US1976688A - Container for liquefied gases - Google Patents

Description

Oct. 9, 1934. 1.5.1. DANA ETAL- y CONTAINER FOR LIQUEFIED GASES l Filed April 19. 1952 Z'Sheets-Sheet l E d. d

Oct. 9, V 1934.

L. l. DANA ET AL CONTAINER FOR LIQUEFIED GASES Filed April 19, 1932 zsheets-Shee 2 U//UU/ ,wH/f/y ////////H/ www Patented Ont. 9, 1934 .UNITED STA TES PATENT OFFICE 1,976,688 l CONTAINER ron moverme cAsss Leo I. Dana and George B. Zenner, Buffalo, N. Y., minors to The Linde Air Products Company,

a company of Ohio Application Ani-u 19, i932, serial' No. 606.269

1o claims. (c1. 22o-9) and has relatively low evaporation losses from- .the liquid.

More specifically, it is an object to provide a container of the character indicated having an inner vessel for the liquefied gas with an improved'internal construction including a member in the insulating means which reduces the heat leakage to the liquid containing vessel at all times to a relatively small amount.

Another object of the invention is to provide a liquefied gas container with means which absorbs and stores a considerable quantity of heat in a manner which prevents it from reaching theliquid containing vessel, thereby shielding the liquid from external heat sources and reducing the evaporation .to a relatively low rate.

Another object of the invention is to provide a liquefied gas container with means for conserving the refrigerating effect of the gas material, particularly when recharging the container at a time when it may have reached a substantially uniform temperature corresponding to the surrounding atmosphere, such means `being located in the insulating material which is homogeneously distributed for supercooling the same when the container is being filled.

Another object is to utilize the available refrigerating effect of any vapors which may arise from evaporation of the liquefied gas within the container in a Amanner which conserves the refrigerating effect in the container.

Still another object is to provide the container with insulation preserving means for the. 'insulating material disposed about the liquid containing vessel whereby the insulating properties are not impaired by the ordinary breathing action caused by the expansion'and contraction of heat absorbing parts in the container, especially that caused by the thermal shield here employed.

Other objects of the invention will in part beobvious and will in part appear hereinafter.

'I'he invention accordingly comprises the features of construction, combination of elements, and arrangement of parte, which will be exempliiied in the construction hereinafter set forth and the scope of the application of which will indicated in the claims.

For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description taken. in connection with the accompanying drawings.' in which:

Fig. 1 is a,` vertical sectional view of a container constructed to employ a. thermal shield and insulation preserving means in accordance with` the invention; I Fig. 2 is an enlarged fragmentary view show- -ing details of a trap employed as part of the insulation preserving means the invention; and

Fig. 3 is a sectional view similar to Fig. l showing a modied form of thermal shield.

Referring now tothe drawings and particularly to Fig. 1, 10 denotes generally avvessel for holding a liquefied gas 11. This vessel may have any convenient form, for example, a thin'walled receptacle ore-basket 12 mounted within and in accordance with .spaced from the heavy wall of an outer casing orpressure vessel 13. Associated with theliquid containing vessel is a withdrawal pipe 14 that` leads from a. point near the bottom of the receptacle or basket 12, and a liquid llingpipe 15 that discharges into the basket at a point near the top. A-vapor withdrawal pipe 16 is also associated with the vessel 'and leads from a point within the vessel normallyv above the liq'uid level therein. Both the pipes 14 and-16 are preferably arranged to have circuitous paths coiled about the vessel in a manner hereinafter more fully explained. These pipes have`discharge termini shown at 14a and 16a respectiveLv. -The gas withdrawal pipe 16 -is also preferably provided with a. safety Vvalve 17 to relieve the undue'accumulation of pressure that might occur therein. Thermal insulation .18 is disposed about the vessel 10 in a manner such as to reduce heat leakage from an external source to the liquid within the vessel 10 'to a relatively low value, this insulation in turn being protected by an external casing or envelope 19 which may be of any suitable material that is strong and durable, for example, sheet metal. This casing is constructed vso as to be substantially air-tight and moisture-tight, while the enclosed vinsulation is entirely devoid of channels for aeration.

In order to minimize the nent that may pass vions from an` external source or otherwise leak through the insulation to vthe liquid containing vessel, there is interposed in accordance with the .present invention a body of relatively high heat conductivity and constructed to-intercept a.

substantial portion of the heat tending to pass to the liquid containing vessel. This body is preferably ofmetal and may have relatively high specic heat and is arranged to be cooled either continuously or intermittently -so as to prevent its absorbing sufllcient heat to become a secondary source of heat within the container that might otherwise tend to pass to the liquid containing vessel. In this manner, it is seen that the interposed body and its associated cooling means operate to shield the liquid containing .vessel from substantially a large portion of the external heating effects.

In the arrangement here shown, the interposed body is in the form of a cylindrical metallic closure which is supported by the insulation and substantiallycompletely surrounds the vessel 10. In order thatthis casing may be cooled, as above indicated, the coiled portions of panaions and contractions of the vessel 10 and the surrounding insulation 18 due to repeated withdrawals and fillings of the vessel 10 cause the air trapped in the insulation to expand and contract so that in general leaks develop in the 4casing 19 and the moisture thus entering from the outside air will then cause the insulation to deteriorate. Masses of heat absorbing parts that are repeatedy heated and cooled, as here proposed, are particularly conducive to this eiect. Means are, therefore, provided in accordance with the present invention to insure against the cause of this deterioration. To this end the casing 19 .has associated with it means permitting a so-called breathing action,` or inward and outward passage of air from the atmosphere, only with dehydrated air, i. e. of' air deprived of substantially all moisture. The dehydrating means may Vconveniently have the form of a moisture' trap 30 formed as a depending cylinder having 34, and communicates with the outeratmosphere through one o r more apertures 35 formed in the contracted lower end of the cylindrical portion ofthe trap.

The thermal shield of the present invention operates in the following manner: When no fluid is being withdrawn', the various parts of the container assume temperatures according to a certain temperature gradient, the coldest part ,being the inner vessel, and the warmest being the outer casing. Therefore, the thermal shield will in time assume a temperature that is between the extreme temperatures and is approximately that of the insulationin its vicinity. When gas or liquid is withdrawn, the cold fluid, having the temperature of the liquefied gas, absorbs heat from the thermal shield and from the insulation in its vicinity and the temperature of the shield is lowered. The cooled thermal shield then has power to absorb, because of its heat capacity, a considerable amountl of heat .the interposed body 200.

that constantly leaks in through the insulation fr'om the outer casing, thereby preventing this amount of heat from reaching the body of liquid and causing evaporation and loss of the liqueed ,in casing 19 to protect the liquefied gas against undue losses by evaporation. This shield also reduces the rate of pressure building due to the normal evaporation after the filling valve is closed'.`

The conserving of the refrigerating effect by the shield when the container is initially filled will be understood from the following example of operation: `Assume the container to beat room temperature and it is to be filled with liquid oxygen at a temperature of K. Under these conditions, the evaporation losses will initially be relatively large. As the fluid passes in thermally conducting relation with the shield, the refrigerating effect in large measure is stored and conserved thereby, the cooled shield p in turn cooling the insulating material that is between it and the liquid containing vessel.

The trap associated with the casing 19 functions asr follows: When the thermal shield is cooled by liquid or gas withdrawals so as 'to remove a relatively large quantity of heat from it and the surrounding insulation, a relatively large contraction ensues which results in the sucking in of air from outside the casing 19. This air can. enter only through the openings 35 and, in consequence, passes through the drying agent 33 Where it is dehydrated before entering the casing through the pipe 32. Theair exhaled when the thermal shield and the insulation expand passes out through the openings 35, 'but it is seen that moisture is at all times excluded from the insulation, provided, of course, that the chemical agent is renewed sufllciently frequently to keep it in an active drying condition., To make the insulation preserving' means as effective as possible, all joints 'and seams in the casing 19, in the trap 30 and in the connection leading thereto, are formed in a gas-tight manner, forl example, by welding all permanently attached parts and by the insertion of suitable gaskets in all joints.

In the modified form ofthe invention, shown in Fig. 3, the liquid withdrawal conduit is shown' at 141 and the gaswithdrawal conduit at 161, this latter having a portion first coiled about the liquid containing vessel in thermal contact with the pressure vessel 13. It also has a second portion 162 joining onto the ilrst portion coiled about and in contact with an interposed body 200, and terminates in a nozzle portion 163 on the outside of the casing 19'. The interposedbody 200 here is open ended and is seen to not surround completely the pressure vessel 13, but. to screen mainly the sides thereof.' The use of the portion 161 of the gas withdrawal coil for cooling the pressure vessel 13v effectually compensates for any heat eiects that might otherwise'reach the pressureA vessel 13A around in this arrangement the heat absorbing capacity of both the interposed body 200 and the casing 13 of the liquid'receptacle are utilized to intercept the heat effects which it is desired tcprevent reaching the liquefied gas in accordance Thus itis seen that with the invention. 'I'he two-part heat absorbing body thus provided together with the cooling means may thus be regarded as a compound thermal shield. In other respects this form of container for liquefied gas is like the form shown in Fig. 1 and like reference numerals denote corresponding parts.

The operation of this form of the invention is similar to that above described, the very cold gas generated by the evaporation of liquid within the inner vessel passing out through the withcontainer adapted for. holding liquefied gases A fled gas and provided with liquid supplying and` subject to small losses through evaporation by reason of the employment of two paths of high resistances to the entry of heat from an outside source to the liquid, namely, a path through a relatively thick body of insulating material having m'eans for preserving its insulated qualities, and a conduction path through the long coils of the withdrawal pipes which are in thermally conducting relation with a heat absorbing body.

From the foregoing it will be understood that when the casing 19 is suiiiciently heated to become a source of heat radiation which tends to pass to the liquid in the vessel 10, this radiation is intercepted by the heat absorbing body which thereby casts a shadow over a considerable portion of the surface of the liquid containing vessel from which heat radiation is substantially absent. Such shadows will hereinafter be referred to as heat-shadows which are invisible in order to distinguish them from lightshadows which are visible.

It is obvious that the thermal shield provided as above indicated may take many shapes and forms, and that the coil and heat absorbing body may be in numerous different positions and arrangements relative to each other and to the liquid containing vessel. Furthermore,

the structural features of the moisture trap here` illustrated are susceptible of considerable variation without departure from its function in accordanc'e with the invention. The insulation under most conditions preferablysubstantially lls the voids between the outer surface of the inner vessel and the inner surface of the outer casing, but less' insulation may of course be desirable in some cases.`

VHaving described my invention, what IA claim as new and desire to secure by Letters Patent, is:

1. In a container for liquefied gases, the comj bination with a vessel adapted to hold the liquefied gas and provided with liquidsupplying. and. withdrawal means, of an envelope surrounding said vessel and enclosing an insulating space, a body insulatingly supported andv interposed in said space about said vessel having a relatively high thermal conductivity, and means including solid material in heat conducting relation with said Vbody forv transferring' quantities 'of heat therefrom. o

2. In a container for liquefied gases, the combination with a vessel adapted to hold the liquewithdrawal means, of an envelope surrounding said vessel and enclosing an insulating space, a body insulatingly supported and interposed in said space about said vessel having a substantial heatcapacity and a relatively high thermal conductivity, and -conduitmeans associated with said body in heat conducting relation for cooling the same when desired. f

3. In a container for liquefied gases, the combination with a vessel adapted to hold the liquefied gas and provided with liquid supplying and withdrawal means, of an envelope surrounding said vessel and enclosing an insulating space, and .a body insulatingly supported and .interposed in'said space about said vessel having an appreciable specific heat and a relatively high thermal conductivity, said Withdrawal means having pipe convolutions disposed in heat conducting relation with said body and arranged to transfer quantities of heat therefrom;

4. In a container for liquefied gases, the combination with a vessel adapted to hold the liquefied ga's, of an envelope disposed about and enclosing said vessel, means for retarding the transfer of heat between said envelope and said vessel, a screen having a substantial heat capacity and relatively high thermal conductivity Y insulatingly supported and associated with said vessel and casting a heat shadow over a substantial portion of the surface of said vessel, and conduit means leading from said vessel and associated and in conducting relation with said screen for cooling said screen. y

5. In combination with a container for liqueed gases having a boiling point below 273 Kelvin, of an inner vessel for such liquid having means for filling and emptying the same and surrounded by heat insulating material, said insulating material being devoid of aeration passages, an outer casing, a thermal screen comprising a body of appreciable specific heat and relatively high thermal conductivity insulatingly supported and surrounding substanv tially a large part of said vessel, conduction means for 'transferring heat from said thermal screen to eiiiuent uid from said vessel, and means for preventing moisture from entering the space occupied by the insulation with the atmospheric air that enters when said insulation is cooled.

6. In combination withy a container for liqueed gases having a boiling point below 273o Kelvin, of an inner vessel for such liquid having means for filling and emptying the same and surrounded by heat insulating material, said insulating material being devoid of aeration passages, an outer casing, a thermal shield comprising a body or screen of appreciable specific heat and relatively high thermal conductivity insulatingly suspended and surrounding sub--i stantially the major part of said receptacle, and conduit means fortransferring heat from said screen tothe eiiluent iiuidl from said receptacle.

7. In combination with a container for liquefied gases having a vboiling point below 273 for such liquid having means for filling and lid emptying the same, and surrounded by heat insulating material, said insulating material' being devoid of aeration passages, an outer casing, a thermal shield enveloping at least a major part of said 'pressure vessel insulatingly supported and disposed about. said first named vessel, and means for removing heat fromsaid ther- I mal shield comprising a gas withdrawal conduit body oi' insulating material disposed in said spacel coiled in thermal contact with said shield.

8. In a container for liquefied gases, the combination with a vessel adapted to hold the liqueliledgas and provided with liquid supplying and withdrawal means, o1' an envelope surrounding,

said vessel and enclosing a space, a homogeneous and arranged to be devoid of aeration passages, a metallic body interposed in said,space about said Avessel insulatingly supported and having an appreciable heat capacity and a relatively high thermal conductivity, said vwithdrawal means having pipe convolutions disposed in heat conducting'relation with said metallic body and arranged to transfer quantities of heat there-l a body insmaungiy supported in said spate about" said vessel having an appreciable speciiic heat and a relatively nigh thermal conductivity, said withdrawal means having pipe convolutions disposed in heat conducting relation with said body and arranged to transfer 1quantities o! heat therefrom, and means for excluding moisture from the space occupied by the insulating material while permitting the inilux and eiliux of air from said space.

10. Ina containeifor liquefied gases, the comhination with a vessel adapted to hold the lique' ned gas and provided with liquid supplying and withdrawal mea of an envelope surrounding said vessel and enclosing a space, insulating material homogeneously disposed in said space vand arranged to be devoid of., aeration passages, a metallic body insulatingly supported:

in said space about said vessel having a substantial heat capacity and a relatively high thermal conductivity, convection means associated with said body in heat conducting relation for cooling the same when desired,l and means for excluding moisture from the space occupiedby the insulating material while' permitting the in. ux and elliux of air fromsald space.

LEO I. DANA.

GEORGE H. ZENNER.

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