US1779211A - Absorber refrigerating apparatus - Google Patents

Description

Oct. 21, 1930- E. s. HALSEY 1,779,211

ABSORBER REFRIGERATING APPARATUS Original Fil ed Nov. 13, 1925' 2 Sheets-Sheet 1 I! /6 In l'h' Ira 4 m? IIIIIIIII:

Oct. 21, 1930. HALSEY 1,779,211

ABSORBER REFRI GERAT I NG APPARATUS Original Filed Nov. 13, 1925 2 Sheets-Sheet 2' Patented Oct. 21, 1930 UNITED STATES EDWARD S. HALSEY, OF WASHINGTON, DISTRICT OF COLUMBIA ABSORBER REFRIGERATING APPARATUS Application filed November 13, 192 5, Serial No. 68,895. Renewed March 20, 1930.

The nature of my invention is in the form of improvements of that class of absorber refrigeration disclosed by U. S. Patent No. (362,690, issued to Geppert, the characteristic feature of which is an intermediate gaseous absorber medium employed as a carrier agent between the evaporating refrigerant surface and the liquid absorbing surface.

The simple embodiment of which herein disclosed consists of a continuously operating single cellular evaporator-absorber chamber constituted principally by a pair of parallel vertical opposed heat-transmitting walls thermally insulated from each other; down one of which walls trickles the evaporating refrigerant, while the liquid absorbent trickles down the other opposite wall of said chamber.

The vapor is conveyed from the refrigerating side of said cell to the absorber heatrejecting'side by rapid vertical convection currents of an inert gas confined within said chamber. The rich liquor drains off by gravity to a vertical tubular boiler fixed to one side of said unit, said boiler operating continuously in such a manner as to drive off and deliver a constant flow of liquid refrigerant to the top of said refrigerating wall and a continuous flow of cool absorbing liquor to U the top of said absorber heat-rejecting wall.

The objects of my invention are to provide a more simple, reliable, compact and efficient device free from obnoxious or dangerous refrigerants or pressures, and one not requiring expert service attention; one 'that can be more easily and conveniently applied to common household refrigerators, ice cream cabinets, water coolers and the like, said objects being attained by improvements in the general construction and system of operation and arrangement of parts of the absorber'units, the heat-rejecting units, the boiler and circulation elements and heat-rejecting elements. Also by the employment of effective radiant heat shields and heat-insulating sections of the chamber walls, and new and more desirable absorber and refrigerant combinations.

Further objective features will be made apparent by the following specification.

Referring to the drawings which illustrate i not shown.

my invention similar reference characters refer to similar parts throughout the several views, in which:

Fig. 1 is a side elevation of my preferred form in partial cross section. 5

Fig. 2 is a plan cross section thereof on line 22 of Fig. 1.

Fig. 3 is an enlarged section of the insulating boiler feed nipple 22.

Fig. 4: is a fractional side view of amodification adapted to installation on the top of a refrigerator, while Fig. 5 shows by diagrammatic sketch a cross section through a flat modification of my evaporator-absorber in contrast to the annular cell construction of the two other modifications above referred to.

Referring to the details of construction beginning with Fig. 1, A indicates the outer cylinder of the evaporator-absorber equipped with cooling pins F for heat rejection. E indicates the inner wall of the annular chamher which acts as the evaporating refrigerating surface. I indicates an insulating ring one of which seals either end of the annular chamber, compressing a plastic gasket 8 against the cylinders ends. S indicates a cylindrical heat shield intermediate between the inner and outer Walls of the chamber. 16 and 17 are upper and bottom brine-circulating fittings leading from a brine tank, 31 is a condenser coil leading from the top of the boiler to the top of the inner refrigerating wall, depositing the condensed refrigerant onto a distributing cord 13 wound spirally around this cylinder. 23 is a weak liquor duct leading from the top of separating chamber 29 at the top of the boiler leading through the outer shell of the heattransfer coil 20 and up through the weak liquor supply tube L into an annular distributing trough within the upper end of the outer wall formed by an expansion collar 10 which retains a felt collar 12 forming a porous bottom for this trough. This pro 95 vides means for keeping the entire inner surface of the heat-dissipating wall wetted with the absorbent liquid by a trickling flow from top to bottom. D indicates a drainage duct from the bottom of the cylinder which ex 1 tends through the heat-transfer coil 20 to cushion chamber 21. 22 is a heat-insulating nipple leading from 21 to the lower part of cushioned'chamber 24. This nipple is fern ed of Monel metal or the like and has a heatinsulating lining E22. 25 is a vertical tube forming the main body of the boiler in the bottom end of which is a small port 27 draining the bottom of chamber 24. and equipped with a check valve 26. This vertical boiler has brazed to it a continuous copper tin or worm 28 for absorbing heat from the flue gases passing up through the stack 32. Supported above the top end of the boiler tube is a bell deflector 30. R is the terminal of tube 31 for discharging the condensed refrigerant. 37 is a pressure equalizing tube leading from chamber 2 L up to the condenser coil 81. 33 is another equalizing tube leading from the cushion chamber 21 to the upperside of the weak liquor pipe L to equalize the pressure between the two chambers connected thereby. 13 is a catch pocket for the refrigerant, leading it from the condenser to the distributing cord 13.

It should be understood that with this type of absorption refri eration devices the pressure is practically uniform throughout the whole system, with the exception of the static head of the boiler liquid column which would have a pressure differential of less than one pound, and, as disclosed by this Geppert patent, many volatile liquids commonly used for refrigeration may be employed with suit able absorbents. I have discovered through experimentations, however, that methyl alcohol as the refrigerant in combination with a concentrated solution of magnesium chloride or calcium chloride as the absorbent medium has many advantages over any previously used or known combination for this purpose. Methyl alcohol forms a definite chemical compound with magnesium chloride according to the formula (MgCl 6CH .OH) and with calcium chloride (CaCl5-4CPLOH). By utilizing the magnesium chloride solution as the absorbent it may simply be used diluted with the alcohol or with a very small amount of water or other suitable solvents, as I have discovered by experimentation, but with the calcium chloride it is desirable to use a very concentrated solution of the salt with some non-volatilizing aqueous solvent in order to facilitate the breaking up of the chemical compound by distillation, and at the same time prevent crystallization of the salts in the boiler and tubes.

Acetone may also be used as a refrigerant with this device in combination with a concentrated solution of calcium chloride.

As has already been pointed out, this class of devices require an intermediate absorber gas as a vapor-transfer medium between the refrigerant vaporizing surface and the absorber liquid surface, and, While it is convenient to use common air, I prefer to use some inert nonexplosive gas, such as nitrogen or helium, preferably the latter on account of its very light gravity which materially enhances the velocity of circulation of this vehicle gas with which the evaporator-absorber chamber is charged. As this gas absorbs vapor from the evaporating cylinder, it simultaneously becomes heavily laden with the vapors and at the same time greatly chilled, so that the gas column lying between the heat shield S and the evaporating wall is very much heavier than the column lying between the heat shield and the ab sorbing cylinder or wall which has partly or completely given up as vapor burden to the absorber film trickling down the inner wall of the outer cylinder, thereby stimulating rapid convection currents around the heat shield. This enhanced velocity materially facilitating the rapidity of absorption and evaporation.

To facilitate the uniform wetting of the entire inner surface of the outer wall or cylinder by. the absorber, I prefer to prepare the inner surface by chemical action so as to leave a porous, rusty surface.

The heat-dissipating fins F are preferably secured to the shell first by spot or roller welding to the cylinder, after which the thermal conductivity is increased by running the assembled unit through a tinning bath.

ll preferably construct the cylindrical heat shield S of two glass mirrored walls with an intervening vacuum equivalent to the con struction of the conventional thermos bottle, but this shield may be made of any conventional heat insulator, such as cork. I prefer to operate this unit at or near atmospheric pressure, dependent upon the condensing temperature and pressure of the refrigerant employed. With the refrigerants above specified it is desirable to maintain a partial vacuum throughout the system.

To follow out the cycle of operation when sufficient rich liquor has accumulated in chamber 21 to flow into chamber 24: upon its striking the hot spot over the gas flame shown a miniature concussion occurs, arresting the flow of liquid into chamber 2% and expelling the portion already pocketed in the bottom of chamber 24: past check valve 26 into the boiler tube. As soon as this excess pressure has been relieved by the escape of vapor from the boiler chamber through pipe 37 to the condenser this intermittent propulsion of the liquid is repeated, thus constantly raising the ebulating liquor up through the boiler column until it is discharged into the separating chamber 30 at the top. The liberated refrigerant vapor passing to the condenser partly from chamber 30 and partly from chamber 24. The weak liquor separated in the top chamber descends through pipe 23 and through the heat-transfer worm 20, rising through pipe L, discharges into the annular trough at the top of the absorber wall, from which it distributes and trickles down, again absorbing refrigerant vapor from the carrier gas by which it is fully charged, becoming rich liquor by the time it reaches the drain trough at the bottom.

The inertia of the long liquid column in the drainage duct D extending around through the coil 20 is sufficient to prevent an appreciable backward movement of the drainage flow at the period of concussion when fresh liquor is ejected into chamber 24, but I may use a sensitive check valve in this drainage tract at a suitable point before it discharges into chamber 24 in such cases as it may be desirable to use a more direct flow of liquor from the absorber to the cushion chamber.

Referring to the modification shown by Fig. 4, this operates exactly in the same mannor as the form shown in Fig. 1, with the exception that the brine circulation is not led in at the top of the cooling sleeve E, as in Fig. 1, but, in order to adopt this for installation on top of an ordinary ice box with a brine tank T below the top of the box, both inner and outer cylinders of the unit are headed over or made ofclosed shells, the inner shell or cylinder being supported from the head of the outer cylinder by a non-metallic bolt 15 having a plastic gasket under its blind nut, thus sealing it against the atmosphere. The tension of thi bolt or stud makes a compression tension on the two plastic gasket rings which seal the joints between shoulders of the two cylinders at the lower end and the molded insulating collar I. In this modification the refrigerating cylinder wall is extended down through a hole in the top of the refrigerator and through a hole in the top of the brine tank for some distance, and in order to create a definite circulation through this cylinder and brine tank, a smaller brine draft tube is fitted within the refrigerating cylinder and secured by a T head or cross duct sweated into opposite openings through the refrigerating cylinder below the brine level, so that as the brine in contact with the refrigerating cylinder in the upper portion increase in density it descends around the inner draft tube, drawing up warm brine from the upper part of the brine tank, as indicated by arrows, maintaining an efiicient'circulation throughout the refrigerating cylinder and brine tank.

The flat modification of my evaporatorabsorber shown by Fig. 5 is introduced to show how my invention may be applied to the flat side of a brine or water tank or refrigerator space that it is desired to cool. In this modification the heat shield S. as well as both the evaporating refrigerating wall E and absorber heat-rejecting wall A, would be flat plates, and the liquid-distributing troughs at their upper edges would extend from one end of the evaporator-absorber chamber to the other. The heat shield in this flat construction. of course, would have to be constructed without an internal vacuum.

In claimingmethyl alcohol as a refrigerant it is understood that' either the natural or synthetic product may be used.

To enhance its low boiling point and volatility I prefer to utilize natural methyl alcoh 01 having a small acetone content, preferably from 2% to 5%.

To show the advantages of methyl alcohol a refrigerant I Wish to attract attention to the following fact: it is exceptionally volatile and has a much lower freezing point than ammonia. Its latent heat of evaporation at ordinary refrigerating temperatures is about the same as that of ammonia, while its specific heat capacity is only a little more than one-half of that of ammonia, consequently from a thermal viewpoint at least methyl alcohol is distinctly the most-efficient available refrigerant yet discovered excepting water. However, water has proven impractical in automatic machines for various reasons, the most notable of which are its high freezing point and the extreme difficulty of continuously maintaining the excessively high vacuum necessary for its successful operation. Furthermore, methyl alcohol is very cheap. is not obnoxious or dangerous, it can be operated at atmospheric pressure or under a moderate vacuum, consequently it can be safely and conveniently handled by unskilled persons.

As I have already pointed out, either magnesium chloride or calcium chloride in suitable concentrated solutions, preferably with a solvent not easily driven from the salts by boiling, may be employed as the absorbent medium. I prefer, however, to employ both of said salts combined in such a solvent solution with the quantity of magnesium chloride predominating.

- As is indicated by the drawings, both of the pressure equalizing tubes shown leading from the tops of chambers 21 and '24, respectively, are of very small bore.,so proportioned as to institute the proper time interval or lag for the relief of the sudden intermittent pressures developed. in said chambers. Said time intervals maybe adjusted and regulated by further restricting the passages of said tubes by pinching or other means.

v I wish to emphasize the several important advantages secured over that of my predecessors disclosure (above referred to) by my construction of the evaporator-absorber chamber having both the evaporator and absorber heat-conducting sufaces arranged in vertical banks opposite each other with their entire outer vertical surfaces directly contacting, respectively, with convection currents of the cooled and cooling. fluids, so that a most cfiective circulation of both or said fluids is automatically maintained.

Further, by the introduction of an intervening heat shield between them which not only prevents direct radiant and conduction losses between opposite sides of the shield, but also prevents promiscuous intremediate convection losses. Furthermore. the interposed partition established definite and much accelerated down and up circulation of the gas on the cold and warm sides of the partition, at the same time crowding its draft directly against the wetted refrigerating and absorbing surfaces arranged on opposite sides thereof.

The process of absorption is materially enhanced by the trickling movement of the absorbent distributed over the entire vertical absorber surface. The viscosity of the absorbent as delivered by the distributing trough is quite dense and tenacious. As it moves downward it constantly exposes fresh molecules to the refrigerant vapor, which upon being absorbed thins down the absorbcnts viscosity at the surface film so as to flow downwards more and more rapidly as it progressively thins it, thus constantly exposing a more dense and avid under layer of the absorbent film to the action of the vapor.

The process of evaporation is also enhanced by its constant trickling movement down its vertical walls.

As previously pointed out, I have only atteinpted herein to show my invention in its simplest forms and I do not wish to be limited simply to the forms shown, as numerous modifications will immediately be obvious to all skilled in the art. For instance, while I have simply shown a capillary wick band as an outlet for the distributing trough, it is obvious that any distributed series of capillary outlets could be used. Likewise, while I have only shown the simplest forms of the vertical absorber and refrigerating walls. consisting of a single tubular wall each, it is obvious that for larger capacities these sur' faces should be increased by the addition of an encircling series of vertical tubes piercing the chamber from top to bottom or by vertical corrugations of the simple walls shown.

I claim:

1. In a device of the class described, an enclosed evaporator-absorber chamber unit constituted essentially of a vertically disposed evaporator refrigerating wall, a vertically disposed heat rejecting wall arranged opposite to and parallel with the first said wall, heat insulating means for enclosing and sealing the juncture in the walls of said chamber intervening bet-ween said walls extrcmities consisting of heat insulating material, means for constantly wetting the top of one of said walls by liquid refrigerant, and means for constantly circulating a liquid absorbent through said chamber.

ea ers 2. In a device of the class described, an inelosed evaporator-absorber unit cell constituted primarily by an opposed pair of vertically disposed heat-conducting walls, nonmetallic insulating means for inclosing and sealing the juncture of said cell between said walls, a vertical heat shield fixed intermediately between said walls, a free gas passage above and below said shield, means for constantly wetting the top of one of said walls with refrigerant, and means for constantly wetting the opposite wall with an absorbent, and means for draining away the rich liquor from the bottom of said cell.

3. In a device of the class described a closed annular evaporating absorber unit cell constituted by a pair of vertical cylindrical walls, one within the other, heat insulating.

absorber, a port through the bottom end of said tube, a check valve in said port, an enveloping liquid pocket close beneath said port, a liquid duct adapted to intermittently squirt the drainage from said absorber into said pocket, a gas expansion chamber in said duct close to said pocket adapted to enhance said intermittent action, a separating chamher at the top of said tubular boiler for directing the refrigerant and weak liquor separately back to the respective tops of the evaporator and absorber, and suitable means for heating the boiler from the bottom upwards.

5. In a device of the class described an evaporator-absorber chamber formed primarily by an expansive vertical parallel pair of heat conducting walls, heat insulating means for closing the juncture between said primary walls and sealing said chamber consisting of heat insulating material, a distributing trough extending substantially throughout the width of one of said walls, having a porous bottom of capillary material, and suitablemeans for constantly wetting said opposite opposing wall.

6. In operating connection with an evaporator-absorber device of the class described, an automatic circulating, elevating, distilling tract for the rich liquor comprising a vertically inclined boiler tube, a horizontally inclined rich liqu or drainage duct leading from said absorber to a bottom junction of said boiler tube, suitable means of heating the latter, and a sensitive check valve in said tract adapted to sustain the static head of said liquor in said boiler tube, and intermittently pass slugs of fresh liquor into the boiler at each spasm of ebullition in said junction.

7. In a refrigerating device for cooling a brine tank within a box by refrigerating means above the box; a vertical brine tube E with a sealed top and open bottom end piercing the top of said box and extended into a brine tank within the box, a concentric updraft brine-flue within said tube with its upper open end spaced from the head of said tube and its bottom end terminating in a lateral duct opening through the side of said tube a short distance below the brine level in said tank, and means external to the upper end of said tube for refrigerating the brine therein and causing a free circulation of said brine throughout said tube and brine tank.

Having described my invention, I hereunto set my hand.

EDWARD S. HALSEY.

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