US1861957A - Artificial refrigeration - Google Patents

Description

June 7, 1932. J. G. DE REMER ARTFICIAL REFRIGERATION 1925 2 shets-sheet "1 Original Filed Dec. 22.

BY Vis; l ATroRNEY 4 June 7, y1932.

J. G. DE REMER ARTIFICIAL REFRIGERATION 22. 1925 2 Sheets-Sheet 2 Original Filed Dec.

ATTORNEY Patented June 7, 1,932

- UNITED STATES- PATENT 01 F1Cl=` :TAY DE REMEIMOF GREENWICH, CONNECTICUT, ASSIGNOR, BY MESNE ASSIGNMENTS, TO J'. G. DE REMER RESEARCH CORPORATION, OF JERSEYCITY, NEW JERSEY, A

CORPORATION 02|? NEW JERSEY aminorar. nEFmeEnATIoN- Application led December 22, 1925, Serial No. 76,961. Renewed October 24, 1980.

The object of this invention is to maintain substantially constant temperatures by mechanical refrigeration, particularly temperatures lower than 32 F., such as required for preserving ice-cream. and other goods, and the inventiony consists in the method and means herein disclosed for that purpose.

V more or less diagrammatically, a suitable ar- The accompanying ldrawings illustrate,

rangement of apparatus bymeans of which the invention can be carried out;

Fig. 1 representing -thegeneral organization in dia ram. Y

Fig. 2 heet 2) is a vertical section of a refrigerator unit. A

Fig. 3 a section on line IIL-III.

Fig. 4 atop plan with the .header brokenl away.l y

Fig. 5, a broken out side elevation. Fig. 6 a larger scale section on VI-VI of Fig. 5; and

Figs. 7 and units.

Referring to the diagram, the refrigerant 8 show the application of the circuit includes a compressor l of any suitable design, driven b a motor 2 and connected through a con enser3 and expansion valve 4, and inlet pipe 4, to an evaporator 5, from which the vreturn pipe 6 leads back to the compressor; for economy of heat the re- -turn pipe is coiled about the expansion valve to cool the liquid refrigerant therein. The

expansion valve is merely a chamber containing a float which controlsthe outlet, at thebottom, to the evaporator. rlhe evaporator 5 consists of one or more plate-form chambers of extended area placed inside of one or more receptacles 7, whichlatter con-tain a medium adapted to befrozen and when frozen, to

keep the food or storage compartment 8 at the low temperature desired during intervals L between the operation of the compressor.

' The receptacles 7 may serve asthe lining of the box or storage space 8 and the latter is of course adequately insulatedjfrom the surrounding temperature, as indicated by the dotted lines in 1,- but the particular vdisposition of said receptacle and the freezing medium in it will presently be seen to be susceptible of applicationv to refrigerator apassociated with thereceptacle 7 so as to be subject to the temperature thereof, or a like temperature, and controls, through appropriate electrical connections, the.power circuit j of the motor, so that the compressor is set in action whenever the temperature of the medium inthe receptacle 7 rises above some pre-determined point, and`vice versa. The

detail of this thermostat forms the subject of a copending application.

The freezmg medium/ in the'receptacle 7 is l compounded with reference to the constant temperature which it is desired to maintain in the storage compartment. It may consist of an aqueous salt solution, the eutectic freez;

ing point of which approximates that temperature. lAs is well known, the solution of p a s alt in water freezes at a'lower temperature than the water alone and, within limits, the more salt that is added, the lower in general becomes the temperature of freezing. If a salt solution, of less than saturation strength, be subjected to a decreasing temperature, the eect is first to freeze out some of the water lin the form of pure ice crystals, and correspondingly concentrate the remaining liquid until it.A becomes a saturated solutionat a particular temperature. If this particular temperature is' not lw enough to freeze such a saturated solution, further depression of the temperature will cause a precipitation of some of the salt untila temperature is reached at which the solution, still saturated, freezes,l producing a conglomerate mass of mixed crystals closely interwoven. rIhe temperature at which this occursl is termed the eutectic freezing point of the mixture of the salt and water, and is different for 'different salts. rlhe solid or frozen product is termed the cryohydrate. ln accordance with this-invention, thesalt employed for the freezing I medium of receptacle 7 is selected` withgeference to its eutectic-point, so that the later i, 'Y i' shall approximate the constant temperature which it is desired to maintain or two or more such salts are employed in the freezing medium to provide such temperature, as later explained. When the cryohydrate of such a mixture or solution is used for refrigerating purposes, as in the receptacles 7, the temperature thereof does not increase above the eutectic point until it is nearly all converted back to liquid form, this being recognized, of course, as the effect of the latent heat of fusion of the cryohydrate. It will be seen, therefore, that if the freezing medium in the receptacle 7 be frozen, it will maintain the storage space at a corresponding low temperature, which may be Well under 32 F. for a long period of time, variable, of course, with the rate of leakage and the heat absorbed from such articles as may be on storage and even if the cryohydrate isycompletely melted, the cold solution will continue to have a refrigerating effect, superior to ordinary iceboxes, until its temperature rises to 32 F. If the solution should be of sodium chlorid the eutectic temperature would be about 6 F.; if potassium chlorid, about 121/ F.; if sodium carbonate about 22 F. The eutectic points of other salts are known and they may be yused according to this invention in so far as they are not injurious to the receptacle and are sufiiciently inexpensive to be commercially available.

In order that the receptacle may be well Afilled withvthe cryohydrate of the particular solution employed, the solution is made of such strength that it will be saturated at 32 F. This avoids the preliminary production of the ice crystals above referred to during the cooling period and enables the space which theywould occupy to be occupied by the more effective cryohydrate. It is satisfactory v to prepare the solution saturated at normal or room temperature; it will then be saturat ed at 32 F.

In the practical use of such a solution wherein it is repeatedly converted from solid to liquid -state, the amount of cryohydrate produced on each successive operation tends to become smaller and smaller and the duration of vthe low temperature period maintainedv thereby tends to becomecorrespondingly shorter and the efficiency of the system as a whole correspondingly impaired. I have ascertained the cause of this tendency to arise from the fact that during the lower- `ing of the `temperature of a saturated solution to its freezing point, some of the salt is cooled out of it, following the law that the strength of K,saturation is inverse to the temperature of the solution. The eliminated salt tends to precipitate and collect in the bottom of the receptacleand on any subsequent rise ofthe tempetatu're of the solution is not in a position to/go back into'solution automatically, except perhaps locally or near the bottom 'of the receptacle. The solution, being thus robbed of some of its salt, is thus noV longer saturated on a rising vtemperature but asit may still be below 32 F. the excess water at once freezes, forming ice crystals just to the extent necessary `to restore saturation strength at the particular. temperature. Such ice crystals are produced in increasing quantity as the temperature rises back to 32 l". and, unless preventive measures are taken, the repeated Warming and cooling of the receptacle 7 produces larger and larger quantities of clear ice therein, and more and more precipitated salt, eventually destroying the eficiency of the system for maintaining constant low temperature in the storage compartment.

The appropriate remedy for this condition consists either in preventing the isolation of the salt eliminated on cooling or in the provision of means for redissolving it in the solution as thetemperature rises, so as to keep the solution saturated at all times. A slight agitation of the solution will suffice for restoring it to solution and can be accomplished by the use of any common type of agitating means, such as a small impeller or the like, or even by so forming the relceptacle as to produce slow currents therein by difference of temperature between different parts of the receptacle, all of which measures are to be understood as included in this invention. I prefer, however, to accomplish the same ultimate result by preventing the precipitation or elimination of the salt in the first instance, as by providing a suitable support for it, so that, on the next warming, it will be well distributed throughout the mass of the solution and thus be retained in posi- .tion where it can be automatically taken up by the solution to restore it to saturation progressively as the temperature increases. Certain sponge-like materials or fillers are available for this purpose, for example sawdust, which can be filled into the receptacle 7 so as to fill it more or less completely, thus providing an infinite number of surfaces on which the eliminated salt may rest u ntil again taken up for restoring the saturation strength. Also if the solution be thickened so as to be buoyant to such eliminated' salt, the same effect will obviously be produced. The addition of starch to the solution so as to give it a somewhat jelly-like consistency has-produced excellent results without apparent effecten y solution of a single salt availablewithin commercial limits, and lotherwise satisfactory,

which has a eutectic freezing point corresponding to this temperature. However, I have ascertained that such temperature, or any desired temperature, may be maintained by employing a solutionof two or more salts having different eutectic points. By a proper selection of such salts and of their relative amounts'it is possible to produce a mixture of which the e'utectic pointl is as desired, and different fromthat of either salt in single solution. For example, I have found that normal sodium carbonate in saturated solution has a freezing temperature of about 28 F. and in melting will hold the temperature in general belowl 29. By introducing enough sodium carbonate' to a saturated potassium chlorid solution, which freezes at about l21/2 F., I have obtained a constant freezing temperature. 0f about 8 25 with a-melting temperature of between 8 and 10 F. By adding a proper portion of sodium bicarbonate to this double solution a constan/t freezing temperature rof 5 F. is obtained. The preferred freezing medium is produced,

in accordance with this principle, by dissolving in 160 pounds of water, 50 pounds of o'tassium chlorid, 22 pounds of sodium car onate Vand 13 pounds of sodium bicarbonate.l This is a solution which is saturated at 32 F. The colloid added to this solution for the purpose of suspending or preventing4 precipitation of the eliminated salt is added in the form of starch, about ltwo pounds, such starch having first been brought -to the boil- 40 ing point in a separated portion of thesolution and then mixed with the remainder.

This mixture is filled into the receptacle or receptacles 7 leaving enough air space at the top to accommodate the expansion.

45 When the compressor motor is started the solution temperature is reduced to its eutectic y temperature and freezes solid. The thermostat then shuts off the motor and thestorage space 8 .will thereafter be maintained at a low temperature corresponding to the eutectic of that particular solution. This temperature continues substantially constant V,until the cryohydrate is mostly melted, vat which time the thermostat #callsthe motor again into action and the solution is refrozen and so on. The intervals between motor ,operation may be several days,in practice, depending VQn the temperature of the-stored material and indefinite repetitions of the 00 cycle have no efect on the eticiency or the lengthkof theinterval between motor operations. Thelllostatic control-is not necessary,- except as a bor-saving convenience because the motor operations are normally so infre- 05 quent that they can be personally attended to whenever aninspection of the solutiori'liin the receptacle, as by tapping the side Wall thereof, indicates that to be necessary.

The long interval between motor o ra- -tions is the result of the saturated condition of` the freezing medium at normal temperature or at least at 32 F. and of keeping it up'to its proper strength during any rise of temperature, thus preventingobjectionable accumulation of ice crystals and always 7l insuring 'the maximum amount of .cryohydrate for a given -size of refrigeratorcompartment, this last consideration bein `of particular importance in household fre rigerators and ice-cream cabinets where space zo limitations are exacting. p. As indicated in Figs. 2' to 6 the receptacle 7 which contains the-freezing medium is thin in proportion to its height-and length, being about 21A inches thick, and is made of B5 sheet metal folded and flange-jointed as indicated in Fig. 3; its joints are suhcently strong if united by solder. The evaporator 5 is also made of sheet metal. It consists of a v horizontal gas header 1() with a hollow, plate-v 90' form extension depending from its under side and constituting the evaporator body. When assembled in the 'receptacle 7, the plate-form evaporator occupies the central plane thereof so that the freezing is from 95.

lthat plane outwards, and the header 10,

which is wider than the body, forms the top closure for the receptacle 7 being united thereto in any suitable way, with a gasket 11 intervening, to prevent escape of the eutec- 1 00 tic mixture ifthe device should be tipped over. The inlet and `outlet pipes are c0n' nected to the header lO, at the end or side as l A i preferred. To keep thel thin'evaporator body steadyA in the receptacle, the sidewalls of the latter are provided with opposed inward projections l2, these being preferably formed by indenting each sheet metal side wall with a vertical rib or bead as shown; obviously the same support could be provided in other no Ways. As thus constructed `the combined evaporator 5 and the container 7 constitute' a unit which can be adapted to refrigerators or ice-cream'l cabinets in various ways being treated in all-respects as though it were 118.

merely a section of lining for the storage compartment, and in the case of existing vapparatus, built for the use of a packing of' ice l and salt, as customary, these units can take/V' the place of such packingl and occupy the same space. Thus for an ice-cream cabinetI intended for a single row of icelcream cans as shown at 13 in Fig. 7 the units' are -placed along the side walls, each being connected in the refrigerant circuit in multiple relation 12B occupy the space originally designed for the i time.

The constructional detail of the evaporator is of course subject to variation but this invention includes its formationout of two closely parallel metal walls spaced apart about M1 inch and brought together at their edges and united by welding, forming a marginal seam as indicated at 14. These Walls are kept parallel by forming one of them with a series of indentations 15 and spot Welding the bottoms of the` latter to the opposite wall, thus tying the two walls together over the whole side of the evaporator body and thereby adapting the device to be made of much lighter gauge stock and hence thinner, than would otherwise be practical.

As shown by Fig. 4, the header 10 is not required to be of the same length as the evaporator body and it is preferably somewhat shorter, which provides a space or shoulder on the unit for the introduction of the bulbmember 18 of the thermostat 9. For this purpose the walls of the evaporator body are spread apart at one end, and within the solution receptacle, (Fig. 6) to accommodate a tapered tube 16 which is welded at its top and bottom or otherwise fastened to the evaporator walls, so that the refrigerant will surround it on all sides and so thatfthe tapered bulb member 18 of the thermostat can be inserted into it from one end. This `enlarged part of the evaporator body is enclosed in the receptacle 7 the top closure plate 17 of the latter being apertured in registry with the top of the tapered tube to accommodate the insertion of the thermostat i bulb, from the outside of the receptacle. For

omitted and the evaporator body may be of uniform thickness from end to end as indicated in dotted line'sin Fig. 7. The thermostat bulbv 18 contains the same eutectic solution as the receptacle 7 'and thus freezes and thaws ,with it. Its expansion on freezing develops pressure` which is transmitted by a tube 9 to the motor switch mechanism 19 which opens the motor circuit when freezing has taken place and opensl it before the cryohydrate has completely or substantially dis' appeared. Constancy of temperature requires in practice that the motor be started when the cryohydrate is at least melted Abut for safetys sake 'it is customary to set the thermostat for even earlier operation, and

thus maintain a steady temperature indefinitely.

The following is claimed:

1.' The process of` refrigeration which includes repeatedly freezing a saturated salt solution While maintaining precipitated salt in a suspended condition in the liquid.

2. In a refrigeratingl system, the combination with a refrigerant circuit including an evaporator, a receptacle containin a solution, saturated at 32 F. adapted to e'ffrozen by said evaporator, means for maintaining said solution in a saturated condition at varying solution ltemperatures less than 32 FH and thermostatic means for controlling the ice and salt mixture, a thin plate-like evaporator mounted within said receptacle, substantially co-extensive with the height and length thereof and located midway between the side walls thereof, said evaporator having a header disposed along the outer edge of the receptacle and the evaporator and substantiall equal in width to the width of saidreceptac e, and a freezing mixture occupying the space in -said receptacle on opposite sides of said thin evaporator.

4. In a refrigerating system, the combination of a refrigerant means, a container holding a salt solution, saturated at 32 F., and

. adapted to be frozen by said means and also holding means to maintain precipitated salt in distributed'condition in the liquid.

5. The process of refrigerating a chamber which comprises associating with said chamber a body of salt solution saturated when in operation, periodically depressing the temperature of said solution to or below its eutec ic freezing point, allowing it to refrigeratesaid chamber in the intervals between the depressions and coincidently maintaining precipitated salt particles in distributed rela- -tion throughout the solution.

6. The process of lrefrigerating a chamber which comprises periodically depressing the temperature of a saturated salt solution containing a colloid to or below its eutectic freezing point, and causing the frozen mass to refrigerate the chamber during the intervals between the depressions, said colloid being present in amount sufficient to prevent settlement of precipitated salt.

A7. The process of refrigerating a chamberv `which comprises periodically depressing the temperature of asaturated salt solution contaimng starch to or below its eutecti'c freezing point and utilizing the frozen mass to refrigerate s aid chamber, in the intervals between depressions, said starch being adapted to maintain precipitated. salt in-"suspended condition in the solution.

8. The combination of a chamber to be refrigerated, a refrigerant. system adapted for periodic operation, abody of saturated salt solution adapted to be repeatedly frozen by said system and servin to refrigerate said chamber in the intervals etween operations of said refrigerant system said solution having a euteetic freezing point `corresponding to the temperature at which it is desired to keep said chamber' and having means to maintain precipitated salt particles in distributed relation in said solution.

9. The combination of a chamber to be refrigerated, a refrigerant system, thermally.

controlled means for periodically operating said system, a body of saturated salt solution repeatedly frozen to or below its eutectic freezing point by said system and associated with said chamber to refrigerate the same in the intervals between the operations of said system, and means for suspending precipitated salt particles in the solution, thereby maintaining the strength of the solution after repeated thawings.

In testimony whereof, I have signed this specification.

` JAY G. DE REMER.

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