US2634592A

US2634592A - Vacuum vaporization-condensation cooling system

Info

Publication number: US2634592A
Application number: US189466A
Authority: US
Inventors: Melville W Beardsley
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-10-10
Filing date: 1950-10-10
Publication date: 1953-04-14
Anticipated expiration: 1970-04-14

Description

A ril 14, 1953 M. w. BEARDSLEY 2,634,592

VACUUM VAPORIZATION-CONDENSATION COOLING SYSTEM Filed 001:. 10. 1950 INVENTOR. MEL was 14 55400315? Patented Apr. 14, 1953 UNITED STATE PTENT QFFICE VACUUM VAPORIZATION- CONDENSATION COOLING SYSTEM Claims.

My invention relates generally to the cooling and refrigeration of comestibles, and more particularly, to the pre-cooling of such produce as lettuce,-sweet corn, prior to its shipment. A method and apparatus for this general purpose are disclosed in my co-pending application, Serial No. 146,784, filed February 28, 1950, and entitled Method and Means for Cooling Produce by Use of Reduced Pressures, of, which the present application is a continuation-in-part.

One customary practice in cooling produce such as lettuce prior to and during shipment thereof is to interlayer the produce with crushed ice while it is being packed into the shipping crates, and also to cover the closed crates with ice in the refrigeration cars in which they are shipped. As stated in the above-identified co-pending application, the disadvantages of the conventional procedure just described are that the crushed ice tends to bruise tender vegetables such as lettuce; the water from the melting crushed ice causes considerable deterioration and discoloration of the produce during shipment thereof, and is generally a nuisance; and the crushed ice, in spite of great care in distribution, does not maintain as uniform a temperaure throughout the body of the packed shipment as is desired. Still further, the operation of packing the crushed ice into crates or other containers with the produce is a costly and time-consuming phase of the packing and shipping operation.

The above-identified co-pending application discloses a method and means for precooling produce by means of a vacuum causing evaporation of the surface moisture therefrom, a process described generally as vacuum cooling. The present invention concerns further improvements in the method and apparatus for vacuum cooling. In current practice, the vacuum cooling process employs steam jet pumps to evacuate the air and water vapor from a closed chamber containing-the produce in process. Steam jet pumps have proven more satisfactory for this Bearing in mind the general purposes of vacuum pre-cooling and also the fact that steam+ operated plants currently in use are of a permanent type, it is a major object of the present invention to provide a light-weight, portable, vacuum pre-cooling plant adapted especially for use with seasonal produce such as lettuce.

Another object 01 the invention is to reduce the size and expense of vacuum pre-cooling plants even of the permanent installation type.

A further object of the invention is to provide for the use of ice in connection with the'process of vacuum cooling, and also for a minimum of handling of such ice without the necessity of placingv the same in direct contact with the produce being cooled.

Yet another object of the invention is to provide a system adapted for the use of mechanical refrigeration in connection with the vacuum cooling process.

A still further object is to reduce the power requirement of a vacuum cooling plant.

An additional object is to increase the speed and facility with which produce may be precooled by the vacuum cooling method.

Yet another object is to provide a vacuum cooling plant in which the refrigeration and vapor condensing unit is separate from and readily detachable from the main produce-containing chamber, whereby the condensation unit may be used successively with a number of different produce-containing chambers.

A still further and general object is to provide apparatus for materially increasing the speed and efficiency of ice refrigeration from the standpoint of the theoretical absorption capacity of the ice.

Yet another object is to provide in a vacuum cooling system, efficient means for removing water in an ice-vacuum cooling refrigeration system, efiicient means for. removing water from the refrigerating chamber without wetting the produce.

The foregoing and additional objects and advantages of the invention Will be apparent from a consideration of the following detailed description of several forms thereof, such consideration being given likewise to the attached drawings, in which:

Figure 1 is a side elevational view of a presently preferred form of the invention using ice, and in a which a pump and refrigerated condensation unit is mounted on the tractor portion of a trucktrai1er combination, and in which a produce-containing, cooling chamber trailer portion;

is mounted on the Figure 2 is an enlarged elevational longitudinal section taken through the condensation and treatment chambers of the apparatus shown in Figure 1;

Figure 3 is an enlarged elevational section taken through a modified form of condensation chamber in which refrigerating coils are employed in place of the ice shown in Figure 2; and

Figure 4 is a further modified form of the invention employing an external ice bunker in place of the internal ice bunker of the apparatus shown in Figure 2.

Briefly, the apparatus employing my invention comprises a main produce-conta ning chamber H and a vapor-condensing chamber [5, the two chambers being interconnected by means of a flexible conduit having a quick-disconnect joint or fitting 27 therein. Incorporated in the condensin chamber unit is a vacuum pump 29-- and a cold body to effect condensation of moisture, such body'be'ing, for example, the ice I! shown -in Figure 2, or mechanical refrigeration cold coils-35 in the form shown in Figure 3.

The'quick-operating connection joint 2'! provided in the interconnecting conduit 15 provides for the successive connection of the condensation chamber [5 with a number of different main chambers H.

Before proceeding with a detailed description ;.of the apparatus embodying the present invention, the principles of operation will be described briefly-as follows. The first principle made use of is that evaporating -moisture absorbs heat of evaporation from surrounding media. Thus, if the surface moisture on, let us say, a head of lettuce is caused to evaporate by reducing the surrounding vapor pressure, the heat of evaporation necessary to cause the same will be absorbed from the head of lettuce, thus cooling the same. .Thisprinciple-is also employed in the apparatus described in theabove-identified co-pending application.

The second principle employed in the present invention is that vapor brought intocontact with a surface colder than the dew point of such vapor at its then pressure will cause the vapor to condense vwith the result that a corresponding amount of heat is released by the vapor and absorbed by the. cold surface. Such condensation 'also of course, results in reduction of pressure ifit is accomplished in a closed chamber.

The third. principle employed herein is that the vapor pressure of a given liquid depends on the" temperature thereof; thus, if two vesselsv .Qcont'aining separate bodies of the, same liquid at 'difier'ent temperatures are interconnected and all air and other non-condensable gases are removed, vapor of the liquid will flow from the vessel of higher temperature to the vessel of lower temperature because of the higher vapor pressure of the higher temperature liquid.

These three general principles are employed in the present apparatus by placing in one chamher the material to be cooled and in the connected chamber, means for maintaining a low temperature; and then removing the air and noncond'ensable gases from the two interconnected chambers. It will be apparent that, as the air ,and non-condensable gases are removed, the 'pressure in the two chambers will ultimately be reduced to a value equal to the vapor pressure of the surface moisture present on the produce. At this point, the absolute pressure in the condensing chamber is approximately equal to the vapor pressure of the surface moisture, but according to Avogadrcs law, it is comprised of the lower vapor pressure of the colder moisture (or ice) plus the partial vapor pressure of the air and non-condensable gases which are also present. As air is continuously removed from the condensing chamber, the total pressure therein will be reduced until, when all air and other non-condensable gases are removed, the total condensing chamber pressure will become equal to the vapor pressure of the colder condensate or ice.

Under the conditions last above described, vapor will flow at high velocity from the main chamber to the condensing chamber. The vapor continues to be boiled off the produce and to flow into the condensing chamber until the vapor pressurein both chambers is substantially equal. This condition of equality, of physical necessity, means that the surface moisture on the produce has been reduced to the same temperature as the moisture or ice in the condensing chamber. For leafy produce such as lettuce, this is tantamount to a reduction to this temperature. of the entire, mass of the produce. Thus, in summation, it is seen that the vacuum cooling process consists in removing heat from the produce and transmitting the same to ice or other refrigerant through the medium of evaporated and recondensed vapor.

From the preceding discussion, it will be seen that when the air has been substantially removed from the two chambers, there is theoretically no need for further evacuation. I' have found by experience, however, that there is still a substantial amount of air present in the chambers'by the time the point of rapid evaporation and flow of water vapor commences therein. In addition to the condition just stated, there may be a slight amount of air leakage in the chambers, and furthermore, non-condensable gases, such as carbon'dioxide, are given off by the produce being treated. Thus, I have found it necessary and desirable to continue the evacuation,

though at a reduced rate, throughout the process in order that the cooling will continue at a maximum rate.

Whenever any small amount of air or other non-condensable gas is present in the condensing chamber, it will, according to Avogadros law above-mentioned, add its partial pressure to that of the vapor pressure of the condensate, so that the total may be great enough to equal the vapor pressure of the surface moisture on the produce, and thus stop the entire process. Furthermore, if any air is allowed to remain in the condensing chamber, even though the partial pressure thereof may not be sufiicient, theoretically, to halt op erations, it soon collects in an insulating blanket on the ice or other condensingsurface and prevents or greatly inhibits further condensation. The formation of such a blanket is due to the fact that the condensation at the cold surface removes the water from the air-water-Vapor mixture thereat, leaving relatively pure air. Thus, it is of further advantage to continue the pumping during the entire cooling cycle in order to keep the aforesaid blanket of air from forming and to continuously draw water vapor into contact with the condensation surface.

In the preferred form of the apparatus illustrated in Figure 1, the main chamber I! is charged with produce while the connected condensation chamber I5 is charged with ice. The

chambers are thereafter substantially evacuated of air, the heat transfer starts automatically and is allowed to continue until the idesir'edfpr'ecooling temperature of the produce has been reached. a

An important feature of the present process is that substantially no work or energy is expended in pumping vapor out of the main chamber containing the material being processed, substantially the only material removed therefrom being air.

It will be realized that this is a major advantage of the present equipment over apparatus employing steam jet pumps and continuing the pumping operation to reduce the vapor pressure in the treatment chamber. In the latter type of apparatus, the major portion of all the energy required is used in pumping water vapor out of the treatment chamber.

As described in my above-mentioned co-pending application, I have found it possible to closely calculate the amount of ice required to produce a given reduction in temperature in a given weight of produce. Experience has shown, however, that often an undesirable amount of time and labor is required to load the chamber with a calculated amount of ice. Furthermore, it is usual practice to provide a safety factor by placing in the condensing chamber slight y more ice than the theoretical amount necessary to produce the desired cooling effect. Thus, there is a residuum of ice after the process has been completed which must usually be disposed of because it is of odd'and undesirable shape for optimum operation.

As a means of reducing this labor and undesirable ice residuum, I have found is desirable to make the condensing chamber sufiiciently large to contain enough ice for cooling several loads of produce; thus, the ice can be loaded relatively infrequenly and without regard to the exact amount needed to pre-cool any particular load of produce.

As a means of accelerating the cooling process, particularly toward the end of a cycle, I have found it expedient to spray on the cold surface in the condensing chamber a chemical solution which lowers the melting temperature of ice and also reduces the vapor pressure of condensate formed therein.

Referring now to Figure l for a more detailed description of the preferred form of apparatus embodying the Jresent invention, it will be seen that the treatment chamber II is of cylindrical configuration, having a hinged access door I3 formed in one end thereof, and a simple circular bulkhead closing the other end. The cham er II is mounted on a trailer 5i which is adapted to be towed by a truck 5G carrying-the condensation chamber I5 and the vacuum pump 20, together with other refrigeration equipment. During the time that the cooling process is in operation, the main chamber II is connected to the condensation chamber I5 through the interconnecting conduit I6 having the quick-disconnect joint 27 therein. The interconnecting conduit I6, while adapted to withstand external atmospheric pressure when the interior thereof is substantially evacuated, is made flexible in order to facilitate operation of'the joint 21 and also to permit operation of the truck-trailer 5il5l while the cooling process is continuing.

A'valve Ita is incorporated in the interconnecting line I6 and manually operable to close the chamber II so that the vacuum therein may be -m'aintained even thou h the chamber II is disconnected from the condensing chamber I5. --As seen best in Figure 2, a series of conveyor rollers I 4 is mounted in the chamber I I to receive crated produce for movement into the chamber in conventional roller conveyor manner. A flow-directing baffie 38 is installed under the conveyor rollers I4, extends completely across and throughout the length of the chamber II, except for a small gap adjacent the access door I3, and serves to establish a uniform vapor flow path out of the chamber II, a indicated by the flow arrows in Figure'2.

At the top of the condensing chamber I5 is a hinged and sealed bulkhead type door I9 through which ice I! may be loaded into an internal ice compartment 30 within the chamber I5. The ice compartment 30 is formed with a heat-conducting inner wall I8, having a sloping bottom so as to slide the ice forwardly against the for.- ward wall of the chamber I5.

A vacuum pumplll is connected by a suction line 2| to the interior of the chamber I5 adjacent the lowest point in the ice compartment 30. At

the lowermost point in the compartment 30, a

condensate drain pipe 24 serves to drain away condensate and. melted ice'to a, condensate tank 23 which may be conveniently mounted at any point substantially below the lowermost point in the chamber I5. An air inlet valve 45 is connected in the suction line 2|, and is selectively operable to admit air to the system after completion of the cooling cycle.

The system illustrated in Figure 2 operates as follows. After the ice I! and the produce in crates I2 have been loaded into the respective chambers I5 and II, and the doors I3 and I9 have been closed, an air-tight system containing the ice I1 and produce crates I2 at ambient temperature is established. Air is then pumped out of the system by means of the pump 20 through the conduit 2|, the inner end of which is connected to a series of laterally disposed exit ports 28 in the inner wall of the ice compartment 30 adjacent the bottom thereof. By this arrangement all gas, whether air or water vapor, which is removed from the interior of the cooling chamber I I, must pass through the condensing chamber I5 and the inner ice compartment 30 in close proximity to the surface of the blocks of ice I! therein. The water vapor constituent of the moving gas mixture is largely removed by condensation of the ice I I, thus making it necessary for the pump to move only substantially pure air. This, in turn, makes possible the use of a pump of relatively small volumetric capacity, as compared with vacuum cooling systems which operate by pumping out all gases including evaporated water vapor.

When the total pressure in the cooling chamber II and in the condensing chamber I5 is equal to or slightly greater than the vapor pressure of the moisture on the produce, then the system is in equilibrium and will remain so if the pumping is discontinued. However, if the pumping is continued past the point where the system total pressure is equal to the vapor pressure of the produce moisture, then boiling of the produce surface moisture occurs. This boiling will continue until the vapor pressure of the moisture in the cooling chamber I I-is equal to the total pressure in the condensing chamber I5. Thus, if all air and non-condensable vapors are removed from the condensing chamber I5, the total pressure therein will be that corresponding to the moisture on the surface of the ice. Therefore, moisture in the cooling chamber II will continue to evaporate until the moisture tem- =perature in the same-is the same as the moisture on the surface of the ice [1, and the-condensin chamber 15.

During the cooling process, the vapor formed by the evaporation. of the produce surface moisture flows into the condensing chamber through the interconnecting conduit 15, and is caused: by a deflecting baffle 29' to impinge on a. sloping heat transfer surface 26 down which is flowing water consisting of melted ice and condensate.

Since this water flowing down the surface of the sloping wallZE has. a temperature of approximately 32 degrees, it causes condensation of a substantial proportion of the water vapor impinging: against the undersurface and absorbs heat therefrom. Thus, the mixture of condensate and melting ice approaches the temperature of the vapor impinging upon the wall 28 as such liquid mixture leaves the compartment 35 through the drain pipe 2 That portion of the vapor which is not con- "densed by impingement against the heat ex- ."change surface 26 passes, as indicated by flow arrows, around the substantially horizontal baffle 29 and along the outer surface of the ice compartment wall l8, up to the top of the ice compartment 39 where it comes in direct contact with the ice II. Since the vacuum pump 29 is continuously operating, any air or non-condensable gas that is mixed with the vapor will be drawn through the ice-containing chamber "30, and out through theexit ports 23 after passing in intimate heat transfer contact with the ice II so that substantially all vapor is condensed.

As the ice i1 is melted by the released latent heat of evaporation, the melted ice and condensate drains, as aforesaid, to the bottom of the ice compartment 39 and out through a series of laterally disposed drain tubes 3| into an inner drain reservoir 33. When this small reservoir 33 is full, the liquid therein overflows and down the sloping bottom surface 26, as described. This system of drain tubes 31 and the reservoir 33 serves as a trap at the bottom of the ice compartment 39 so that the vapor must follow the flow path previously described and therefore enter the ice compartment as at the top and pass downwardly therethrough. In this way, maximum condensation effect is achieved.

In this connection, I have found that, as compared to other flow directions, a generally downward flow path over the ice, or other cold condensating surface, is of considerable advantage andefiects-a considerable improvement in efficiency since air, being more dense than water vapor, will tend to flow naturally to the bottom of the chamber containing the condensation surface, into the discharge ports 28, and thence to 'the vacuum pump. 11?, on the contrary, the flow of vapor-air mixture were to be upward past the condensing surface, the air would tend to form an insulating blanket against the surfaces, since the light water vapor constituent tends to rise and the heavier air constituent tends to slide down "along the cold surface counter to the flow direction, thus preventing eflicient vapor condensation of ice surface temperature and vapor pressure is accomplished in the present instance by injecting a solution containing a chemical such as common salt or calcium chloride against the ice surface. For this purpose, in the present embodiment a solution tank 34 is provided and con-'- nected by a suitably valved conduit 39' to the interior of the ice compartment 30 so that by operation of the valve 35a in the conduit 36, solution is sprayed through a set of interior nozzles 35 onto the ice I1.

Efhciency of the system is also greatly improved by covering the condensing chamber IS with a layer of insulating material 31 in order that heat will not be absorbed from atmosphere.

Such insulation is particularly necessary on the sloping heat transfer surface 26 to prevent the melted ice and condensate mixture from absorbing heat and increasing its vapor pressure, thus reducing overall efficiency. Unless the vapor pressure of all liquids in the chamber I5 is maintained as low as possible, the final desired temperature may not be reached, even though pumping is'continued and all of the ice consumed.

An alternate form of the invention is illustrated in Figure 3 wherein cold coils 39 of a mechanical refrigeration system of known design are employed instead of ice in the condensirig chamber It. In this modified form, refrigerating coilste of a conventional mechanical refrigerator are mounted in heat transfer contact with the bottom surfaces of a number of horizontally disposed condensate trays 45.

A compartment 39a, analogous to the ice compartinent 39, of the previous embodiment, is provided in the form shown in Figure 3, and the trays it are staggered and spaced vertically in the compartment 39a so as to act as baffles and provide a tortuous downward path for vapors passing through the compartment. vThis arrangement causes the air and water vapor mixture moving through the condensing chamber [5 to sweep in close contact with both the upper and lower surfaces of the trays 49, and the coils 39 secured to the undersurfaces thereof. The refrigeration equipment necessary to supply cold refrigerant to the coils 39 is of conventional design and need not be described in detail herein. Such a mechanical refrigeration plant can be mounted on the tractor 59 and powered either by the prime mover of the tractor itself, or by a suitable auxiliary power plant.

The operation of the modified form shown in Figure 3 is similar to that of the previously described embodiments. Vapor fiows from the main chamber I I through the interconnecting conduit it into the condensing chamber I5 and is deflected by a baffle 29 to impinge on the sloping liquid-heat transfer surface 26. Uncondensed vapor and any entrained air leaving the surface 28 flows upwardly, as indicated by the flow arrows in Figure 3, to the top of the compartment [5 and thence downwardly over the coils 39 and their adjacent trays :19 to discharge ports 52, thence into the suction line 2| leading to the vacuum pump 20. Condensate from the vapor condensing on thecoils 39 drips downwardly into the trays 49 until these are filled to the level of an overflow tube in each, identified by the reference character 4!. After reaching this level, additional condensate runs out of the overflow tubes 4! into small sealing reservoirs or traps 10 located at the ends of each of the tubes 4| and mounted to the wall I80. of the inner chamber 39a. When the reservoirs 10 are filled with condensate,.the

sameyoverfiows and drops downwardly to the sloping heat exchange surface 26 and out the condensate drain pipe 24.

The purpose of the condensate trays 40 is to retain a substantial mass of liquid condensate so that it may be frozen into ice by the refrigerating coils 39 during the period in which the main chamber H is beingunloaded and reloaded with additional produce for the next cycle. By this means, the refrigerating plant supplying the coils 39 can be operated continuously, the trays 40 and the frozen condensate therein serving as a heat absorbing ballast and thus building up the,

heat absorbing capacity of the system. This arrangement makes possible the use of a comparatively smaller refrigerating plant (for a given rate of cooling) than would be required if all the heat of vapor condensation were absorbed directly by the refrigerating coils during the initial part of the cooling cycle. The same general result can be accomplished by spraying water over the refrigerating coils during the loading period. This water, if sprayed at the proper rate, will form ice on the refrigerating coils and thus build up heat absorbing capacity as set forth above.

When refrigeration coils are employed, as shown in Figure 3, the flow path of air and vapor mightbecome blocked because of the accumulationof ice on the coils, particularly on the coils adjacent the discharge ports 42. This is particularly true when a counterflow system is employed in which the refrigerant enters the coils at the end adjacent the ports 42.

-As a means'of preventing the aforesaid blocking of flow due to the formation of ice, -I have found it expedient to provide a flexible flap or 'membrane 43 mounted so that its free edge rests on a transverse length 390. of the refrigerating coils 39 immediately adjacent the discharge ports 42. With this arrangement, when the ice formation blocks the normal flow path, the suction created in the vacuum line 25 lifts this membrane 43 sufficiently to permit the continued flow of air and vapor out of the discharge ports 42, such continuous flow passing in intimate contact with the aforesaid coil length 39a.

Additional, or in some cases alternative means are provided for preventing the blocking of flow by the formation of ice, such additional means being a nozzle 44 mounted adjacent the port 42 and adapted to spray a chemical solution of freezing point lowering material such as calcium chloride whereby to melt the accumulated ice and unblock the flow. The addition of such a chemical solution also has the favorable effect of reducing the vapor pressure of the condensate contained in the condensate pan 4%) immediately below the exit port #2.

In the embodiment illustrated in Figure 4, the released latent heat of evaporation is removed fromthe condensation chamber by conduction through the walls themselves. To porduce this effect, the condensation chamber [5a is cylindrical in form and a portion of the outer surface is cooled by the application of ice I? thereagainst, the ice being supprted in an external bunker H. In the operation of this embodiment, vapor enters the condensation chamber 15a through the interconnecting conduit l5 and is deflected by the bafile 29 in the manner of the previous embodiments. Thus, the incoming air-vapor mixture is caused .to follow theinner wall surface of the chamber 15, as indicated by the flow arrows. As thevapor flow follows the refrigerated surface, the vapor condenses and the condensate drains to the bottom of the chamber l5d where it is removed through the drain pipe 240., in the man-.

ner previously described. Any air or non-condensable gas mixed with the vapor is carried on around the wall surface to the laterally spaced exit ports 28a, and leaves the chamber in the manner previously described.

As the heat of vaporization from thecondensmg vapor is conducted through the wall of the chamber 15a, the ice I1 is melted and the resultant water drains down into a liquid flow space 52 between the bunker H and the chamber l5a. In the space 52, th melted ice-water is 0 strained to flow along the exterior surface of the condensing chamber Walls so that an additional heat transfer is effected between the condensing vapor and the melted ice-water. maximum refrigerating efliciency is obtained since the melted ice-water is heated to nearly the same temperature as the entering vapor before it finally leaves the system through an overflowice drain 53.

A nozzle 54 serves to introduce a melting point reducing solution into the contact surface between the exterior surface of the chamber 15a and the ice ll, thus reducing the temperature at this point.

In order to achieve a maximum possible rate of cooling, I have found it desirable and expedient to incorporate within the condensation chamber.

15a (or in the chamber [5 of the previous forms) a blower 55 which increases the rate of condensation on the inner chamber wall surface. The blower 55 is arranged to discharge onto the inner wall surface, as indicated in Figure 4. The increased velocity of surface flow and the turbulence created by this blower increase the rate of condensation, both by removal of the aforementioned air blanket that tends to form on the condensing surface, and also by agitating and moving the condensed water so that the uncondensed vapor obtains more direct contact with the cold wall surface.

In all of the embodiments illustrated, airis admitted to the system after the desired precooling temperature is reached by means of the. air inlet valve 45 connected to the end of thepump suction line 2|. All of the illustrated embodiments employ the same method and means for dumping the condensate drain tank 23 at the.

end of the pre-cooling cycle. Referring to Figure 2, it will be seen that a condensate tank discharge valve plug 25 is attached to one end of a pivoted lever 60 which is supported on a pin joint BI, and has a counterweight E3 thereon on the opposite side of the pin 6! from the valve plug 25. A metal actuating bellows 64 is connected at one end to the lever arm 86 and at the other end to a fixed portion of the structure. tuating bellows 64 is communicated with the main suction line 2! by a tube and a fitting 66.

Thus, when the vacuum pump 20 is started at the beginning of any particular cooling cycle, the pressure in the actuating bellows 64 is reduced, causing the same to contract under the influence of atmospheric pressure. Such contraction of the bellows 6d raises the valve plug 25 into the adjacent discharge valve seat. When seated, the.

valve is further held shut by the action ofatmospheric pressure thereon, and no leakage occurs at this point. Weight 63 is so adjusted that only a small force need be exerted by the bellows 64 to close the plug 25 as aforesaid. When air is readmitted to the system and thus also to the bellows 64, it and the By this means,

The interior of the ac-.

lhe position of the counter 11 weight of the water above the plug 25 cause the valve to open, dumping the contents of the condensate tank 23.

It will be noted that in all of the forms illustrated the flow through the condensation chamber is so organized that air-vapor passing therethrough must pass in heat transfer relation with the cold condensation surface before reaching the exit ports. Also bafile means are provided in each case to prevent any substantial body of condensate water from being located immediately adjacent the exit ports. This creates a condition of optimum efficiency in that relatively great proportions of air are moved by the pump as compared to the vapor moved thereby.

While the forms shown and described herein are fully capable of achieving the objects and providing the advantages hereinbefore stated, they are capable of some modification without departing from the spirit of the invention. For this reason, I do not mean to be limited to the forms shown and described, but rather to the scope of the appended claims.

I claim:

1. In a vacuum cooling system of the class described: a hermetic enclosure having a scalable access door to receive material for treatment in said enclosure; evacuation and condensation means including a chamber having a cold surface therein, a vacuum pump connected to said chambet to evacuate the same, and conduit means connected to said enclosure to inter-communicate said'chamber and enclosure; and means to direct liquid condensate forming on said cold surface to a point in said chamber adjacent the infiuxof vapor and air from said conduit means whereby the air-vapor mixture drawn from said enclosure through said chamber first passes in heat transfer relation past said condensate and then in contact with'said cold surface.

2. 'In a vacuum cooling system of the class described: a hermetic enclosure having a scalable access door to receive material for treatment in said enclosure; evacuation and condensation means including a chamber having'a cold surface therein, "a vacuum pump-connected to said cham ber to evacuate the same, and conduit 'means connected to said enclosure to intercommunicate said chamber and enclosure; means to direct liquid condensate forming on said cold surface to a'point in said chamber adjacent the influx of vapor and air from said conduit means; and baffle means'positioned between said influx and the point of connection of said vacuum pump and said chamber whereby air-vapor mixture drawn from said enclosure through said'chamber first passes in heat transfer relation with said condensate and then in contact with said cold surface;

3. In a vacuum coolin system of the-class described: a hermetic enclosure having a scalable access "doorto receive material for treatment'in said enclosure; a chamber communicated with said enclosure; a mechanical refrigerator having thecold coils thereof positioned in said chamber; avacuum pump connected to said chamber to evacuate the same and said enclosure; and reservoir means in said chamber to retaina body of 'water in heat transfer contact with'said coils whereby to provide a heat absorbing ballast therein.

Ina vacuum cooling system of the class described: a hermetic enclosure having a'sealable access door'to receivematerial for treatment in said enclosure; a'chamber communicated with 12 said enclosure; a mechanical refrigerator-having the cold coils thereof positioned-in saidchamber';

a vacuum pump connected to anexit port'insaid chamber to evacuate the same and said-enclosure; and yieldable flow constricting means posh tioned adjacent said exit port of said chamber and adapted to constrain exiting gases to flowpast acoldest portion of said "coils, said yieldable constricting means being adaptedto move tccpre= vent blocking of said exit port asice builds upon:

said coldest coil portion.

5. The method of vacuum coolingcomes'tibles having surface moisture thereon comprising the steps of: placing said material to be cooled in a hermetically sealed system; refrigerating aninterior surface of said system; evacuating said'sys: tem; draining condensate from said refrigerated surface; and passing-watervapor from saidco mestibles in heat transfer relationfirst with said condensate and then downwardly pastsaid re frigerated surface.

I 6;- A ortable vacuum COOIiI-Tg plant'comprismg" in combinations a tractor; a trailer connectedtd said tractor to bedrawn thereby; a hermetic enclosure mounted "on said trailer and having a rear access door and conveyor means therein-to receive packed produce for treatment in samenclosure; an insulated, hermetically scalable-chainber mounted on-said tractor having ah access door for loading ice into "saidchamber; adldxible conduit having a quick-disconnect-ioint therein; said conduit being connected be nsaidch'amher and enclosure to interccmmunicat'e thesamey an inner compartment in said chamberhaving an open top to receive'said ice and comfnunicate said inner compartment with said chamber; said inner compartment'having separate vapor and liquid exit ports adjacent the bottom thereoi and said inner compartment having one vertical wall thereof spaced from a vertical wall of said chamber whereby to form a vertical flue; a vacuum pump mounted on said tractor connected to sai-d vapor exitports to withdraw air from theem closed system comprisin said i'nner ccm'part ment, chamber, and enclosure; water trap means in said liquid exit ports to preventccuntei-new of vapor therethrough; an inclined inte'rior surface in said chamber below-said inner compartment to receive condensate an-d melted ice from -said liquid exit ports; and baflie-means in said chain'- her to direct vapor'flowing into said chamber from said conduit in heat transfer contact against saidinclined surface -and thereaftei' up said fine to enter said-inner compartment "at said open top thereof.

7. In a vacuum cooling plant of thetype having a scalable enclosure to receive material for treatment therein, means to evacuate-said enclo sure and condense vapor withdrawn therefrom, comprising in combination: an insulated, hermetically scalable chamber havingan access door for loading ice into saidchamber; a flexible conduit having a quick-disconnect joint therein, said conduit being adapted'for connection between said chamber and enclosure to 'intercommunicate the same; an inner compartment insaid chamber havingan open top to 'receivesaid ice :a'nd'communicate said inner compartment with 1 said chamber, said inner compartment having separate vapor and liquid exit ports adjacent' the bottom thereof, and said inner com artment h'av. ing one vertical wall thereof spaced froma verti cal wall of said chamber -whereby to form aver tical flue: a vacuum pump connected to said vapor exit ports to-"withdraw-air from-the err-- closed system comprising said inner compartment, chamber, and enclosure; water trap means in said liquid exit ports to prevent counterflow of vapor therethrough; an inclined interior surface in said chamber below said inner compartment to receive condensate and melted ice from said liquid exit ports; and baflie means in said chamber to direct vapor flowing into said chamber from said conduit in heat transfer contact against said inclined surface and thereafter up said flue to enter said inner compartment at said open top thereof.

8. In a vacuum cooling plant of the type having a sealable enclosure to receive material for treatment therein, means to evacuate said enclosure and condense vapor withdrawn therefrom, comprising in combination: an insulated, hermetically sealed chamber; a flexible conduit having a quick-disconnect joint therein, said conduit being adapted for connection between said chamber and enclosure to intercommunicate the same; an inner compartment in said chamber having an open top to communicate said inner compartment with said chamber, said inner compartment having separate vapor and liquid exit ports adjacent the bottom thereof, and said inner compartment having one vertical wall thereof spaced from a vertical wall of said chamber whereby to form a vertical flue; a vacuum pump connected to said vapor exit ports to withdraw air from the enclosed system comprising said inner compartment, chamber, and enclosure; water trap means in said liquid exit ports to prevent counterflow of vapor therethrough; an inclined interior surface in said chamber below said inner compartment to receive condensate from said liquid exit ports; and baflle means in said chamber to direct vapor flowing into said chamber from said conduit in heat transfer contact against said inclined surface and thereafter up said flue to enter said inner compartment at said open top thereof.

9. A portable vacuum cooling plant comprising in combination: a hermetic enclosure having an access door and support means therein to receive packed produce for treatment in said enclosure; a hermetically sealable chamber structurally separate from said enclosure and having refrigerating means to cool an interior surface thereof; a conduit interconnected between said enclosure and chamber, said conduit having a quick-disconnect joint therein to permit physical removal of said chamber from said enclosure; and a vacuum pump connected to said chamber to withdraw air therefrom whereby to cause air and vapor to discharge from said enclosure through said conduit into said chamber for condensation of said vapor on said refrigerated surface.

10. The construction of claim 9 further characterized in that said refrigerating means includes a body of ice in said chamber.

11. The construction of claim 9 further characterized in that said refrigerating means includes a set of refrigerant circulating coils insaid chamber.

12. The construction of claim 9 further characterized in that said refrigerating means includes a heat transmitting portion in the wall of said chamber and exterior bunker means to support ice against the exterior surface of said wall portion.

13. The construction of claim 9 further characterized by having a sump substantially out of heat transfer relation With said chamber and means interconnecting said sump and chamber to drain condensate from said chamber into said sump.

14. The construction of claim 9 further characterized in that said plant includes a tractortrailer combination with said chamber mounted on said tractor, and said enclosure mounted on said trailer.

15. In a portable vacuum cooling system of the class described: a hermetic enclosure having a sealable access door to receive material for treatment in said enclosure; evacuation and condensation means including a chamber having a cold surface therein, a vacuum pump connected to said chamber to evacuate the same, and conduit means connected to said enclosure to intercommunicate said chamber and enclosure, said conduit means including a quick-disconnect joint to permit physical separation of said enclosure and chamber; and means to direct liquid condensate forming on said cold surface to a point in said chamber adjacent the influx of vapor and air from said conduit means whereby the air-vapor mixture drawn from said enclosure through said chamber first passes in heat transfer relation past said condensate and then in contact with said cold surface.

MELVILLE W. BEARDSLEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 211,821 Wickes Jan. 28, 1879 222,122 Bate Dec. 2, 1879 1,458,403 Glessner June 12, 1923 2,345,548 Flosdorf Mar. 28, 1944 2,505,201 Peterson Apr. 25, 1950