US2449005A - Shipping container refrigerated by dry ice - Google Patents

Description

Patented 7, -1948 UNITED STATES PATENT OFFICE SHIPPING CGNTAINER BEFBIGEBATED BY DRY ICE Andrew J. Nicholas, North HavenQConn., assignor to The Grenby Manufacturin r Company,

Plainvilie, Conn., a corporation of Connecticut Application May 2s, 194s, serial No. msu

.(ci. ca -91.5)

ll Clllml.

The present invention relates to refrigeration and more particularly to a refrigerating unit uti" lizing solidifiedA carbon dioxide or its equivalent as a primary refrigerant. which unit is admirably adapted to use in a portable refrigerator in the nature of a refrigerated shipping. container. There is definite utility for a shipping 'container of 4modertae size which may be handled very much as' any ordinary container oi' equivalent size but which container comprises a portable refrigerator. In particular. -such a refrgierated 2 erated space as to cause positive circulation Aof the'atmosphereinsuch space. l ",It is a further object of thepresent invention to' provide a portable refrigerator having a loadcai'ryin'g compartment into which a ooinirioliity*v needing refrigeration may be placed and a read-- ily removable reirigerating unit which may .be inserted into the refrigerator and removed thereshipping container is of great value in providing for refrigerated shipment of relatively small quantities of perishable materials from scattered temperature.- For example, the temperatre of .y

solidified CO2 is -108 F.- and such temperature is of course incompatible with such perishable commodities as fresh-vegetables and the like.

It is a. further object of the prsent invention to provide a refrigerating-unitutilizing solidied CO2 as a primary refrigerant and which Willoperate to maintain adesired moderately cooll temperature without moving parts or mechanical regulating devices.

It is a further object of the present invention to provide a refrigerating unit of the type described which will operate for periods of time sufficient to permit relatively long distance shipment of a refrigerated commodity without the necessity for recharging' or servicing of the re f rigerating unit. l f

It is a'. further object of the present invention to provide .a refrigerating unit whichutilizes solidied G02 as a primary refrigerant and which utlizes a. liquid' secondary refrigerant having a predetermined freezing point and to provide for heat exchange between evaporated gaseous CO2 and the secondary refrigerant.

It is a further object of the present invention to provide a. refrigerating unit as set forth in the next preceding object in which the gaseous CO: isI conducted after heat-exchange with the secondary refrigerant to such a point in the refrigfrom for serviclngyrecharging* or replacement Without disturbing the commodity.'

4It is a further object of the-present invention.

to'provide a refrigerated shipping container adapted to receive a load of material' needing reff frlgeration and which is provided with a'readily removable refrigerating unit solidified CO2 asf a primary' refrigerant and which may be replaced or recharged along theline of'shipment.'

Other and further objects of the present invention will becomehpvparentI from a consideration of the following detailed description' of a preferred form of the invention taken in connection with the drawings .accompanying `and forming a part of this specification.

25. In the drawing the gure is a sectional view of a refrigerator made in accordance with the present invention. f

Referring' now to the drawing. there is shown a refrigerator. comprising a cabinet i0 having afood storage or load-carrying'l compartment l2 and one or more movable closures Il providing access to the compartment It.. The refrigerator also comprises a refrigerating unit indicated generally at I6 which isl insertable into the body of the cabinet through an Opening of suitable size which is closed by a movable closure Il. It isto be understood that the cabinet :il may have any suitable shape. `The .form illustrated is generally rectangular in shape. having end walls 20, front and back walls 22. only one of which is shown ,in thedrawing, a bottom wall 24 and a top wall Il. Each 0f the Walls 2l, 22, I L'and 2| as well.

. ATheopening '62 which is closed by'theclosure I6 is preferably square in shape. 'I'his openingV tical edges to the front and rear walls 22 as byy brackets 46. This foraminous enclosure thus is preferably a permanent part of'the refrigerator cabinet and serves to prevent direct contact between the perishable commodity stored therein and the refrigerating unit I6. Furthermore, the provision of such an enclosure assures that the refrigerating unit I6 may be removed and replaced without disturbing the load within the cabinet. It will be understood that the foraminous en- 'closure need only be slightly larger than the refrigerating unit I6, and that in the event the cabinet I6 is so proportioned as to be considerably wider'in a direction perpendicular to the plane of the sectional view of the drawing than is the unit I6, the foraminous enclosure may take the form of a basket closed on all four sides by screen or other suitable material similar to the panels 66.

The refrigerating unit I6 comprises upper and lower rigidly connected containers 42 and 44, respectively, which willbe described in greater detail herein below. The upper container 42 is provided with elongated angles 46 secured adjacent all four upper edges thereof, the horizontally extending flanges 46 of which rest upon the flanges 66 within the opening 32. The refrigerating unit i6 is thus supported on all four. sides merely by resting upon the flanges 36 and the unit may thus be readily lifted from the refrigerator when the closure i6 is opened.

The refrigerating unit I6 will now be described in detail. The upper container 42 is adapted to receive a block 50 of solidified CO2. Preferably, the container 42 is provided with an inner basket l2 made of screen or other suitable foraminous material which serves to keep the solidified CO2 out of direct contact with the walls of the container 42.

The container 42 is preferably made of metal and is adapted to be closed in a substantially gastight manner. To this end, there may be provided a gasket '54 made of rubber or other suitable material extending around the upper operi end of the container 42. A closure 56 is provided to rest upon the gasket 64 and may be drawn tightly into place by a suitable number of screws 66 provided around the margins of the closure 66. The screws 56 may be threadably received in fixed nuts 60 provided within the angles 46. Preferably, the gasket 54 is relatively thick and soft in order to provide not only for sealing of the container 42 under normal conditions, b ut also to permit escape of gas therearound in the event a dangerous pressure is developed within the container 42. A handle 62 may be secured to the closure 66 to facilitate lifting of the unit i6 and removal of the closure 66 from the unit when desired.

The lower container 44 is preferably supported by the upper container42 and is spaced therefrom in order to provide substantially no direct heat transfer between the two containers 42 and uid in operation of the device.

44. To this end a plurality yoi' angle brackets 64 are-secured as by welding to the lower exterior surface of the upper container 42. The brackets,E 64 are spaced from one another as faras practicable, having due regard to strength re quirements. the brackets 64 extend outwardly beyond the exterior surfaces of the vertical walls of the upper container 42 and thus the vertically disposed arms of the brackets 64 are spaced outwardly from such vertical surfaces. An intermediate container 66 is secured to the outer vertical surfaces of the brackets 64 and this intermediate container comprises four vertical walls 66 which extend hori- Izontally beyond the upper container 42 and a relatively narrow shelf-like bottom 10 extending around all four sides thereof. The bottom 'I6 is formed with downwardly turned flanges 12 which are in turn secured to the exterior surfaces of the lower container 44 and thus serve to support the same.

The intermediate container 66 is open ati-ts y top all the way around the upper container 42, such opening existing between the angle brackets 64 and within the space between the walls 66 of the intermediate container and the vertical walls of the upper container 42. The intermediate container 66 is thus positioned to catch water from melting frost on the surfaces of the upper container 42 and to hold such accumulated moisture until such time as it may be removed by operation of a suitable pet cock 14.

The lower container 44 is provided for a liquid secondary refrigerant and is therefore liquidtight. It is also gas-tight except for the passages provided therein for the introduction and removal of gas in the operation of the device. A liquid secondary refrigerant 16 is positioned within the lower container 44 and the quantity thereof is such as to leave a substantial head space thereabove within the container 44.

Particularly where the refrigerating unit is to be used in portable equipment it is desirable to provide a suitable number of baille plates 16, 66 and 62 to reduce surging of the liquid. It has been found desirable to keep the level of the liquid below that of the lower surface of the up, permost baille plate 62. The baille plates 16, 6l and 62 are so positioned as to permit free circu-l lation of the liquid within the container 44 and to permit free passage of gas through such liq-l As shown in the drawing, the upper baille plate 62 is preferably so positioned as to permit flow of gas around the edges thereof with as little restriction as possible and thus this baille plate may be supported by suitable angle brackets 64 secured to side walls of thecontainer 44.

The exterior surfaces of the lower container 44 are preferably provided with fins 66 to increase the area of the surfaces of the container. The fins 66 may be formed from metallic angles welded or otherwise secured to the surfaces of the container 44.

Heat exchange between the solidified CO2 in the upper container 42 and the secondary refrigerant in the lower container 44 is, except for minor conduction through the 'brackets 64 and walls 66 of the intermediate container 66, solely effected by the passage of gaseous CO2 formed upon evaporation of the solidified C02. To this end one or more tubes or conduits 66 are provided. the upper ends 66 of which open into the upper container 42. The conduits 66 are extended downwardly through the walls 66 and through The horizontally disposed arms of a,449,oos

the top 92 of the lower container 44. 'Ihe con-l for a substantial distance' upwardly of the conduit 99, All of the openingsi 94 should be located below the level of the top of the secondary refrigerant 16. v v

'The top wall 92 of the lower container 44 also has formed therein one or more openings 99 providing for the escape of gas leaving the surface ofthe secondary refrigerant. It is preferred to provide conduits 99 in each of such openings 99 which conduits extend upwardly to a point adjacent the top of the refrigerating unit I6 and in proximity to the surfaces of the upper container 42. Ordinarily a lconduit 99 will be provided for at least two of the external vertical surfaces of the upper container 42 and if desired, such a conduit may be provided for all four vertical walls. The conduits 99 are open at their upper ends to permit escape of gas in a region which not only is in proximity to the upper exterior surfaces of the upper container 42, but also is the upper region of the load-carrying compartment itself.

In order that the operation of the refrigera- `tion unit may be understood, it will be described first in general terms and then in a specific embodiment. A -secondary refrigerant 16 is chosen having a freezing point such as to meet the requii'ements at hand. For example, =water may be chosen. The secondary refrigerant is placed in the lower container 44 .and the quantity thereof is so chosen as to fill the container 44 to approximately 75%-80% of its capacity. A quantity of solidified CO2 is placed in the upper' container 42 and the closure 56 is secured. The unit I9 is then positioned Within the cabinet I0 and the closure I 9 is closed.

Assuming 'that there is no food load in the compartment I2 and assuming thatthe air in said compartment is at a normal room temperature of 70 F., it will be apparent that the solidified CO2 50 will begin to sublime or evaporate and that the gaseous CO2 will soon begin to flow through the. conduit 89. When sufficient 'pressure has developed, the gaseous CO2 will begin to bubble upwardly through vthe secondary refrigerant water 16. Some of the CO2 will be dissolved in the secondary refrigerant and the remainder will bubble completely through it and escape into the head space above the baille l2 from which it will be discharged through the conduit or conduits 98. As theV gaseous CO2 passes through the water 16, heat exchange occurs and the CO2 is relatively warm as it leaves the upper end of the conduit 98. It is still colder and heavier than the atmosphere ofthe compartment I2 and furthermore is discharged in a. region adjacent the relatively cold exterior surfaces of the upper container 42. Thus the gaseous CO2 will descend along the exterior surfaces of the upper container 42, the intermediate container. 6'6 and the finned lower container 44. This produces a positive scrubbingl of such exterior surfaces and produces a positive circulation of th'e'atmosphere in the compartment I2.

Such operation proceeds until the atmosphere has been considerably cooled and the temperature of the secondary refrigerant has been brought down substantially to the freezing point thereof.

In the meantime a portion of the moisture in the atmosphere lof compartment I2 will have been deposited on the exterior surfaces of 'the upper container 42,111 the form of a layer of frost. Such frost layer will build up quickly in view of the largely indirect heat transfer between the walls of container 42 and the extremely cold solidified CO2 therein. The4 frost layer serves to insulate the upper container 42, sharply reducing the rate of sublimation of the CO2 therein and also exposing the gaseous CO: emerging from conduit 98 to a much higher temperature than that encountered at first. `The atmosphere of the compartment I2 is much cooler than at first thus further gqucing the rate of sublimation of the solidified It will be recognized that the conditions just described have a strong tendency toward equilibrium and if it -were not for heat ,inflow through the cabinet I0 the secondary refrigerant would eventually freeze solid. The equilibrium is not too precarious, however, because of such heat inflow and because' of the tremendous amount of energy required to remove the latent heat of fusion of a liquid and bring about freezing thereofy when it is substantially .at its freezing point. As a consequence the secondary refrigerant 76 serves as heat flywheel. The temperature' of the secondary refrigerant will hover substantiallyat the freezing point thereof, irrespective of relatively great changes in the other conditions established at which the atmosphere of the compartment I2 is maintained by selection of secondary refrigerants having different f freezing points. When water is used and no food load is carried in the compartment, it has-been found that the atmosphere will be maintained at a temperature of about 34 to 36 F.. assuming of course that the unit I6 is properly proportioned to .thecompartment III. The equilibrium established in a well insulated empty compartment is rather delicate but this is not a condition which would be encountered in normal use ofthe device; A food load produces heat, different foods having different characteristics, as is well known; For example, string beans produce a relatively great amount of heat and have been Aconsidered to be g difoult to ship under refrigeration. .In the normal use of the present invention, the heat produced by the food load plus the heat inflow in the cabinet will keep a unit I6 of proper size working at a relatively slow rate with no danger of freezing up. It has been found that excellent results are achieved when the compartment temperature is established at about 10' or 12 F. higher Ithan the freezing point of the secondary refrigerant.

When the unit is is in operation at its best efficiency. the secondary refrigerant will usually freeze and thaw to -a certain extent,` at most to a point where some slush will float to the top. As pointed out above the apparatus must be designed to avoid solid freezing inasmuch as this would prevent bubbling of the gaseous CO2 through the openings will remain open. The plurality of openings is preferable to a single opening, say

' merely the open end of the conduit itself, be-

cause of the tendency towardformation of ice at this point of nrst contact between the cold CO2 gas and the liquid. When 'a plurality of openings is provided good circulation is assured -and the building up of ice at the openings is avoided.

' The circulation of the secondary refrigerant 16- within the lower container u results in rapid heat transfer and in effect the interior walls of the container u are scrubbed in much the same manner as the exterior walls.

A specific embodiment of the invention comprises an outer cabinet Ill made of aluminum alloy, insulated with spun glass and having an interior volume of twelve cubic feet. The foraminous enclosure 38 and refrigerating unit I6 therein occupy three cubic feet thus leaving nine cubic feet Afor storage of a commodity. Three and one-half gallons of water having one and threefourths pound of CaCl: dissolved therein is placed in the lower container M as a secondary refrigerant. The container 44 is eighty percent full. If approxim-ately fifty pounds of solidified CO2 (about ya ten-inch cube) is placed in the upper container and the compartment l2 is filled with string beans, for example, a temperature of from 35 F. t0 37'? F. will be maintained in the compartment I2 for a period of about four days. The freezing point of the CaCl: solution used as a secondary refrigerant is 25 and as pointed out above a food load will lead to maintenance of a compartment temperature about 10 to 12 F. higher than such freezing point.

Obviously itwould be advantageous to precool the food load-to prolong the effectiveness of a given quantity of solidified CO2. If the shipment requires more than the three or four day period for which the original charge is good the shipping container must he serviced.

Servicing of the shipping container may be carried out by removing the unit I6 therefrom and inserting an identical unit having a proper quantity of solidified CO2 therein. Suitably located servicing depots may be established for this purpose. Alternatively, the shipping container may be serviced merely by adding solidifled CO2` to the upper container 42.

When a unit I8 is exhausted of its charge of solidified CO2 and warms up the frost on the upper container 42 will melt, dripping into the intermediate container 66. Ordinarily this will not occur when the unit Ii is positioned within a shipping container filled with a commodity inasmuch as it is contemplated that the units will be removed or serviced before exhaustion. However, the construction just described will prevent water damage t the contents of the shipping container inthe event defrosting should occur.

It is thus apparent that there has been disclosed a refrigerator and refrigerating unit therefor which accomplishes the objects of the invention. The description is presented in an illustrative rather than in a limiting sense, and it 8 in the art within the scope of the following claims. For example, any solidified material which exists as a gas at ordinary atmospheric temperatures and pressures may be substituted for the solidified CO2 if so desired.

Iclaim:

1. In a refrigerator having a load-carrying compartment for storage of articles in a refrigerated gaseous atmosphere, a substantially gas-tight container for solidified CO2 located within said compartment, a container having a secondary refrigerant therein located within said compartment substantially out of direct heat-exchanging relationship with solidified CO2 in said firstnamed con-tainer, means to conduct evaporated gaseous CO2 from said first-named container into heat-exchanging relationship with said secondary refrigerant,and means for continuously discharging'said gaseous CO: after heat-exchange with said secondary refrigerant into an upper region of said refrigerated compartment whereby `to cause forced circulation of the atmosphere in said compartment.

2. In a refrigerator having a load-carrying compartment for storage of articles in a refrigerated gaseous atmosphere. a substantially gastight container for solidied CO2 located within said compartment, a container having asecondary refrigerant 'therein located within said compartment substantially out of direct heat-exchanging relationship With solidified CO2 in said rst-named container, means to conduct evaporated gaseous CO2 from said first-named container into heat-exchanging relationship with said secondary refrigerant, and means for thereaf-ter conducting said gaseous CO: to a zone in proximity with the upper exterior surfaces of said first-named container.

. ship with said secondary refrigerant and means for thereafter conducting said gaseous CO: to a position for release into said compartment in a zone adjacent the upperexterior surfaces of said first-named container whereby said relatively cool, relatively heavy released gaseous `lvCO: will descend along the exterior surfaces", of said firstn'amed container and then along .the exterior surfaces of said second-named container.

' 4. In a refrigerator having aiload-carrying compartment for storage of articles in a refrigerated gaseous atmosphere, a substantially gasf tight container for solidified CO2, said container will be understood that modifications and variabeing located within and near the top of said compartment. a second container having a secondary refrigerant therein. said second container being spaced from said-first container to substantially prevent direct heat-exchange between said secondary refrigerant and solidified CO: in

tionship with said secondary'refrigerant, and

means for continuously discharging said gaseous C02 after heat-exchange with said secondary refrigerant into said refrigerated compartment.

5. In a refrigerator having a load-carrying compartment for storage of ar-ticles in a refrigerated gaseous atmosphere. a substantially gastight con-tainer for solidified CO2 located within said compartment, a second container. a secondary liquid refrigerant positioned wi-thin said seo- -ond container, means for mountlngsaid second container in predetermined spaced relationship with-said first,co'ntanier substantially to Vprevent direct heat-exchange between said secondary refrigerant and solidified CO2 in said first container, at least one conduit connecting said first container` and said second container, said conduit having an opening vlocated below the level o'f the .top of said secondary refrigerant whereby ievaporated gaseous CO2 will be conduc-ted from said first container to said second container and may bubble through said second-ary refrigerant for heat-exchange therewith, and said second container having an opening formed therein above the level of said secondary refrigerant for the discharge from said second container of said gaseous CO2 after it leaves said secondary refrigerant.

6. In a refrigerator having a load-carrying compartment for storage of articles in a refrigerated gaseous atmosphere, a substantially gastight container for solidified CO: located within said compartment, a second container, a secondary liquid refrigerant positioned within said second container, means for mounting said second container in predetermined spaced. relationship with said first container substantially to prevent direct heat-exchange between said secondary refrigerant and solidified CO2 in said first container, at least one conduit connecting said ilrst container and said second con-tainer, said conduit terminating adjacent the bottom ofsa'id secondcontainer and being provided with a plurality of openings therein loca-ted within iand below .the level of the top of said secondary' refrigerant whereby evaporated gaseous CO2 will be conducted from said first con-tainer to said second container and may bubble through said second-ary refrigerant for heat-exchange therewith, and said second container having an opening formed therein above .the level of said secondary refrigerant for the discharge from said second container of said gaseous CO2 after it leaves said secand being provided with a plurality of vertically spaced openings therein located within and below the level of the top of said secondary refrigerant whereby evaporated gaseous CO2` will be conducted from said iirst container to said second container and may bubble through said secondary. refrigerant for heat-exchange therewith, land at least one conduit opening into said second container above, the level of said secondary refrigerant and extending upwardly to a regionv in l0 proximity with the exterior surface of Said lint container for discharge of said gaseous CO: into said region.

8. In a portable refrigerator having a loadcarrying compartment for storage of articles in a refrigerated gaseous atmosphere, a substantially gas-tight container for solidified CO: located within said compartment, a second container, a secondary liquid refrigerant positioned within said second container, the quantity of said secondary refrigerant being such as to leave substantial v in proximity with the upper exterior surfaces of head space in said second container above the level of the top .of said secondary refrigerant. a plurality of baille plates positioned in said second container to minimiz"e surging'of said secondary refrigerant during movement of said refrigerator,

means for mounting said second container in piredetermined spaced relationship with said first container substantially to prevent direct heatexchange vbetween said secondary refrigerant and solidified CO2 in said first container, at least one conduit connecting said flrst container and said second container, said conduit having at least one opening located within and below the level of the top of said secondary refrigerant whereby evaporated gaseous CO2 will beconducted from said first container to said second container and may bubble throughl saidsecondary refrigerant for heat-exchange therewith, and said second container having an opening formed in the head space portion thereof for' the discharge theresaid container.

10. In a refrigerator having a load-carrying compartment for storage of articles in a vrefrigerated, gaseous atmosphere, a substantially gastig-ht container for solidified C0: located within said compartment, means for holding a supply of a liquid secondary refrigerant within said compartment in spaced relationship with said container substantially to prevent direct heat-exchange lbetween said secondary refrigerant and solidified CO2 in said container, at least one conduit extending from said container and having an opening located. below the level of the top of said secondary refrigerant from which evaporated gaseous CO2 may bubble through said secondary refrigerant for heat-exchange therewith, and means for discharging said gaseous CO2 after it leaves said secondary refrigerant into an upper region of said refrigerated compartment whereby to cause forced circulation -of the atmosphere in said compartment.

11.. A refrigerated shipping container comprising a heat-insulated body having at least one closure movable for providing access to a loadcarrying compartment therein; a foraminous enclosure secured within said compartment and defining a sub-compartment from which articles -stored in said load-carrying compartment are excluded by said foraminous enclosure; at least n one closure movable for providing access to said ing unit arranged to utilize solidied CO2 as a 5 primary' refrigerant and having a secondary liquid refrigerant through which gaseous CO2 may bubble upon evaporation of said solidified CO2, and said rei'rigerating 4unit including means for continuouslyr discharging the gaseous CO2 leaving said secondary refrigerant into the loadcarrying compartment to cause forced circulation of the atmosphere within said compartment.

ANDREW J. NICHOLAS.

l2 REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES 'PATENTS Number Name vDate 1,825,068 Jones et al Sept. 29, 1931 i 1,969,643 Fuchs et al. Aug. 7. 1934 10 2,142,569 Maranette Jan. 3, 1939

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