US2747378A - Defrosting arrangement for a refrigerating coil - Google Patents

Description

H. T. NOONE May 29, 1956 DEIFROSTING ARRANGEMENT FOR A REFRIGERATING COIL 2 Sheets-Sheet 1 Filed March 18, 1955 INVENTOR.

H. T. NOONE May 29, 1956 DEFROSTING ARRANGEMENT FOR A REFRIGERATING COIL Filed March 18, 1955 2 Sheets-Sheet 2 INVENTOR. MA 77 WW BY United States Patent-O DEFROSTING ARRANGEMENT FORA REFRIGERATING COIL Howard T. Noone, Atlanta, Ga., assignor to Carrier Corporation, Syracuse, N. Y., a corporation of Delaware This invention relates to a defrosting arrangement for a refrigerating coil subject to the air of a refrigerated space maintained at temperatures below the freezing point of water and to the method of defrosting the coil.

It is customary in low temperature refrigeration in which a space is required to be constantly maintained at temperatures below the freezing point of water to employ a refrigeration coil placed in the refrigerated space or in a position connected to the refrigerated space, and a fan to pass air through the coil to supply cooled air to the refrigerated space. Under these conditions, of course, frost collects on the surfaces of the coil so that periodic defrosting is required to remove the frost from the coil.

It has been proposedheretofore to spray water from a spray panor spray nozzles over the surfaces of the coil to remove frost therefrom. In many cases, thisarrangement presented a diificult'problem for'frequently a film-ofwater formed across the orifices of the spray nozzles or spray pan, the water freezing to clog or block the nozzles. Thus, when defrosting of the coil was 'again required; it was impossibleto'spray waterthereover because'the water could notpass through the orifices.

Under these circumstances-,it was necessary for the operator to discontinue operation of the refrigeration system and enter the refrigerated space to clear the nozzle orifices of i'ce preventing passage of'the defrosting mediu'msuch as water over the surfaces of the coil. This is: disadvantageous not only because the operator is forced to work at temperatures considerably below the' freezing point of water, but chiefly because during this extended shut down of the refrigerationsystem", temperatures 'in the refrigerated space mayrise to apoint-in which the food products stored therein are subject to spoilage as wellas permitting the formation of heavy layers of frost over the coil which are extremely difiicult to remove. The

present invention provides a simple andhighly effective I means for defrosting which obviates these disadvantages.

The present invention relates to the combination with 1 a refrigerated space ofa coil adapted for periodic defrosting, water, distributing means placed to distribute water over the coil to defrost thecoil, a fan to move air of the periodwhen the fan is inoperative, and compressed air supply means connected to the watersupply linerfonsupplyinggcompressed air to the waterv distributing. means. to remove any water film formed across-the distributing orifices.

This invention further relates to a method of defrosting a refrigerating coil adapted to cool a refrigerated space having in combination therewith a water supply line and spray nozzles for: distributing water over the coil to remove frost therefrom, characterized by the steps of spraying water over the coil to. remove the frost therefrom, then, when defrosting is substantially completed, discontinuing the supply of water to thespray nozzles draining thewater supply line and supplying. compressed air to the water supply line through the spray nozzlesto remove any water film formed across the orifices thereof.

The attached drawings illustrate a preferred embodiment of the invention, in which' Figure 1 is adiagrammatic view of a refrigerated space embodying the present invention;-

Figure 2 is a view-in-elevatio'n of the coil unit and defrosting arrangement with the casing of. the -coil unit removed-to display the coil anddefrosting line:

Referring to-the drawings, there is shown in Figure 1 a refrigerated space 2 such as thestorage space. of'a warehouse designed to bemaintained at a temperaturebelow freezing. A penthouse 3 is placed on the roof of the structure and is connected to refrigerated space 2 by opening .4 through which air is'drawn into the penthouse: and duct 5 through which cooled'air is discharged into the refrigerated space to maintain circulation of coldair therethrough.

In the penthouse 3 is placed a plurality of cooling coils 6 which function as theevaporator of arefrigeration system (not shown). The high*side of the -refrigeration system'is placed withoutthe refrigeratedareaand isconnected to-the coils in the usualmanner; It will be appreciated refrigerated brine may be passedthrough coils 6 or if'desired' direct eXpansioncoils-may beemployed. Fan 7 actuated by a suitable motortnotshown) serves'to draw-air from refrigerated-space 2 .into the penthouse 3 passing the air through co-ils- 6 and then discharging the cooled air through-duct 5 into the refrigerated space-:so that a continuous circulationoficooled air ismaintained throughout thev refrigerated area. An air-distribution duct (not shown) may be provided in the refrigerated space ifdesired to assure any-desired 'circulation of'cooled air therethrough: It will be understood while I havedescribed a plurality of cooling coils, the invention'is applicable to a single coil.

A plurality of flapqdoors-S are provided at "the discharge side of' the. coils,6,-the doors being closed during a defrosting operationin order to discontinue gravity-flow of air through the coils to the refrigerated area which might inadvertently raise the temperatureini-the refrigerated space. Below the coils is placed a drip pan-9 which serves to collect water and meltedfrost from'the-coils.

An inclined drain pipe 10'eXtends downwardly fromthe drip panto a point without penthouse 3.. Preferably the drain pipe .10 is closedexteriorly of the penthouse 3 by a cap .11. It will be appreciated, if desired, a loop in drain pipeltlexteriorly of the penthouse may be pro-videdinstead of cap 11. The: purpose ofathe .cap;or loop, of course, is to prevent.warm,moisture ladenedair' entering the drain pipe during the refrigerating operation-since the moisture from such air might condense,- formingice to.v prevent drainage through pipe 10..

A plurality of sets. of spray nozzles 12 are placedadjacent the top of each coil tospray waterthe-reover during a defrostingoperation. Referring to Figure 2, it will-be observed that spray. nozzles .13 areprovided torspray water over. the underside of the coil 6 during. the defrostingoperation. The. spraynozzleslZ areconnected to headers 14 which, inzturn, are connected to pipe 15. Spraynozzles' 13 areconected to headers*16which in turnare also. connected to pipe 115. The headers 14, 16 are inclined so that water will flow backwardly therein to pipe 15. Pipe 15 extends vertically so that water therein will flow downward when supply of water is discontinued. Pipe 15 is connected to an inclined pipe 17, which extends downwardly to a point without the refrigerated space and is connected to a source of supply of water which may be, for example, a city water supply. A valve 18 is placed within pipe 17 exteriorly of the refrigerated space. Valve 18 serves to control supply -of water to the defrosting arrangement. A drain pipe 19 is connected to pipe 17 without the refrigerated space, a valve 20 being placed in pipe 19. When valve 2! is in an open position, water in pipe 17 is free to drain therefrom so that the greater portion of the water in spray nozzles 13, 12, headers 14, 16 and pipe 15 is free to flow in a backward direction without the refrigerated space and be discharged to any suitable drain.

Connected to pipe 17 between valve 18 and the point of connection of drain pipe 19 is a compressed air supply line 21, for a purpose hereinafter explained. A valve 22 is placed in compressed air supply line to control passage of compressed air therethrough. Line 21, of course, is connected to any suitable source of supply of compressed air such as a compressor.

It will be appreciated that valves 18, 20, 22 may be manually or automatically operated. Preferably, such valves are solenoid valves, electrically actuated.

Considering the operation of the system, the refrigeration system is started to cool brine. A brine pump (not shown) is actuated to pass cold brine through coils 6, fan 7 serving to draw air from the refrigerated space 2 through the coils thereby cooling the air and to discharge the cooled air into the refrigerated area. Under these circumstances, frost collects on the coils so that periodic defrosting of the coils is required for efficient, economical, operation. When it is desired to defrost the coils, opera tion of the fan is discontinued. Operation of the brine circulating pump is also discontinued. The flap doors on the air leaving side of the coils is closed. Cap 11 closing drain pipe is removed to permit drainage of water and melted frost from the drain pipe. Valve 18 is then opened permitting supply of water through pipe 17, pipe and headers 14, 16 to spray nozzles 12, 13 which serve to discharge the water over the coil surfaces to melt the frost therefrom.

After the frost has been substantially removed from the surfaces of the coil, valve 18 is closed and valve 20 "is opened to permit water to drain from pipe 17, pipe 15,

headers 14, 16. Under some circumstances, of course, films of water may form across the spray nozzle orifices. When it appears that water has completed drainage from pipe 17, valve 20 is closed and valve 22 is opened,permitting compressed air to pass from line 21 into pipe 17 and be supplied to the spray nozzles and discharged therefrom so as to break any water film formed across the spray nozzle orifices. Compressed air is discharged through the spray nozzle orifices for any short period of time sufficient to assure that a film of water does not form across the nozzles. This film of water, of course, if permitted to form, would freeze thereby preventing defrosting when the coils again require the removal of frost from the heat exchange surfaces thereof.

Valve 22 is closed discontinuing supply of compressed air to the spray nozzle orifices. Cap 11 is replaced on drain pipe 10 and the flap doors 8 are opened to permit air from the refrigerated space to be drawn through the coils. The fan is then started to circulate air through the coils and the refrigerated space. The pump of the brine system is actuated to circulate cooled brine to the coils 6 in heat exchange relation with air passing therethrough so that the system is again placed in its refrigerating cycle.

While I have described this arrangement as employing a cooled brine for refrigeration purposes, it will be understood that the coils may be, if desired, direct expansion coils connected directly to a refrigeration sys- The present invention provides a simple, economical, effective defrosting arrangement for coils placed in a refrigerated space. While I have shown the refrigerating coils placed in a penthouse connected to a refrigerated space, it will be appreciated temperatures in the penthouse are approximately the same as the tempera tures in the refrigerated space. In some installations, of course, the refrigerating coils will be placed directly in the refrigerated space rather than in an area connected thereto.

The present invention permits the use of water to defrost refrigerating coils subject to the temperature of an area below the freezing point of water. To assure that no water remains in the Water lines during a refrigerating operation, positive means have been provided for assuring removal of all water from the water lines subject to temperatures below the freezing point of Water. The present invention prevents the formation of a water film across the spray nozzle orifices, thus preventing formation of ice in the spray nozzles which would prevent a subsequent defrosting operation.

While I have described a preferred embodiment of the invention, it will be understood that the invention is not limited thereto since it may be otherwise embodied within the scope of the following claim.

I claim:

In a defrosting arrangement, the combination of a first compartment adapted to contain articles to be refrigerated, a second compartment in communication with said first compartment, a fan associated with said second compartment adapted to induce an air stream from said first compartment through the second compartment and back into said first compartment, at least one evaporator coil located in said second compartment, said evaporator being in heat exchange relation with the air stream induced through second compartment, a plurality of spray nozzles operatively associated with -said evaporator so that fluid issuing from said spray nozzles will substantially cover the evaporator surface, a header operatively connected to said spray nozzles and adapted to supply a defrosting fluid to said spray nozzles, said header passing from said second compartment to points remote from said first and second compartments, a drain valve located in said header remote from said second compartment, a line operatively connected to a source of defrosting fluid, a line connected to a source of compressed gas, said last mentioned lines being operatively connected to said header valve means being located in each of said lines and being adapted to selectively pass defrosting fiuid or compressed gas through said header, said header being so disposed so that gravity will drain substantially all fluid from said lines through said drain valve when said valves in said lines are in closed position, a drip pan disposed below said evaporator to collect all defrosting fluid dripping therefrom, said drip pan being connected to a drain line adapted to pass defrosting fluid from said second compartment, closure means associated with said last mentioned drain line adapted to minimize heat transfer through said drain line into said second compartment, at least one damper member being located in said second compartment, said damper member being adapted to be closed during the defrosting process so as to restrict the flow of air through the second compartment during the defrosting process.

References Cited in the file of this patent UNITED STATES .PATENTS 2,480,346 Watts Aug. 30, 1949 2,527,368 McGrath Oct. 24, 1950 2,583,271 Mellion Jan. 22, 1952 2,607,202 Garland Aug. 19, 1952

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