US1991944A - Refrigerating method and apparatus - Google Patents

Description

Feb. 19, 1935. D, F. KEITH 1,991,944

- REFRIGERATING METHOD AND APPARATUS FiledOct. 29, 1928 7 Sheets-Sheet 1 Feb. 19, 1935. D. F. KEITH REFRIGERATING METHOD AND APPARATUS Filed Oct; 29, 1 928 7 Sheets-Sheet 2 lu z . z m m m 3 Feb. 19, 1935. D, 1,991,944

REFRIGERATING METHOD AND APPARATUS Filed Oct. 29, 1928 7 Sheets-Sheet u n I J I f O 3/ an-neuter, 3 map Feb. 19, 1935.

D. "F. KEITH -1,991,944

REFRIGERATING METHOD AND APPARATUS Filed Oct. 29, 1928 7 Sheets-Sheet 4 Feb. 19, 1935. D, n- 1,991,944

REFRIGERATING METHOD AND APPARATUS F ile'd. Oct. 29, 1928 7 Sheets-Sheet 5 Feb. 19, 1935. I D. F. KEITH I 1,991,944

I REFRIGERATING METHOD AND APPARATUS Filed Oct. 29, 1928 7 snets sheet 6 Feb. 19, 1935. KEITH 1,991,944

REFRIGERATING METHOD AND APPARATUS Filed Oct. 29, 1928 7 Sheets-Sheet 7 Patented Feb. 19, 1935 UNITED STATES PATENT OFFICE Y 1,991,944 REFRIGERATING METHOD AND APPARATUS Application October 29, 1928, Serial No. 315,621

7 Claims.

This invention relates to improvements in refrigeration apparatus, particularly of the intermittent absorption class, an example of. which will be foundin my co-pending application Serial No. 242,574, filed December 2'7, 1927, that resulted in Patent No. 1,816,975, dated August 4, 1931. The invention has to do, also, with a unique method of refrigeration.

In prevailing types of refrigeration apparatus of the class referred to there is the disadvantage that the, relatively hot liquid refrigerant that collects in the evaporator during the heating period raises the temperature of the refrigeration chamber unduly and melts to a greater or less extent any ice that has been frozen by the evaporator during the preceding cooling period.

Therefore, my present invention has for its broad object to provide means for stabilizing the temperature of the refrigeration space or chamber of refrigeration apparatus of the intermittent absorption class, and particularly preventing the melting of the ice during the heating period.

Pursuant to this broad object, the invention has as a more specific purpose the provision of means that will prevent to any appreciable extent the transfer of heat from the evaporator to the refrigeration chamber during the heating peri odwhen the evaporator is aboverefrigeration temperaturebut will not interfere with the exchange of heat from the refrigeration chamber to the evaporator during the cooling or evaporation period.

In the carrying out of my invention I desirably insulate the evaporator from the refrigeration chamber and locate in said chamber a cooling vessel containing a volatile liquid, which may be termed the secondary refrigerant (as distinguished from the primary refrigerant that is distilled over into the evaporator during the heating period and evaporates therein during the cooling or absorption period) whose vapors, by a suitable means of communication, are intimately subjected to the temperature changes of the evaporator. Preferably the evaporator is insulated also, to such extent as is practicable, from the cooling vessel so that the contents of the latter will be little affected by the warmth of the evaporator during the heating period.

' There is a further advantage in insulating the evaporator from the relatively cool refrigeration chamber that will be readily appreciated when it is remembered that the vapors of the primary refrigerant condense during the heating period in the coolest wart of the system. When the evaporator is exposed to the temperature of the refrigeration chamber a certain amount of condensation occurs therein and raises the temperature .of the surrounding air in the refrigeration chamber, whereas, by insulating the evaporator, it is caused to warm up quickly at the beginning of the heating period and confine the condensation of the primary refrigerant vapors to the condenser.

So that the nature of my present invention may be better understood 1 may mention at this time that, during the heating period, very little of the heat of the evaporator is transmitted to the secondary refrigerant in the cooling vessel because the evaporator is more or less effectively insulated from said vessel, and, furthermore, the vapors of the secondary refrigerant that have access to the evaporator are a poor conductor or transmitter of heat. Consequently, during the heating period there is no appreciable action in the cooling vessel, the conditions being not conducive of vaporization of the secondary refrigerant, and little heat interchange takes place between the secondary refrigerant in the cooling vessel and the refrigeration chamber of the apparatus. During the cooling period, however, the vapors of the secondary refrigerant are condensed by intimate subjection to the now relatively low temperature of the evaporator and the resultant condensate drains back into the body of liquid in the cooling vessel. This condensation of the vapors results in a lowering of the pressure in the cooling vessel, with 9. corresponding drop in the boiling point of the secondary refrigerant, and said refrigerant starts boiling, abstracting heat to promote such action from the refrigeration chamber, and this action continues during the entire cooling period.

Thus it will be seen that during the heating period, when the warm primary refrigerant is collecting in the evaporator and practically no action is taking place in the cooling vessel, the temperature of the air surrounding said vessel is little affected and any ice that has been frozen in the refrigeration chamber is conserved; and during the cooling period, when the secondary refrigerant is boiling within the cooling vessel; there is a condition existing analogous to, or in fact identical with, that attending the evaporation of the primary refrigerant in the evaporator and as a result of this condition there is an abstraction of heat from the surrounding air in the refrigeration chamber, It is found that, when the apparatus is properly designed and constructed and certain liquids are used, as water and ammonia in the main portion of the system and ammonia in the cooling vessel, there is a very slight difference between the temperatures of the primary and secondary refrigerants during the cooling period.

If desired, I may combine with the cooling vessel a receptacle containing brine that becomes chilled during a cooling period and tends to stabilize the temperature of the cooling vessel during the subsequent heating period and further prevents melting of the ice.

Various embodiments of the invention by which the foregoing objects, with others hereinafter appearing, are attained, are illustratedin some instances more or less diagrammatically in the accompanying drawings wherein Fig. 1 represents a sectional elevation of a refrigeration apparatus incorporating the invention; Fig. 2 is an enlarged sectional detail, taken in the same plane as Fig. 1, of the evaporator and cooling vessel, the present view showing certain structural details that are omitted from the former view for clearness; Fig. 3 is a section substantially on the line 3--3 of Fig. 2; Fig. 4 is a sectional detail on the line 4-4 of Fig. 3; Fig. 5 is a diagrammatic sectional elevation of an apparatus involving two separate and distinct refrigeration units that operate alternately to maintain cool two intercommunicating freezing tubes that are common to both units; Fig. 6 (Sheet 2) is a section through the evaporators of two refrigeration units, like those illustrated in Fig. 5, the cooling vessel in this case consisting of a single freezing tube that is maintained cool by the evaporators of the two units; Fig. 7 is a sectional elevation of an apparatus involving another form of cooling vessel and a brine tank or receptacle;

Fig. 8 is a section, on a somewhat larger scale; taken on the line 8-8 of Fig. '7; Fig. 9 is a viewsimilar to Fig. 8 showing the same cooling vessel as is illustrated in Fig. 8 but with enclosed brine tanks or receptacles; Fig. 10 is an embodiment of the invention wherein two U-shaped cooling vessels or tubes are employed, this form incorporating a further modification of the brine tank or receptacle; and Fig. 11 is a section on the correspondingly numbered line of Fig. 10.

,While, for illustrative purposes, I have shown my present invention associated with apparatus disclosed and claimed in my previously mentioned Patent No. 1,816,975, it is to beunderstood that the present invention is not limited to such a construction. As will be obvious from the following description, it is applicable to various types of intermittent absorption refrigerators.

Describing first the refrigeration system, exclusive of the cooling vessels or freezing tubes,

and the brine tanks or receptacles of my present invention, and referring by like numerals to the parts common to the various embodiments disclosed, including those illustrated in Figs. 5 and 6 wherein two refrigeration units are employed, 1 designates a generator absorber, 2 an evaporator, 3 a delivery conduit that leads from the generator absorber to the evaporator, and 4 a return conduit by which the refrigerant vapors-are conducted from the evaporator to the generator absorber. Parts of the delivery conduit 3 constitute, respectively, a dehydrator 5 and a condenser 6, the former being shown as a portion of said conduit that is inclined downwardly toward the generator absorber from a point where it joins, through an abrupt drop, the inlet end of the condenser, while the latter is shown as consisting of a coiled portion of the delivery con- .is in the form of a bottle.

duit. Both the dehydrator and condenser are located within a' box or casing 7, shown as equipped with a filling cap 8, and adapted to permanently contain, preferably to its full capacity, a cooling agent, such as water.

The delivery conduit 3 leads downwardly through the top of a gas dome 10, that rises from the evaporator 2, and terminates adjacent the bottom of the evaporator, preferably within a sump 11 that is formed in the bottom wall of the vessel so that as long as practically any liquid is present in the evaporator it will seal said conduit against the escape of the refrigerant vapors from the evaporator through said conduit.

The generator absorber may be equipped with heat abstracting veins 15, and it may be located in a vertical flue 16. The refrigeration chamber is designated 17 and it is enclosed by insulated walls 18. The evaporator 2 is located within the upper portion of the refrigeration chamber and it is shown as having its top disposed within a recess in the top wall of the chamber so that its upper portion and the gas dome 10 are in some measure insulated from the refrigeration chamber.

Situated below the generator absorber is *a heating device which, in the present instance, consists of an oil'burner 20, preferably of the so-called wickless type, that receives fuel through a pipe 21 from a cup 22 within which is adapted to be placed, in inverted position, a font or reservoir 23 which, in the present case, This font or reservoir is preferably of such capacity as will accommodate just enough oil to supply heat for initiating one cycle of operation of the apparatus so that after the user lights the burner he need give it no further thought as the same will go out when the limited oil supply is exhausted. Obviously, gas, electric, or other heaters may be substituted for the oil heater so far as the present invention is concerned.

A siphon 25, for returning residue liquid from the evaporator to the generator absorber at the beginning of each heating period, leads from the bottom of the vaporator up through the top of the gas dome 10, thence laterally and downwardly, incidentally through the adjacent end portion of the delivery conduit 3, into the generator absorber 1. It will be noted that the return conduit 4 connects at one end with the upper portion of the gas dome 10 while its opposite end is extended downwardly through the top wall of the generator absorber and terminates within this vessel below the minimum liquid level therein which level is indicated by the dotted line a. A sleeve 27 is shown as surrounding the outlet end of the conduit and is suitably supported within the generator absorber with its lower end spaced from the bottom wall of said vessel.

The system is hermetically sealed and contains a quantity of a suitable refrigerant and an absorber or a solvent therefor which, for the present purpose, may be considered, respectively, ammonia and water. This aqua ammonia, or other equivalent mixture of refrigerant and solvent, is what is commonly referred to as the refrigerant liquor, and when all the liquor is present in the generator absorber 1 it stands at about the level indicated by.the dotted line b.

To start the apparatus in operation a reservoir 01' font .23, filled with oil, is inverted within the cup 22 and the burner 20 is lighted. Considering now the embodiments of the invention wherein only one refrigeration unit is employed, the amount of oil accommodated by the reservoir or font is intended to keep the burner in operation approximately one hour before the oil supply is exhausted, and during this hour the temperature of the generator absorber is raised to substantially 300 F. Said hour represents the heating period, or the interval of active heat. During this hour of active heat the pressure within the system rises to a value of-from 160 to 200 pounds, the most abrupt rise occurring within the very early stages of the heating period. On the cessation of heat-that is, after the fuel supply has been exhausted-the temperature of the generator absorber and the pressure in the system immediately start to drop.

During the heating period, the refrigerant in the generator absorber is driven out of solution and in the form of vapor rises through the delivery conduit 3 and while passing through the portion of said conduit that constitutes the dehydrator designated by the reference numeral 5, all or a large percentage of the absorber vaporsin the present case water vaporswherewith the refrigerant gas is situatedcondenses and flows back into the generator absorber, the refrigerant gas continuing on through the portion of the conduit that constitutes the condenser 6 and condenses therein, the resultant liquid refrigerantanhydrous ammonia in this instance-being collected in the evaporator 2.

At the conclusion of this phase of the operation the evaporator contains its maximum amount of liquid, the level of which is indicated by the line 0, and this body of liquid may contain a relatively small amount of the absorbent or aqueous condensate, it being practically impossibleto obtain a complete dehydration of the refrigerant vapors. I

The cooling period starts with the cessation of heat and it continues on until the next heating period which, in the embodiments of the invention incorporating asingle refrigeration unit, is substantially 23 hours distant. Each cycle, including a heating and a cooling period, consumes about 24 hours. As previously stated, very soon after the heat is removed from the generator absorber, the pressure within the system starts to drop abruptly. Under these conditions the liquid refrigerant or anhydrous ammonia in the evaporator starts to vaporize and, in promotion of such vaporization, abstracts heat from the sur-- rounding air. Also, under the low pressure now prevailing in the system, the absorbent or solvent in the generator absorber attracts the refrigerant gas through the return conduit 4. The passage of the gas from the evaporator to the generator absorber through the return conduit is assured by the fact that the discharge end of the delivery conduit 3 is sealed by the liquid refrigerant in the evaporator, and this seal remains effective until the liquid level falls below the end of the delivery conduit. As the refrigerant gas escapes from the discharge end of the return conduit it is instantly absorbed by the solution in the generator absorber.

During the early stages of the heating period, the pressure within the system rises very rapidly, and almost instantly this pressure becomes practically uniform throughout the system, including the'interior of the siphon 4, the pressure, being communicated to the central portion of the siphon through the intervention of the liquid that is present in and about the legs of the siphon. That is to say, as the pressure rises it tends to equalize throughout the system and asa result thereof it forces the refrigerant liquor' approaches a state of continuity throughout the length of the siphon with the result that a siphonic action is instituted, the flow being in the direction away from the evaporator and toward the generator absorber. This siphonic action continues as long as there is any refrigerant liquor in the evaporator to supply the siphon or, in other words, until the evaporator is practically emptied of the liquor,

In cases where two refrigeration units are employed, as in the embodiments illustrated in Figs. 5 and 6, the units are operated alternately; and, in size they may, though not necessarily, be of about one-half the capacity of the refrigeration apparatus of a single unit embodiment. In considering the operation of a double unit outfit, where the same incorporates two units of approximately half the capacity of those employed in a single unit outfit, and taking as a basis for such consideration a proportionately shorter I time interval than that used in describing the operation of the single unit embodiment, the cycles of operation of the respective units of a double outfit are started about twelve hours apart, and the heating periods are of approximately one-half hour duration. It is also apparent that about themiddle of the eleven and one-half hour cooling period of each unit, when the evaporator is abstracting heat from the sur-' rounding air and thus performing its refrigeration function, the evaporator of the other unit is warm for a period of something less than onehalf hour while the relatively hot refrigerant condensate is collecting therein.

While in actual practice the twenty-four hour cycle for single unit embodiments has been found convenient, it is to be understood that cycles of any arbitrary duration may be decided upon, and the capacity of the apparatus altered where necessary tosuit the same, and where the double unit outfit is described above as incorporating individual refrigeration units of approximately one-half the capacity of those employed in a single unit outfit, this is only illustrative and may be changed as desired.

I will next describe the means that constitutes the substance of the present invention, and which, broadly, had its conception in the thought of providing an enclosure containing a volatile liquid which is, at one and the same time, ex-

.posed to the refrigeration space of the apparatus and to the temperature changes of the evaporator, the same preferably serving to insulate the evaporator from the refrigeration space or, at

One form of the invention is illustrated in Figs 1 to 4, where a shell 30 surrounds and is spaced from the cylindrical evaporator 2 of the refrigeration apparatus, and disposed belowthe shell are two double wall cylinders 31, which enclose cavities that are open at their forward ends for the insertion and removal of ice trays 32 within which liquids or mixtures may be placed for freezing. Though this constitutes no,part of my invention, it may be explained that the ice trays may be divided by removable partitions 33 for forming ice cubes, which is in accordance with common practice. Because of their function, the cylinders 31 are ordinarily referred to as freezing tubes. respective cylinders 31 are sealed at their forward ends while at their rear ends they communicate with each other, through a tube 35, and with the space between the evaporator 2' and the shell 30 through a branch tube 36. The shell 30, the cylinders 31, and the tubes 35 and 36 may be considered together as the enclosure or cooling vessel that contains the volatile liquid herein referred to as the secondary refrigerant and which is subjected to the temperature changes of the evaporator and exposed to the refrigeration space. Any one of several kinds of liquids may be used in the cooling vessel or enclosure, but I find that anhydrous ammonia is especially suitable when aqua ammonia is employed as the primary refrigerant of the system. The liquid normally stands in the cooling vessel at about the level indicated by the line d in Fig. 2.

In operation, while the relatively hot primary refrigerant is collecting in the evaporator,--the same being conveyed thereto by the delivery conduit 3 from the condenser 6 above-the evaporator becomes warm and, inasmuch as its temperature is above that of the vapors of the secondary refrigerant in the cooling vessel, it has little effect thereon, and obviously less upon the liquid itself that is present in the cylinders 31 because, first, said vapors are a poor conductor of heat and, secondly, the evaporator is more or less effectively isolated from the cylinders 31. Consequently, there is little or no action going on in the enclosure or cooling vessel during this time and very little heat exchange between the secondary refrigerant and the refrigeration space of the apparatus and the ice in the ice trays.

As soon, however, as the cooling or absorption phase of the cycle of operation begins, when the relatively pure primary refrigerant in the evaporator 2 (anhydrous ammonia, for example) starts to vaporize and pass back in gaseous form through the return conduit 4 to the generator absorber l where it is absorbed by the solvent therein, the evaporator cools and condenses the secondary refrigerant vapors that are in contact with its exterior and the resultant condensate drips from the evaporator and drains back through the tubes 36 and 35 into the body of liquid contained in the spaces between the walls of the cylinders 31. This cooling and condensing of the vapors causes the pressure within the enclosure or cooling vessel to drop with the effect that the boiling point of the secondary refrigerant also becomes lower whereupon said refrigerant starts to boil under the influence of the relatively warm surrounding air in the refrigeration space. This results in the secondary refrigerant continuing to abstract heat from the surrounding air for the promotion of its vaporization, and the vapors rise from the liquid body of the secondary refrigerant up through the tubes 35 and 36 into the space between the evaporator and the shell 30 and condense upon the evaporator and drip back into the body of liquid, as aforesaid, and this action is uninterrupted as long as the primary refrigerant continues to vaporize.

The spaces between the walls of the Thus it will be seen that, in my present invention, the secondary refrigerant acts in precisely the same manner during the cooling period as the ordinary refrigerant acts during the same phase of the operation in prevailing refrigeration apparatus of the intermittent absorption type. Upon initiation of the succeeding heating or condensing period, however, the evaporator becomes warm and the vapors of the secondary refrigerant cease to condense and action in the, enclosure or cooling vessel subsides and conditions remain substantially dormant therein until the next cooling or absorption period.

The shell 30 and the space between it and the evaporator2'serve to insulate the evaporator from the refrigeration space or chamber 17, and to further this end the top portions of the shell and evaporator are embedded within the top wall of the refrigeration chamber.

As a structural refinement, the portion of the shell 30 below the top wall of the refrigeration chamber, and the cylinders 31, are enclosed within a box-like metal casing 40 that is shown as secured to the top wall of the refrigeration chamber; and to more effectively insulate the evaporator 2 from the cylinders 31 and from the refrigeration space or chamber 17, insulating shields 41, which may consist of slabs of cork or other suitable material, may be disposed about the shell 30. These structural details are shown in Figs. 2, 3 and 4, but are omitted for the sake of clearness from the more or less diagrammatic view of Fig. 1. In furtherance of this insulation of the evaporator'2 from the body of liquid in the cylinders 31, a radiation shield or baffle 42 may be suitably supported across and in spaced relation to the end of the tube 36 where it joins the shell 30, the same beingshown in Fig. 3. It will be understood that the front wall of the casing 40 has openings that register with the cavities of the cylinders 31 for the passage of the ice trays 32.

In the modification of the invention illustrated in Fig. 5, where two refrigeration units cooperate to maintain the refrigeration space or chamber of the apparatus cool, the evaporator 2 of each apparatus is enclosed by a shell 30, which is 'spaced a suitable distance from the wall of the evaporator, and the space between the evaporator and shell communicates through a tube 36 with the space between the inner and outer walls of a double wall cylinder 31 therebelow. The annular spaces of the two double wall cylinders, in turn, communicate through a tube 35 The operation of this embodiment of the invention will be readily understood from the foregoing description of the first embodiment, though it may be explained briefly that the two refrigeration units are heated alternately at intervals of approximately one-half cycle apart. That is to say, each unit goes through its heating and condensing period at about the middle of the cycle of operation of the other unit. Consequently, there is a condensing of the secondary refrigerant going on allof the time, so that the cooling vessel is continuouslyfperforming its refrigeration function, notwithstanding the fact that at intervals one of the evaporators is warm and is not condensing the secondary refrigerant vapors during a relatively brief period of time. The parts are so arranged that the secondary refrigerant condensate drains from the shells 30 into the cylinders 31. l

Fig. 6 is a detail of an embodiment which m be identical with that of Fig. 5 excepting for the fact that here only one double wall cylinder is used, the same being designated 31. Shells 30 surround the evaporators 2 of the refrigeration units, and the spaces between the shells 30 and the respective evaporators communicate with the space between the inner and outer walls of the cylinder 31 through pipes 35 and 36 The operation is the same here as in the form last described.

Figs. 7 and 8 illustrate a form of the invention in which a shell 45 surrounds the evaporator 2 and constitutes the enclosure or cooling vessel that contains, to about the level indicated by the line e, a volatile liquid that forms the secondary refrigerant. Situated within the lower portion of the shell 45 and having its forward end extended a suitable distance beyond the corresponding wall of the shell is a. freezing tube 46 for the accommodation of an ice tray 47, the front end of the freezing tube being open for the insertion and withdrawal of the tray, it being understood that the open end of the tube is, in practice, pre sented toward the door of the refrigeration space or. chamber 17. Suitably supported within the shell 45 and immediately beneath the evaporator 2 is a radiation shield 48 that is shown as following the general contour .of theevaporator, even to the inclusion of a depression 49 that accommodates the sump 11, the depression having a drain opening 50 at its lowest point. The action here is the same as in the previously described embodiments, the vapors of the secondary refrigerant condensing upon the wall of the evaporator 2 during the cooling period and dripping therefrom onto the shield 48 and draining down the same and through the opening 50 to the body of liquid in the bottom portion of the shell 45, this action continuing throughout the entire cooling period, and the secondary refrigerant extracting heat from the surrounding space and that within the tube 46 the while this vaporizing and condensing of the secondary refrigerant continues. As soon as the heating period is started, and the evaporator becomes warm, all action within the shell 45 ceases.

Shown associated with the present form of the invention is a tank or receptacle that is in the form of a drum 55, the same containing'a quantity of brine, the level of which is-indicated by the line ,1. The purpose of this is to intercept any heat exchange between the cooling vessel and the refrigeration space or chamber during the heating periods, thereby to stabilize the temperature of the latter.

A modification of the brine tank feature of the invention is illustrated in Fig. 9 where the same is shown associated with a form of cooling vessel like that illustrated in Figs. '7 and 8. The corresponding parts of the two embodiments-that is, the ones illustrated in Figs. 7 and 8 on the one hand and in Fig. 9 on the other-insofar as they, pertain to the evaporator and cooling vessel, are designated by the same reference characters. In Fig. 9, two containers 56, shown as triangular in crosssection, are situated within the lower por-' tion of the shell 45 on OPDOSltG SIdBS of the freezing tube 46. These are closed containers and have permanently sealed in" them a quantity ofv brine. The brine becomeschilled during the cooling period, and during the heating period serves to stabilize the temperature of the surrounding secondary refrigerant. I,

In Figs. 10 and 11, there are shown two cooling vessels or enclosures for the secondary refrigerant 'and each is designated 60 and is in the form of a U-shaped tube that is closed at both ends, one of the legs of the respective vessels being disposed within the evaporator 2 while the other leg is enclosed within the upper portion of a brine tank or receptacle 61. In this case, the freezing tube 62 is incorporated in the lower portion of the brine tank and opens through the front wall thereof so that an ice tray 63 can be placed within and removed from said tube. The upper portion of the evaporator is embedded within the top wall of the refrigeration space or chamber, while its remaining portion, and parts of the cooling ves-= sels 60 between the evaporator and the brine tank 61, are encased within a covering 64 of insulating material.

The normal level of the secondary refrigerant in the vessels 60 is indicated by the line 9, in Fig. 10, and during the cooling period the vapors of said refrigerant that are present in the upper portions of the vessels 60 are condensed on the walls thereof .and drain back to the bodies of liquid in the lower portions of the vessels, the condensation causing a lowering of the pressure in the vessels and a consequential lowering of the boiling point of the secondary refrigerant so that said refrigerant boils and extracts heat from the brine within the tank 61, there being, in turn, a corresponding heat exchange between the brine and the air within the refrigeration spaceor chamber wherein the tank is located. During the heating period there. is practically no action taking place in the vessels 60 and no appreciable heat interchange between the secondary refrigerant and the contents of the brine tank 61 and consequently the brine will remain cool excepting as it may be affected by conditions within the refrigeration space or chamber. The refrigeration space or chamber is protected from the heat .of the evaporator 2 and the cooling 'vessels 60 during the heating period by the covering 64 of insulating material.

If desired, brine tanks may be incorporated in the forms of the invention illustrated in Figs. 1 to 6, where the. sameare shown in dot-anddash lines and designated '70.

Having thus described my invention, what I claim is:--

1. In refrigeration apparatus of the intermittent absorption type, in combination with the evaporator, a shell spaced from the wall of the evaporator and forming therewith a chamber, a vessel in heat exchanging relation to the refrigeration space of the apparatus and whose interior is in communication with the aforesaid chamber, the shell and ,vessel forming a sealed enclosure, said vessel containing a volatile liquid and so positioned with respect to said chamber that vapors of said liquid when condensed upon the wall of the evaporator will return by gravity to the body of liquid in the vessel, and a radiation shield protecting the body of liquid from the temperature of the evaporator.

2. In refrigeration apparatus of the intermittent absorption type, in combination with the evaporator and the refrigeration chamber, the latter having an insulated top wall, a shell surrounding the evaporator and having its upper portion embedded within said top wall, a double wall freezing tube situated below said shell, the space between whose walls contains a volatile liquid, anda conduit through which said space communicateswith the space between the shell latter having an insulated top wall, a shell surrounding the evaporator and having its upper portion embedded within said top wall, a double wall freezing tube situated below said shell, the space between whose walls contains a volatile liquid, a conduit through which said space commu nicates with the space between the shell and evaporator, and a casing enclosing the shell and freezing tube and having an opening registering with the cavity of said tube for the passage of an ice tray.

v4. In refrigeration apparatus of the intermittent absorption type, in combination with the evaporator, a shell spaced from the wall of the evaporator and forming therewith a closed chamber, the lower portion of said chamber containing a volatile liquid, and a radiation shield disposed between the evaporator and said liquid.

5.. In combination with a plurality of refrigeration units of the intermittent absorption type that operate in rotation, each having its individual evaporator, a shell surrounding each evaporator, an enclosure in heat exchanging relation to the refrigeration space of the apparatus, and a conduit through which said enclosure communidenser, both condensation and evaporation tak-.

ing place at substantially the same pressure.

7. Refrigerating apparatus including a closed fluid circuit comprising a plurality of condensers and an evaporator and connections between said condensers and said evaporator, and means for alternately cooling said condensers whereby liquid refrigerant continuously evaporates in said evaporator and condenses alternately in said condensers, the condensers and the evaporator being maintained at substantially the same pressure.

DAVID FORBES KEITH.

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