US2257564A - Refrigeration - Google Patents

Description

Sept. 30, 1941.

w. H KITTO REFRIGERATION Filed Sept. 16, 1939 III! a- Hlllll INVENTOR William-12112170 ATTORN EY ac ed Sept. 30, 1941 UNITED STATES PATENT OFFlCE- anrmaaas'non wunam n. Kitto, omits, Ohio, assignor to The Hoover CompanpNoI-th Canton, Ohio Application September 16, 1939,3613! No. 2.95.223

. l iOlaims. This invention relates to the art of refrigeration and more particularly to absorption refrigwhich theliquid evaporates; This evaporator is satisfactory but it cannot conveniently be constructed over 12" in height without necessitating a cumbersomely large fan for circulating the inert gas or without producing an excessive pressure drop between the gas inlet and outlet por-' tions of the evaporator.

Accordingly, it is a principal object of the present invention to provide an "evaporator adapted for use in three-fluid absorption refrigerating systems in which the inert gas propels the liquid.

refrigerant through only a portion of the evaporator whereby, the evaporator may be made of relatively great height without necessitating an increase in the size of the circulating fan or an objectionably large pressure drop within the evaporator.

It is another object of the invention to pro-- vide an evaporator of the type above referred to in which the evaporator includes-a box-cooling section connected between a pairof ice-freezing or low temperature refrigerating sections.

It is a further object of the invention toproduce an evaporator of the type above referred to in which the liquid refrigeralntis supplied intermediate the top and bottomportions thereof and divides into two streams one of which flows downwardly from its point of supply from the condenser and the other of which travels first upwardly through one portion of the evaporator and then downwardly through another portion thereof. r

It is a further object of the invention to provide an evaporator of the type above referred to which will have relatively stable, constant, and equal temperature distribution throughout the various portions thereof.

Other objects andadvantages of the invention will become apparent as the description proceeds when taken in connection with the accompanying drawing, in which:

There is illustrated diagrammatically an absorption refrigerating system of the three-fluid oi. sz- 'uas) type embodying an evaporator which is illustrated on an enlarged scale and in perspective.

The refrigerating system comprises a boiler 13,

an analyzer D, an air-cooled rectifier-R, a tubu- 5 lar air-cooled condenser C, an evaporator E, a

gas heat exchanger G, a tubular air-cooled absorber A, a liquid heat exchanger L, a solution reservoir 8, and a'circulating fan F which is driven by an electrical motor M. These elements are suitably connected by various conduits to form a plurality of gas and liquid circuits constituting a complete refrigerating system to which reference will be made in after. I a

The above described refrigerating system will be charged with a suitable refrigerant, such as more detail hereinammonia, a suitable absorbent, suchas water,

and an inert pressure equalizing medium, preferably a dense inert gas" like nitrogen.

The boiler B may be heated in any suitable or desired manner as by an electrical cartridge heater or a combustible fuel burner.

The circulating motor and the heater for the boiler may be controlled in any suitable manner. A preferred control mechanism is. disclosed and claimed in the co-pending application of Curtis C. Coons, Serial No. 148,424, filed June 16, 1937. Though the invention is concerned primarily with the evaporator construction, it is necessary to describe the system in considerable detail in order to achieve an understanding of the evaporatorconstruction and operation. Therefore,

the system will be described first in order to provide proper background for a description of the evaporator.

The application of heat to the boiler B generates refrigerant vapor from the strong solution therein contained. The vapor so liberated passes upwardly through the analyzer D in counterflow relationship with the strong solution flowing downwardly therethrough. The heat of con-.- densation of absorptionsolution vapor liberated in the boiler serves to generate further refrigerant vapor in the analyzer. The refrigerant vapor is conveyed from the analyzer to the upper portion of the condenser C by the conduit II which-includes the rectifier R. The rectifier R causes condensation of vapor of absorption solution which passes through the analyzer D.

Theweak solution formed in the boiler by the therefrom to the solution reservoir 8 by means of the conduit II, the outer path of the liquid heat exchanger L, and the finned air-cooled solution pre-cooler It. The solution collecting in generation of refrigerant ;vapor is conveyed the solution reservoir 8 is enroute to the upper portion of the absorber A. However, it is apparent that the upper portion of the absorber is at an elevation considerably above the elevation of the boiler'analyzer system wherefore some means must be provided to elevate the absorption I lift action.

\ The absorption solution flows downwardly through the absorber A by gravity counter to the rich mixture of pressure equalizing medium and refrigerant vapor flowing upwardly therethrough. The refrigerant vapor content of the mixture is absorbed in the solution and the heat of ab-' sorption is rejected to cooling air flowing over the exterior walls of the absorber vessel and the fins attached thereto. The strong solution formed in the absorber is returned therefrom to the up- 7 per portion of the analyzer D by way of conduit it, the inner path of the liquid heat exchanger L, and the conduit to.

A small vent conduit H is connected between the upper portion of the solution reservoir S and the suction conduit it in order'that the suction pressure of the fan ma prevail in the reservoir 8 wherefore the maximum possible pressure differential available in the system is utilized to operate the gas lift pump it.

The lean pressure equalizing medium formed n t e abs rber A is conveyed therefrom by condui' it into the suction side of the circulating fan F in which it isplaced under pressure. The

pressure equaliz'ng medium placed under pressure of the fan F is conveyed therefrom to the bottom portion of the evaporator E by way of the conduit It, the outer path of the gas heat exchanger G and the conduit 25.

It is not necessary to describe the exact construction and operation of the evaporator at this time.- For the present purpose it is sufficient to note that the inert gas passes through the evaporator in contact with the liquid refrigerant which evaporates into the inert gas stream to produce refrigeration. The rich gas formed in the evaporator is removed therefrom through the conduit 23 into the inner path of the gas heat exchanger G from which it is returned by way denser and is discharged therefrom into'the evaporator through a conduit 22 which includes a U shaped'sealing portion. The liquid refrigerant supply conduit 22 is provided with a small vent conduit 28 connected between the condenser side of the liquid seal in the conduit 22 and the ric gas side of the gas heat exchanger.

Beginning with the gas inlet conduit 25 the evaporator E comprises a large diameter conduit section including a horizontal bottom U-shaped coil 30 which is connected by a riser conduit 3| to a parallel superposed U-shaped coil 33 terminates in a riser conduit 3|.

The riser 34 telescopically receives a portion of a riser conduit 35 of smaller diameter which connects to a horizontal superp sed U-shaped conduit 31 parallel to the U-shaped conduits 30 and II. The coil section 31 terminates in a riser conduit 38 which connects to a top box-cooling U-shaped coil 39. 'lli'he leg of the U-shaped coil 39 not connected to the riser 38 terminates. in a riser conduit 40 which connects to another u-shaped horizontal coil section 4| lying in the plane of the which coil section .31. Similarly, coil sections at and l5 are U-shaped and lie in the planes of the coil sections 33 and 30, respectively. However, all the evaporator conduit elements having reference characters higher than 34 are small diameter condu ts. The coil section 45 terminates in the ricli gas-discharge conduit 23. Riser conduits 42 and to correspond to the riser conduits 35 and 3|, respectively. Therefore, it will be seen that the evaporator comprises a plurality of pairs of U- shaped coil sections which are superposed and lie in parallel horizontal planes and which are serially connected at their top portions by 'the U- shaped box-cooling conduit 39 and its associated riser conduits.

The gas outlet conduit 23 adjacent its point of 'connectionwith the coil section 65 is provided with a small dam Eli. 2A U-shaped conduit 5i connects the gas outlet portion of the coil section 35 ahead of the dam W to the gas inlet portion of the coil section 30 inwardly of the point of connection between the drain conduit 28 and the gas inlet conduit 25.

The operation of the invention is as follows: lhe liquid refrigerant formed in the condenser is conveyed to the riser conduit 35 by means of the conduit 22, wherein it meets a high velocity conduit sections having reference characters of and above are purposely made small, for example, V inside diameter for use with a fan developing approximately 4 of .water pressure differential, so as to insure that the inert gas will flow therethrough with a velocity sufficient to sweep or drag the liquid refrigerant through the conduit under the impetus of the gas stream. However, the conduit sections 30 to 34, inclusive, are made of a relatively large diameter, for example 1" inside diameter, so that the gas will flow therethrough at a slow rate and the liquid will counterfiow to the gas stream under the influence of gravity.

Liquid supplied to the conduit section 35 divides into two streams one of which discharges into the coil section 33 and the other'of which is elevated into the coil section 31. The construction and operation of the conduit sections 34 and 35 is disclosed and claimed in the co-pending application of Curtis C. Coons and William H. Kitto, Serial No. 220,187, filed July 20, 1938, and will not be described in detail herein. The refrigerant liquid is propelled through the coil section 31 by the inert gas stream and is thereafter elevated through the riser conduit 38 into the finned box-cooling conduit 39 through which it is also propelled by the inert gas. After passing through the finned box-cooling conduit 39, the liquid refrigerant is propelled downwardly through the riser conduit 40, coil section 4|, riser l2, coil section 43, riser H, and coil section 45 to the drain conduit 6| which carries any unevap'orated liquid into the inlet portion of the coil section 30 through which it flows to the drain 2|.

ber.

fan which develops a pressure differential on the order or 4 of water.

this purpose and will fit conveniently within the denser may have a large vertical dimension without extending above the top wall of the cabinet,

' The evaporator will be encased in a suitable chamber including ice tray supporting shelves scribedthe inert gas is circulated by a very small .Usingnitrogen, a fan of approximately 4" in diameter is satisfactory for cooling air flue normally provided in therear portion of refrigerator cabinets'to provide space for the condenser and absorber, etc. and also to provide for cooling of these elements. However, if the resistance of the inert gas circuit should be greater than 4%" of water, it will be necessary to increase the size of the fan which will necessitate either an increase in the depth of the cooling air flue which greatly increases the cost of the apparatus and greatlydecreases space efllciency thereof or it will be necessary to decrease the resistance of the absorber and gas heat exchanger which is highly undesirable.

With'systems of the type above referred to approximately 3" of water is the maximum resistance allowable in the evaporator. This pressure differential is sumcient if the evaporator is not to be over 12" {in height and does not have extremely long and complex coils. However, with some types of the domestic refrigerators it is desirable to provide an evaporator exceeding 12" in height and alsohaving a very wide spread coil construction. The instant invention provides an evaporator which will meet these requirements without exceeding theallowable gas flow resistance.

The major ,portion of the resistance to gas flow in evaporators of this type occurs in the riser conduits thereof on the lifting side at which point the inert gas is continuously blowing its way, through a body of "refrigerant collected in the riser. Of a course, some resistance to gas flow is offered by substantially horizontal conduit sections in which the liquid refrigerant is traveling in the form of a stream under the frictional drag of the gas stream flowing thereacross but this resistance is not large.

With the construction illustrated it will be noted that the inert gas is actually elevating the liquid only through about one-half of the total evaporator height. Through one-half theevapo rator height theinert gas is travelling at a rather slow rate counter to a gravity propelled stream of liquid and through one-half of the evaporator the inert gas is travelling with a generallydownwardly flowing stream of liquid which will not offer a large resistance to the flow of the inert gas. Therefore, the evaporator may have an extensive, height without offering an excessive resistance to gas flow and without imposing a burdensome liquid refrigerant lifting load on the circulating fan. I

The apparatus above described will be housed in a'suitable cabinet with the evaporator in the top portion of an insulated storage chamber and the balance of' the apparatus suitably positioned in a rear air duct and bottom mechanism cham- Due to the fact that the liquid inlet to the evaporator is well below the top thereof, the conresting upon the horizontal coil sections. The gas inlet and outlet connections to the evaporator lie in the lowest plane thereof which facilitates connections tothe as heat exchanger and prevents interference between the condenser, refrigerant conduit and inert gas conduits. This arrangement permits the inert gas connections to the evaporator to be disposed in heat exchangerelationship and to lie in a common opening in the panel element customarily provided in the rear wall of domestic refrigerators to allow the evaporator to be inserted into the storage chamher after it is welded into the system.

The instant invention furthermore provides a very efficient arrangement of the coil construcmore ice trays. Moreover, if desired, the coils tion in that the coils may be widely separated and each of the individual U-shaped coil sections may be arranged so as to provide freezing for one or may be spread widely apart whereby to provide two widely spaced ice-freezing sections which are joined by an upper intermediate box-cooling coil. Such an arrangement, for example, would be very advantageous in a refrigerator normally called upon to refrigerate extremely tall bottles or like ing the air within the refrigerating compartment and for refrigerating tall receptacles. With such an arrangement the flnned'air-cooling .coil 3! would be. centrally located with respect to the cabinet and between the separated coil sections; also it would not be necessary, to elevate the coil iii! 38 above the level of the coils 31 and ll, thus'replacing risers '38 and 40 with simple horizontal return bend conduits.

The present invention is highly efllcient and useful because of the wide scope of its design without materially altering the gas flow resistance therethrough and withoutimposing an unmade in the proportion, arrangement and construction of parts without departing from the spirit of the invention or the scope of the ap pended claims.

I claim:

1. Absorption refrigerating apparatus comprising an inert gas circuit including an evaporator and an absorber, a solution circuit including a boiler and said absorber, means for propelling inert gas through said inert gas circuit, means for liquefying refrigerant vapor generated in said boiler, said evaporator comprising two freezing sections serially connected by a finned air cooling section, one of said sections comprising a lower portion of large cross-section-- al area connected to receive inert gas at its bottom and an upper portion of small cross-sectional area such that inert gas flowing therethrough will propel refrigerant upwardly. the other of said sections being connected to discharge inert gas from its bottom portion, and means for supplying liquid refrigerant to an intermediate portion 'of said one section whereby a portion of the liquid flows downwardly through said portion of large cross-sectional area, and the balance of the liquid is circulated through the remainder of the evaporator by the inert gas.

2. Absorption refrigerating apparatus comprising an inert gas circuit including an evaporator and an absorber, a solution circuit includinga boiler and said absorber, means for propelling inert gas through said inert gas circuit, means for liquefying refrigerant vapor generated in said boiler, said evaporator comprising a spaced pair of sections each comprising serially connected vertically spaced U-shaped conduit elements, a U-shaped finned box-cooling conduit connected to the top portion of each of said sections, means for connecting said evaporator in said inert gas circuit to cause gas to flow up one side and down the other side thereof, and means for supplying refrigerant to said evaporator.

3. Refrigerating apparatus comprising an evaporator consisting of a plurality of sets of coplanar coils, the coils in each set of coplanar coils being serially connected to corresponding .coils in another such set to form groups of serial- ,ly connected coils, certain of the coils in one of propelling a dense inert gas through said coils, the arrangement being such that the liquid is circulated through the coilsof small cross-sectional area by the frictional drag of the inert gas.

4. Refrigerating apparatus comprising an evaporator consisting of a plurality of sets of coplanar coils, the coils in each set of-coplanar coils being serially connected to corresponding sponsor of. small cross-sectional area, means for llquefying refrigerant vapor produced in said generator and for supplying the liquid to said evaporator adjacent the junction of said portions of large and small cross-sectional area, and means in said inert gas circuit for propelling inert gas upwardly through said portion of small cross-secutilizing a refrigerant, an absorbent for the refrigerant and a pressure equalizing medium inert with respect to the refrigerant and the absorbent which includes the steps of propelling the pressure equalizin medium upwardly through one section of an evaporating zone and downwardly through another section thereof, supplying liquid refrigerant to an area of the evaporating zone in which the gas flows upwardly, flowing the liquid refrigerant through a portion of the.

evaporating zone by gravity counter to the upwardly flowing gas, and propelling the'liquid refrigerant through another portion of the evapcoils in another such set to form groups of serially connected coils, means serially connecting each group of coils, means for supplying liquid refrigerant to said coils, means for propelling an inert gas through said coils to circulate the refrigerant therethrough a s, it is evaporating, means for draining unevaporated matter from the gas outlet portion of one of said groups of coils into the gas inlet portion of the other of said groups of coils, and means for removing unevaporated material from said other group ofcoils.

, 5. Absorption refrigerating apparatus comprising an absorption solution circuit including a generator and an absorber, an inert gas circuit includin said absorber and an evaporator, means for liquefying refrigerant vapor produced in said generator and for supplying the liquid refrigerant to said evaporator, said evaporator comprising a pair of vertically extending coil sections serially connected at their upper ends by a space cooling element, the gas inlet and outlet connections to said evaporator being coplanar and adcooling element at their upper ends, one of said freezing sections comprising a lower portion of large crosssectional area and an upper. portion orating zone under the frictional drag of the inert gas.

8. That improvement in refrigerating systems utilizing a refrigerant, an absorbent for the refrigerant and a pressure equalizing medium inert with respect to the refrigerant and the absorbent which includes-the steps of propelling the pressure equalizing medium upwardly through one section of an evaporating zone and downwardly through another section thereof, supplying liquid refrigerant to an area of the evaporating zone in which the gas flows upwardly, flowing the liquid refrigerant through a, portion of the evapo-,

rating zone by gravity counter to the upwardly flowing gas, propelling the liquid refrigerant upwardly through another portion of the evaporating zone under the frictional drag of the inert gas, and flowing the liquid refrigerant in the same direction as the gas stream in another portion of the evaporating zone. Y

9. Absorption refrigerating apparatus comprising an inert gas circuit including an upstanding evaporator and an absorber, an absorption solution circuit including a boiler and said absorber, said evaporator being connected to said inert gas circuit in suchfashion that inert gas flows upwardly in one side thereof and downwardly in the other side thereof, means for liquefying refrigerant vapor produced in said boiler and for supplying the liquid to said evaporator at a level intermediate the top and bottom portions there! of on the gas upflow side thereof, and an inert gas circulator in said inert gas circuit for circulating the inert gas therethrough with sufficient an inert gas outlet connected to the bottom of v the other of said sections, means for supplying liquid refrigerant to the gas upflow section, and means for propelling the inert gas through at least a portion of the gas upflow section with a velocity sumcient to sweep or drag the refrigerant liquid upwardly therethrough whereby liquid refrigerant flows upwardly and then downwardly in parallel flow relationship through at least part of said evaporator.

l1. Absorption refrigerating apparatus comprising an inert gas circuit including an evaporator and an absorber, a solution circuit including a boiler and said absorber, means for liquefying rei 'i erant vapor generated in said boiler, said evaporator being constructed of a conduit having inert gas inlet and inert gas outlet portions, said conduit extending upwardly from said inert gas inlet portion and themdownwardly to said'inert gas outlet portion, means for conducting liquid refrigerant from said liqueiying means to the said upwardly extending part of said evaporator, and 1 means in said inert gas circuit for propelling inert gas through at least a part of the upwardly extending portion of said evaporator with a velocity sufficient to propel liquid refrigerant upwardly therethrough by the frictionaldrag' of the inert gas whereby refrigerant liquid flows upwardly through a part of said conduit under the propulsionof the inert gas and flows downwardly through another part of said conduit in contact with the inert gas.

12. Absorption refrigerating apparatus comprising an inert gas circuit including an evaporator and an absorber, a solution circuit including a boiler and said absorber, means for liquefying refrigerant vapor generated in said boiler, said evaporator being constructed of a conduit having inert gas inlet and inert gas outlet portions, said conduit extending upwardly from said inert gas inlet portion and then downwardly to said inert gas outlet portion, means for conducting liquid refrigerant from said liquefying means to an intermediate level of the said upwardly extending part of said evaporator, and means in said inert gas circuit for propelling inert gas through at least a part of the upwardly extending portion of said evaporator with a velocity sufiicient to propel liquid refrigerant upwardly therethrough by the frictional drag of the inert gas whereby refrigerant liquid flows upwardly through a part of said conduit under the propulsion of the inert gas and flows downwardly through another part of said conduit in contact with the inert gas.

13. An evaporator construction comprising a first upstanding chilling coil section, a gas supply connection to said first chilling coil section adjacent the bottom thereof, a second upstanding chilling coil section positioned laterally of said first chilling coil section, a gas outlet connection to said second chilling coil section adjacent the bottom thereof, a space cooling coil section serially connecting the upper portions of said chilling coil sections, and a liquid refrigerant supply connection to said first chilling coil section.

14. An evaporator construction comprising a first upstanding chilling coil section, a gas supply connection to said first chilling coil section adjacent the bottom thereof, a second upstanding chilling coil sectionpositioned laterally of said first chilling coil section, a gas outlet connection to said second chilling coil section ad-' jacent the bottom thereof, a finned space cooling coil section serially connecting the upper portions of said laterally positioned chilling coil sections and positioned therebetween, and a liquid refrigerant supply connection to said first chilling coil section.

WILLIAM H. KI'I'I'O.

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