US2479866A - Liquid air refrigerator - Google Patents

Description

Filed Dec. 7, 1945 6 v H Mk n, l

Aug. 23, 1949. T, w. RosEBAUGH 2,479,866

I LIQUID AIR REFRIGERATOR Filed Dec. '7, 1945 2 Shets-Sheet 2 v l W ZO /\O Patented Aug. 23, 1949 UNITED STATES ,PATENTYOFFICE i LIQUID AIR REFRIGERATOR Theodore W. 4Ros'ebaugh, `Oakland, Calif., allsignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application December 7, 1945, Serial No. 633,362

(ol. s2- 92) 6 Claims.

This invention relates to the cooling orrefrigeration of foodstuffs by means ofl liquid air and is particularly concerned with the safe and economical preservation of foodstuffs during storage.

The invention is primarily concerned with keeping fresh foodstuffs at a suillciently low temperature sothat 'deterioration of the foodstuffs is prevented.l

It is an object of this invention to provide new and useful apparatus for the refrigeration of foodstuffsusing expendable liquefied gas or mixture of liquefied gases.

It is another object of this invention to provide a new and useful refrigeration system which may be adopted for household use.

AIt is another object of this invention to provide a new and useful apparatus by which the deep freezing of foodstuffs as well as the normal refrigeration of foodstuffs may be accomplished in the home.

It is a further object of this invention to provide an apparatus using liquefied air as an expendable refrigerant.

By the term liquid air" I include all liquefied mixtures of oxygen and nitrogen. In other words I include liquid air consisting of oxygen and nitrogen in the proportions they occur in nature as well as liquid air produced as a byproduct of industrial processes wherein'the proportions of oxygen and nitrogen may vary considerably from the proportions occurring in nature.

The further advantages and objects of my invention will be apparent from the following description of a household refrigerator utilizing the invention.

Referring to the accompanying drawings:`

Figure I is a front elevation (with part of door removed) of a. household refrigerator employing liquid air as the refrigerant.

Figure II is a plan view of a household refrigerator taken along line II-II of Figure I.

Figure III is a vertical section of a household refrigerator taker along the line III-III of Figure I.

Figure IV is an end elevation of an alternate construction of the lower portion'of the refrigerator.l

4Figure V is an enlarged cross sectional view of the gas conduit shown in Figure I, It and III.

Referring to Figure I, II and III numeral I represents generally an insulated refrigerator cabinet provided with the usual hinged door 2 in the front face. The door 2 is of course also insulated. In the lower section of the refrigerator,

2 shelves 3 are provided for the placement of the various food items it is desired to cool or preserve'.

In the upper part of the refrigerator there is located a sheet metal low temperature compartment 4 having an insulated lid or lhatch cover 5 so that access to this compartment is obtained without opening the door 2.

Slidably mounted on a plate 8 located in the cabinet below the low temperature compartment 4 are several trays 'I for the making' of ice cubes. Recessed in the inner back panel 8 of the refrigerator and on the inner side of the insulation 8 is a vertical duet I 0 which may be of composite construction as will be explained hereinafter. The duct I0 terminates at its upper end near the top of the low temperture compartment 4 and extends downward and is connected at its lower end to a Dewar flask Il mounted in thecabinet underneath the refrigerator compartment. This Dewar flask II is of usual construction having an inner shell and an outer shell. The Dewar flask is provided with a fill spout I2 which extends to the front of the cabinet and is provided with a snap lid I3 at its outer end.

Depending into the Dewar ilask II to close to its bottom is a copper or other metal plate Il which leads upward to form one side of the neck I5 of Dewar flask and extending further forms the front face I6 of the duct l0.

Copper fins I1 are attached to the outer side of the front face I6 of the duct. Located under the ice trays 1 near the back of the refrigeration space is a small electric fan I8 provided with an adjustable thermostat I9 connected in series with the fan and a source of electric power. The electric fan I8 is arranged so that when operating it will cause air to ilow toward the ns I'I.

A director ring 20 surrounds the electric fan I8 to increase its eiiiciency and serves also to shield the fan from possible damage.

The operation of my refrigeration system is as follows:

The Dewar flask II is lled with liquid air 2| from an outside source through the ll spout l2. This liquid air is at a temperature of about 315 F. varying slightly upon its composition.

The heat gained through the walls of the Dewar flask is comparatively small owing to the eiective insulation inherent from the construction. f

However some heat is transmitted to the liquid air by the copper plate I4 which dips into the liquid air.

This copper plate due to the high heat conductivity of the metal draws heat from its upper section, which as will be noted from the drawings, forms the front face I6 of the duct I0.

The copper plate in turn draws heat from the contents of the refrigeratorl compartment through the contact of the air in the refrigerator with the copper plate and the fins I1 attached to it.

The heat thus transmitted from the refrigerator compartment to the liquid air in the Dewar flask II causes ebullition of some liquid air.

This vaporized liquid air (at considerably below F.) passes upward through the duct Ill withdrawing more heat from the walls of the duct.

As will be apparent to those skilled in the art, the emciency of the system will be somewhat improved if the side and back walls of the duct III are made of non-metallic material, such as for example, an asbestos cement composition. This detail may be more clearly seen by referring to Figure V wherein numeral 22 represents nonmetallic duct material.

'I'he cold vaporized liquid air after absorbing heat by heat exchange with the interior of the refrigerator in its upward journey is eventually discharged from the upper end of the duct into the low temperature compartment 4.

The cold air still considerably below 32 F. flows downward (owing toits density being greater than the existing air in the refrigerator) over any articles of food in the low temperature compartment.

The cold air then ows out through the bottom of low temperature compartment through openings 23 and then ilows across and around the ice trays 7.

The cold air eventually flows through openings 2d in the rear of the plate 6 into the lower or normal refrigeration section. The path of flow of cold air as above described can be readily seen from an examination of Figure III ofthe drawings wherein arrows indicate the ow.

As should be realized the copper fins I'I and the copper plate I6 forming one wall of the duct I0 and also serving as the heat transfer means for conveying sumcient heat to the liquid air 2I inthe Dewar flask Ii will soon become coated with a layer of ice due to the freezing thereon of the water vapor in the normal air of the refrigerator. This layer of ice will reduce the refrigeration effect and serve as a partial insulator. Therefore if further refrigeration is required, a removal or partial removal of some of the ice coating should be effected. For this purpose the electric fan I8 is provided. Upon a desired temperature in the compartment being exceeded the fan motor starts up due to the thermostat control I9 and by causing a more rapid movement of air across the surface of ins I l and copper plate I6 improves the heat transfer and effects a further lowering of the temperature of the air in the refrigerator compartment (and in turn of its contents). As air is being supplied to the interior of the refrigerator it is necessary that some provision be made for the escape of air from the compartment. For this purpose air off-take pipes 25 are provided.

In Figure IV I have shown an alternate construction for the lower part of the refrigerator. Referring to this Figure IV it will be noted that the Dewar flask Il is not sepaarted by insulation 9 from the interior of the refrigerator, but is enclosed within the insulation surrounding the refrigerator compartment. By this construction any Aheat gain through the walls of the Dewar flask II will be heat removed from the contents of the refrigerator compartment.

While in the above description of my preferred refrigerator I have shown a specific construction, it should be understood that I contemplate that variations and changes can be made to meet particular situations.

For example, where there is not a readily available souree of power to provide an increase in circulation of air across the copperplate I6 other means of increasing the degree or rate of refrigeration may be employed.

Although I have shown my refrigeration system as applied to a refrigeration cabinet containing both a low temperature section and normal refrigeration section, it will be apparent that the system may be used in a cabinet provided solely with a low temperature section or solely with a normal refrigeration section.

Furthermore while the unit described is specically arranged for household use, it is contemplated it could be utilized for the refrigeration of' larger insulated compartments such as cold storage warehouses, meat packing plants and the like.

The system moreover could be applied to transportation of foodstuffs in mobile units such as by railroad refrigerator cars, by motor trucks or by air transport.

In application to such units the Dewar ask could be located Within the refrigerator compartment so as to insulate it from the outside heat.

If desired, where the system is applied to air transportation, some of the vaporized liquid air supply could be diverted by suitable piping for the use of the occupants of the plane when fiying at high altitudes.

I further fully appreciate that where desired liquid air could be forced in its liquid state into the refrigeration compartment by the use of an eduction pipe and the creation of a slight pressure upon the surface of the liquid air in the Dewar flask, or by other means.

I claim as my invention:

1. Apparatus for using liquid air as a refrigerant comprising a heat insulated refrigeration compartment, a highly insulated container for liquid air, a high heat conductor located in said compartment and extending into said liquid air container, and a vapor duct from said liquid air container passing in heat exchange with the wall of said refrigerator compartment along a substantial portion of the length thereof and terminating in the interior of said refrigerator compartment. Y

2. Apparatus for using liquid air as a refrigerant comprising a heat insulated refrigeration compartment, a heat insulated container for liquid air, a heat conductive metallic plate located in said compartment and extending into said liquid air container, air guiding means for' leading air from the vapor space of said liquid air container terminating in the interior of the refrigerator compartment, and a thermostatically controlled electric fan in said refrigerator compartment disposed to' circulate air along said heat conductive metallic plate.

3; Apparatus for using liquid air as a refrigerant comprising a heat insulated refrigeration compartment, a heat insulated container for liquid air, a heat conductive metallic plate located in sad compartment and extending into said liquid air container, air guiding means for leading air from the vapor space of said liquid air container disposed to conduct vapors in heat eX= 5 change with said heat conducting metallic plate and opening to the interior of the refrigerator compartment, and a thermostatically controlled electric fan in said refrigerator compartment disposed to circulate air along said heat conductive metallic plate.

4. Apparatus or using liquid air as a refrigerant comprising a heat insulated refrigeration compartment, a heat insulated container for liquid aix', a heat conductive metallic plate located in said compartment and extending into said liquid air container, expanded meta] surfaces on said heat conductive metallic plate within said compartment, a duct from the vapor space of said liquid air container opening to the interior of said refrigerator compartment, at least a portion of the wall of said duct being formed -by said heat conductive metallic plate, and a thermostatically controlled electric fan in said refrigerator compartment disposed to circulate air along said exgn audace sub-compartment and extending into said liquid air container, air guiding means for leading air from the vapor space of said liquid air container passing in heat exchange with the wall of said warmer sub-compartmentv along a substantial portion of the length thereof and opening to the interior of said low temperature sub-compartment, a passageway between said low temperature sub-compartment and said warmer sub- 10 compartment, and a thermostatically controlled 15 said heat conductive metallic plate forms at least a portion of the wall of said duct.

THEODORE W. ROSEBAUGH.

REFERENCES crrEn The following references are oi! record in the ille of this patent: 4

UNITED STATES PATENTS u Number Name Date 1,719,692 Des Jardins July 2. 1929 2,346,837 Grooms Apr. 1.8. 1944

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