US2625800A

US2625800A - Absorption refrigeration

Info

Publication number: US2625800A
Application number: US164059A
Authority: US
Inventors: Norton E Berry
Original assignee: Servel Inc
Current assignee: Servel Inc
Priority date: 1950-05-25
Filing date: 1950-05-25
Publication date: 1953-01-20
Anticipated expiration: 1970-01-20

Description

Jan. 20, 1953 N. E. BERRY ABSORPTION REFRIGERATION Filed May 25, 1950 INVENTOR.

BY d

fivefrafi/vf M F W w Patented Jan. 20, 1953 UNITED STATES PATENT orrice ABSORPTION REFRIGERATION Norton E. Berry, Newburgh, Ind., assignor to Servel, Inc., New York, N. Y., a. corporation-of Delaware Application May 25, 1950, Serial No. 164,059

Claims. (01. 62-119) The present invention relates to absorption refrigeration systems and more particularly toa method of and apparatus for lifting absorption liquid for gravity flow through the system by vapor expelled therefrom.

Vapor liquid-lifts of the bubble and climbing film types have been commonly used in absorption refrigeration systems. In the bubble type lift, vapor bubbles are introduced into liquid at the base of a lift tube of relatively small di-- ameter to reduce the density of the mixture which rises in a continuous liquid phase in the tube. This type of lift operates well at high pressures but does not operate satisfactorily at low pressures. More specifically, the bubble type lift is not suitable for use in vacuum type absorption refrigeration systems when the liquid being lifted is at a temperature near its boiling point as theceeds the capacity of a single lift tube it is neces-' sary to use multiple tubes which increase the cost of the apparatus and introduce another factor which may result in erratic and uncontrolled circulation of liquid.

In the climbing film type of lift, vapor is expelled from solution in a tube of relatively small diameter, usually heated throughout its length, and the expelled vapor flows upwardly through the center of the tube at high velocity. The drag of the high velocity vapor on the solution produces a rising film of solution on the wall of the lift tube. This type of lift operates well at low pressure but an individual tube has 'a limited capacity and also requires a relatively high hy drostatic reaction head. The limited capacity is due to the fact that the periphery of the tube on which the film is lifted varies as the first power of the radius of the tube while its cross-sectional area which controls the vapor velocity varies as the square of the radius. Therefore, only one tube size will produce a particular relative circulation of vapor and liquid and when a greater capacity is desired than can be produced by a single tube, a plurality of tubes must be provided.

When such a climbing film tube is heated the problem is further aggravated by the unequal variation in the peripheral heating surface and vapor velocity with changes in the radius of the tube. In other words, the tube requires a fixed heat transfer surface to transmit the amount of heat necessary to generate vapor at a rate correlated with a cross-sectional area to produce the required velocity. As the periphery of the tube is the heat controlling factor, which increases as the first power of increments of increase in radius,

and the cross-sectional area is the velocity controlling factor, which increases as the square of' increments of increase in radius, there is only one optimum tube diameter which will give the heat transfer surface and cross-sectional area required to produce anoptimum climbing film action.

Such a tube is of relatively small diameter, onehalf inch inside diameter in a vacuum type absorption refrigeration system using a water solution of 50% lithium bromide by weight when heated by steam at atmospheric pressure, sothat' two or more lift tubes must'be used when the desired circulation rate exceeds the capacity ofia single tube.

Also, in the climbing film type of lift, the pres-.- sure drop in the lift tube consists of the forceof gravity acting on the climbing film and the frictional drag of the climbing film on the wall of thetube which is equal to and opposes the frictional drag of the vapor on the climbing film.

The height of the hydrostatic head of liquid required to balance these forces is a considerablepart of the total height of the lift tube and in practice constitutes nearly one-third of the total height.

One of the objects of the present invention is to i provide a method of and apparatus for lifting liquid by vapor expelled therefrom which requires only a single lift tube at any capacity andpro duces controlled, reproducible relative circulation of liquid and vapor.

Another object is to provide a method of and apparatus for raising liquid in the form of smalldroplets suspended in and carried by vapor fiow-' ing upwardly in continuous vapor phase at high velocity.

Another object is to provide a method of and apparatus for lifting liquid by vapor'expelled therefrom which raises liquid with arelatively low hydrostatic reaction head.

Still another object of the invention isto provide an apparatus of the type indicated which is of simpler construction, more economical to manufacture and of less comparative height'than those heretofore used.

These and other objects will become more apparent from the following description and draw} ings showing apparatus for carrying out the tion, reference being had for this purpose to the appended claims. In the drawing:

Fig. 1 is a diagrammatic view of a vacuum type absorption refrigeration system incorporating one form of vapor liquid-lift for practicing the method of the present invention;

Fig. 2 is a charge showing two curves in which relative circulation is plotted against rate of vapor generation for producing a desired relative circulation with a minimum, reaction head andat two different vapor rates, respectively;

Fig. 3 is a diagrammatic view of another form of vapor liquid-lift for performing the methodof the present invention, and

Fig. 4 is a sectional view taken on line 4-4 of Fig. 1, showing the layers of liquid, froth and vapor in the generating vessel and the droplets of liquid being carried by high velocity vapor flowing upwardly through, the lift tube in continuous vapor phase.

The method of the present invention comprises thesteps of expelling refrigerant vapor from liquid absorbent by the application of heat; directing the vapor upwardly in a confined path in continuous vapor phase; dividing a portion of the liquid into small droplets and deliveing the dropletsint the confined path of flowing vapor; correlatingthe rate of vapor generation and crosssectional area of the confined path to produce a velocity sufficient to lift the droplets to a higher level at the desired, rate; and then separating the vapor and droplets at the higher level.

The method may bepracticed with the aid of a generator or vapor expelling vessel and an upright lift tube connected to the vessel. Heat is applied to the liquid in, the vessel to generate vap01 at a rate correlated with the cross-sectional area of the lift tube to produce the required vapior Velocity therein and a reaction force sufficient, to depress the liquid level in thegenerating vessel below the bottom of thelift tube. In other. words, a. body of vapor is continuously maintained between the liquid level in the gen.- erating vessel and thebottom of the lift tube. The vapor then flows upwardly through the lift tube at high velocity in continuous vapor phase.

andlifts droplets of liquid deliveredinto the path ofv flow to a higher level. The surface arearof each droplet acted upon by the high velocity.

vaporand consequently theupwardly directed force thereon Varies as. the square. of. its. radius while the weight of the droplet. variesas a cube ofitsradius- Therefore, at any particular vapor velocity those droplets having. greater thana predetermined radius will fall back. through the upwardly flowing vapor inv the lift tube, those having less than the predetermined radius willmove upwardly in the tube. with thevapor and those having a predetermined critical radius will merely float in the tube without moving either upwardly r downwardly.

When liquid is lifted by the method of the present invention, the rate of relative circulation, ratio of pounds of liquid raised for each pound of vapor, increases as the vapor rate, increases until a maximum or peak is reached and then decreases as illustrated by the curves in Fig. 2, other factors such as the size of the lift tube and height of the hydrostatic reaction head remaining constant. Therefore, when a particular relative circulation is desired with a predetermined vapor rate, usually fixed conditions, a lifttube is provided-having across-sectional area which will produce a maximum relative circulation at said vapor rate. Inother words, a size of lift tube is selected which will operate at the peak a of the lower curve as illustrated in Fig. 2 with an abscissa at the desired: relative-- circulation and an ordinate at the desired vapor rate. For this particular condition of operation, the height of the hydrostatic reaction head required will be at a minimum. It will be understood, however, that other factors such as the cross-sectional'area'of; the lift tube and the height of the hydrostatic reaction head of liquid may be fixed and the relative circulation varied by varying the vapor rate. Thevapor-liquid will then operate at a point on the curve at one side or the other of the peak. Controlled, reproducible relative circulation is obtained when the apparatus operates at the peak of. the curve and for some distance at either side of the peak but is apt to be erratic beyond certain limits especially on the ascending portion of the curve- Preferably. however, the apparatus is designed to operate at two different vapor rates, corre sponding to half or full input conditions, to pro.- duce the same relative circulation with the same lift tube and hydrostatic reaction head. This may be accomplished by selecting a size of tube and height of hydrostatic reaction head to produce the upper curve as illustrated irrFig. 2 in which two points b and c on the curve at opposite sides of the peak have the same abscissa corresponding to a particular relativecirculation and separate ordinates corresponding to vapor rates of the desired magnitude for half and full input.

The dividing of liquid into droplets of the desired size may be accomplished by any suitable apparatus utilizing the flow of vapor at high velocity. For example, one or aplurality of devices may be provided for delivering liquid at a predetermined rate into the vapor flowing through the tube. Such devices may deliver the liquid in the form of droplets of the desired size or the arrangement may be such that the liquid is delivered in one or a plurality of streams and then.

broken up into droplets of the desired size by the flow of vapor at high velocity. It has been found in practice, however, that the agitation of the liquid by boiling is of itself sufficient to form the droplets of liquid and deliver them into the vapor. It is believed that the generation of vapor produces a froth or foam on the surface of the liquid in the generator which is swept. into. the bottom of the lift tube with the vapor. The foam is torn apart by the high velocity vapor flowing. to or in the lift tubes and coalesces to form small droplets,

of liquid. Certain of the dropletswill be too large and fall back through the upwardly flowing vapor,

but this method of liquid division has been found to consistently provide a sufficient number of droplets of the proper size to produce the desired relative circulation. Thus, the formation of droplets and the delivery of the droplets into the high velocity vapor is automatically controlled anclit has been found in practice that relative circulation rates are reproducible and constant for a given set of conditions.

The reaction head or, in other words, the height of a hydrostatic column of liquid necessary to balance the rising column ofvapor and liquid droplets will'be equal to the forces opposing the upward flow of the vapor in the lift tube. These forces are gravity acting on the droplets and the inertia of the droplets, the product of their mass and. actual acceleration, which produces a corresponding frictional drag on the vapor in the lift tube. As the friction of vapOr on the walls of the lift tube is a head is substantially less than that required to produce the same relative circulation in a climbing film type of liquid lift. The present method of lifting liquid eliminates the friction of liquid on the walls of the lift tube and is more efficient in imparting kinetic energy by direct impingement on the droplets throughout the cross-sectional area of the tube than by africtional drag on the surface of a film as in a climbing film type lift. Thus, liquid may be lifted by the present method with a relatively low hydrostatic reaction head which reduces the over-all height of the apparatus required. For example, it has been found in a vacuum type absorption refrigeration system of five tons ice melting capacity utilizing water as a refrigerant in a 50% lithium bromide solution by weight, that when water is expelled by heat at the rate of one pound per minute, an upright lift tube 50 inches high with an inside diameter of1.83 inches lifts 18 pounds of solution per minute with an 8 inch hydrostatic reaction head. This compares with an 18 inch reaction head on a climbing film type vapor liquid-lift operating under the same condition and having nineteen tubes of the same height each with an inside diameter of 0.570 inch.

The mixture of refrigerant vapor and droplets of liquid absorbent issuing from the upper end of the lift are then separated to adapt the liquid absorbent to flow by gravity through the absorption solution circuit. The vapor and liquid may be separated in any suitable way as by impinging the mixture against suitable baffles.

Referring to Fig. 1 of the drawing, one form of vapor liquid-lift for practicing the method of the present invention is shown applied to a vacuum type absorption refrigeration system. The vapor liquid-lift comprises a vapor expelling vessel or generator 5, a lift tube extending upwardly from the top of the generator and a separating chamber 1 at the upper end of the lift tube. The generator 5 is illustrated in the form of a horizontally arranged cylindrical vessel having an axial flue B. A source of heat such as a gas burner 9 heats the interior of the flue which, in turn, heats the solution in the generator to expel refrigerant vapor therefrom. It is to be understood, however, that the generator 5 may have other shapes and the solution therein may be heated by any suitable heating means.

In the illustrated embodiment the lower end of the lift tube 5 is connectedto the generator 5 so that its lower end is flush withthe top wall of the generator vessel 5 but may project a short distance into the generator vessel. The upper nd of the lift tube 6 extends through the bottom wall of the separating chamber 1 containing baffles II] for separating vapor from solution. Thus, the vapor liquid-lift comprises a vapor expelling vessel 5, a vapor liquid-lift tube 6 and a separating chamber 1 at the upper end of the lift tube.

A conduit 1 I connects the top of the separating chamber 1 to a suitable liquefier or condenser i 2 and-the opposite end of the condenser is connected to an evaporator I3 by a conduit l4 having an orifice therein as described and claimed in my prior application S. N. 725,000, filed January 29, 1947, for'maintaining the difference in pressure. Evaporator 13 comprises a plurality of substantially horizontal tubes I5 having their opposite ends projectin into spaced headers l6 and I1. Cups l8 at the end of each tube underlie the end of the next higher tube so that liquid refrignegligible factor the reaction erant continuously flows by gravity fromeach' tube to the next lowermost tube from the top to the bottom of the evaporator. The lower ends of the headers l6 and I! open into an absorber 19 in the form of a cylindrical vessel. Mounted in the absorber I9 is a bank of vertically arranged coils 20 providing gas and liquid contact surfaces and a liquid distributor 21 for delivering absorption solution for flow over the surface of the coils. Cooling water is supplied'through a conduit 22 and header 23 for flow through the coils 20 in absorber l9 and from the absorber flows through the header 24 and conduit 25 to the condenser l2 and the cooling Water is discharged from the condenser through a conduit 26.

Absorption solution weak in refrigerant flows from separating vessel 1 through a solution circuit comprising a conduit 2'! connecting the bottom of the separating chamber 1 to one pas-sage of a liquid heat exchanger 28 and a conduit 29 connecting said passage of the heat exchanger to the liquid distributor 2|. Liquid strong in refrigerant is delivered from the bottom of the absorber 19 through a conduit 35 to another passage of the heat exchanger 28 and flows from the heat exchanger to a reservoir vessel 3| through a conduit 32. A conduit 33 connects the bottom of the reservoir vessel 3| to the bottom of the generator vessel 5. The reservoir vessel 31 is adapted toreceive and hold a body of surplus solution therein to maintain a hydrostatic column of the solution on the generator 5 of a predatormined and substantially constant height, the lateral dimensions of the reservoir vessel being such that variations in operating conditions of the system will not substantially vary the height of the hydrostatic reaction head. During operation of system columns of solution will stand in

conduits

29 and 30 to balance the difference in pressure between the generator 5 and absorber I9, liquid standing at some level as in conduit 21 connected to the conduit 29 through heat exchanger 28, at level y in conduit 30 and at level 2 in reservoir vessel 3 l.

A purging device 35 generally similar to that illustrated and described in the United States Letters Patent to C. A. Roswell, No 2,384,861, issued September 18, 1945, and entitled Refrigeration, is provided for withdrawing non-condensable gases from the absorber is and delivering them to a storage vessel 35. Also a concentration control 36 of the type illustrated in the United States Letters Patent to Lowell McNeely, No. 2,465,904, issued March 29, 1949, is provided for varying the concentration of the absorption so lution to compensate for variations in operating conditions.

In accordance with the present invention a single lift tube 6 is provided for apparatus of any capacity and the cross-sectional area of the tube is correlated to the rate of vapor generation to cause vapor to flow upwardly through the tube in continuous vapor phase at sufficient velocity to raise small droplets of absorption solution from generator 5 to the separating chamber 1 at a controlled, reproducible rate. In any particular application the relative circulation of vapor and liquid and the rate of vapor generation to give the desired refrigeration capacity are usually fixed conditions. A tube 6 is then selected having a cross-sectional area which will produce the desired relative circulation with the lowest reaction head for the particular rate of vapor generation. This tube size can be determined experimentally for the particular lift desired and for theparticular refrigerant and absorbent used.

The hydrostatic reaction head of liquid h is produced by positioning the reservoir vessel 3! above the top of the generator 5 so as to produce a difference in liquid levels in the vessels of a height equal to the reaction head desired. The liquid then will be depressed in the generator to a level d below the end of the lift tube 6 to provide a vapor space e from which vapor flows upwardly through the tube 6 in continuous vapor phase, see Fig. 4. The liquid level d in generator 5 relative to the fixed liquid level a in reservoir vessel 3| is determined by the resistance forces in the left tube 6 which are balanced by the hydrostatic reaction head h of absorption liquid between the reservoir vessel and generator, respectively. The resistance forces are the weight and friction of the vapor on the tube 6 which are relatively small factors, gravity of the droplets of liquid and the inertia of the droplets which isthe greatest factor comprising the product of the mass of the droplets and their acceleration caused by the frictional drag of the vapor.

The lower curve in Fig.2 typically illustrates the relative circulation of pounds of liquid to pounds of vapor with increases in vapor velocity when using a 50% water solution of lithium bromide in a lift tube 50 inches long having an internal cross-sectional area of 3.41 square inches with a hydrostatic column h of solution 6.75 inches high acting on the generator as a .reaction head. This curve was produced by increasing the vapor rate but it will be readily apparent that a similar result can be obtained by maintaining the vapor rate constant and using progressively smaller tubes. It will be seen by reference to Fig. 2 that the relative circulation increases with increases in the vapor rate until a peak a is reached after which the rel- I;

ative circulation decreases with further increases in the vapor rate. In the example illustrated in Fig. 2, an optimum controlled and reproducible relative circulation of 16 pounds of solution for each pound of vapor is obtained when operating at the peak a of the curve with a vapor rate of approximately .6 pound per minute corresponding to 3 tons ice melting capacity in twenty-four hours with a minimum reaction head of 6.75 inches of solution. To increase the relative circulation with the same vapor rate, a lift tube of smaller diameter should be used if operating at the left of peak a of the curve as illustrated' in Fig. 2; a tube of larger diameter if operating at the right of peak a, or by using a greater head it if operating at the peak of the curve. To increase or decrease the relative circulation with the same lift tube the rate of vapor generation may be varied. From the curves illustrated in Fig. 2, it will be apparent that the rate of relative circulation of liquid to vapor and thus the actual rate of liquid circulation for any particular reaction head it may be varied over a considerable range, 14 to 24, by using a single tube 6 having a given crosssectional area and varying the vapor rate or by holding the vapor rate to constant and selecting tubes having different cross-sectional areas. Thus, the present invention consists of correlating the size of the lift tube with the rate of vapor generation to produce a velocity sufiicient to raise droplets of liquid to produce any selected one of a range of controlled, reproducible rates of relative circulation desired and arranging the generator 5 with respect to the reservoir vessel 31 to produce the required reaction head for the particular conditions.

The upper curve in Fig. 2 illustrates how the same relative circulation can be obtained in. the lift tube at different vapor rates corresponding to half and full inputs by operating at opposite sides instead of at the peak a of the curve, The lower curve of Fig. 2 shows the operating characteristics obtained with a tube 50 inches long and having an inside diameter of 2.08.4 inches for producing a relative circulation of 16 at the peak a of the curve with a reaction head h of 6.75 inches as previously explained. The upper curve shows the operating characteristics of the same tube with a reaction head h of 8 inches for producing a relative circulation of 16 at substantially .5 lb. of vapor/min. and 1 lb. of vapor/min, respectively. The apparatus having now been described in detail, the mode of operation is explained as follows.

At the beginning of a period of operation absorption solution will stand at some level a in both the reservoir vessel 3l and lift tube 6. When heat is applied to the flue 8 of the generator 5 by the gas burner 9,, refrigerant vapor will be expelled from solution in the generator and after an initial preheating of the solution vapor be expelled at a rate proportional to the amount of heat supplied. The vapor will ascend through the lift tube 6 at an increasing rate and the resistance to the flow of vapor through the tube due mainly to frictional drag on the liquid therein, causes a pressure drop through the tube and a resultant increase in pressure at the bottom of the tube. This, in turn, depresses the liquid level in the generator and thus decreases the quantity of liquid entering the tube until an equilibrium condition is reached when liquid is depressed to the approximate level d below the end of lift tube 6 in generator 5 to produce a pressure or hydrostatic reaction head it of solution between the levels a and d which balances the forces opposing the flow of vapor through the tube. Vapor then flows upwardly from said space e through the lift tube 6 in continuous vapor phase at high velocity and at the same rate as it is expelled in the generator 5.

The constant boiling and agitation of the solution in the generator breaks up a portion of the liquid into small parts, probably in the form of a foam, in the space 6 which is drawn into the base of the lift tube 6 with vapor. The liquid, in whatever form, is coalesced into small droplets in the vapor space e adjacent to the lift tube 6 or in the latter which are carried upwardly through the tube with the high velocity vapor, see Fig. 4. .It has been found that with a proper size of lift tube that liquid is lifted at .a controlled, reproducible rate.

The vapor with the droplets of liquid therein enters the separating chamber 1 where the droplets of liquid are separated from the vapor by the baflies Ill. Vapor then flows through conduit I i into the condenser [2 where it is liquefied. The liquefied refrigerant flows from the condenser |2 through the conduit l4 into the top of the evaporator I3, an orifice in the conduit I 4 maintaining the pressure difference between the condenser and the evaporator. The liquid refrigerant then flows by gravity through successive tubes l5 from the top to the bottom of the evaporator I3.

Absorption solution weak in refrigerant or, in other words, concentrated salt solution which is separated from refrigerant vapor in the chamber 1 flows by gravity to the liquid distributor 2| in the absorber |9 in a path of flow including conduit 21, first passage of liquid heat exchanger 28 and conduit 29. The absorption solution is divided by the liquid distributor 2| for gravity flow over the cooling coils 2|) in the absorber |9. Due to the absorption of refrigerant vapor in solution in the absorber IS, the vapor pressure of the refrigerant in the evaporator tubes I5 is reduced causing the refrigerant to evaporate at a low pressure and temperature to cool air or other medium flowing over the exterior of the tubes. The refrigerant vapor flows from the evaporator tubes |5 into the headers l6 and l! in communication with the absorber |9 where it is absorbed in the solution.

Absorption solution rich in refrigerant or, in other words, dilute salt solution flows from the bottom of the absorber I9 to the reservoir vessel 3| in a path of flow including the conduit 30, second passage of the liquid heat exchanger 28 and conduit 32, the difference between the level 1/ in conduit 30 and level 2 in the reservoir vessel 3| representing the difference in pressure between the high and low pressure sides of the system. The absorption solution then flows by gravity from the reservoir vessel 3| to the base ofthe generator 5 through a conduit 33. The liquid column h between 2 and d rep-resents the reaction head balancing the resistance forces in the lift tube 6. The absorption liquid delivered to the generator 5 then repeats the cycle as previously described.

Fig. 3 illustrates a modified construction in which a lift tube 40 has its lower end projecting into a vessel 4| and its up er end projectin into a separating chamber 42. Generator t3 is connected to the vessel 4| by a vapor conduit 44 and by a liquid conduit 45. Vapor conduit 44 is connected between the top of the generator 43 and the side of the vessel 4| above the lower end of the lift tube 40 and the liquid conduit 45 is connected between the bottom of the generator and the bottom of the vessel and projects upwardly in the latter in alignment with the lift tube 6. The construction illustrated in Fig. 3 operates in substantially the same way as the construction illustrated in Fig. l. Vapor expelled in the generator 43 flows through the vapor conduit M and upwardly through the lift tube All in continuous vapor phase at high velocity and liquid is delivered through the conduit 45 into the path of flowing vapor which tears the liquid apart and divides it into small droplets which are carried upwardly with the vapor to the separating chamber 4-4.

It will now be observed that the present invention provides a method of and apparatus for lifting absorption solution for gravity flow through an absorption refrigeration system by means of refrigerant vapor expelled therefrom. It will still further be observed that the present invention provides a novel form of vapor liquid lift which utilizes the velocity of vapor flowing upwardly through a restricted conduit to raise small droplets of liquid. It will still further be observed that the present invention provides a correlation between the size of a lift tube and the rate of vapor generation to produce the velocity necessary to raise droplets of liquid at a controlled, reproducible rate.

While two embodiments of the invention are herein illustrated and described, it will be understood that further modifications may be made in the construction and arrangement of parts with- 10 out departing from the spirit or scope of the invention. Therefore, without limitation in this respect, the invention is defined by the following claims.

I claim:

1. In an absorption refrigeration system, a circuit for absorption solution including a vapor liquid-lift for raising absorption solution therein, said lift comprising a vessel, a separating chamber above the vessel, and a riser connecting the upper portion of the vessel to the separating chamber, means for heating the solution in the solution circuit to expel refrigerant vapor in quantities sufiicient to continuously maintain a body of vapor between the liquid solution and lower end of the riser, and means in the solution circuit for delivering absorption liquid in finely divided form into the vapor escaping from the body in the vessel into the riser.

2. In an absorption refrigeration system a ,circuit for absorption solution including a vapor liquid-lift for raising absorption solution therein, said lift comprising a vapor expelling vessel, a separating chamber above the vessel, and a riser connecting the upper portion of the vessel to'the separating chamber, means for heating absorption liquid in said vessel to expel vapor therefrom in quantities sufficient to continuously maintain a body of vapor between the liquid and lower end of the riser, the expelled vapor delivering droplets of liquid into the body of vapor escaping from the vessel into the riser, and the riser having a cross-sectional area to produce a vapor velocity suflicient to lift the droplets of liquid contained therein.

3. In an absorption refrigeration system, a circuit for absorption solution including a vapor liquid-lift for raising absorption solution therein, said lift comprising a vapor expelling vessel,.a separating chamber above the vessel and a riser connecting the upper portion of the vessel to the separating chamber, a. reservoir vessel in the solution circuit above the vapor expelling vessel to deliver absorption liquid to the vessel and maintain a hydrostatic column of liquid on the liquid in the vessel, means for heating absorption liquid in said vessel to expel vapor therefrom in quantities sufiicient to continuously maintain a body of vapor between the liquid and lower end of the riser, the expelled vapor delivering droplets of liquid from the body of liquid into the body of vapor escaping from the vessel into the riser, and the riser having a cross-sectional area to produce a vapor velocity sufficient to lift the droplets of liquid contained therein. 1

4. In an absorption refrigeration system, a circuit for absorption solution including a vapor liquid-lift for raising absorption solution therein, said lift comprising a vapor expelling vessel, a separating chamber above the vessel and a riser connecting the upper portion of the vessel to the separating chamber, a reservoir above the vapor expelling vessel and connected to deliver absorption solution to the vessel and maintain a hydrostatic column of liquid on the liquidin the vessel, means for heating absorption liquid in said vessel to expel vapor therefrom in quantities sufficient to continuously maintain a body of vapor in the vessel between the liquid therein and the lower end of the riser, the expulsion of'vapor in the vessel delivering droplets of liquid into the body of vapor escaping from the vessel into the riser, the riser having a cross-sectional area to produce a vapor velocity suflicient to lift the droplets of liquid contained therein, and the pres- 1,1 .lsuremdropof Jtheupwardly flowing. column of vapor insaid. riserbalancingthe hydrostatic reaction head between theliquid levels in the reservoir and vapor expelling vessels to maintain a substantially constant, relative circulationv of vapor andliquid. .5 In absorption refrigeration system a cirouit;.ifor absorption solution including avapor .l-iquid lift'ior raising absorption solution therein, rsaideliit comprising a vessel, 3, separating chamlbenabovethe vessel anda riser connecting the .uppenportion .of the vessel tothe separating chamber, avap'or expelling vessel in said solution -.circuit,-.a-conduitconnecting the top of the vapor olip lli'n 'vesselto the. lift vessel and a conduit :connecting thebottom of the vapor expelling vessel;toithe;liit vessel, aireservoir vessel'inlthesolution circuit. above the vapor 'expellingvessel and connected to'deliver absorptionliquid tothelatter, and maintain a hydrostatic column of" liquid "I011 the'liquidqin'the vessel, means forjheating abvlsorption "liquid in said vapor expelling vessel to lexpel vapor therefrom in. quantities sufficient to continuously maintain a body of vapor between the liquid in the vapor expelling chamber and theilower end of the riser, said conduit between the bottom of the vapor expelling chamberand Iift deliveringdroplets' of liquid into the body of vapor escapinginto the riser, and the riser having aicrossesectional-area toproduce a vapor velocity sufficient 'toi'lift the droplets of liquid contained therein.

f6. Th'e'm'ethod ofliiting'liquid absorbentbyre- 'f'rlgerant vapor expelled therefrom to produce a controlled reproducible relative circulation of liquid and vapor. in anabsorption refrigeration .system which comprises delivering absorbent Jliquid toa place to be heated, heating the liquid ,to expel vapor in quantities toproduce a body of vaporabove the liquid being heated, permitting the expelled vapor to continuously escape from the .body'of vapor in continuous vapor phase through a confined path from a lower to a higher level, delivering droplets of liquid from the body 20f. liquid 'into the vapor escaping through the confined path, controlling the flow of vapor in said confined path to produce a vapor velocity sufficient to raise the droplets of liquid suspended therein from the'lower'to the higher level, and

separating the liquid. droplets, and vapor at the higher level.

I 'TQThe method of lifting liquid absorbent by .:rerigerant vapor expelled therefrom to produce a controlled reproducible relative circulation of liquidand vapor in an absorption refrigeration system which comprises delivering absorbent liquid to apla'ce to be heated, heating the liquid to. expel vapor in quantities-to produce a body of vapor above'the liquid being heated, permitting 'theexpelled .vapor to continuously escape from thebody of vapor through a confined path in continuous vapor phase from a lower to a higher level, utilizing the expulsion and flow of vapor to 'dividefa" portion of theliquid into small droplets landdeliver the droplets into the vapor escaping into the confined path, controlling the flow of vapor in said confined path to produce a vapor velocity sufficient to raise the droplets of liquid suspended therein from the lower to the higher Tlevel; and separating the'liquid droplets and vapor atthe higher level.

8. The method of lifting liquid absorbent by a l2 refrigerant vaporexpelled therefrom-to produce a controlled reproducible relative circulation of liquid and vapor in an absorption refrigeration system which comprises delivering absorbent liquid to a place to be heated, heating the liquid to expel vapor in quantities to produce a body of vapor above the liquid being heated, permitting the expelled vapor to continuously escape from the body of vapor in continuous vapor phase through a confined path from a lower to a higher level, delivering droplets of liquid from the body of liquid into the vapor escaping through the confined path, correlating the volume of vapor expelled and the cross-sectional area of the confined path to cause vapor to flow upwardly at a velocity sufficient to lift the droplets of liquid to-a'higher level, and separating the liquidand vapor at the higherilevel.

9. The method of lifting liquid absorbent -by refrigerant vapor expelled therefrom to produce a controlled reproducible relative circulation of liquid and vapor which comprises delivering absorbent liquid to a place to be heatedyheatingthe liquid toexpel vapor at the desired rate, directing expelled vapor through a confined path from a lower to a higher level, utilizing the expulsion and flow of vapor to divide a portion of the liquid into small droplets and deliver the droplets into the path of flowing vapor, depressing the liquid level to'provide a body'o'f vapor between the liquid and the confined path-and producing a velocity of vapor in said'pathsuffi'cient to raise the droplets to the higher level by correlating the rate ofvapor generation and cross-sectional area of the confined path, and separating the liquid and vapor at the higher level.

10. The method of raising absorption solution for gravity flow through the solution circuitof a vacuum type absorption refrigeration system which comprises delivering absorbent liquid to a place to be heated, heating the liquid to expel vapor in quantities to produce a body of vapor above the liquid being heated, permitting the expelled vapor to continuously escape from the body of vapor through a confined path in continuous vapor phase from a lower to a higher level, utilizing the expulsion and flow of vapor to divide a portion of the liquid into small droplets and deliver the droplets into the vapor escaping into the confined path, depressing the liquid level to provide the body of vapor between the liquidand confined path and producing a vapor velocity in the confined path sufficient to lift the droplets suspended therein from the lower to the higher level by correlating the rate of vapor generation and cross-sectional area of the confined path,,and separating the vapor from the droplets of liquid at the higher level.

NORTON E. BERRY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS.

Number Name Date 669,934 Thoens Mar. 12, 1901 2,278,133 Nesselmann Mar. 31, 1942 2,393,630 Grossman Jan. 29, 1946 2,399,922 Grossman May 7, 1946 2,446,988 Flukes Aug. 10, 1948 2,465,904 McNeely Mar. 29, 1949