in the eutectic, means for controlling the operation of said heating device, and means for heating said eutectic during normal refrigeration operations, said means comprising a line leading from the compressor to the condenser and passing through said tank whereby the heat inherent in the hot gases flowing through said line is absorbed by the eutectic.

8. In a defrosting apparatus of the character described, a vapor generator including a header, a conduit leading therefrom, one or more reversely curved tubes depending from the header and each terminating in a cosed lower end, and a series' of heat-absorbing fins rigidly attached to each tube at intervals throughout its length, said header, conduit, and tubes being immersed in a body of liquid maintained at a high temperature within a hermetically sealed tank.

9. ,In a secondary defrosting system of the character described, a vapor generator including a header, one or more tubes depending from the header and each terminating in a closed lower end, a series of heat-absorbing ns rigidly attached to each tube at intervals throughout its length, a conduit leading from the header to a valve selectively operable to permit or prevent flow of the vapors generated to that portion of said system located in proximity to an evaporator, said header, tubes, and a portion of said conduit being immersed in a body of liquid maintained at .a high temperature within a tank not located in proximity to said evaporator, and a vapor tube the upper end of which opens into a portion of said system inthe upper zone thereof, the lower end of which opens into a portion of said system in the lower zone thereof.

LOUIS F. LA PORTE.

REFERENCES CITED The following references are of record in the le oi' this patent:

UNITED STATES PATENTS Number Name Date 1,890,085 Hill Dec. 6, 1932 1,912,841 Haymond June 6, 1933 1,937,288 McGraw Nov. 28, 1933 2,081,479 Fink May 25, 1937 2,095,017 Wilkes et al. Oct. 5, 1937 2,181,276 Kogel et al Nov. 28, 1939 2,286,205 Grubb June 16, 1942 2,452,102 Cocanour Oct. 26, 1948

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