US1908290A - Refrigerating system and method - Google Patents

Description

J. c. GOQSMANN REFRIGERATING SYSTEM AND 'METH'OD May 9 Filed O61'.

NEU

Patented May 9, 193.?.l

UNITED STATES'HP'AT n f 1,908,290v

ENT OFFICE:

JUSTUS C.` GOOSMANN, OF CHICAGO, ILLINOIS BEFBIGERATING- SYSTIEIJIBIy METHOD Application led October 1.3, 1930. Serial No. 488202.'

This invention relates in general to refrigeratings stems'andmeth'ods.

One o the objectsof the invention is to provide a refrigerating system and method employing carbon dioxide refrigerant in its solid, liquid, and gaseous phases. A

Another v object of this invention is the provision of apparatus and methods by means of which solid carbon dioxide may be employed to do useful refrigerating .work by heat exchange between the solid CO2 and the space or the medium to be refrigerated.

Another object of this invention is the provision of apparatus and methods by means of. which maximum economy may be elect-ed in utilizing solid carbon dioxide for refrigerating purposes.

Astill further object of this invention is the provision of means whereby a complete heat exchange between the solid CO2 refrig-l erant andthe medium to be refrigerated isv effected, together with the application of eX- ternal' heat which is automatically introduced when necessary to make the heat exchange cycle complete and automatically op-v erative. Y

Another object of "this invention is the provision of relatively low and moderately high temperature refrigerating cabinets with carbon dioxide gas and liquidl coils connected together for the purpose of utilizing solid carbon dioxide for refrigerating purposes, together with means for changing the state of the medium in the cycle.

A still further object of this invention is the provision of a systemfrom which the carbon dioxide gas may be withdrawn after doing useful refrigerating work-for such other purposes as may be available, such as., for liquid carbonating purposes.

These and many other objects as will` appear from the followingidisclosure are secured by means of the apparatus and methods of this invention. l

This invention resides substantially in the combination, construction, arrangement, relative locationof parts, steps and series of steps, -all as will be explained in greater detail in the following specication The accompanying drawing is a'diagrammatic view with some parts in cross section of the apparatus of this invention.

The general object of this inventionisto provide apparatus and methods by means of which the cooling properties of solid carbon dioxide may be utilized to the maximum extent in doing useful refrigerating Work. In general the system comprises a container forz the solidcarbon dioxide so proportioned with' respect to the volume of solid CO2 placed 60 therein that the gas generated therefrom will be liquefied in a primary condenser coil 10- cated at the bottom ofof the container by the combined action of the built-up pressure in the container and the cooling work of thesolid COZ in close proximity with the said primary condenser coil. The liqueiiedl car# bon dioxide is then passed into a refrigerating chamber and circulated through the liquid coil, delivered to a gas coil, and there permitted to vaporize. This vaporization ofl the liquid is caused by absorption of vheat fromthe refrigeratingchamber thereby cooling it.' Means is provided between the liquid and gas coils for insuring that liquid Idelivered to the ygas coils may vaporize therein. This vapor is then circulated in heat exchange relation with the container holding the solid carbon dioxide through a secondary condenser coil whereby it is cooled and gives up heat to effect further vaporization or sublimation of the solid'carbon dioxide. The liquid, or .a mixture of liquid and vapor, is then -circu- .l lated through another refrigerating space which is maintained at refrigerating tem- 8 5 peratures that are higher than those in the first refrigerator. The gas is then delivered vto astorage tank from which it may be removed for any purpose, an example of which is for carbonating beverages.

VThe physical changes which occur in the operation of this apparatus will now be described lin greater detail. One end of the prim ary condenser'coil extends into the vapor space, and' since it is open it permits the CO2 95 to enter it as the solid CO2 in the container sublimes. The bulk of this coil is located atv the bottom ofthe container where it is lin contact with and subjected'to the coolingaction of the solid CO2. During sublimation ,100

heat is supplied to the solid CO2 through heat contacting wall of the container, the pressure rises and liquefaction of the CO2 in the coil occurs. This liquid is immediately expelled from the condenser coil into a receiving coil located outside of the container where the liquid is momentarily held in readivness for use. T he pressure-,temperature relation for sublimation in the containerand hquefaction in the prlmary condenser coil 1s i then 150 lbs. pressure absolute 'and a liquid is only by temperatureof minus 40 F.A .l

The assumption of 150 pounds of pressure way of example since this pressure may be varied'between wide limits, depending upon the adjustment of the blow-off relief valve 34,01 the adjustment of a relief with this apparatus, liquid carbon dioxide will of course form in container l-at the same time that solid carbon dioxidel is present, to-` gether with carbon dioxide gas. In otlierr words, Whenthe triple point temperatureand pressure conditions for carbon dioxide `are attained within the container l1, carbon dioxide will be present in gaseous, liquid and solid form. This fact does not, however, prevent the apparatus from operating, nor prei vent the formation of liquid carbon dioxide in the liquid'coil 10 andin the other parts of the system as disclosed. 4

It is well known and has long been observed that carbon dioxide in process of liquefaction behaves diderently than other well known gases such as for example ammonia. Ammonia during its processof liquefaction cannot be cooled to a lower temperature than that of the water overflow from the cooling con-l denser, while' carbon dioxide on the other hand may be sub-cooled below the overflow temperature of the water. It has been observed in many tests that the temperature of carbon dioxide gas in a condenser vduring eondensationvaries considerably and this variation 'can be traced to the point of change in state,.that is, wherehthe gas changes into a liquid. This is duexin' a considerable measure to the fact that the heat does not readily travel through a layer of carbon dioxide aas or vapor. The insulatinV property of this gas is high, in fact, much igher than that of air s o that the temperature of the liquid at the end of condensation, and where this telnthe into gas.

the container is approximately perat'ure is lowest, is not aiiected by the higher temperature of the gas within the condenser, although the gas as Well as the liquid,

is at the saine pressure.

This condition becomes more drastic and more apparent and is easily observed when solid carbon dioxide sublimes in a pressure vessel. In this case there appears'to be an enti-re disruption of the relationship between temperature and pressure. For'instance,the solid carbon dioxide at the bottom of the containcris little inliuenced by the pressure present in the same container. The temper'- ature of the solid carbon dioxide deviates little from its temperature orv *109 F. regardless of .the vpressure which develops in the con'talner by the sublimation ofthe solid The temperature -o the `liquid must necessarily be regulated above the temperature of crystallization which is adjusted by the flow of liquid out of the container into the liquid receiver. It is necessarily true that if the liquid which has collected at the bottom of the container is allowed to remain there in a static condition, it will be cooled by the solid carbon dioxide to the point of crystallization and thus solidified.

However, when thisliquid is drawn from the container at a temperature above crystallization, it will not `freeze as will readily be apparent. The pressure on the other hanfl which is developed by the continuous sublimation of the enclosed solid carbon dioxide .mounts'steadily to higher levels. Therefore, temperatures at great variation can be observed in the container; for instance, which collects near may approach the temperature existingon the outside thereof. Atl the approximate mid-distance between the top and the bottoni of the container, the temperature will be found considerably lower; at the vbottom where the liquid exists, temperatures of -40Q F. occur, and, at the same time, the temperature of the metal bottom of the container upon which the solid carbon dioxide .rests will be as low as 100 F. During all of this time, the pressure in the container will be close to that corresponding with lthe temperature of the gas near the top. if the temperature of the gas near the top of pressure within the container `would be found to be above 700 pounds per square inch.

Here again, it seems apparent that'the in-y the gas the top of the container.

In other words..

60 F., uw

sulating property of the gas prevents even temperature equalization of the gaseous body within the container.

Experiments carried on by competent physicists have shown that the volume of solid carbon dioxide limation at the rate of .085% Aper 1 F. increases in temperature.

increases during sub- In this respect, solid carbon dioxide behaves opposlte/to waterice';

the latterLincreSes in volume duringireeing rao ' and decreases 'in `volume' on melting; while the triple point, but

carbon dioxide' decreases in volume while freezing and increases in volume when meltsolid field is, therefore, 1 F. per 1,544 pounds pressure. Tammann and Bridgeman found that the sublimation of solid carbon dioxide l can be prevented only at an enormous pressure. For instance, 'solid carbon dioxide which has a pressure at the triple point of 75.14' pounds per square -inch absolute and a corresponding temperature of -69.86 F. requires an increase in this pressure to 14,220 'pounds per square inch with a rise in its temperature to 35.14 F. This demonstrates that the sublimation of solid carbon dioxidecan be prevented only at an enormous increase in pressure.

This explains the increase in pressure Within they container during the sublimation of solid carbon dioxide to above 700 pounds per square inch when enclosed in -a pressure vessel, while the liquid temperature near the bottom may be as low as 40 F. with a still much lower temperature at the bottom where solid carbon dioxide is in direct contactwith the metal ofthe container.

The equilibrium condition for the fluid phases of solid carbon dioxide'shows that the pressure in the container would still climb much higher if none of the enclosed carbon .dioxide is withdrawn. Hence, in practice, the apparatus is provided with a safety disc proportioned to break at 1,20() pounds per square' inch, so that the Vcontainer will not be subjected to dangerous `pressure conditions. 1

Thevliquid is now available ,for refrigerating requirements which is accomplished .by allowing it to "aporize in cooling coils or v'other heat absorbmg bodies. During this va-` porization the. heat absorbed in a refrigerator, for example, is then equivalent to all of the heat carried by the cold liquid out of the solidl CO2 container. Thus. in giving up its low temperature heat while doing refrigeratingwork, or,-` in other words byA absorbing heat from t e refrigerator space as well as the goods placed therein the liquid completely vaporizes and finally itsyapor bccomes super-heated. This super-heated vapor is then returned to the 'solid CO2 container through a secondary condenser coil wound around the outside of the container.

in the container thefvapor in the secondaryv condenser coil is cooled and finally recondensed.v Hence the heat lnecessary to provduce sublimation of the solid CO2 is the identical quantityof heat absorbed in the refrigerator during the vaporiation -of'the liquid and the super-heating of the vapor. Theoretically, therefore, the heat exchange between the solid carbon dioxide in the container and the heat in the refrigerator is 100%; it being understood that heat losses are substantially eliminated by adequate insulation.

However, it has been found in practice that there isda deficiency in vheat which is carried back from the refrigerator to the solid CO2 and that by reason of such deficiency there developes a shortage in vapor sublimation and therefore of liquefaction. This deficiency is obviously small and can easily be supplied by heat from some external source. In the system of this invention a small electrical heating element automatically controlled by a thermostat-ic switch placed inside ofthe refrigerator is employed. Due to the insufficiency of heat carried into the solid carbon dioxide the solid carbon dioxide docs not sublime in suicient quantity so that y the temperature in the refrigerator space will .slowly rise. As soon as the upper predetermined temperature limit has been reached in the refrigerator the thermostatic switch `automatically closesy to complete the circuit to the electrical heating element. The heat generated by this heating element within .the solid CO2 container causes a greater quantity of solidl CO2 to sublime, and as a `consequence provides more liquid to increase refrigeration and to lower the temperature in the refrigerator. At a predetermined lower. temperature limit in the refrigerator the thermostatic switch automatically opens and the process then continues as a closed cycle.

There are other objects of this invention as will appear from the following detailed disclosure.

Referring to the drawing', the 'container for the solid carbon dioxide is shown at 1 havin a movable cover 2 which is held in sealing relation with thecontaine'r by any suitable clamping means 3. This container is supported within a heat insulating cabinet 4 provided with a removable cover 5. Within the container 1 and spaced a suitable distance from the bottom thereof is a transverse perforated wall 6 on .which one or more blocks 7 of solid carbon dioxide are supported. The volume of the container 1 with respect to the volume of solid placed therein must be such that the solid may vaporize and lgenerate pressure. Opening intocontainer 1 is a pipe f 10 into oneend of which is connected the pipe During the heat exchange with the solid CO2 8. The other end of this condenser' coil is connected by pipe 11 to the liquid coil 12 within the refrigerator 13,-which may be fa manner, or may itself vbe made of heat insulating material such asrefrigerator cabinets and the like.

The other end of liquid coil 12 is connected by pipe 16 to a oat valve 17 of any well known construction. The outlet of the float valve is connected by pipe 18 to a header 19. The float valve is arranged with respect to the header 19 so that a suitable body of liquid carbon dioxide will be maintained therein as indicated in the drawing. At 21is another header which is connected to the header 19 by a plurality of parallel pipes 20. v

' Near the top of header 21 is provided a pipe connection 22 leading to a thermostatic control valve 23. This thermostatic control valve may be of oany well known type and is placed withinthe, refrigerator so as to be subject to thev temperature conditions therein. It is, of course, adjusted so as to prevent the temperature within the cabinet falling below the predetermined value and acts to Shut off the flow of gas when that value is attained. The outlet of the thermostatic control valve 23 irs-connected by pipe 24 which extends to a secondary condenser coil 25 which encircles the container- 1 in heat exchange relation. The outlet of coil 25' is connected by a pipe 26 to a cooling coil 27. This cooling coil 27 is within a space 28 formed by the glass'wall 29 and the rear wall 30. The space 28 provides, 33

.for example, refrigerated display cabinet such as used in stores selling perishable products. This cabinet is provided with a suitable door 31 by means of which access to the interior may be had.

Suitably mounted within the container 1 is an electrical heating coil 40 of any suitable constructon. At 41 is a thermostatic switch /which is exposed to the temperature conditions within the refrigerator 13. 43 repre.- sents any suitable current source connected to the heater element and the thermostatic switch by wires 42. Itis, of course, apparent that this invention is not limited to an electrical heating means for supplying external heat since other well knownforms of heating devices may be used.

The outlet of coil 27 is connected by pipe 32 to a gas storage receiving tank 33.- This tank is provided with a suitable release valve v. cover 2 and clamp 3. The insulating cabinet' 34 for permitting the escape of the gas vif the pressure therein tends to build abovela predetermined value. This tank is also provided with a delivery pipe 35 and control valve 36 by means of `*which the gas may be deliv ered for any'use, suchas for example the carbonating of beverages.

The operation of this apparatus is as follows: A suitable quantity of solid carbon dioxide in the form of blocks 7 is placedwithin the container 1, which is sealed by means o 4 is then closed by means of the cover 5. i As the solid carbon dioxide sublimates the gas by the lformed withinthe free space the container then flows down through pipe 8 of cooling coil 10 where it is cooled suiiiciently to liquefy. The liquid then iiows through pipe 11 to f the refrigerators and the articles therein, as

does the relatively cold gas flowing through the pipes 20. This flow of gas is controlled gas then condenser coil 25 where it is cooled and again liquefied, giving up its heat to effect further gasification of the solid carbon dioxide within the containeril. The liquid, or the mixho ture of liquid and vapor then flows through pipe 26 to the coolingqoil .27 withinthe second refrigerating space 28 where it absorbs heat therefrom, as' well as from thev articles therein.v The gas is then delivered through pipe 32 to the storage receiving tank tion that this process is a very economical one.l With the apparatus disclosed and the' method employed the very cold solid carbon dioxide is transformed into liquid and gaseous phases and employed to do useful work in absorbing heat from articleslto be cooled. Furthermore, the heat absorbed is employed to leect further yvaporization of the solid, and finally the still relatively cool gas at a thermostatic control valve 23. Theflows from pipe 24 to thesecondary.

lt will be apparent from the above descrip-Sv super-atmospheric pressure is available for` other uses.

Any deficiency in this heat exchange is 'Y then supplied by heat from an outside source so controlled by the thermostatic switch that only suchheat velop is made up side source.A i

The approximate temperatures and pressures involved will be given in an illustrative sense and with no intention of restricting the scope of the invention. The solid carbon dioxide is at approximately minus 109"4 F. When it is permitted to vaporize within the from any convenient outf deficiency as may actually de" container 1 the. gas pressure therein rises to approximately 150 pounds pressure per square inch. This gas at this pressure vand temperature when it flows throughthe primary condensing coil 10 in heat exchange relation with the soild is under such conditions f that it liquefies. `The liquid flowing from the coils through pipe 11 intoliquid coil 12 is at approximately minus 40 F., andl 150 lbs.

pressure. The gas flowing from the gas pipes 20 through pipes 22 and 24 is at approximatel minus 10 F. and 115-lbs. pressure. After flowing through the cooling coils 25 the gas vis at approximately minus 50 F. and 100 lbs. pressure. After 1leaving the coil 27 the gas is at from minus 10 ,to 0o F. and at approximately 80 lbs. pressure. It isvstored within the gas storage tank at approximately 80 lbs. pressure.

Among the many uses to which this still relatively cool gas at super-atmospheric pressure may be applied is that of vcarbonating beverages.- Beverages are usually carbonated at about lbs. pressure per square inch, so that the gas in the storage tank is at once available for this purpose.

The check valve 9 is provided in the -pipe 8 so that when the container 1 is open for the admission of further solid carbon dioxide the pressures within the various pipes and coils w1ll not escape into the atmosphere as it would do if no check valve were provided.

From the foregoing disclosure it will be apparent that this invention involves Acert-ain .principles of construction and operation which may be readily embodied in other apparatus and methods as will be apparent to those skilled in the art. I do not, therefore, desire to he strictly limitedby the disclosure, either inthe drawing or spec1ficat1on,

-as given for the-purpose of illustrating my invention, but ratherto the scope of the appended claims. U y

What I seek to sec re by Unlted States Letters Patent is:

l1. In a refrigerating apparatus, the combination comprising two refrigerators, re-

frigerating coils in said refrigerators, and means connected to said coils for recelvlng solid carbon dioxide from which liquid carbon dioxide refrigerant is delivered to the coils of said refrigerators.

2. In a refrigerating apparatus, the combination comprising a container for solid,

carbon dioxide, a refrigerating cabinet having a cooling coil therein, connections between the container and the cooling coil, a coil surrounding said container and connected to the coolingcoil of the refrigerating cabinet, a second refrigerating cabinet havin a cooling coil therein, and connections etween the cooling coil in the second refrigerating cabinet and the cooling coil surrounding the container. type described, the combination comprising a container for solid carbon dioxide, a cooling coil in heat exchange relation' with said container and 'opening into the interior thereof, a refrigerating cabinet, a cooling coil in.'

. said cabinet connected to said rst cooling coil, another coil encircling the container and connected to the cooling coil within the refrig- 4erating cabinet, a second refrigerating cabinet having a cooling coil' therein, and con- .erating cabinet frigerating .cabinet having a coll and a.l gas vcooling' coil therein, connections 3. In a refrigerating apparatus of they nections between the cooling coil in the second refrigerating cabinet and the circling` said container.

4. In a refrigerating apparatus of the type described, the combination comprising a container for solid carbon dioxidea. cooling coil in heat exchangev relation with said container and opening into the interior thereof, a refrigerating-cabinet, a cooling coil in said cabinet connected to said irst cooling coil, another coilencircl ing the container and connected to thecooling coil within the refrigerating cabinet, a second refrigerating cabinet having a cooling coil therein, connections between the cooling coil in the second refrigerating cabinet andthe cooling coil encircling said container, and means within said first cooling cabinet'in the connections between the cooling coil therein and the cooling coil encircling said container for maintaining a predetermined temperature 4condition Within that cabinet.-

5. type described, the combination 'comprising a container for solid carbon dioxide, a cooling coilin heat exchange relation with said container and opening into the interior thereof, a refrigerating cabinet, a cooling coil in said cabinet connected to said first cooling coil, another coil encircling` the container and connected to the cooling coil within the refrigerating cabinet, a second refrigerating cabinet having a cooling coil therein, connections between the cooling coil in the second refrigand thecooling coil encircling said container, and gaseous carbon dioxide storing means connected to the cooling coil within 'the second refrigerating cabinet.

6. Ina refrigerati-ing apparatus of the type described, the combination comprising a refrigerating cabinet having a liquid cooling coil and a gas cooling coil therein, connections between said coils including a iioat valve for controlling the delivery of liquid from the liquid' coil to the gas coil, and means fordelivering liquid carbon dioxide to coolingcoil enthe liquid coil.

7. In a refrigerating apparatus of the type described, the combination comprising a reliquid cooling between said coils including afloat valve for controlling the delivery of liquid from the liquid coil to the gas coil, andv means for transforming solid carbon dioxide into liquid carbon dioxide connected to the' liquid coil of the refrigerator. Y i 8. In a refrigerating apparatus of the type described, the combination comprising a container for receiving solid. carbon dioxide, a condensing coil in heat'exchange relation In a refrigerating apparatus ofthe with said container Aand opening therein, a

refrigerator having a liquid coil and agas coil therein connected'together, a vconnection between the condensing co1l and the liquid coil, a cooling coil in heat exchange relation with said container, a connection between that cooling coil and the gas coil of the refrigerator, a second refrigerator having a cooling coil therein, and a l connection between the cooling coil of the second refrigerator and the cooling coil in heat exchange relation with the container.

9. In a refrigerating apparatus of the type described, the combination comprising a container for receiving solid carbon dioxide, a condensing coil in heat exchange relation with said container and opening therein, a rel frigerator having a liquid coil and a gas coil therein connected together, a connection between the condensing coil and the liquid coil, a cooling coil in heat exchange relation with said container, a connection between that cooling coil and the gas coil of the refrigerator, a secondvrefrigerator having a cooling coil therein, a. connection between the cooling cooling coil coil of the second refrigerator and the cooling coil in heat exchange relation with the container, and means in the connection between the liquid coil and the gas'coil of thel refrigerator for maintaining a predetermined quantity of liquid in the gas coil.

l 10. In a refrigerating apparatus of the type described, the combination comprising a container for receiving solid carbon dioxide, a condensing coil in heat exchange relation with said container and opening therein, a refrigerator having a liquid coil and a gas coil therein connected together, a connection between the condensing coil and the liquid circulating the gaseous carbon dioxide in heat,

exchange relationwith the solid carbon dioxide to liquefy it, circulating the liquid cari bon dioxide within aspace to be refrigerated,

transforming the liquid carbon dioxide to gaseous carbon dioxide within that space, circulating the gaseous carbon dioxide in lheat exchange relation with solid carbon dioxide to cool it, and circulating the cooled carbon dioxide gas in heat exchange relation with the refrigerating space.

12. In a-refrigerating method of the type described, thelsteps ofsublimating solid carbon dioxide to form gaseous carbon dioxide, circulatingthe gaseous carbon dioxide in heat exchange relation with the solid carbon dioxide to liquefy it, circulating the liquid carbon dioxide within a space to be refrigerated, transformingthe liquid carbon dioxide to gaseous carbon dioxide within that space, circulating the gaseous carbon dioxide'in heat exchange relation withsolid carbon dioxide to cool it, circulating the cooled carbon dioxide gas in heat exchange relation with the refrigerating space, and storing the carbon dioxide gas atvsuper-atmospheric pressure.

18. A refrigerating cycle employing solid carbon dioxide comprising transforming solid carbon dioxide into gaseous carbon dioxide,

circulating the gaseous carbon dioxide in heat exchange relation to the remaining solid c arbon dioxide to liquefy it, circulating the liquid carbon dioxide in heat exchange'relation with articles to be cooled, transforming the liquid carbon dioxide into gaseous carbou dioxide and circulating the gaseous carbon dioxide in heat exchange relation with artlcles to be cooled,circulating the relatively warm gaseous carbon dioxide in heat exchange relation with the solid carbon dioxide to coolV the gas and effect further vaporization of the solid, and circulating the cooled carbon dioxide gas in heat exchange relation with articles to be cooled.

14. A refrigerating cycle employing solid carbon dioxide comprising ltransforming solid carbon dioxide into gaseous-carbon dioxide, circulating the gaseous carbon dioxide in heat exchange relation to the remaining solid carbon dioxide to liquefy it, circulating vthe liquid carbon dioxide in heat exchange relation with articles to be cooled, transformingv the liquid carbon dioxide into gaseous carbon dioxide and circulating the gaseous carbon dioxide in heat exchange relation with articles to be cooled, circulating the relatively warm gaseous carbon dioxide in heat exchange relation with the solid carbon dioxide to cool the gas and effect further vapori'zation of the solid, circulating the cooled carbon dioxide gas in heat exchange relation with articles to be cooled,l and `using theA carbon dioxide gas to carbonate beverages.

.15. In a refrigerating apparatus, the combination comprising a container for solid carbon dioxide, a refrigerating cabinet having a cooling coil therein, connections between the' container and the cooling coil, a coil surrounding said container and connected to the cooling coil of the refrigerating cabinet, a second'refrigerating cabinet having a cooling coil therein, connections between the cooling coil in the second refrigerating cabinet and the cooling coil surrounding the con,- tainer, and means for supplying external heat to the container. y

16. In a refrigerating apparatus, the combination comprising a container for solid carbon dioxide, a refrigerating cabinet having a cooling coil therein, connections between the container and the cooling coil, a

coil surrounding said container and con` y automatically energizing it.

17. In a refrigerating apparatus, the combination comprising a container for solid carbon dioxide, a refrigerating cabinet having a cooling coil therein, connections between the container and the cooling coil, a coil surrounding said container and connected to the cooling coil of the refrigerating cabinet, a second refrigerating cabinet having a cooling coil therein, connections between the cooling coil in the second refrigerating dioxide to liquid carbon dioxide, comprising a closed vchamber and a condensing coil with-A in said chamber, said condensing coil being open to the interior of the chamber.

In testimony whereof I have hereunto set my hand on this 10thday of October, A. 1)

JUSTUS C. GOOSMANN.

cabinet and the cooling coil surrounding the v container, an electrical heating device withinv said container, a thermostatic switch within the rst refrigerating cabinet and connections between the electrical heating device n and the thermostatic switch whereby the electrical heating device is energized upon the 'increase sublimation.

development of predetermined temperature conditions within the refrigeratin cabinet.

18. In a refrigerating method o the type described, the steps of sublimating solid carbon dioxide to form gaseous carbon dioxide,

circulating the gaseous carbon dioxide in heat lexchange relation With the solid carbon dioxide .to liquefy it, circulating the liquid carbon dioxide within a space to be refrigerated,

transforming the liquid carbon dioxide toA gaseous carbon dioxide within that space,

circulating the4 gaseous carbon dioxide in heat exchange relation with solid carbon dioxide to coolit, circulating the cooled carbon dioxide gas in heat exchange relation with the refrigerating space, and supplying external heat-to the solid carbon dioxide to 19.v In a-refrigerating method of the type described, the steps of sublimating solid carbon dioxide to form gaseous carbon dioxide, circulating the gaseous carbon dioxide in heat exchange relation with the solid carbon dioxide to liquefy it, circulatin the liquid carbon dioxide within a space toe refrigerated, transforming the liquid carbon dioxide to gaseous carbon dioxide Within that space, circulating the gaseous carbon dioxide in heat exchange relation with solid-carbon dioxide to cool 1t, circulating the cooled carbon dioxide gas in heat exchange relation with the refrigerating space, and supplying external heat under control of the temperature con-.-

ditions in the lirst refrigerating space to lincrease the sublimation of the solid carbon d1ox1de.

20. A converter for changing solid carbon

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