US2913883A - Evaporative cooling system - Google Patents

Description

Nov. 24, 1959 M. BURGEss `EvAPoRATIvE COOLING SYSTEM Filed Jan. 3, 1 956 INVENTOR s x 3 6p Wand. M Q 5 f Z, v.4 B

United States Patent ''cooiiv"G SYSTEM Leslie M.v Burgess; Burbank, Calif. Application January '3f956gseriaNu 356,880 11 claims; (c1-.162mm This invention relates to evaporativeeoolingsysterns for precooling articles of produce and 'the like priorto shipment and particularly to 'a metho'dand apparatus for this purpose utilizing a liquidspr'ay condensing medium.

The evaporative cooling process `is"`wel1` understoodin the art and involves the pl'cing of thefarticles 'to 'b'e cooled in a sealed chamber, evacuation Vof die chamber to` an absolute pressure equal to or slightly less than `th"e vapor pressure of the surface moisture on the articlest'o cause such moisture toevapora'te and Vboil off, With resultant cooling of the articles, land removal of tlie Water vapor or steam as it is formed so as to maintain the vapor pressure in the chamber sbstantiallybelov thesaturated :vapor pressure of the sur-face'moisture, or ice', t its then temperature. l p

A primary object of this invention ifs the provision :of an improved method and 'apparatus for such"`evap'orative precooling of articles of produce and the` like.

Various systems have beenprop'osed for 'effeetively'r'fenoving the large volumes of vapor evolved' during the cooling process so as to maintain the latter-process 'atan optimum rate.

precooling of articles of produce or the like'ivnvolvinig the use of a liquid 'spray astheeondensiiig medium.

One general form of spray-type condensing system `utilizes a container which is initially filled with the condensing liquid, the latter being `maintained at a low temperature by the immersion of ice or cooling ycoils therein. During operation of the system, the cold liquid isvvithdrawn from the container and sprayed into a condensing chamber for contact with theevolvd vapor. The condensed vapor and condensing liquid become inter- 4mixed and areA collected in a suitable reservoir'from which they are discharged to a waste facility. `While'spray-type condensing systems of -this character possess the 'advantage of enabling the condensing liquid to be effectively maintained at the required-W temperature necessary for rapid and eflicient condensing of the relatively low temperature vapor evolved during the -latter `stages of the cooling process,` they are deficient in that in evaporative cooling apparatus of any substantial capacity, the initial supply of condensing 'liquid Vmust be `of considerable volume to provide suicient condensing uid'for the entire "cooling'process p Such large volume of` condensing liquid, obviously, results inacooling plant of substantial lfriagnitude and one which is suitable for onlyY permanent 4 installations.

To avoid this deficiency, spray-type condensing systems have been proposed wherein a relative1y"smallvolume of 'condensing liquid is continuouslyfrecircultedthrough the -4System. This recirculationlof the" condensing liquid, "s

will V be-apparent, requires continuous recooling thereof, after its Contact with 'the vapor, to *the 10Wv temperature necessary to efcient land rapid condensation of the vapor.

Moreover, since rapid and ecient condensation of the evolved vapor is promoted by a high velocity spray, `providing for more eicient heat transfer between the vapor and condensing liquid droplets and more rapid movement of the heated droplets and condensed vapor from the condensing zone, the condensing" liquid must be recirculated at a rapid rate through the system. Accordingly, cooling of the recirculating condensing liquid must be rapidly and eiciently accomplished.

Existing spray-type condensing. systems of this latter nature generally accomplish `the recooling of the Vcondensing liquid by recirculating it through a tank containing cooling coils. Efficient recooling of the condensing liquid is not thereby obtained since only a small `portion of the liquid in the -tank will `Contact the coils, and the relatively slovv movement of the condensing liquid over the coils results in the `creation lof astagnant, insulating `layer of liquid about the coil surfaces which substantially impedes the transfer of heat from the main -body of the liquid to the coils. p i' A further object of this invention is therefore the provision of a method and apparatus for evaporative precooling yof articles of `produce and the like utilizing a recirculating liquid spraytype condensingmedium and `wherein recooling ofthe reirculating liquid condensing fluid is more rapidly and effectively `accomplished than heretofore possible. Y p

Still 'a further object of the invention is the provision of a method and apparatus of the class described which employs chopped ice as the agent for recooling the liquid condensing fluid, andwhereinheat transfer from the condensing liquid to the recooling agent is rapidly and effectively accomplished by impinging the spray of the liquid condensing medium directly on theparticles of chopped ice.- a Yet a further object of `the invention is the provision of an evaporative cooling method and apparatus wherein chilled condensate -maybe returned tothe produce after chilling of the latter for rehydrating purposes.

Alstill further o bject is Ythe provision of vacuum cooling apparatus of the class described which embodies a novel meansof loading ice, for recooling the liquid condenser, into the system.

And a further obect is the provision of an evaporative cooling method and apparatus'of the class described which is-adapted to a` semi-portable installation, relatively inexpensive to use and manufacture, and which-possesses a substantially reduced cooling period.

These and other objects -of the invention are accom- Aplished by `evacuating Ithe cooling chamber, containing ythe articles to be cooled, to cause the surface moisture on such articlesto evaporate and boil off with resultant chilling of the articles. The aqueous vapor evolved during the cooling process is contacted with a high velocity spray o f recirculated, cold, condensing liquid whereupon the Vevolved vapor condenses and intermixes with the condensing liquid. The high velocity spray, consisting nowof droplets, of condensing liquid and condensed varpor droplets, is `impinged directly `on the surfaces of particles of chopped ice, for recooling of the condensing liquid. The recooled liquid and condensed vapor are then returned to the spray nozzles for repetition of the cycle. The high velocity of the spray effects intimate 'contact of the liquid therein with the surfaces ofthe chopped ice particles, which tend to float at the surface of the more dense liquid, lsov'as to provide for rapid and effective heat-transfer fromthe liquid to the ice. Also, constant agitation of tlrebo'dy'of` liquid and'fthe chopped ice particles by 'the'spray further" promotes cooling of the liquid and inhibits fusing of the particles together. ing of the particles is, of course, undesirable since it results in a reduction of the effective heat transfer surface area of the ice.

The preferred and illustrative embodiment of the present apparatus includes a novel means for loading ice into the apparatus prior to its operation.

The preferred embodiment of the invention also includes means for returning cooled liquid from the condensing chamber to the articles being cooled at the termination of the cooling process for cooling process for rehydrating of the articles.

A better understanding of the invention may be had from the following detailed description and .attached drawings wherein:

Figure l is a schematic illustration of the present vacuum cooling apparatus;

Figure 2 is a section taken along line 2-2 of Figure l; and

Figure 3 is a view schematically illustrating a modiiied form of the present apparatus.

Referring now to Figures l and 2 of the drawings, the present vacuum cooling apparatus illustrated therein comprises a hollow, cylindrical retort integrally closed at one end by an end wall 12 and closed at the other end by a hinged door 14 which may be releasably locked in its solid line, closed position, wherein it seals the open end of the retort 10, by means of suitable holding devices 16. Door 14 is movable to its dotted line, open position to permit the introduction of a load of produce 18 or other articles to be chilled into the interior of the retort. Tracks 20 may be secured to the lower portion of the interior wall of the retort, as illustrated, for supporting a wheeled platform 22 on which the produce may be loaded.

The interior of the retort 10 is separated, by a partition 24 of suitable heat insulating material, into a pair of chambers 26 and 28, the former of which forms the cooling chamber and the latter of which forms the condensing chamber of the present evaporative cooling apparatus. The upper edge of the insulating wall 24 terminates somewhat short of the upper portion of the inner cylindrical wall of the retort so as to provide a space through which vapor may flow from the cooling 'chamber 26 to the condensing chamber 28, as Will presently be more fully described.

Mounted in the upper portion of the condensing chamber 28 are a series of headers 30 each mounting along their length a plurality of downwardly directed spray nozzles 32. The headers 30 are connected through a uid conduit 34 to the discharge side of a pump 36, the intake of which is communicated via a fluid conduit 38 to the bottom of the condensing chamber 28. Line 34 includes a three-way valve 40 having one position whereon the headers 30 are connected to the discharge of pump 36, a second position wherein the headers are connected to a line 41 leading to a supply, not shown, of condensing liquid for initially charging of the system, and a third closed position.

Evacuation of the cooling chamber 26 and condensing chamber 28 to provide for the initial evaporation and boiling off of the surface moisture on the articles to be cooled is accomplished by a vacuum producing means 42 having its intake side connected to the upper portion of the condensing chamber 28, on the end thereof remote from the cooling chambers 26, by a line 44, the lower ends of the discharge nozzle 32 being disposed somewhat above the plane of the opening of the conduit 44 into the condensing chamber 28, as shown. A bathe 45 is disposed between the nozzles and open end of conduit 44, as shown.

In use of the present apparatus, as will be presently more fully described, the condensing chamber 28 is initially filled with Water W, or other condensing liquid having a speciiic gravity greater than ice, from line 41 by Fusoperation of valve 40 to said second position, to a level,

designated as L1. Means 42 is now operated to evacuate the cooling and condensing chambers 26 and 28, as previously described, and the evolved water vapor tlls the cooling chamber 26 and the condensing chamber 28. Valve 40 is turned to its aforesaid rst position, and pump 36 is operated to draw the condensing liquid W from the bottom of the condensing chamber 28, through the intake line 38, and discharge it through the line 34 to the headers 30 whereupon it issues as a series of sprays through the discharge nozzles 32. The water vapor, evolved from the articles being cooled, comes in contact with the droplets of condensing liquid in these sprays and is condensed and intermixed with such condensing liquid and falls therewith to the bottom of the condensing chamber. Substantially all of the water vapor will be condensed in this manner so that the evacuating means 42 is loaded only to the extent of removing non-condensible gases. Due to such condensation of the water vapor, the pressure in the retort is maintained at the value necessary to assure boiling off and evaporation of the surface moisture of the articles being cooled, especially during the latter stages of the cooling process. The baille 45 prevents the spray issuing from nozzles 32 from being drawn into the means 42 while permitting removal of non-condensible gases.

It will be seen that the condensed vapor and initial condensing liquid W are continuously recirculated by the pump 36 through the spray nozzles 32 so that means must be employed for recooling the condensate and condensing liquid prior to their recirculation to the nozzles 32, to a temperature suiciently low to provide for continuous, rapid and effective condensation of the vapors.

Recooling of the condensate and condensing liquid, as preliminarily mentioned, is accomplished through the use of chopped ice. To this end, a pair of ice hatches 50 are provided on the top of the retort over the condensing chamber 28 through which ice may be loaded into the latter. Another method of loading ice into the retort involves a sluicing process, and for this purpose there is provided a second line 52, including a valve 54, leading from the discharge side of pump 36, to a nozzle 56 which discharges into a hopper 58. Hopper 58 is provided with an opening 60 through which chopped ice from a supply 61 may be introduced into the hopper. For most etiicient operation of the system, the individual chunks or particles of ice should weigh no more than ten pounds. A discharge conduit 62 leads from the hopper 58, through the end wall 12 of the retort, into the condensing chamber -28 at a point above the initial liquid level L1 in the chamber. This conduit includes a valve 64. In operation of the sluicing system, valve 40 in the line 34 leading to the spray nozzles 32 is closed and valve 64 in the discharge conduit 62 from the hopper 58, and valve 54 in line 52 are opened. Pump 36 is then operated to pump liquid from the condensing chamber 28 through the line 52 to the discharge nozzle 56. Chopped ice is introduced into the hopper 58 from the supply 61, such ice being forced into the condensing chamber 28 by the liquid discharging from the nozzle 56. A valve 66 provides for the discharge of pump 36 to a drain conduit 68 for draining of excess liquid from condensing chamber 28. This drain conduit may include a meter 69 for indicating the quantity of liquid drained olf so that a predetermined volume of liquid may be removed from the chamber 28 at the termination of each run to return the liquid to the level L1.

As previously mentioned, it is often desirable to return cooled liquid to the articles of produce after chilling of the latter. To this end a third conduit 70, including a valve 72, leads from the discharge side of pump 36 to means 74, adjacent the open end of the retort 10, for returning the condensate to the produce. The means 74 is illustrated as being a spray nozzle through which cooled liquid from condensing chamber 28 may be dis- `flowing overthe surfacesto the hody of liq imelts, the level of the body of liquid' W willoh or water W7 from line 41, tothe level L1', as previously 'described. The condensing islloa'ded'with chopped ice, either through the hatches.50 or by the previously described operationlof the, sluicingsystern S6, 8,

61, to a higher level designated bythe'letter L2. Owing tothe lesser density of the;ice,2 the ice particles P will tend to rise to and float atv the surface, of the liquid W.

Means 2 is now operated to `evacuate the cooling'and condensing chambers 26 and 28, until thev absolute pressure in such chambers isequal toor` .slightly lessthan the vapor pressure of the surface moisture on the articles to becooled. Duringthis process,. surfacemoistre will first evaporate and thenboil off with the'resul'tant formationof atrelatively largevolume of aqueous vapor which llsthe cooling chamber 26 andkrcondensingchalmber 28. Pump 36 is startedgand: thevalving of the apparatus is appropriately positionedso `that liquid drawnfrom the bottom of the condensingcharnbergZV and ,discharged as high velocity sprays 1through tl'iey `noz es 32. lfhe vapor evolved from the articles being chilled is drawn into contact with t h is spray/,becauseio'f the lower vapor pressure of thev spray, and becomes condensed thereon and interrnixed therewithmThis condensation of the vapor results in maintenance.,of,fthe vapor pressure in the retort'at a value necessary tomaint'ain evaporation `and boiling off of the lliquid :moisture on the articles l cooled. The liquid inthesprfay impinges the surfaces of the ice particles HP, andisfthereby cooled, such liquid f id W at the bottom of the condensinggzchambenfor Vrecirculation ti the nozzles 32. This: bodyl'ofliquid will, of course, be further lcooled by the ice therein.. hf

As the evolved Vapor is condensed, and as ice . v i v t l l t n 1 J rise above the level L12 The ice particles.Pwill, however,

float in vthe liquid so as to remainV at the surfaceth'ereof L andbe exposed to the spray for continuousimping'enient of thelatter on theice surfaces. l m A highly important feature oftheinventionresidesin this direct impingement of the highV velocity "sprays from nozzles 32 on the surfaceof the'ice particles P. rlfhe high velocity of the spray actstobripgpthe ycondensed `vapor and condensingeliq'uid into intimate contact with the ice surfaces and to 'thoroughly agitate the boidy of liquid W andthe ice particleslsoasftolamconfplishfmoe rapid and effective heat transfe fromthe conde nstt'efandY condensing liquid to ice `thn is` pos hle `with` systems relying on mere immersionofltherec i 'ng agentinfa relatively static body of,conderisi`ng liquid`. Also, `this agitation inhibits fusing togetherof "the icepiarticles which would result in ak reductionof the K'effective heat transfer surface areaof the ice.` m

An alternative form ofthe vpresent` apparatus, illustrated in Figure 3, comprises'separate coolingandcondensing retorts 100 and 102 interconnected lbyaduct 104. The condensing retort 102 includes an ice hatch 106, as in the apparatus of Figures 1 and 2. A series of transversely extendingheaders 112 are positioned within the upperend of thefcondensing retort and mount a plurality of downwardly dischargingspray nozzles 114. The `headers112are connected by a line 116 to the discharge of a pump 118 whose intake isconnected by a line 120 to the bottom ofithe condensing retort 102. The lcondensing and cooling retorts `a`re evacuated by operation of a vacuum producing device 122 `whose intake is connected by a line124 to`,:tlieminterior of the condensing retort. The appartusiof Figure `3 rf'ngement for loading ice in`to`the` condensing "retort,

` means jfor returning the; .cooled condensatel to the uce, a 'n' d the valving for draining and initiallych'afrging thesysmwith the condensing liquid'W. Theselthave',l `for the: sake of clarity,A been omitted frornF gre 3, i N

Operation ofthe latter forms of apparatus is identical with that previously presented so that no discussion thereof is deemednecessary. Suffice it to say that the hodyof condensing liquid W will be initially at a level L1; The cbndensing chamber is loaded with chopped ice to a level L2.u Thus, as in the case of the apparatus of Figures l and 2, the spray from the nozzles 114 will impinge the surfaces ofthe chopped' ice particles' P t`o Irovide more eflcient heat transfer between the liquid in the spray and theirecooliiigagent.

While certain preferred embodiments of the invention have been described and illustrated, it will be apparent that numerous'modications in design, arrangement'of parts, and procedure are 'possible within the scope'of the following claims.

I claim:

Evaporative cooling apparatus comprising: hermetic chamber means including'a cooling chamber for receiving hydrous articles to` be chilled and a condensing chamber communicating with said cooling chamber;V evacua'ting means communicating with said `condensing chamber for evacuating the latter and cooling chamber whereby to produce an inff'unjof vapor evolved from articlesin the cooling chamber into the condensing chamber; saidcondensing chamber defining a condensing zone adjacent the influir4 of vapor into the condensing'chamber and a' reservoir at one side of said zone; means for recirculating `a in the spray collecting in the reservoir, 4`and means for pumping liquid from said reservoir back` to saidl spray formingrneans; and means for initially fillingsaid reser- Voir tona'given level with chopped ice to be viriipinged by the spray, said last mentioned means comprising a hopper adapted to contain chopped ice, a conduit having an unobstructed passage capable ofpa's'sing the particles o f ice communicating said hopper and "reseriioir, andia nozzle to be connected to a source of fluid under presse and arranged to discharge through said hopper 'into vsaid conduit to force the particles of chopped ice from'the hopper, through the conduit, into said reservoir.

2. The subject matter of claim l including Aconduit means connecting said nozzle and pumping means for pumping of liquid from the reservoir through said nozzle when filling ther'eservoir with chopped ice, "and valve means whereby liquid 'may be pumped from the' reservoir selectively to said spray forming' means or nozzle.

3.l In evaporative cooling apparatus of `the class de- 'scribed,'a condensing chamber, means for loading chopped ice into said chamber including a hopper adapted to receive a quantity 'of chopped ice; `conduit means connecting said hopper and chamber and having an unobstructed passage therethrough capable of passing the particles of chopped ice from -the hopper to the chamber; a nozzle arranged to discharge through said hopper into conduit means; and means for supplying said nozzle with a liquid under pressure.

4. The subject matter of claim 3 wherein said chamber defines a reservoir adapted to contain a quantity of a liquid; said last mentioned means comprising pump means having its intake connected to said reservoir and its discharge connected to said nozzle. y

5. Evaporative cooling apparatus comprising: hermetic chamber means Aincluding a lcooling chamber for receiving hydrous articles to be chilled and a condensing chamber communicating with said cooling chamber;

evacuating means communicatingwith said condensing chamber for evacuating the latter and coolingchamber whereby to produce an influx of vapor evolved from articles in the cooling chamber into the condensing chamber; said condensing chamber defining a condensing zone adjacent the inilux of vapor into the condensing chamber and a reservoir at one side of said zone; means for recirculating a liquid through said zone including spray forming means at the opposite side of said zone arranged to discharge a liquid spray into said zone for contact with the vapor entering the condensing chamber, liquid in the spray collecting in said reservoir, and means for pumping liquid from the reservoir back to the spray forming means; a quantity of chopped ice at said one side of the zone located to be directly impinged by said spray; and means connected with said pumping means for selective pumping of liquid from said reservoir to a desired point outside of said chamber means for rehydrating of said articles after chilling thereof.

6. In evaporative cooling apparatus of the class described, hermetic chamber means having a sealable access opening through which hydrous articles to be chilled may be loaded into the chamber means, evacuating means for evacuating said chamber means to cause boiling off of the water content of hydrous articles in the chamber means, condenser means in the chamber means for condensing the aqueous vapors evolved from the articles and including nozzle means for creating a water spray through which said vapors pass to be condensed, a reservoir for receiving the spray and the condensed vapors, a conduit leading from said reservoir to said nozzle means, a pump in said conduit for pumping liquid from said reservoir to said nozzle means, a liquid line leading from said conduit at the discharge side of said pump to the outside of said chamber means through which liquid from the reservoir may be' applied to chilled articles after removal of the latter from the chamber means, and valve means for controlling liquid flow through said conduit and line.

7. A method for condensing a condensable gaseous substance comprising the steps of: directing a spray of a liquid condensing medium having a specific gravity greater than ice through a condensing zone into a body of said liquid medium having a free surface exposed to said spray and containing particles of chopped ice which oat at said free surface of said body whereby said ice particles are impinged and agitated by the spray to promote heat transfer from the liquid medium to the ice particles and inhibit fusing of the latter, recirculating liqquid from said body through said zone, and passing said substance through said zone for contact with the droplets of the spray. p

8. An evaporative cooling process comprising the steps of: placing hydrous articles to be chilled in a hermetic space, evacuating said space to cause aqueous vapors to be evolved from said articles, passing said vapors through a condensing zone in said space, directing a spray of a liquid condensing medium having a specific gravity greater than ice through said zone into a body of said liquid medium having a free surface exposed to said spray and containing particles of chopped ice which float at said surface of said body whereby said ice particles are impinged and agitated by the spray to promote heat transfer from the liquid to the ice particles and inhibit fusing of the latter together and recirculating liquid from said body through said zone.

9. Evaporative cooling apparatus comprising: hermetic chamber means including a cooling chamber for receiving hydrous articles to be chilled and a condensing chamber communicating with said cooling chamber; evacuating means communicating with said condensing chamber for evacuating the latter and cooling chamber where by to produce an inuX of vapor evolved from articles in the cooling chamber into the condensing chamber; said condensing chamber defining a condensing zone adjacenty voir anda higher specific gravity than said ice whereby chopped ice particles oat'at said free surface; and means for recirculating liquid from the reservoir through said zone Yincluding spray forming means at the top of the zone arranged to direct a high velocity spray of said liquid through said zone into said reservoir and against the ice particles floating at said free surface of said liq- Vuid in the reservoir whereby to promote heat transfer from the liquid in the spray tothe ice particles and agitation of the particlesto inhibit fusing thereof together,

'and a pump having its suction communicating with said reservoir below said given level and its discharge communicating with said spray forming means, the wall of said condensing chamber having a scalable opening through which said` chopped ice may be loaded into said reservoir. i

10. Evaporative cooling apparatus, comprising an elongate, hermetic retort; a liquid tight transverse partition sealed to the inner wall of said retort and defining at opposite sides a cooling chamber and a condensing chamber; said retort having a sealable opening through which hydrous articles to` be chilled may be loaded into said cooling chamber; a quantity of chopped ice and a condensing liquid filling the lower portion of said condensing chamber, said liquidfhaving a higher specific gravity than ice and a free surface at a given level in said condensing chamber whereby particles of chopped ice iloat at said free surface of the liquid, there being an opening vcommunicating said lchambers above said given level; evacuating means communicating with said condensing chamber above said given level for evacuating saidchambers to produce an influx of vapor evolved from articles in the cooling chamber into said condensing chamberjmeans for recirculating said liquid through the condensing chamber including nozzle means in said condensing'chamber adjacent said opening, and a pump having its suction communicating with said reservoir below said given level and its discharge communieating with said nozzle means for pumping said liquid from the lower portion of the condensing chamber to said nozzle means, said nozzle means being arranged to spray said liquid into the path of the vapor entering the condensing chamber from the cooling chamber and against the particles of ice at said free surface of the liquid in the lower portion of the condensing chamber to promote heat transfer from the liquid to the ice particles and agitation of the latter to inhibit fusing thereof together, the wall of said condensing chamber having a scalable opening through which said chopped ice may be loaded into said reservoir.

1l. In evaporative cooling apparatus of the class described, condensor means comprising: a hermetic condensing chamber dening a lower reservoir; a quantity of chopped ice and a condensing liquid in said reservoir, said liquid having a specific gravity greater than ice and a free surface at a given level in the reservoir whereby particles of chopped ice float at said free surface of said liquid; and means for recirculating said liquid through the chamber including spray forming means above the reservoir, and a pump having its suction communicating with said reservoir below said given level and its discharge communicating with said spray forming means for pumping liquid from the reservoir to the spray forming means; said spray forming means being arranged to spray said liquid toward the reservoir and against the particles of chopped ice at the free surface of the liquid in the reservoir whereby to promote heat transfer from the liquid to the ice particles and agitation of the latter to inhibit fusing thereof together, the wall of said condensing chamber having a sealable opening through 9 which said chopped ice may be loaded into said reservolr.

References Cited in the iIe of this patent UNITED STATES PATENTS 1,708,253 Bell Apr. 9, 1924 1,756,992 Quiggle May 6, 1930 2,065,358 Zarotschenzeft Dec. 22, 1936

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