US2990693A - Refrigerator system - Google Patents

Description

M. E. HOUPLAIN 2,990,693

REFRIGERATOR SYSTEM July 4, 1961 2 Sheets-Sheet 1 Filed Aug. 7, 1958 M. E. HOUPLAIN REFRIGERATOR SYSTEM July 4, 1961 2 Shets-Sheet 2 Filed Aug. 7, 1958 2,990,693 REFRIGERATOR SYSTEM Marcel E. 'Houplain, Paris, France, assignor of one-half to Compagnie lndustrielle des Procedes Raoul 'Pictet,

Paris, France, a company of France 'Filed Aug. 7, 1958, Ser. No. 753,702 Claims priority, application France Sept. 4, 1957 '7 Claims. (Cl. 62-139) This invention relates to refrigerating systems of the type using an intermediate fluid ,betwen the cold source and the medium to be cooled serving as 'an accumulator of the cold produced.

Refrigerating systems utilizing an intermediate fluid have already been proposed; In one conventional system, a highly volatile intermediate liquid is used (coldgenerating or frigorigenic liquid) and the cold source contacts the vapour phase of this iliquid while the liquid phase is in heat-exchange relation with the medium to be cooled. Thus the heat from this medium vaporizes' the liquid and the resulting vapour is again condensed by the cold source, so that negative heat units are continually being transferred from the cold source to the medium to be cooled. However in view of the low specific heat of the intermediate liquids available, the cold build-up or accumulating capacity ofisuch systems is extremely low.

It has been suggested, especially in connection with the rapid cooling of large amounts 'of fluid, to use a freezable liquid, such as water, as the intermediate liquid, and immerse therein both the cold source, e.g. in the form of the evaporator coil'of a refrigerator unit, and a cooling circuit through which the fiuid to be cooled is passed. Thus, a layer of frozen liquid forms upon the surfaces of the evaporator which provides a store of cold and is capable of melting when required, to cool the fluid to be cooled.

Systems operating on these lines have yielded poor results because heat transfer in them is essentially produced by slow convection currents within the non-frozen intermediate liquid, and in order to improve the heat transfer mechanical agitator means have to be provided for the body of liquid.

It is an object of this invention to provide an improved refrigerating system of the cold-accumulating type, wherein the defects and difliculties inherent to prior systems of this type are eliminated and, more specifically, greatly to increase the heat exchanges through a liquid medium between the cold source and the exterior medium without requiring the use of external energy for agitation, such as mechanical agitators or the like. An object is the provision of a refrigerating system having a greatly increased, and controllable, accumulating capacity.

A system in accordanc with this invention comprises, within a sealed enclosure or tank, a solid phase, at least one liquid phase of the same substance asthe solid phase and at least one gaseous phase filling a free space at the top of the enclosure and comprising the vapour of at least one liquid phase, a source of cold near the top of the enclosure, and heat exchanger means establishing a heat exchange relation between said liquid phase positioned at the base of the enclosure and the medium to be cooled, and wherein the pressure of the .free gaseousphase is predetermined to permit the last-mentioned liquid phase to boil under the heat imparted to it within the enclosure fromthe heat exhanger means.

All three phases, liquid, solid and gaseous, may belong to a single substance or a single mixture of substances, in which case the operating temperature of the system and the vapour pressure within the tank would substantially correspond to the temperature and pressure as determined by the triple point of the substance, i.e. the point in the pressure-temperature coordinate plane at which the solid,

United States Patent time liquid and vapour phases of the substance coexist simultaneously.

In such a case itcan be considered, disregarding temperature gradients and variations within the system, that the cold source freezes the liquid at the temperature defined by the triple point and that the liquid, subjected only to the pressure of its own vapour, also boils at this same temperature on receiving heat from the exchanger.

The vapour bubbles formed, which seek to reach the free upper space, are thus brought into contact with the solid phase, causing it to melt and return, after condensation, into the body of liquid, thereby supplying negative heat units to the exchanger, substantially at the temper-a ture of the triple point. I

The temperature at which boiling of the liquid sets in can, however, be increased, i.e. the boiling retarded, by adding an inert gas into the said free space, so that its pressure will add to that of the vapour. In such case, the intense heat exchange effects occurring at the boil will first set in at a higher temperature level, 'in other'words the negative heat units are yielded at a temperature higher than the freezing point of the liquid.

The use of a single liquid in equilibrium with its solid and vapour phases may, however, pose some rather'serious difficulties in regard to regulation and control. Hence, in one desirable form of the invention, the cold accumulating function and the function of forming vapour in order to accelerate heat exchanges, are separated from one another and two separate liquids are used, the one heavier and volatile, and the other lighter and readily freezable, which liquids are not miscible with each other.

In such a case the system would comprise, in upwardly superimposed relationship within the sealed enclosure or tank, a volatile liquid, a freezing liquid, lighter than and practically unmiscible with the volatile liquid, and a free space at the top of the tank, with a cold source being immersed in the freezing liquid, while the volatile liquid may be placed in heat exchanging relation through an exchanger with the medium to be cooled.

In such a system the gaseous phase in the free space would contain at least saturated vapour of the volatile liquid. There are two liquid phases stacked in accordance with their densities and the solid phase consists of the frozen part of the lighter uppermost liquid in contact with the cold source. Just as in the case of a single liquid, reversible heat exchange occurs between the vapour .of the volatile liquid formed on contact with the heat exchanger and seeking to reach the free space, and the saturated vapour already contained within said space, and which on condensing will return by gravity to the bottom of the enclosure through the remaining freezable liquid.

These drops of condensed vapour are cooled on passing through the freezable liquid, causing partial melting of the frozen part of said liquid. They therefore act to cool the volatile liquid when they reach it and cause said volatile liquid to yield negative heat units through the exchanger to the medium to be cooled.

The tank and the heat exchanger may be so arranged relatively to each other that the vapour of the volatile liquid formed on contact with the exchanger, is directly led to the free space at the top of the tank to condense thereat and fall back dropwise through the freezable liquid so as to be cooled in passing through the latter. Alternatively however, the heat exchanger may be disposed within the body of volatile liquid so that the vapour bubbles will rise directly through the freezable liquid, in which case it is possible for such bubbles to condense at least partly within the body of freezable liquid before they have reached the free space. As in the first instance,

the free space may be arranged to contain only the vapour' of the volatile liquid (as well as a small amount of the vapour of the freezable liquid) without any added gas,

the vapour tension being at the value corresponding to the temperature of the free upper space. This temperature is necessarily determined by the freezing point of the freezable liquid since the free space is in direct heat exchange contact with the freezable liquid. The vapour phase of the volatile liquid is thus in equilibrium with the liquid phase thereof, which in turn is subjected to the pressure of said vapour phase plus the head of the freezable liquid overlying it. Now, the volatile liquid may be so selected that its vapour tension is high at the freezing temperature of the freezable liquid, so that this additional load or head will then be comparatively small and, on supply of heat units from the medium to be cooled, the volatile liquid will therefore begin to boil at a temperature only very little higher than the temperature of its vapour phase, that is, at thetemperature of the partially frozen freezable liquid. In such case the system will be capable of yielding cold at a temperature approximating that of the freezable liquid.

However, just as in the case of a single liquid, the free space may further contain an additional gas, and in such case the pressure to which the volatile liquid is exposed will be increased by the pressure of this gas so that its boiling point will be correspondingly increased. In such case the transfer of cold units (negative heat units) from the volatile liquid to the exchanger will be essentially produced through vaporization of said liquid in contact with the exchanger, and the exchange temperature will be the temperature of the boiling point of the volatile liquid and so may be made substantially higher, by an amount of several degrees Centigrade, than what it would be in the absence of additional gas in the free space.

It thus is made possible to accumulate cold units at very low temperature and only yield them up again at a higher temperature. This can be of interest for example in connection with the cooling of drinks with water as the freezable liquid, since the optimum temperature of cool drinks is on the order of 8 to 10 C.

In all cases therefore, regardless of whether one or two liquids are used, it is possible so to select a freezable liquid as to provide an operating-temperature level in the system and a temperature-pressure relationship which will determine a desired temperature level at which the cold units will be withdrawn from the system.

In apparatus according to the invention, the cold source may provide a continuous cold output while the resulting cold may be withdrawn intermittently; it is only necessary that the total cold output over a predetermined period of time should equal the sum total of the amounts of cold intermittently withdrawn.

Preferably the cold production capacity of the source is selected greater than the average value of the intermittent amounts of cold withdrawn and the apparatus includes means for arresting the operation of the cold source after a predetermined quantity of liquid has been frozen. Such means may desirably be responsive to the volume variation of the mass of freezable liquid on partial freezing, or to the resulting variation in liquid level. Any other suitable effect may be used for controlling the relative quantities of the solid phase with respect to the liquid phase in the freezable liquid.

Such control of the freezing of the freezable liquid will avoid a setting of the liquid in mass in case of an excessively prolonged period through which no cold is withdrawn from the system, a condition which otherwise would prevent normal heat exchange with the volatile liquid from occurring and, in case of violent vaporization of the latter, might result in an explosion of the apparatus.

As the freezable liquid, water may be used to advantage where the desired temperature is in a range surrounding C., since water has a high cold accumulating capacity (80 frigories, i.e. negative calories, per kilogram ice) and moreover the substantial volume increase on freezing facilitates regulation of the quantity of frozen liquid.

Where difierent temperature ranges are desired, other freezable liquids may be used, including solutions which may or may not be eutectics.

The volatile liquid used may advantageously comprise one of the chloro-fluorinated derivatives of methane or ethane commonly known in the trade as Freons, having a high density (about 1.5) and a boiling point lower than normal ambient temperature. Thus Freon 114 which is dichlor-tetrafluoreth-ane has a boiling point of about 4 C. at atmospheric pressure and is practically not miscible with water, and hence is especially suitable for association with water as the freezable fluid.

The ensuing disclosure made with reference to the accompanying diagrammatic drawings will provide a clear understanding of the invention but should not be construed as limiting the scope thereof otherwise than as required by the claims.

FIGS. 1 and 2 illustrate in vertical section two exemplary embodiments of refrigerating systems according to the invention employing a single fluid medium and suitable for use in the cooling of various fluids;

FIG. 3 is a similar view of apparatus employing two liquids; and likewise suitable for the cooling of fluids;

FIG. 4 shows a modified construction of a two-liquid apparatus suitable for space cooling;

FIGS. 5 and 6 illustrate two further modifications of fluid-cooling apparatus;

FIGS. 7 and 8 are temperature-pressure graphs useful in explaining the operating principles of the apparatus described.

The apparatus shown schematically in either of FIG. 1 or 2 comprises a sealed, heat-insulated tank or container 1. Near the top of the tank a cold source is disposed in the form of an evaporator coil 2 of a conventional refrigerator unit not shown. Near the bottom of the tank is a heat exchanger 3 also shown as a helically coiled tube through which the fluid to be cooled is passed.

Now referring more particularly to FIG. 1, the tank is substantially free of any gaseous contents and is substantially filled with a de-gasified aqueous liquid L contained up to a free level ZZ high enough to submerge both the exchanger 3 and evaporator coils 2. The small free space E above the liquid level ZZ contains essentially vapour of the liquid L. On operation of the evaporator 2, a layer of ice G forms over the surface of the evaporator coil and the liquid L as well as the vapour in the space E is cooled to the freezing temperature of the liquid.

Thus, assuming the liquid L is pure water, a temperature-pressure equilibrium is established in the apparatus corresponding to the point T on the temperature-pressure graph of FIG. 7. This point T is the so-called triple point at the common junction of the three curves C C C respectively representing equilibrium between the liquid and vapour phases, the liquid and solid phases, and the solid and vapour phases. As is well-known, the point T in the case of pure water corresponds to a pressure p of 4.5 mm. Hg and a temperature t of almost exactly 0 C. In the temperature-pressure coordinate plane shown, the region I represents the vapour phase, region II the liquid phase and region III the solid phase.

In such conditions, an amount of heat supplied by the exchanger will displace the equilibrium established at point T in the direction indicated by the arrow 1 (at constant pressure), and the water is hence caused to boil. The vapour bubbles on entering the water cooled by the ice G condense, and the condensed liquid drops back to cool the liquid contacting the exchanger 3.

If the liquid is other than pure water, being a solution of some soluble substance whereby the freezing point is lowered, the equilibrium curve between the liquid and vapour phases will not be curve C but some other curve such as C corresponding to a lower vapour pressure, so that the equilibrium would be established with respect to the point T which represents a new triple point for the set of curves .C C and .C The system then operates at apressurep and .a temperature t respectively lower than the values p andi And by suitably selecting the nature and quantity of the solid substance dissolved 'it is possible to predetermine any desired operating temperature t for the system over a substantial range.

However, it should be noted that in an area surrounding the triple point such as T or T the pressures p and p are low in'absolute value and, moreover, the curves such as C and C have a low slope, so that a very small quantity of gas present in the space B will be enough to alter substantially the operating conditions of the system.

Thus, if, the pressure in said free space is p the boiling temperature at the surface of contact with exchanger 3, which is the temperature at which cold is yielded up to the medium to be cooled, will equal a value t substantially higher than the temperature t A very small amount of inert gas added into the free space will therefore greatly .alter the temperature at which cold units are delivered to the medium to be cooled.

In the case of water and aqueous liquids which on freezing undergo a considerable increase in volume, on the order of the amount of ice formed at any time may be sensed by a level-sensing device responsive to immersion into the liquid below the free surface ZZ; examples of such devices suitable for use therein will be described later with reference to FIGS. 3 and 5.

The apparatus arranged as shown in FIG. 1 is suitable for use with aqueous-type liquids wherein the'volume increases on solidification. However non-aqueous type liquids may be used having different pressure and temperature coordinates of the triple point thereof, in order to achieve different operating temperatures not achievable with water and water solutions. Such other liquids will generally show a decrease in volurne on solidification, and in such cases the arrangement shown in FIG. 2 would be used wherein the evaporator 2 is positioned above the free level ZZ of the liquid L In such an arrangement the solid will form over the surface of evaporator 2 outside thebody of liquid. The evaporator surface may desirablybe arranged to retain the condensed liquid momentarily to promote freezing of the condensed liquid. The sensing of the quantity of solid formed may again be effected by liquid level-responsive devices similar to those mentioned above but herein responsive to emergence of the device above the liquid level ZZ, when the desired amount of liquid has solidified over the surfaces of evaporator 2.

This arrangement operates practicallyin the same way as the first arrangement described except that :the'vapour bubbles condense-directly upon the frozen liquid and then drop back in the form of cold drops into the body of liquid L Again in this arrangement a small amount of inert gas insoluble in the liquid L can be used for adjusting the operating temperature of heatexchanger 3.

Owing to the very low vapour pressure values in the area surrounding the triple point and the low slope of the curves such as C the vacuum in tank 1 above the liquid, or the residual gas therein, has to be controlled in a critical way. It is accordingly preferred according to a feature of the invention to use two separate liquids, the one being a freezable liquid and serving on solidification to provide the store of cold, while the other'is a volatile liquid and hence has a high vapour pressure so that the pressure control in the system becomes much less critical. Thus, in FIG. 3, there is contained in the bottom of tank 1 a body of a relatively dense and volatile liquid L such as dichlor-tetra-fiuorethane (C Cl F known as Freon 114, :and the exchanger 3 is immersed in it. The liquid L normally reaches up to a level XX. The tank further contains a body of liquid L which is readily freezable andis lighter than and unmiscible with the liquid L2, so that it remains entirely above .the level XX and reaches 6 up to a level YY such that the evaporator 2 is completely immersed in it. Where the liquid L is Freon 114, the liquid L may be water .or a water solution having a lower freezing point.

Assuming the tank was empty of air at the time the liquids L and L were added into it, then the free space E above the level YY is occupied by the gaseous phase of the volatile liquid L and by a small proportion of vapour of liquid L corresponding to the temperature of this liquid. The pressure obtaining above the liquid L is the pressure in space E (i.e. in accordance with Daltons law the sum of the saturated vapour pressures of both liquids L and L at the temperature under conisderation), ;plus the weight of the liquid column of liquid L overlying the liquid L The tank 1 is formed at its top with two sealed connections '4 and 5 through which electric conductors 4a and 5a are passed, connected respectively with electrodes 6 and 7 positioned in the idle condition of the apparatus above the free level YY and so within the gaseous phase of the volatile liquid L Conductors 4a and 5a are connected to terminals B and B of an alternating voltage circuit including a relay device which normally actuates a relay switch to closed condition in the absence of current through the circuit. Owing to the dielectric character of the vapour of liquid L particularly where this is Freon 114, no current normally flows through the circuit connected with terminals B and B so long as electrodes 6 and 7 are not immersed in the liquid L When voltage is applied to the cold-generating system connected with the evaporator coil 2, the water surrounding the coil is cooled, and begins to freeze and settle over the outer surfaces of the coil forming a solid sheath G. Owing to the increase in volume of the water on freezing the level YY gradually rises, since the level XX remains substantially unchanged. This latter statement is true, because only very low variations in the density of liquid L occur in the operating temperature range of the apparatus and the variations in the mass of the gaseous phase with respect to the mass of the liquid phase are likewise very low. As the rising level YY attains the electrodes 6 and 7, a circuit is established across the electrodes and operates the relay to disconnect the refrigerator or cold-generating unit (not shown), from its voltage supply. Hence, by adjusting the elevation of the electrodes 6 and 7 above the free level YY in the idle condition, the amount of frozen liquid such as ice accumulated on the evaporator 2 can be controlled with considerable accuracy. A small amount of alkaline salts or other suitable substance may be added into the water to increase its conductivity if required.

When a desired amount of ice has thus been built up on the evaporator, and a liquid to be cooled is flowing through the exchanger 3, heat is transferred from this liquid through the walls of the exchanger coil tube to the liquid L thereby bringing this liquid to the boil, provided the temperature of the liquid to be cooled is higher than the boiling point of the liquid L as determined by the pressure in the space E and the pressure head provided by the depth of liquid L used.

Vapour bubbles are thus created in the liquid L and rise up through the liquid L as shown at b in FIG. 3

in the portions of said liquid that are not frozen. These bubbles seek to rise through the cooler portions of liquid L adjacent to the evaporator coil 2 and through the frozen solid adhering to the coil, and in so doing the bubbles are substantially cooled and condense back to liquid form; such condensation occurring in part during upward travel of the bubbles through the body of water or liquid L and in part after the bubbles have reached the surface YY. 'I he vapour of the liquid L thus converted back to a strongly cooled liquid falls back in the form of drops through the body of lighter liquid L owing to the substantial difference in specific gravity between the two liquids. Such returning drops of liquid 7 L serve to transfer cold units to the body of liquid L and thence to the heat exchanger 3. Simultaneously, the ice melts and the level YY gradually drops again.-

After an amount of the solidified liquid L or ice has melted, the level YY drops sufficiently to uncover the electrodes 6 and 7 and thus actuates the relay switch to place back the cold-generating unit into operation. The instantaneous power output available from the compressor is thus added to the cold units released on fusion of the frozen liquid. The graph of FIG. 8 illustrates a typical operating cycle for such a system.

In FIG. 8 the curves C C and C are the equilibrium curves for the liquid L having the same significance as the correspondingly referenced curves in FIG. 7. Curve C is the liquid-vapour equilibrium curve for the liquid L As the temperature of solidification of the liquid L which, in the pressure ranges used, is very close to the temperature of triple point T, the vapour pressure of the volatile liquid L is 2 This pressure can be quite high, say equal to or higher than normal atmospheric pressure. Owing to the vapour pressure of the freezable liquid L and the pressure head of this liquid itself, the pressure in space E is 2 corresponding to a boiling temperature L; in the volatile liquid. Temperature i is quite close to the temperature t owing to the relatively high slope of curve C, which increases as the liquid L approaches its critical point. The relatively high value of the slope of curve C, makes it substantially easier to add a gas into the space E than would be the case if a single liquid were used, in order to exercise accurate control over the operating temperature 2 of the exchanger through adjustment of the pressure p obtaining in the space E. Where the space E thus contains a neutral gas under pressure, such space should be made large enough so that variations in the level YY will not substantially modify the pressure of said gas. Thus, assuming the freezable liquid is water, compression of the gas in space E on formation of ice would tend to increase the boiling point of the volatile liquid so that the value of the cold temperature supplied by the system would then increase as the amount of ice contained in the system increased.

In the embodiment shown in FIG. 4 the exchanger coil 3 is omitted and an exchanger is provided outside the tank, and the entire system is adapted to be received within a heat-isolated enclosure as indicated by the chain lines 14. The system in this embodiment is used for cooling such an enclosure. This enclosure may, for example, constitute a cold storage chamber into which comparatively large and heavy articles are periodically introduced and have to be rapidly cooled. It will be understood that in such an arrangement where the entire system is received within the enclosure to be cooled the walls of tank 1 need not be heat isolated.

The exchanger 13 in this embodiment comprises a conduit connected with the bottom of tank 1, and leading to a circuitous coil section provided with radiating fins having its other end connected with the top of the tank in the free space E thereof. Liquid evaporated in the exchanger 13 is thus directly delivered in vapour form to the free space E where it condenses and falls back in liquid drops to the bottom of the tank 1. To avoid entrainment of the liquid with the vapour bubbles, an expansion chamber 13a may be interposed in the circuit 13 at an elevation corresponding to the particular level to which the liquid L rises in the idle condition of the system to balance the pressure head of the liquid L In the embodiment shown in FIG. 5 means are provided for guiding the convection currents including both the upward flow of the vapour bubbles and the downward flow of the condensed drops of liquid L such guide means being in the form of a vertical cylindrical sleeve 8 extending coaxially in the tank and including an upper section surrounded by the evaporator coil 2 and an enlarged bottom section surrounding the exchanger coil 3.

Further, in this embodiment, a different arrangement is used from that heretofore described and shown in FIGS. 3 and 4 for controlling the amount of frozen liquid allowed to form. The ice build-up control means now about to be described have the advantage of averting the introduction of gas into the free space at the top of the tank.

The ice build-up control means here used comprise a resistance R immersed in the freezable liquid, while a resistance R having a high temperature coefiicient of resistance, such as a thermistor, is arranged somewhat above the level YY. Both resistances have one end connected to an outer terminal B connected with the refrigerator unit control circuit, while the other ends of the resistances are connected to the respective outer terminals B and B These terminals are respectively connected to the one ends of resistances R and R connected to the other control circuit terminal B Thus the four resistances form a Wheatstone bridge which is arranged to be normally balanced and which will become unbalanced in one or the other sense as the temperature responsive resistance R becomes immersed in or emerges out of the liquid. If suitable relay means are connected across terminals B and B it will thus be possible to arrest the operation of the cold-generating apparatus on a change in temperature of the resistance R due to a variation in the level of the plane YY. It should be noted that the level sensing device just described, which has the advantage of utilizing only the difference in specific heat and heat conductivity coefficients of a liquid and a gas, may if desired be used as the level-responsive means in other embodiments of the invention, e.g. in FIGS. 1 and 2.

Yet other equivalent liquid-level-responsive electric circuit control devices such as, for example, well known float switches, may of course be used than those described.

In the modified construction shown in FIG. 6, the evaporator 2 and exchanger 3 are positioned in two separate tanks 9 and 10, e.g. of the horizontal cylindrical form shown in superimposed relationship to each other, and connected by vertical tubes 11 and 12 at their ends. The tubes respectively serve to convey the rising vapours from the liquid L and for the downflow of the condensed liquid L as indicated by arrows. Tube 11 rises up to a point near the top of tank 9 and tube 12 extends down to a point near the base of tank 10.

It will be apparent that many further variations and modifications may be conceived by those familiar with the art without exceeding the scope of the ensuing claims.

What I claim is:

l. A refrigerating system comprising sealed container means; a first body of a relatively heavy volatile liquid filling the lower part of said container means; a second body of freezable, lighter liquid overlying said first body in said container means, a substantial liquid-free space remaining in said container means above the liquid level of said second body; cooling means immersed in said second body and capable of freezing the liquid of said second body; heat exchange means associated with a medium to be cooled and in heat exchange relation to said first body of liquid; and means responsive to variation of said liquid level for controlling operation of said cooling means.

2. A refrigerating system comprising a cooling plant having an evaporator; sealed container means; a first body of a relatively heavy volatile liquid filling the lower part of said container means; a second body of tfreezable, lighter liquid overlying said first body in said container means and enclosing said evaporator, a substantial liquidfree space remaining in said container means above the liquid level of said second body; heat exchange means associated with a medium to be cooled and in heat exchange relation to said first body of liquid; and means responsive to variation of said liquid level for controlling operation of said cooling plant.

3. A refrigerating system according to claim 1 wherein said second body of liquid is an aqueous liquid.

4. A refrigerating system according to claim 1 wherein said second body of liquid is an aqueous liquid, and said first body of liquid is a Freon.

5. A refrigerating system according to claim 1, wherein said heat exchange means comprises a cooling coil fully immersed in said first body of liquid and having said medium to be cooled flowing through said coil.

6. A refrigerating system according to claim 1 wherein said heat exchange means comprises a duct extension of said container means, the lower part of which duct extension partly contains said first liquid body and the upper part of which is in communication with said liquidfree space.

7. A refrigerating system according to claim 1, wherein said container means comprise two superimposed communicating containers respectively containing said liquid bodies, the communication comprising an upwardly directed duct starting from an upper part of the lower one of said containers and directed toward an upper 10 inner part of the upper one of said containers and a downwardly directed duct starting from a lower part of the upper one of said containers and directed toward a lower inner part of the lower one of said containers.

References Cited in the file of this patent UNITED STATES PATENTS 1,700,429 Bright Jan. 29, 1929 1,744,968 Keith Jan. 28, 1930 2,022,764 Gibson Dec. 3, 1935 2,083,396 Philipp June 8, 1937 2,095,008 Philipp Oct. 5, 1937 2,142,828 Smith Jan. 3, 1939 2,142,856 Lieb Jan. 3, 1939 2,146,058 Doyle Feb. 7, 1939 2,219,789 Potter Oct. 29', 1940 2,674,101 Calling Apr. 6, 1954 FOREIGN PATENTS 651,939 Germany Oct. 22, 1937

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