US2665566A

US2665566A - Evaporator defrosting arrangement

Info

Publication number: US2665566A
Application number: US261165A
Authority: US
Inventors: Charles S Grimshaw
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1951-12-12
Filing date: 1951-12-12
Publication date: 1954-01-12
Anticipated expiration: 1971-01-12

Description

Jan. 12, T954 0. s. GRIMSHAW EVAPORATOR DEFROSTING ARRANGEMENT Filed Dec. 12, 1951 lhvehtoFz Charles S. GT'imShaW,

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His Attbr-nqg.

Patented Jan. 12, 1954 EVAPORATOR DEFROSTING ARRANGEMENT Charles S. Grimshaw, Erie, Pa., assignor to General Electric Company, a corporation of New York Application December 12, 1951, Serial No. 261,165

13 Claims.

My invention relates to refrigerator evaporators and more particularly to defrosting arrangement for evaporators.

In many household refrigerators, the evaporator for cooling the food storage compartment is exposed to the air within the compartment and is operated at a temperature below the freezing point of water. As a result, moisture in the air within the storage compartment condenses on the evaporator and collects thereon in the form of frost. This layer of frost on the surface of the evaporator has an insulating effect reducing the efficiency of the evaporator in cooling the food storage compartment. It is accordingly necessary to remove this frost from time to time in order to prevent too serious a reduction in the operating efiiciency of the refrigerating apparatus. In many cases, this defrosting is accomplished manually by stopping operation of the condensing unit and placing trays of warm water on the refrigerated surfaces of the evaporator. Defrosting in this manner is a somewhat timeconsuming and disagreeable operation. By my invention a relatively uniform heating of the evaporator surface is accomplished and defrosting is achieved without the necessity of using trays of warm water and the like, and the time required for the completion of the operation is materially reduced.

Accordingly, it is an object of my invention to provide an improved arrangement for defrosting a refrigerator evaporator.

It is another object of my invention to provide an improved arrangement for defrosting a refrigerator evaporator which maintains a substantially uniform temperature throughout the entire evaporator during the defrosting operation.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In carrying out the objects of my invention, a flooded evaporator including continuous serpentine tubing is employed. Defrosting is accomplished by circulating vaporized refrigerant through the evaporator. The heating and circulating of the refrigerant is achieved by providing means for supplying heat to the continuous serpentine tubing of the evaporator at two points spaced along the series circuit thereof. In the specific embodiment illustrated, the tubing includes a horizontal portion and a vertical portion, one of the heating points being located in the horizontal portion of the evaporator and the other of the points being located in the vertical portion of the evaporator.

For a better understanding of my invention, reference may be had to the accompanying drawing in which Fig. 1 is a side elevation view of a portion of a refrigerator incorporating an embodiment of my invention.

Fig. 2 is an isometric view of the evaporator including a schematic wiring diagram, the walls upon which the evaporator tubing is mounted being shown in dotted lines for clarity.

Referring to Fig. 1, there is shown a refrigerator cabinet I including an outer wall 2 and a spaced inner wall or liner 3, the inner wall 3 defining a food storage compartment 4. The

access opening of the food storage compartment is closed by a door 5.

In order to cool the food storage compartment 4, an evaporator 6 is mounted in the upper portion of this compartment. In the form illustrated, the evaporator 6 includes a supporting sheet structure or wall structure '1 including a vertical rear wall or sheet 8 and a horizontal bottom wall or sheet 9. The refrigerating portion of the evaporator includes a header In which is positioneo. near the top of the rear vertical sheet or wall 8. The evaporator 6 is of the flooded recirculating type and includes continuous tubing H arranged in serpentine form and secured to the supporting sheet structure I. One end of the continuous tubing II is connected to the header ill of the evaporator at 2 below the normal level of liquid refrigerant in the header It. The other end l3 of the continuous tubing II is connected in communication with the interior of the header I0 above the normal level of liquid refrigerant in the header. By this arrangement, the liquid refrigerant flows from the header to the tubing II at the connection [2 and vaporiizged refrigerant is discharged into the header at In the form illustrated, the serpentine tubing H includes a first portion [4 which is arranged in a horizontal plane and secured in any suitable manner, as by brazing or welding, to the exterior or bottom surface of the bottom horizontal wall 9. Liquid refrigerant is supplied to the horizontal portion 54 through a vertical tubing section i5 extending between the connection [2 at the header and the horizontal portion I4 of the tubing. A trap I6 is provided at the bottom of the tubing section [5 immediately preceding the horizontal portion [4. The vertical tubing section i5 is spaced from the vertical wall or sheet 8 of the evaporator, and hence is not in heat exchange relationship therewith. The tubing further includes a second portion I? which is arranged in a vertical plane and is secured in any suitable manner, as by brazing or welding, to the exterior pr rear surface of the rear vertical wall 8. Liquid refrigerant is suppliedftothe evapora tor from a condensing unit (not shown) through a liquid line or capillary tube l8. lary tube is connected to the tubing il in the first or horizontal portion M thereof near 'the junction between the horizontal portion FE and the second or vertical portion il vaporized refrigerant from the header is r turned to the condensing unit through a suction line it.

The evaporator 8 and thetubing ll thereofare exposed to the air within the foods'torage coinpartment 4 during operation of the refrigerator.

In order to maintain a sufficiently low temperature the food storage compartment 4, and in ord 'mteih'etempereuire withintheiompart'riintfforinedby the wall structure I siifficiently m or preservation of lffrozen' fo'o evap- "s'br this"type are'uermeuy'opereteue a V p at'ure siihstantially below 'f'the freezing point of water. As aresult rhoi's'turein'the "air witliin we "food storage compartment condenses on.theevaporator"andcollects thereon as frost, feveiit'iially'forminga manketcr such frost over 'thetubiiig' end walls'of the evaporator, This rresraerses an insulating medium reducing the cooling effector the evaporator and reducingthe einjien'ey'ef therefri'gerating system. It is. desirable therefore to'remove this'blank'et of frost from tinie'to time to maintain operation of the refrigeratingsystem at a reasonably high effi- *eien'e'y. In 'accordai'ic'e'with' invention, -an 'ar- .rangement is provided whereby'heat is supplied to the evaporator for vaporizing refrigerant within the tubingand' for assisting in circulating the refriger'ant through the tubing so that the vaporizedref'rigerant asit reco'ndenses gives up'heat t'o' thejtubing for melting the frost therefrom. "Spe fically,"lfprovide a defrosting"arrangement Tin which heat is supplied to thecontinuous tubj'ingiat two points or sections thereof spaced along jthaseries circuitof the 'continuoustubing. In thef'form illustrated, one of "these sections is located in a horizontal portion of the tubing and the other is located in the vertical portion of the tubing. p 7 a 7 p ,7 Thus one heater'2ii is located adiacentasection 2| of ''a horizontal portion of the tubing l l. The 'heater'20 is located at the beginning of the hori- "zorital portionof the tubing ii, that is, immediat'elyfollowing the trap it. This heater may bean jelectric'heating element or other suitable heating device forsupplying heat to the tubing alndito the refrigerant therein. By way of example; this heater may conveniently be the sheathed "insulated type of heating element sold'under the shade-mark Calrod. A similar type ofrheater 22 isfpositioned in heat exchange relationship'with "a section 123 of the vertical portion of the tubing H... This heater 22 is located near the bottom of this vertical portion ii and the vaporization of liquid refrigerant within the tubing at this point assists in promoting upward circulation of "both vaporized and liquid refrigerant'in the veritic'al'fportion ll. The heater 2% vaporizes refrigerant and,because of the circulation induced by ,heater 22, the' refrigerant circulates through the @tubing of the horizontal portion i i and, in recon- "dens'ingjit gives up heat to the tubing; thereby effecting melting of frost therefrom. The heaters This

oapil

20 and 22 may be secured in heat exchange relat tionship with the sections 21 and 23 of the tubing respectively in any suitable manner. By way of example, the heaters may be held in such heat exchange engagement with the tubing by

clamps

24 and 25, respectively, The clamp 24 is removably secured tothe bottom sheet 9 of the evaporator wall structure in'any suitable manner, as by screws (not shown) and the clamp 25 is similarly removably secured to the rear sheet 8 of this wall structure.

As indicated schematically in Fig. 2, the heaters 20 and 22.are supplied in series with power from "amysuitablefelectrical power supply through lines 28, It is desirable that the

heaters

20 and 22 be connected -series. Should the two heaters beconnected in parallel and should the heater 22 in thevertical portion 11 burn out, the heater 20 in'th'e horizontal portion M might merely form a large pocket of vaporized refrigerant Without effectivecirculation thereof. Such lack of circulation and, hence, lack of replenishment of liquid refrigerant in the area of the heater 20 might result in damagefrom overheating in this region of the evaporator. A switch 2'! is provided-for controlling the energization of the heaters 20 and i2, the'switch 2'! being adapted in its closedposition to engage contacts 28 to close the circuitto the heaters 213 and'22 in series. The switch 21 may be operated in any suitablemanner for initiating energization of the heaters; for example, it may be manually closed to initiatethis heating/it may be closed by some mechanism rm automatically initiating defrosting atpredetermined intervals; etc.

section2! of the'tubing. Refrigerant normally circulates in the direction of the arrows shown in Fig.2 because'of the head of liquid refrigerant imposed on the'tubing'through the connection at 12. During defrbsting'the refrigerant vaporizedby'the heater 2!] in the section 2| circulates in the direction of the arrows moving with it a quantity of liquid depending upon the head produced by the difference in density of therefrigerant in the'two vertical sections I5 and" ll of the closed refrigerant path. 'A circulation rate will be establishedso that the flow losses will be equal to this head. The trap l6 blocks any tendency of refrigerant vaporized by the heater 20 to rise upwardly through the section 15 at the tubing and insures 'circulation'of refrigerant in the normal direction. 'The circulating vaporized refrigerant, in recondensing, supplies heat to the horizontal portion 'M of the tubing, efiecting melting "of frost'from this horizontahportion. The heater 22 on'the vertical portion 17' of the tubing alsoeffects vaporization of liquid refrigerant in the tubing, specifically at the section 23 adjacent the heater, and the rising bubbles of vaporized refrigerant "reduce the head in the vertical 'tubi'ng portion i1, assisting circulation of downwardly 'from"the* header into the horizontal portion M. The vaporized refrigerant in rising upwardly through the tubing portion l1 recondenses therealong, giving up heat to this portion of the tubing and effecting melting of frost therefrom.

The utilization of the two heaters shown and the disposition of these heaters, one at the beginning of the horizontal portion and one at the bottom of the vertical portion causes a relatively uniform temperature to bemaintained throughout the evaporator and allows the utilization of a tubing of relatively small size since the vaporized refrigerant need flow only a substantially shorter distance than would be the case were the defrosting attempted with a single heater. It also provides for effective defrosting of a horizontal sheet which is more acceptable than a sloping sheet for the bottom of an evaporator.

The significance of the flooded recirculating evaporator in the defrosting operation should be noted. In cases where a series system is employed, that is where the capillary tube is connected at one end of the evaporator tubing and the header at the other, it is'possible for the heater to blow the tubing dry. Under these circumstances, continued application of heat by the heater could burn out the heater or cause dam age to the evaporator through local overheating. By my arrangement employing a flooded recirculating evaporator where both ends of the evaporator tubing are connected to the header, a supply of liquid refrigerant to the tubing in the region of the heater is assured, and the possibility of the evaporator being blown dry, with resultant damage, is minimized.

While I have shown and described a specific embodiment of my invention, I do not desire my invention to be limited to the particular construction shown and described, and I intend, by the appended claims, to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A flooded evaporator comprising a header and a single continuous length of tubingconnected at both ends to said header and providing a series circuit for refrigerant, said tubing including a first portion and a second portion in series circuit with said first portion, one end of said tubing being connected to said header below the level of liquid refrigerant therein for supplying liquid refrigerant to said first portion, the other end of said tubing being connected to said header above the level of liquid refrigerant therein for conducting vaporized refrigerant from said second portion to said header, and means for supplying heat to said evaporator at two sections of said tubing spaced along the series circuit thereof for defrosting said evaporator, heat supplied to at least one of said sections being also effective for inducing circulation of refrigerant through said continuous tubing.

2. A flooded evaporator comprising a header and continuous tubing connected at both ends to said header, said tubing including a first portion arranged in a horizontal plane and a second portion in series circuit with said first portion and arranged in a vertical plane, one end of said tubing being connected to said header below the level of liquid refrigerant therein for supplying liquid refrigerant to said first portion, the other end of said tubing being connected to said header above the level of liquid refrigerant therein for conducting vaporized refrigerant from said second portionto said header, and means for supplying heat to said evaporator at two sections of said tubing for defrosting said evaporator, one of said sections being located in the horizontal portion of said tubing whereby heat is supplied to liquid refrigerant in said tubing at said one of said sections to vaporize said refrigerant for defrosting said horizontal portion, the other of said sections being located in the vertical portion of said tubing whereby heat is applied to liquid refrigerant in said tubing at said other of said sections to vaporize said refrigerant for defrosting said vertical portion and for inducing circulation of refrigerant in said tubing.

3. A flooded evaporator comprising a header and continuous tubing connected at both ends to said header, said tubing including a first portion arranged in a horizontal plane and a second portion in series with said first portion and arranged in a vertical plane, one end of said tubing being connected to said header below the level of liquid refrigerant therein for supplying liquid refrigerant to said said first portion, the other end of said tubing being connected to said header above the level of liquid refrigerant therein for conducting vaporized refrigerant from said second portion to said header, and means for supplying heat to said evaporator at two sections of said tubing spaced along the series circuit thereof for defrosting said evaporator, one of said sections being located near the beginning of said horizontal portion for vaporizing liquid refrigerant to defrost said horizontal portion, the other of said sections being located at the bottom of said vertical portion for vaporizing liquid refrigerant to defrost said vertical portion and to induce circulation of refrigerant through said continuous tubing.

4. A flooded evaporator comprising a header and continuous tubing including a first portion arranged in a horizontal plane and a second portion in series with said first portion and arranged in a vertical plane, one end of said tubing being connected to said header below the level of liquid refrigerant therein for supplying liquid refrigerant to said horizontal portion, the other end of said tubing being connectedto said header above the level of liquid refrigerant therein for conducting vaporized refrigerant to said header, and means for supplying heat to said evaporator at two sections of said tubing for defrosting said evaporator, one of said sections being located near the point where liquid refrigerant reaches said horizontal portion from said header, the other of said sections being located near the bote tom of said vertical portion of said tubing.

5. A flooded evaporator comprising a header and continuous tubing including a first portion arranged in a horizontal plane and a second portion in series with said first portion and arranged in a vertical plane, said tubing including a vertical section connected to said header below the level of liquid refrigerant in said header for supplying liquid refrigerant to said horizontal portion, said tubing being formed to provide a trap between said vertical section and said horizontal portion, the other end of said tubing being connected to said header above the level of liquid refrigerant therein for conducting vaporized refrigerant to said header, and means for supply ing heat to said evaporator at two sections of said tubing for defrosting said evaporator, one of said sections being located in said horizontal portion immediately following said trap, the other of said sections being located near the bottom of said gr qa .pqr mois d u ms.-.

ii. A refrigerating system including a condense ing unit and a flooded evaporator, said evaporator comprising a header and continuous tubing including a first portion arranged in a horizontal plane and a second portion in series with said first portion and arranged ina vertical plane, one end of said tubing being connected to said header below the level of liquid refrigerant for supplying liquid refrigerant to said horizontal portion, the other end of said tubing being connected to said header above the level of liquid refrigerant therein for conducting vaporized refrigerant to said header, and means for supplying heat to said evaporator at two sections of said tubing for defrosting said evaporator, one of said sections being located near the point where liquid refrigerant reaches said horizontal portion from said header, the other of said sections being located near the bottom of said vertical portion of said tubing, and a conduit for supplying liquid refrigerant to said evaporator from said condensing unit to said evaporator, said conduit being connected to said horizontal portion of said tubing at a point immediately preceding said vertical portion.

'7. In combination with a flooded evaporator comprising a header and a single continuous length of tubing connected at both ends to said header and providing a series circuit for refrigerant, said tubing including a first portion and a second portionin series with said first portion, one end of said tubing being connected to said header below the level of liquid refrigerant therein for supplying liquid refrigerant to said first portion, the other end of said tubing being connected to said header above the level of liquid refrigerant therein for conducting vaporized refrigerant to said header, a defrosting arrangement for said evaporator comprising a first heater disposed in heat exchange relationship with a section of said first portion of said tubing for supplying heat to liquid refrigerant therein to vaporize said refrigerant for defrosting said first portion, and a second heater disposed in heat exchange relationship with a section of said second portion of said tubing for supplying heat to liquid refrigerant therein to vaporize said refrigerant for defrosting said second portion, said second heater also being eifective for inducing circulation of refrigerant through said continuous tubing;

8. A refrigerating system including a flooded evaporator, said evaporator comprising a header and continuous tubing including a first portion arranged-in a horizontal plane and a second portion in series with said first portion and arranged in a vertical plane, one end of said tubing being connected to said header below the level of liquid refrigerant therein for supplying liquid refrigerant to said horizontal portion, the other end of said tubing being connected to saidheader above the level of liquid refrigerant therein for conducting vaporized refrigerant to said'header, a first heater for supplying heat to said horizontal portion for vaporizing liquid-refrigerant-to effect defrosting of said horizontal portion, said first heater being disposed in heat exchange-relationship with a section of said horizontal portion located substantially in the region where liquid refrigerant reaches saidhorizontal portion from said header, and a second heater for supplying heat to said vertical portion for effecting vaporization of liquid refrigerant to eiiect defrosting of said vertical portion and to induce circulation of refrigerantthrough said tubing,

8 said second heater being disposed in heat exchange relationship with a section of said vertical portion located near the bottom of said vertical portion.

9. A refrigerating system including a flooded evaporator, said evaporator comprising a header and continuous tubing including a first portion arranged in a horizontal plane and a second portion in series with said first portion and arranged in a vertical plane, said tubing including a vertical section connected to said header below the level of liquid refrigerant in said header for supplying liquid refrigerant to said horizontal portion, said tubing being formed to provide a trap between said vertical section and said horizontal portion, the other end of said tubing being connected to said header above the level of liquid refrigerant therein for conducting vaporized refrigerant to said header, a first heater for supplying heat to said horizontal portion for vaporizing liquid refrigerant to effect defrosting of said horizontal portion, said first heater being disposed in heat exchange relationship with a section of said horizontal portion located immediately following said trap, and a second heater for supplying heat to said vertical portion for eiiecting vaporization of liquid refrigerant to effect defrosting of said vertical portion and to induce circulation of refrigerant through said tubing, said second heater being disposed in heat exchange relationship with a section of said vertical portion located near the bottom of said vertical portion.

19. A refrigerating system including a flooded evaporator, said evaporator comprising a header and continuous tubing including a first portion arranged in a horizontal plane and a second portion in series with said first portion and arranged in a vertical plane, one end of said tubing being connected to said header below the level of liquid refrigerant therein for supplying liquid refri erant to said horizontal portion, the other end of said tubing being connected to said header above the level of liquid refrigerant therein for conducting vaporized refrigerant to said header, a first heater for supplying heat to said horizontal portion for vaporizing liquid refrigerant to efiect defrosting of said horizontal portion, said first heater being disposed in heat exchange relationship with a section of said horizontal portion located substantially in the region where liquid refrigerant reaches said horizontal portion from said header, and a second heater for supplying heat to said vertical portion for effecting vaporization of liquid refrigerant to effect defrosting of said vertical portion and to induce circulation of refrigerant through said tubing, said second heater being disposed in heat exchange relationship with a section of said vertical portion located near the bottom of said vertical portion, said first heater and said second heater being connected in a series electrical circuit to insure simultaneous energization and deenergizationof said heaters.

11. A refrigerating system including a flooded evaporator, said evaporator comprising a header and continuous tubing including a first portion arranged in a horizontal plane and a second portion-m series with said first portion and arranged in'a vertical-plane, one end of said tubing being connected to said header below the level of liquid refrigerant therein for supplying liquid refrigerant to said horizontal portion, the other end ofsaidtubing being connected to said header above" the level ofliquid refrigerant therein 1 for zontal sheet and a vertical sheet and continuous 45 2276454 Becker 1942 conducting vaporized refrigerant to said header. tubing including a horizontal portion secured to a first heater for supplying heat to said horizontal said horizontal sheet and a vertical portion in portion for effecting vaporization of liquid refrig- H said tubing, a second clamp for holding said secfrigerant to said header, a first heater for supond heater against a section of said vertical porplying heat to said horizontal portion for vaportion located near the bottom of said vertical l5 izing liquid refrigerant to eifect defrosting of portion. said horizontal portion, said first heater being 12. In combination with an evaporator includdisposed adjacent a section of said horizontal continuous tubing including horizontal and verliquid refrigerant reaches said horizontal portical portions secured to said horizontal and ver- 20 tion from said header, a first clamp secured to tical sheets respectively and a header at the upsaid horizontal sheet for holding said first heater per portion of said vertical sheet having both in heat exchange relationship with said section ends of the serpentine tubing connected thereof said horizontal portion of said tubing for vawith a section of said horizontal portion of tubduce circulation of refrigerant through said tubing for supplying heat to liquid refrigerant therein for vaporizing said refrigerant to defrost said 35 CHARLES S. GRIMSHAW.

horizontal sheet, and a second heater disposed in heat exchange relationship with a section of References cued m the file of thls patent said vertical portion of tubing for supplying heat UNITED STATES PATENTS to liquid refrigerant therein for vaporizing said refrigerant to defrost said vertical sheet and to 40 ggia i ff Aug 32 circulation of refrigerant through said 29241612 sulzberger 17, 1935. 13. A refrigerating system including a flooded 5333 333 2335 3? evaporator, said evaporator comprisinga hori-