US2207838A

US2207838A - Refrigeration

Info

Publication number: US2207838A
Application number: US107852A
Authority: US
Inventors: Albert R Thomas
Original assignee: Servel Inc
Current assignee: Servel Inc
Priority date: 1936-10-27
Filing date: 1936-10-27
Publication date: 1940-07-16
Anticipated expiration: 1957-07-16

Description

16, A. R. THOMAS 38 REFRIGERATION Filed Oct. 27, 1936 8 Sheets-Sheet 1 INVENTOR l. WWJ'ZMM' ATTORNEY.

y 6, 1940. A. R. THOMAS 2,207,838

' REFRIGERATION Filed Oct. 27, 1936 8 Sheets-Sheet 2 IN VENT OR.

ATTORNEY.

July 16, 1940- A. R. THOMAS REFRIGERATION Filed Oct. 27, 1956 s sheets-shee't s INVENTOR. WWVZMMJ ATTORNEY.

Filed Oct. 27, 1936 July 16, 1940.

. 8 Sheets-Sheet 4 IN VENTOR.

ATTORNEY.

y 16, 1940- I v A. R. THOMAS 2,207,838

REFRIGERATION Filed Oct. 27, 1936 8 Sheets-Sheet 5 ATTORNEY.

y 16, 1940- A. R. THOMAS 2,207,838

REFRIGERATION Filed Oct. 27, 1956 a Sheets-Sheet s 10 2 =4 3 10 o m o o J m 163 T INVENTQR. WWM! ATTORNEY.

July 16, 1940. v THOMAS 2,207,838

REFRIGERATION Filed Oct. 27, 1936 8 Sheets-Shget 7 ll war/A 'Q INVENTOR. F ,"10, Quzfiwd a; if;

ATTORNEY.

A. R. THOMAS REFRIGERATION Filed Oct. 27. 1936 July 16, 1940.

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PatentedJuly 1 6 1940 UNITED STATES PATENT OFFICE 2,201,838 nnrmcnaanon Albert R. Thomas. Evansville, Ind; assignor to Servel, Inc., New York, N. Y. a corporation of Delaware Application October 2'1, 1936, Serial No. 107,852

31 Claims.

use of evaporation of refrigerant in the presence of inert gas.

It is an object of the invention to provide an improved refrigeration system of this type having greater capacity and efficiency. I accomplish this in a manner which will appear as I describe and explain an embodiment of the invention in a refrigeration system which is generally like that described in U. S. Patent 1,609,334 granted Dec. 7, 1926, to von Platen and Munters', and'as illustrated by the accompanying drawings, forming part of this specification, of which:

Fig. 1 is a vertical sectional view of an evaporator embodying the invention;

Fig. 2 is a more or less diagrammatic view with parts in vertical section illustrating a refrigeration system embodying the invention including the evaporator shown in Fig. 1;

Fig. 3 is a detail sectional view on line 3-3 in Fig. 2;

Fig. 4 is an enlarged view of a portion of the apparatus shown in Fig. 2;

Fig. 5 is a view like that of Fig. 2 illustrating a modification;

Fig. 6 is a front view with parts broken away of a refrigeration apparatus unit involving the parts and system illustrated in Fig. 2.

Fig. '7 is a rear view'of the apparatus unit shown in Fig. 6;

, Fig. 8 is a sectional view on line 3-3 in Figs.

6 and If Fig. 9 is a. sectional view on line 9-4 in Figs. 6 and '7;

Fig. 10 is a sectional view on line 10-10 in Fig. 9, so that this figure is substantially a top view of the unit; and

' and absorber.

Fig. 11 is a chart showing the effect of variation in the slope of the piping in the evaporator In the system described in said patent granted to von Platen and Munters, refrigerant, such as ammonia, is expelled from solution in an-absorption liquid, condensed, and conducted to a ves sel, called an evaporator; which is in heat exchange relation with a body to be cooled. 'In thev evaporator, the liquid refrigerant evaporates in the presence of an inert gas, such as hydrogen, which flows through the evaporator. The evaporation of the liquid refrigerant producesrefrigeration, the heat of evaporation being transferred to the refrigerant from the body to be cooled which is in heat exchange relation with the evaporator.

The amount of refrigeration produced depends upon the rate of heat transfer from the body to be cooled to the liquid refrigerant and the rate of evaporation of the refrigerant. The refrigeration temperature depends upon the par-v tial pressure of the refrigerant vapor in the evaporator which in turn depends upon the. rate of removal of the refrigerant vapor from the presence of the refrigerant liquid. It will now be understood that both the relationship of the re- 10 frigerant and the inert gas, and the heat transfer relationship between the refrigerant liquid and the body to be cooled are important. It is desirable that the relationship between the body to be cooled and the liquid refrigerant afford the 15 greatest rate of heat transfer and. that the relationship between the refrigerant and the inert gas afford the desired rate of evaporation.

Referring to Fig.1, there is shown an evaporator l2 comprising a generally upright cylindrical casing 31 inside of which there is a cylinder 38 concentric with the casing 31. The upper end of the inner cylinder 38 has a reduced portion or neck 39 which opens within the upper end of the outer casing 31. The inner cylinder 38 forms within the outer casing 31 an annular space 40 within which there is located a pipe coil 41 having its turns spaced equally from the outer casing 31 and the inner cylinder 38. Around the neck 39 on the upper end of the inner cylinsteel mesh. This ring of capillary material extends substantially to the bottom on the inside of thetrough 42 and extends downward or hangs uniformly over the edge of the trough 42 and below the bottom thereof. The trough 42 and wick ring 43 are constructed and arranged so that the outer depending edge of the latter is horizontal and located directly above the top turn of the pipe coil 4|. A conduit 51 is connected'to the lower part of the inner cylinder 33 and a conduit '53 is connected to the lower end of the outer casing 31. A conduit 63 extends through the outer casing 31 and has an open end above the trough When the evaporator I2 is connected in a suitable refrigeration system, as hereinafter described, liquid refrigerant, such. as ammonia, flows through the conduit 68 into the trough 42 whence it is carried by'the annular capillary .syphon 43 and deposited on the upper turnof the evaporator coil 41 located in the annular as space 40. As the liquid is deposited on the upper turn of the coil 4|, it spreads out and runs to the under side of this turn. Due to the inclination of the coil turns, liquid also flows downwardly along the length of the coil. Liquid also drops due to its own weight from the bottom of one turn and is interrupted by the top of the next turn. The liquid ammonia thus becomes distributed entirely over the outer surface of the evaporator coil 4| as it descends in substantially a freefalling cylindrical sheet. This liquid distribution may be aided by roughening the outer surface of the coil 4| as, for instance, by electro-deposition which creates a sponge metal surface.

I have discovered that the degree of slope or inclination of the piping forming the coil 4| is of critical importance. Fig. 11 shows a curve obtained experimentally to determine the inclination necessary to obtain maximum covering of the surface of the absorber and evaporator piping by the free-falling or random dripping liquid. This is a qualitative curve obtained by measuring heat transfer to liquid dripping on the outside of a variably inclined conduit from liquid fiowing therethrough. The maximum surface covering occurs when the piping has an inclination of substantially 4 degrees. A greater or less inclination results in less of the surface being covered by liquid and less heat transfer. For instance, the surface covered when the inclination is 2 degrees is substantially the same as that when the inclination is 8 degrees but less than the maximum when the inclination is about 4 degrees. I prefer an inclination of substantially 4 degrees and not less than 2' degrees nor more than 8 degrees.

Inert gas enters the evaporator through conduit 51 and flows upward through the inner cylinder 38, through the opening 39 into the upper end of the outer casing 31, and thence downwardly in the annular space 40 and out through the conduit 58. The liquid which wets the outer surface of the coil 4| evaporates, and its vapor diffuses into the atmosphere of hydrogen which surrounds the coil in the annular space 40. Due to this evaporation, the liquid and gas is cooled to a temperature corresponding to the evaporation temperature at the vapor pressure of the ammonia. This is what has been referred to as refrigeration effect. This refrigeration effect may be utilized for cooling by causing a suitable fluid, such as brine, to flow through the evaporator coil 4|. We may refer to the brine flowing in the coil 4| as the body to be cooled.

The cold refrigerant liquid and the body to be cooled, also a liquid, are in direct thermal conductive relation throughout the entire area of the wall of the evaporator coil 4|, the refrigerant liquid covering the entire outside of the coil and the liquid to be cooled contacting the entire inner surface of the coil. In this manner we have heat transfer from liquid to liquid through a uniformly short metallic path throughout the extent of the evaporator.

In an evaporator constructed in accordance with my invention, as just described, thesurface wetted by liquid refrigerant is completely surrounded by inert gas. The turns of the evaporator coil 4| are equally spaced from each other and equally spaced from the walls formed by the inner cylinder 38 and the outer casing 31. The smaller the spacing between the coil turns, the greater the evaporation and heat transfer sur face for a given size evaporator. This spacing, however, should not be so small that liquid runthe tubes II.

ning downwardly over the coil bridges the spaces between the coil turns. The spacing should be such that during operation liquid drops clear from one turn and on to the next. Likewise, the spacing of the outer surface of the coil 40 from the inner surfaces of the cylinder 38 and casing 31 should be as small as possible without incurring bridging of liquid between the coil and the walls. The reason for this is that bridging of liquid creates localized fiow of the descending liquid, interfering with the desired cascading thereof which completely covers the outer, surface of the coil. I have found that a distance of less than between coil turns and between the coil and evaporator walls is liable to incur bridging of liquid. I therefore prefer a spacing between coil turns and between the coil and the inner surfaces of the annular space 40 of not less than A; inch but as near this dimension as practicable, that is, on the order of three sixteenths of an inch.

Referring to Fig. 2 of the drawings, there is illustrated more or less diagrammatically a refrigeration system including a generator III, a condenser II, the above described evaporator I2, and-an absorber I3. The generator I0 and the absorber I3 are connected for circulation of liquid therebetween by members including a liquid heat exchanger I4. The evaporator I 2 and the absorber I3 are interconnected for circulation of gas therebetween by members including a gas heat exchanger I5. The generator Ill is connected to the condenser I I' for flow of vapor from the generator to the condenser, and the condenser II is connected to the evaporator I2 for flow of liquid from the condenser to the evaporator by members hereinafter described.

The generator I0 comprises a casing I6 in the form of an upright cylinder. A plurality of flues or fire tubes I1 extend vertically through the easing I6. At the bottom of the casing I6 is a heating or combustion chamber I8, and the lower ends of the fire tubes I! open in the'upper part of this chamber. A flue, not shown in this figure, may be provided for conducting flue gases from the upper ends of the tubes IT. A suitable heater such as a gas burner I9 is located beneath the combustion chamber I8 so that the burner flame is projected into this chamber and thence into The tubes I! provide 'a desired surface for transferring heat to liquid surrounding these tubes in the casing I6.

A pipe coil 20 is located in the chamber I8 above the burner I9 so as to be heated directly by the burner flame. The lower end of the coil 20 is connected to the lower end of an upright conduit 2|. nected to the lower part of the generator casing I6. The upper end of the coil 20 is connected by a rising conduit 22 to the upper part of a gas and liquid separating vessel 23. The upper end of the generator casing I8 is also connected to the upper part of the vessel 23 by a conduit 24. The internal diameter of the conduit forming the coil 20 and the rising conduit .22 is advantageously su'fiiciently small that gas and liquid cannot pass each other therein so that gas formed by vaporization of liquid in the coil 20 will be trapped as bubbles in liquid, thereby adding a piston effect to the resulting decrease in weight of a fluid column in the coil 20 and conduit 22 compared to an equal column of liquid to effect upward flow of liquid in the coil 20 and conduit 22 into the vessel 23. Although only one coil 20 and rising conduit 22 are illustrated in this figure, it will be un- The upper end of the conduit 2| is conr to derstood that a plurality of such coils and rising conduits may be provided.

The upper part of the generator casing I6 is connected to the lower end of a slightly tilted but generally horizontal conduit 25, which will be herein referred to as an analyzer. The analyzer 25 is provided with a plurality of baflies or partitions 26 each provided with an opening 21 in the upper part thereof and an opening 28 in the lower part, thereof. These openings may best be seen in Fig. 3. The upper opening 21 is in the form of a horizontal slot having serrations in the upper edge thereof. The lower opening .28 may be a circular hole. The upper end of the analyzer 25 is connected to the lower part of a vessel 29 which may be considered'as part of the analyzer.

The upper part of the analyzer vessel 29 is connected by means of a conduit 36 to the lower end of a rectifier 3|. The rectifier 3| comprises an upright tube 32 surrounded by'a jacket 33. The

lower end of the tube 32 projects through the bottom of the jacket 33, and the upper end of the tube 32 is open in. the-upper part of the jacket 33. The interior of the tube 32 may be provided with suitable fins or baflles 34. The upper end of the rectifier jacket 33 is connected to the upper end of the condenser The lower end of the condenser II is connected by means of a conduit 35 to the righthand leg of a U-shaped conduit 36. The right hand leg of the conduit 36 extends appreciably above. the lower end of the condenser II, and the, left-hand leg of the conduit 36 is very short and connected to the rectifler jacket 33 at a point appreciably below the lower end of the condenser II.

The evaporator |2 has been described in connection with Fig. 1 and the parts are indicated by the same reference numerals as in Fig. 1.

The absorber I3 is constructed somewhat similarly to the evaporator l2. It comprises an upright cylindrical casing 44 and an inner cylinder 45 concentric therewith and forming therebetween an annular space 46. Within the annular space 46 is located a pipe coil 41 with its turns spaced equidistant from the outer casing 44 and the inner cylinder 45. The-upper and lower ends of the inner cylinder 45 are closed, except that the lower end is provided with an opening 48 and the upper end is connected by means of a conduit 49 to the upper end of the right hand leg of the U-shaped conduit 36 previously described. On the upper end of the inner cylinder 45 is located an annular trough 56. Over the outer rim of the trough59 is located a ring of capillary material 5| of inverted U- shape, the inner edge extending substantially to the bottom of the tray'or trough 50, and the outer edge being horizontal and depending uni 'formly below the bottom of the trough and located directly over the upper turn of the pipe coil 41. This structure is best shown in the enlarged detail view of Fig. 4.

The gas heat exchanger |5 comprises a generally horizontal cylindrical casing 52 containing a plurality of horizontal tubes 53. The tubes 53 connect end chambers 54 and 55 formed by partitions in the casing 52. The end chambers 54 and 55 connected by the tubes 53 form one passage of the gas heat exchanger, andthe space around the tubes 53 forms the other passage 01' the heat exchanger. The upper part of-the absorber I3 is connected by a conduit 56 to one end chamber 54 of the gas heat exchanger, and

the other end chamber 55 is connected by a. conof the evaporator l2. The lower part or the outer casing 31 of the evaporator I2 is connected by a conduit 56 to one end of the space around the tubes 53, and the other end of this space is connected by a conduit 59 to the lower part of the absorber l3.

Referring now to the connections for circulation of liquid between the generator In and the absorber I3, the lower part of the gas and liquid separating vessel 23 is connected to the upper part of tneabsorber I3 by a conduit 69, the inner passage of the liquid heat exchanger l4, and a conduit 6|. The upper end of the conduit 6| depends above the absorber tray 50. The lower part of the absorber I3 is connected to the analyzer vessel 29 by a conduit 62, the outer pas-- sage of the liquid heat exchanger l4, and a conduit 63.

Adjacent the top of the evaporator I2 is a looped conduit 64, which may be referred to as a high temperature evaporator or precooler. The upper part of the ends of this evaporative precooler are connected by conduits and 66 respectively to the chamber in the gas heat exchanger |5 which surrounds the tubes 53. A conduit 61 is connected from the bottom of the U-shaped tube 36 to one end of the conduit 64, and one end of a conduit 66 is connected to the other end of the conduit 64. The other end of conduit 69 extends into the evaporator l2 and depends above the evaporator trough 42.

The upper end of the evaporator coil 4| is connected to the upper end of a cooling coil 69 in a chamber to be cooled 10. The lower end of the cooling coil 69 is connected to a suitable pump II or other liquid displacing means which in turn is connected to. the lower end of the evaporator coil 4|.

The upper end of the absorber coil 41 is con-. nected by a conduit 12 to a condenser cooling coil .13. The other end of the condenser cooling coil 13 is connected to a conduit 14 which extends in thermal contact with a,portion 15 of conduit 30, which will herein be referred to as a first rectifier or high temperature rectifier. The lower end of the absorber coil 4'! is adapted to, be connected to a source of cooling water by means of and a certain condenser temperature which may be a fairly high cooling water temperature, or

room temperature'should the condenser "be aircooled. The liquid assumes the lowest possiblev level in the system, and the space above the liquid is filled with gas. When the burner I9 is lighted, heat from the burner is transmitted directly to the coil 26, and by means of the fire tubes IT to the liquid in the generator casing 6. Heating of liquid in the coil 26, causes expulsion of ammonia vapor out of solution. The expelled vapor creates in the coil 20 and the rising conduit 22 a fluid column lighter than an equivalent column of liquid only. so that the combination vapor and liquid column .rises in conduit22 into the gas and liquid separating vessel 23. From the vessel 23; the gas flows in conduit 24 to the 24 upper part of the generator casing l6. Heating of liquid in the generator casing It also causes expulsion of ammonia vapor out of solution when the boiling point of the solution is reached. This vapor rises into the upper part of the generator casing l6. The vapor which accumulates in, the upper part of the generator casing l6 escapes therefrom by bubbling through liquid in the analyzer conduit 25 and the analyzer vessel 29. The baffle plates 26 in the analyzer conduit 25 prevent the vapor from merely flowing along under the top of the conduit 25, and cause the vapor to pass downwardly and through the slots 21 in the discs 26. The serrations in the upper edge of the slots 21 break up the vapor flow so as to create a more extensive contact of the vapor with the liquid as they flow in countercurrent relationship through the analyzer conduit 25. Liquid from the separation vessel 23 flows through conduit 60, the inner passage of the liquid heat exchanger Hi, and conduit 6| into the upper part of the absorber l3. During operation of the system, ammonia vapor is expelled from solution in the generator casing at a first temperature, and more ammonia vapor is expelled from solution in the coil 20 at a higher temperature, so that liquid which enters the ab sorber l3, as just described may be referred to as weak absorption liquid, this phraseology having reference to the relatively low concentration of ammonia; In the absorber l3, the weak absorption liquid becomes enriched by absorption of ammonia vapor, as hereinafter described, and the enriched absorption liquid flows from the lower part of the absorber through conduit 62, the outer passage of the liquid heat exchanger l4, and conduit 63 into the analyzer vessel 29 and the analyzer conduit 25 back to the generator ID. The lower openings 28 in the analyzer baflles 26 permit the flow of liquid in the analyzer 25 countercurrent to the previously described flow of vapor therethrough. The ammonia vaporpasses out of contact with liquid in the analyzer vessel 29 at a place where the liquid has a high concentration of ammonia. The purpose of this is to decrease the amount of water vapor leaving the generator.

Vapor flows from the upper part of the analyzer vessel 29 through conduit 30, the high temperature rectifier I5, and the liquid cooled rectifier 3| into the upper end of the condenser ll. Water vapor condensed in the rectifiers flows back through conduit 30 to the liquid circuit. In the condenser ll. ammonia vapor, substantially at the total pressure in the system, is condensed to liquid by heat transfer to water flowing through the condenser cooling coil l3. The liquid ammonia flows from the lower end of the condenser ll through conduit 35 into the U- shaped conduit 36 and the rectifier jacket 33. It will now be understood that the liquid in the rectifier jacket 33 causes cooling of the rectifier 3|. Cooling water from the condenser cooling coil 13 flows through conduit 14 in heat exchange P relation with the conduit 30-at I5 and causes cooling of this higher temperature rectifier.

Liquid ammonia flows from the lower part of the U-shaped conduit 36 through conduit 61 into one end of the evaporative precooler formed by the looped tube 64. The liquid flows along the lower part of the tube 64 to the other end thereof whence it flows through conduit 68 into the upper part of the evaporator.

During operation of the system, the inert hydrogen gas is substantially confined to the circuit including the evaporator l2 and the absorber 63 which are interconnected as previously described by the gas heat exchanger l5.

In the evaporator l2 the ammonia evaporates in the presence of hydrogen, as set forth in connection with Fig. l, and the cooling brine or other heat conducting liquid flows through the evaporator coil 4| and thence through the cooling coil 69 in heat transfer relation with air in the enclosure 10. Liquid may be circulated between the cooling coil 69 and the evaporator coil 4| by means of the pump 1|. In the evaporator coil 4!, the brine is cooled by'heat' transfer to the liquid ammonia on the outer surface of this coil. In the cooling coil 69, the brine is warmed by heat transfer thereto from air in the enclosure 10. The pump H is connected and arranged to cause circulation of the brine so that it flows upweirdly through the evaporator coil 4|. The reason for this will be hereinafter explained.

In order that evaporation of liquid ammonia may continue in the evaporator l2 at the desired temperature or temperatures, it is necessary to remove ammonia vapor from the atmosphere around the evaporator coil 4| so. that the partial pressure of ammonia will be maintained at the desired value. To this end. the mixture of gas and vapor, herein referred to as rich gas, is removed from the evaporator and replaced by what is herein termed weak gas, that is, gas containing a relatively small quantity of ammonia vapor.

The strong gas from the evaporator I2 is conducted through conduit 58, the gas heat exchanger l5 and conduit 59 into the lower part of the absorber I3. Weak absorption liquid emerging from the upper end of conduit 6| in the absorber I3 is deposited in the absorber distributing tray or trough 50 from which it is transferred by the annular capillary syphon 5| onto the upper turn of the absorber coil 41 in the annular space 46. The liquid flows downwardly over the absorber coil 41 in the same manner as the liquid ammonia fiows downwardly over the evaporator coil 4|, as previously described. Ammonia vapor diffuses out of the at mosphere in the annular chamber 46 of the absorber and enters into solution at the surface of the liquid'wetting the absorber coil 41. This absorption of ammonia is accompanied by liberation of heat which is transferred from the absorption liquid to cooling water which flows in the absorber coil 41. Weak gas from the absorber is conducted through conduit 56. the gas heat exchanger l5, conduit 51, and the inner cylinder 38 of the evaporator l 2 to the upper part of the evaporator.

The manner in which thegas circulation ocours is as follows: The specific density of ammonia vapor is greater than that of hydrogen,

so that the column of gas formed by diffusion of ammonia vapor into the atmosphere. of the evaporator I2 is heavier than the column of gas formed when ammonia vapor is removed from the atmosphere in the absorber l3. The resulting unbalance between these two columns of gas creates circulation thereof, upward in the absorber l3, and downward in the evaporator l2. In the gas heat exchanger l5, heat is transferred from the weak gas flowing in the tubes 53 to the strong gas flowing in the chamber around, these tubes.

Referring now to the looped tube 64, the ends of this tube are connected by conduits and 66 respectively to the chamber around the tubes 53 of the gas heat exchanger l5. There is, therecircuit.

' orator.

por'in the atmosphere in this tube, the tendency to equalize results in evaporation of liquid and cooling thereof before entrance into the evaporator l2. The formation of vapor in the evaporative precooler 64 results in flow of gas in the path formed by conduit 55, the tube 64-, and conduit 58 due to the difference in weights of the columns of gas in this path.

Referring now to the vessel 45 within the absorber l3, the upper end of this vessel is connected by conduit 49 to the. upper end of the right hand leg of the U-shaped conduit 36, and the lower end of the vessel 45 communicates with the interior of the absorber through the opening '48. During normal operation of the system, the

vessel 45 contains gas having a concentration of ammonia vapor substantially like that in the lower part of the absorber. The conduit 49 normally provides a passage for non-condensible gas which may issue from the lower end of the condenser through conduit 55, the right hand leg of the trap 36, and conduit 49 back to the gas If the temperature of the cooling water in the condenser cooling coil 13 should be abnormally high so that the condenser temperature is too high for condensation of ammonia at the existing pressure in the system, uncondensed ammonia vapor will flow through conduit 48 into the vessel 45, displacing gas from this vessel through the opening 48 into the absorber l8 which is in the active gas circuit. In this manner, a rise in pressure in the system takes place so that condensation of ammonia may continue at thehigher temperature. The vessel 45 is herein referred to as a pressure vessel. During periods when the cooling water temperature is high, the pressure vessel 45 acts as a continuation of the condenser, and ammonia vapor condensed herein returns to the liquid circuit through the opening 48 in the bottom.

Let us return now to the structures of the evaporator l2 and the absorber l3 in Figs. 1 and '2, these structures being essentially the same as far as gas and. liquid contact is concerned. Re-

ferring more particularly to the evaporator 12,

we have previously described the location of the helical pipe coil 4| as being in an annular space 40 between the inner and outer walls of the evap- This of course istrue, but this location of the coil 4| further divides the annular space 40 into two annular spaces, one on the inside of the coil 4| and the other on the outside of the coil 4|. The liquid refrigerant, ammonia, is dripping or cascading downward over the coil 4| so that the inert gas, hydrogen, flows in two annular paths with respect to the liquid ammonia. The ammonia evaporates atthe surface of the .liquid on the coil 4| and the resulting ammonia ture and pressure of the ammonia. Howeven, -this state of equilibrium is not reached during operation because, due to circulation of gas as previously described, the rich gas is continually replaced in the evaporator by weak gas. Whether the gas is flowing or standing still, there is a maximum distance through which ammonia yapor has to move from where it is formed at the liquid surface in tending to establish equilibrium. 5

Since the coil 4| is located centrally of the annular-space 40, the maximum diffusion distance from the .coil into the space 40 is less than the Width of the space 40. Since all the diffusion distances, that is, the distances in directions nor- 10 mal to the liquid surface, are not all exactly the same, we may better refer to the mean diffusion distance.- It has been found that the capacity or quantity of liquid evaporated per unit of time is increased upon decrease in the mean diffusion 15 distance. This is the reason that, ,as previously set forth, the spacing between the coil 4| and the walls of the evaporator is made as small as possible. In the present embodiment, bridging of liquid is a limiting factor of this spacing. I ,0

wish to point out, however, that I may replace the coil 4| by a cylinder of, for instance, capillary material, and obtain a very small gas space normal to the liquid surface. Also, I may distribute the liquid over both the inner and outer wall 25 surfaces of the space 40 rather than over a member in the center of the space 40 and still have a diffusion distance less than the width of the space 40. In. this case the gas would still flow in two annular paths with respect to the 30 liquid surface in a small evaporator, provides for better heat transfer from the liquid ammonia to the liquid to be cooled which flows in the coil, and effects a novel and eificient gas flow as will hereinafter appear.

The diffusion distance cannot be made zero 40 because this would mean that there wouldbe no gas and therefore no evaporation of ammonia at a temperature lower than the condenser temperature and no refrigeration would be produced.

Neither should the decrease in diffusion distance 45 of ammonia vapor in the gas which leaves the evaporator l2 through conduit 58, referring to Fig. 2. The density of the weak gas is determined by the average concentration of ammonia vapor in the gas leaving the absorber l8, through conduit 56. Throughout the evaporator and the absorber there is a gradient density'between that of the rich and weak gas. As previously explained, it is the inherent force within the system due to the difference in specific densi-- ties of the rich and weak gas columns which causes the gas circulation. Part of this force causes actual movement of gas and another part of this force is expended in overcoming-resistance in the gas circuit comprising the evaporator, the

absorber, the gas heat exchanger, and the inter- 7o connecting conduits previously described. I have therefore provided in the evaporator and the absorbr a path of gas flow having a very small difl'usion distance but a large cross sectional area.

In the evaporator this is the cross sectional area 7 of the annular space between the coil 4| and the inner wall 38 plus the cross sectional area of the annular space between the coil 4| and the outer wall 31. I may make the evaporator l2 as large or as small as desired and by keeping the same width annular space 40 the diffusion distance in the large evaporator will be no more than in the small evaporator although the cross sectional area in the path of gas flow will be greater to accommodate more gas in the larger evaporator.

From the above it will be understood that other things, such as liquid surface and heat transfer, being constant, the capacity varies with the rate of gas flow and inversely with the mean diffusion distance. Under constant conditions evaporation of liquid into a moving stream of gas isproportional to the square root of the velocity. However, in the refrigeration system we have to take into consideration that gas flowing between the high temperature absorber and the low temperature evaporator incurs a heat loss which is cut down only within the efficiency of the heat exchanger. Other things being constant, then, the maximum efficiency would be obtained when the gas flowing from the evaporator to the absorber contains saturated ammonia vapor. This is not obtained on account of the concentration gradient of ammonia vapor from the surface of the liquid ammonia in the direct.on of the diffusion distance into the gas stream. With a smaller mean diffusion distance, a desired average concentration of gas leaving the evapor; or is reached in a shorter length of time, that is, a unit quantity of gas passes through the evaporator in a shorter length of time and the velocity of gas flow through the evaporator is thus increased resulting in an increase in capacity without'sacriflcing emciency.

As the gas flows through the evaporator I2, and the same thing happens in the absorber l3, it passes alternately into annular streams on each side of the coil 4| and then in a single large annular stream between the turns of the coil. The cross sectional area of each of the two separated streams being much less than the cross sectional area of the intermediate large stream, the resulting alternations in energy of flow produce turbulence. This turbulence in the gas stream results in convection of ammonia vapor from the surface of the liquid ammodia into the gas stream. This aids the natural diffusion of ammonia and results in an increase of efliciency and also greater capacity because a desired average concentration of ammonia in the gas is reached in a shorter length of time. In the absorber the convection aused by turbulence abets natural difiusion oi .nmonia vapor out of the gas stream to the surface of the absorption liquid. Herein I have used the word difiusion in a technical sense of either dispersion or concentration of one vapor'or gas in a space occupied by another gas. With respect to the evaporator we say that the ammonia vapor diffuses into the'hydrogen and with respect to the absorber we say that theammonia vapor difluses out of the hydrogen.

In Fig. 5 is shown a system like that previously described in connection with Fig. 2 and like parts in these two figures are indicated by the same reference numerals. Whereas in the system illustrated in Fig. 2 the absorber l3 and the condenser II are cooled by a supply of water which goes-to waste, I may provide an evaporative cooling circuit or spray tower for the absorber l3 and condenser II as illustrated in Fig.

5. The condenser H is located in a housing 11 having a water tank 18 in the lower part thereof. Air enters the casing 11 through an opening 19 below the condenser II and is discharged by a fan or blower 90 above the condenser, thus causing a flow of air over the condenser coil Water is admitted to the tank 18 through a conduit 8| regulated by a float controlled valve 82. The tank 18 is connected by a conduit 83 to the lower end of the absorber coil 41. The upper end of the absorber coil is connected by a conduit 84 to a pump 85 which is in turn connected by a conduit 86 toa spray nozzle 81 above the condenser coil Cooling water from the tank 18 flows through conduit 83 into the absorber coil 41 and is then raised by the pump 85 through conduits 84 and 86 to the spray nozzle 81 from which the water is showered onto the condenser coil Due to the upward flow of air through the casing 11,- the water, sprayed downwardly therein is cooled toward its wet bulb temperature. Water lost by evaporation into the air stream is replaced from conduit 8| under the control of the float operated valve 82.

The upper end of the evaporator coil 4| is connected by a conduit 88 to a spray nozzle 89 in a casing 90. A water tank 9| in the lower part of pump 93 raises water from the tank 9|; through the evaporator coil 4| to the spray nozzle 89 which showers the water down through the casing back to the tank 9|. Air froni a room 95 to be cooled is circulated by a fan or blower 96 through a conduit 91 and a conduit 98 to the .lower part of the spray tower 90, and thence upwardly through the spray tower to a conduit 99 through which the air is returned to the room 95. Fresh air may be admitted through a conduit mo. The air in passing upwardly through the spray tower 90 is cooled by the cold water from the nozzle 89. Suitable baffle plates llll may be provided to disentrain free water from the stream of air before it is returned to the room 95.

In both of the arrangements illustrated in Figs. 2 and 5, water or brine is circulated upwardly through the evaporator coil 4|. The gas flows downwardly-in the annular/passage 40 in which the coil 4| is located. Since the partial pressure of ammonia in the gas increases in the direction of the gas flow, the region of lowest partial pressure and, therefore, the lowest evaporator temperature is in the upper part of the evaporator adjacent to where the weak gas enters. Thus, the water flowing upwardly through the evaporator coil 4| is progressively cooled and leaves the evaporator substantiallyat the place of lowest temperature, thereby utilizing the full cooling effect of the evaporator.

absorber I3 is provided with the desired annular'gas passage by locating therein the cylindri-,

cal pressure vessel 45, thereby effecting the desired absorber structure and at the's'ame time eliminating the requirement of additional space I for a pressure vessel.- The evaporator precooler y no to the evaporator 212.

For instance, it may be thermostatically regulated responsiveto temperature of the evaporator I 2.

In Figs. 6 to 10 is shown a refrigeration apparatus unit embodying my invention. The parts of this apparatus are substantially as described in connection with the system shown diagrammatically in Fig. 2, and are connected in the same manner. The apparatus is mounted in a rectangular frame 209 composed of angle irons. The generator 210 is located substantially centrally in the lower part of the frame. The liquid heat exchanger 214 is formed by a concentric tube coil which encircles the generator casing 216-. A fiue 208 is provided for conducting spent.

and have their lower ends connected to the lower end of the upright conduit 221, the upper end of which is connected to the lower part of the generator casing 216. The upper ends of the coils 220 are connected by means of rising conduits 222 to the gas and liquid separating vessel 223. The

26 upper part of the vessel 223 is connected to the generator by means of -a conduit 224, and the lower part of the vessel 23 is connected to the liquid heat exchanger 214 by conduit 260. The analyzer'225 and analyzer vessel 229 are like that 30 .described in connection with Fig. 2. The generator 210, the liquid heatexchanger 214, the separating vessel 223 and its connections, and the analyzer 225 are-enclosed by suitable thermal insulating material 201, such as mineral wool which is retained in place by a light sheet metal casing 206. Any suitable heater, not shown, may be arranged directly beneath the coils 220 in the heating chamber 218.

V The evaporator 212 and the absorber 213 are 40 located at opposite ends of the frame 209, the absorber 213 being at a level above that of the generator 210,'and the evaporator 212 being somewhat higher than the absorber 213. Members interconnecting the-absorber and the evaporator include a gas heat exchanger 215 similar to that described in connection with Fig. 2. The evaporative precooler coil 264 is located directly above the upper end of the evaporator 212, and this precooler, the evaporator, and adjacent portion of the gas heat exchanger 215 are encased by suitable thermal insulation material 205.

I The condenser 21 I comprises a concentric tube coil located adjacent the top of. the frame 209 -and encircling the leg of the rectifier U-tube 236 which is connected by the vent conduit 249 to the pressure vessel 245 within the absorber 213. The lower part of the U-tube 236 is connected by the conduit 261 to the evaporative precooler 264 which in turn is connected by conduit 268 The evaporator precooler 264 is connected to the gas heat exchanger 215 by

conduits

265 and 266. The absorber 213, the condenser 2| 1, and the high temperature rectifier 215 are cooled by water 65 which flows from conduit 216 upward through the absorber coil 241, then through conduit 212 to the condenser cooling coil, and thence through conduit 21.4 which extends in thermatcontact conduit 268 into the evaporator 212.

evaporator coil respectively and to which connection may be made for fiow of fluid to be .best be followed by reference to Fig. 6. Vapor expelled from solution in the coils 220 causes upward flow of vapor and liquid in the rising conduits 222 into the separating vesse1223 in the manner previously described. Vapor flows from the vessel 223 through conduit 224 into the upper part of the generator casing 216, from where all the vapor bubbles through liquid in the analyzer .225 and passes into the analyzer 'vessel 229.

From the vessel 223, liquid flows through conduit 260, the liquid heat exchanger 214 and conduit 261 into the upper part of the absorber 213. Enriched liquid fiows from the lower part of the absorber 213 through conduit 262, the liquid heat exchanger 2,14, and conduit 263 into the analyzer vessel 229 from where it flows to the analyzer conduit 225 into the generator.

Vaporflows from the upper part of the analyzer vessel 229 through conduit 230 to the liquid cooled rectifier 231. Watenvapor condensed in the high temperature rectifier 215 and in the liquid cooled rectifier 231 flows back to the liquid circuit through conduit 230. Ammonia vapor (here see Fig. 7) flows from the low temperature rectifier 231 into the upper end of the condenser coil 211. In the latter, the ammonia vapor, substantially at the total pressure in the system, is condensed to, liquid which fiows through conduit 235 into the rectifier U-tube 236. From the lower part of the U-tube 236, liquid ammonia fiows through conduit 261, the evaporative precooler 264, and In the evaporator, theliquid flows downwardly over the evaporator coil 241, in a manner previously described, and evaporates, producing a refrigerating effect to cool fluid in the coil .241. The vapor diffuses into the atmosphere of inert gas, hy-

drogen. Rich gas fiows from the evaporator 212 through conduit 256, the gas heat exchanger 215, and conduit 259 into the absorber. In the latter, ammonia vapor diffuses out of the gas and is absorbed into weakened solution flowing downwardly over the absorber coil 241. The weak gas returns from the absorber to the evaporator through conduit 256, gas heat exchanger 215, and conduit 251. Rich gas from the gas heat exchanger 215 flows through conduit 265, the evaporative precooler 264, and conduit 266.

Although I have described and explained my invention as embodied in a particular type of system'in which gas circulation is automatically produced by a force within the system, it will be understood that it may be practiced in any system whichmakes use of evaporation of refrigerant in the presence of inert gas, whether gas circulation is produced by a fan, blower, injector, turbine, or other gas impelling means. It. will also be understood that there may be variations in structure as, for instance, the use of banks of tubes or pipes instead of the helical coils in the evaporator and absorber, or both. My 111-.

an I

ventlon, therefore, is not limited except as indicated by the following claims.

What I claim is:

l. Refrigeration apparatus of the absorption type employing an inert gas including structure for effecting gas and liquid contact comprising piping having sections thereof arranged one above the other, and means for delivering liquid upon said piping so that the liquid descends by gravity from one section to another and over the exterior surface of said piping, said piping having a slope of substantially four degrees to effect substantially maximum wetting of the exterior surface thereof by the descending liquid.

2. Refrigeration apparatus of the absorption type employing an inert gas including structure for effecting gas and liquid contact comprising piping having sections thereof arranged one above the other, and means fordelivering liquid upon said piping so that the liquid descends by gravity from one section to another and over the exterior surface of said piping, said piping having a slope lying in a range between and including two and eight degrees.

3. Absorption type refrigeration apparatus employing an inert gas including a generator, a condenser, an evaporator, an absorber, a pressure vessel located within said absorber and communicating therewith, and a conduit connected from the outlet end of said condenser to said pressure -vessel.

4. Absorption refrigeration apparatus employing an inert gas including a generator, a condenser, an evaporator, an absorber, said absorber having inner and outer walls forming therebetween a substantially annular space for flow of inert gas, said inner wall enclosing a storage chamber for inert gas, a connection from said chamber into the absorber space, and a conduit connected from the outlet end of said condenser to said chamber.

5. In an absorption refrigerator, a generator, a condenser, an evaporator, an absorber, and members connecting said parts to form a system for flow of refrigerant, absorption liquid, and inert gas, said absorber including a cylindrical member constituting a pressure vessel, an outer shell concentric with said vessel, means to provide a cascade of absorption liquid midway between said vessel and said outer shell, a connection between said vessel and a point in the system between the generator and the evaporator, and said vessel being connected to the absorber space outside the same.

6. In a refrigerating apparatus of the kind in which refrigerant evaporates into inert gas, an evaporator including spaced vertical walls, vertically spaced pipe portions between said walls equidistantly spaced therefrom, said pipe portions being disposed for dripping of liquid from one to another along tneir length and being spaced vertically to prevent bridging of liquid, said pipe portions being so close to said vertical walls as to provide minimum diffusion distance, without bridging of liquid, means to cause flow of gas between said walls, means to supply liquid refrigerant to flow over said pipe portions, and means to circulate fluid to be cooled through said pipe portions.

'7. In a refrigeration system of the kind in which refrigerant liquid evaporates and diffuses into an inert gas, the improvement which consists in alternately flowing the liquid refrigerant inert gas on each side of the free falling liquid refrigerant in direct contact therewith in paths of like characteristics and of a width on the order of three sixteenths of an inch.

8. A refrigeration system including structure forming an annular place of evaporation, a member for conducting liquid refrigerant fluid to said place of evaporation, members for conducting inert gas to and from said place of evaporation, and a pipe coil arranged concentrically in saidannular place and constructed and arranged to form a downward path of flow for liquid refrigerant fluid on its exterior surface and interiorly conduct a fluid to be cooled, the width of said annular place being such that with said pipe coil therein, there is a minimum diffusion distance for refrigerant in inert gas without bridging of liquid.

9. A refrigeration system including an evaporator formed by two concentric upright cylindrical members providing an annular space therebe' tween, a pipe coil located in said annular space substantially equidistant from both said members, a member for conducting liquid refrigerant fluid to the upper part of said annular space, means for conducting inert gas through the in ner upright cylindrical member and to one mid of said annular space, and means for conducting inert gas from the opposite end-of said annular space, said pipe coil being constructedand arranged to interiorly conduct fluid to be cooled, a receptacle for liquid conducted to the upper part of said annular space, and a capillary syphon for distributing liquid from said receptacle onto an upper turn of said pipe coil.

10. In a refrigeration system of the kind in which refrigerant liquid evaporates and diffusesinto an inert gas, the improvement which consists in dripping liquid refrigerant in a sheet-like path in free falling condition, obstructing the free fall of liquid in said path, flowing inert gas on each side of said sheet-like path in direct contact with the liquid refrigerant in paths of like characteristic and of a width on the order of three sixteenths of an inch, and transferring heat from an object to be cooled to the obstructing medium.

11. In a refrigeration system of the kind in which refrigerant liquid evaporates and diffuses into an inert gas, the improvement which consists in flowing liquid refrigerant in free falling condition in a sheet-like path of annular form, flowing a medium, to be cooled through said path in indirect heat transfer relation with the liquid refrigerant and thereby obstructing the free fall of liquid refrigerant, and flowing inert gas in narrow unobstructed paths of like characteristics, including width and variations of width, on each side of the sheet-like path in direct contact with the liquid refrigerant, the width of the inert gas path being such as to provide a minimum diffusion distance without bridging of liquid.

12. In a refrigeration system of the kind in which refrigerant liquid'evaporates and diffuses into an inert gas, the improvement which consists in flowing liquid refrigerant in free falling condition in a sheet like path of annular form, flowing a medium to be cooled through said path in indirect heat transfer relation with the liquid refrigerant and thereby obstructing the free fall of liquid refrigerant, flowing inert gas in narrow unobstructed paths downward on each side of the sheet-like path in direct contact with the liquid refrigerant, and conducting inert gas prior to contact with the liquid refrigerant in indirect heat exchange relation with the inert gas in one vent bridging of liquid, means to cause flow of gas between said walls, means to supply weak absorption liquid to flow over said pipe portions, and means to circulate cooling fluid through said pipe portions.

14. An absorption refrigeration system including structure forming a substantially annular place of absorption, a member for conducting absorption liquid to said place of absorption, members for conducting gas to and from said place of absorption, and a pipe coil arranged substantially concentrically insaid annular place and constructed and arranged to form a downward path of flow for absorption liquid on its exterior surface and interiorly conduct a cooling fluid.

15. An absorption refrigeration system including an absorber formed by two upright cylindrical members providing an annular space therebetween, a pipe coil located in said annular space substantially equidistant from both said members, a member for conducting absorption liquid to the upper part of saidannular space, members for conducting gas to and from opposite ends of said annular space, said pipe coil being constructed and arranged to interiorly conduct cooling fluid, a receptacle in the upper part of said annular space and to which liquid is conducted,

and acapillary siphon for distributing liquid from 7 said receptacle onto an upper turn of said pipe coil.

16. In a refrigeration system of the kind in which refrigerant liquid evaporates and diffuses into an inert gas and is thereafter absorbed, the improvement which consists in alternately flowing absorption liquid in free falling condition and in heat exchange relation with a cooling medium, and flowing a mixture of refrigerant vapor and inert gas on each side of the descend,-

ing liquid in direct contact therewith in paths of like characteristic and of a width on the order of three sixteenths of an inch.

17. In a refrigeration system. of the kind in which refrigerant liquid evaporates and diffuses into an inert gas and is thereafter absorbed, the

improvement which consists in flowing absorpv tion liquid in a sheet-like path in free falling condition, obstructing the free fall of liquid in said path, flowing a mixture of refrigerant vapor and inert gas on each side of said sheet-like path in direct contact with the absorption liquid in paths of like characteristic and of awidth on the order of three sixteenths of an inch, and cooling the obstructing medium.

18. A cooling element including wall structure forming a horizontally narrow, vertically elongated space a plurality of conduit sections located one above another centrally in said space and adapted to interiorly conduct a fluid to be cooled, means for delivering refrigerant liquid upon the exterior of said conduit sections, and members for conducting gas to and from said space, the horizontal width of said spacebeing such as to provide a minimum diffusion distance without bridging of liquid.

19. A cooling element including a' plurality of inclined conduit sections located one above another so that liquid will flow along the exterior of said sections and drop from one upon another, wall structure forming a closed space around said conduit sections equidistant from diametrically opposite sides of the conduit forming said sections, means for delivering liquid refrigerant above said conduit sections members for conducting gasto the upper part of and from the lower part of said space, and connections for flow of fluid to be cooled interiorly of said conduit sections, the distance of said wall structure from said conduit sections being such as to provide a minimum diffusion distance without bridging of liquid.

20. A refrigeration system including structure forming a substantially annular place of evaporation, means for conducting liquid refrigerant fluid to said place of evaporation, members for conducting inert gas to and from said place of evaporation, and a member for conducting liquid in contact withthe gas and located centrally in said place of evaporation, said structure and members being spaced to provide a minimum difiusion distance without bridging of liquid.

21. Refrigeration apparatus of an absorption type including a condenser, an absorber, means for conducting water in cooling relation with said absorber, means for causing flow of air in contact with said condenser, and means for flowing water which has been heated by said absorber and conducting the heated water into contact with said condenser, whereby the water is cooled by evaporation into the air stream to increase its capacity for cooling the condenser.

22. In the art of producing refrigeration with the aid of a system having an absorber and a ing structure forming a substantially annular place. of absorption, means for conducting absorption liquid to said place of absorption, means for conducting gas .to and from said place of absorption, and a member for conducting absorption liquid in contact with gas and arranged in said place of absorption so that liquid flows substantially concentrically in said annular place in contact with two annular streams of gas.

24. Refrigerating apparatus including a generator for expelling refrigerant from solution, a condenser connected to receive and adapted to condense the expelled refrigerant, a principal evaporator connected to receive the condensed refrigerant from the condenser for primary evaporation, said evaporator including an outer relatively wide vessel, a pipe coil situated relatively close to the inside wall of said vessel, an inner wall spaced inward of said pipe coil equal to its spacing from the outer wall, a liquid holderand spreader above said pipe coil for equalizing distribution of liquid refrigerant thereon, an absorber, means to circulate absorption liquid between the generator and the absorber, means 'to conduct weak gas from the absorber and introduce the-same into said evaporator, and means to conduct rich gas from the evaporator to the absorber. I

25. Refrigerating apparatus including a generator for expelling refrigerant from solution, a condenser connected to receive and adapted to condense the expelled refrigerant, a principal evaporator connected to receive the condensed refrigerant from the condenser for primary evaporation, sai'd exaporator including an outer relatively wide cylinder, a pipe coil situated relatively close to the inside wall of said cylinder, an inner cylinder spaced inward of said pipe coil equal to its spacing from the outer wall, said inner cylinder having a diameter at least equal to several times the width of the space between the cylinders, a liquid holder and spreader above said pipe coil for equalizing distribution of liquid refrigerant thereon, an absorber, means to circulate absorption liquid between the generator and the absorber, means to conduct Weak gas from the absorber and introduce the same into said evaporator, and means to conduct rich gas from the evaporator to the absorber.

2'6. Refrigerating apparatus including a generator for expelling refrigerant from solution, a condenser connected to receive and adapted to condense the expelled refrigerant, a principal evaporator connected to receive the condensed refrigerant from the condenser for primary evaporation, said evaporator including an outer relatively wide vessel, a pipe coil situated relatively close to the inside wall of said vessel, anenlarged conduit portion forming an inner wall spaced inward of said pipe coil equal to its spacing from the outer wall, a liquid holder and spreader above said pipe coil for equalizing distribution of liquid refrigerant thereon, an absorber, means to circulate absorption liquid between the generator and the absorber, means to conduct weak gas from the absorber to and through said enlarged conduit portion and into said evaporator, and means to conduct rich gas from the evaporator to the absorber.

27. Refrigerating apparatus including a generator for expelling refrigerant from solution, a condenser connected to receive and adapted to condense the expelled refrigerant, a principal evaporator connected to receive the condensed refrigerant from the condenser for primary evaporation, said evaporator including an outer relatively wide vessel, a pipe coil situated relatively close to the inside wall of said vessel, an inner wall spaced inward of said pipe coil equal to its spacing from the outer wall, a liquid holder and spreader above said pipe coil for equalizing distribution of liquid refrigerant thereon including a wick having a horizontal lower edge, an absorber, means to circulate absorption liquid between the generator and the absorber, means to conduct weak gas from the absorber and introduce the same into said evaporator, and means to conduct rich gas from the evaporator to the absorber;

28. Refrigerating apparatus including a generator for expelling refrigerant from solution,-a condenser connected to receive and adapted to condense the expelled refrigerant, a principal evaporator connected to receive the condensed refrigerant from the condenser for primary evaporation, said evaporator including an outer relatively wide vessel, a pipe coil situated relatively close to the inside wall of said vessel, an ,inner Wall spaced inwardly of said pipe coil equal to its spacing from the outer wall, a liquid holder and spreader above said pipe coil for equalizing distribution of liquid refrigerant thereon, an absorber including an outer relatively wide vessel, a pipe coil situated relatively close to the inside wall of said last-mentioned vessel, an inner Wall spaced inwardly of said pipe coil equal to its spacing from the outer wall and a liquid holder and spreader above said last-mentioned pipe coil, means to circulate absorption liquid between the generator and the absorber, means to conduct weak gas from the absorber and introduce the same into said evaporator, and means to conduct rich gas from the evaporator to the absorber.

29. Refrigerating apparatus including a gen-- erator for expelling refrigerant from solution, a

condenser connectedto receive and adapted tocondense the expelled refrigerant, a principal evaporator connected to receive the condensed refrigerant from the condenser for primary evaporation, an absorber, said absorber including an outer relatively wide vessel, a pipe coil situated relatively close to the inside wall of said vessel, an inner wall spaced inwardly of said pipe coil equal to its spacing from the outer Wall, a liquid holder and spreader above said pipe coil for equalizing distribution of liquid refrigerant thereon, means to circulate absorption liquid between the generator and the absorber, means to conduct weak gas from the absorber and introduce the same into said evaporator, and means to conduct rich gas from the evaporator to the absorber.

30. In refrigerating apparatus of the kind in which refrigerant diffuses into inert gas, a vessel including means for flow of a first liquid having a surface, means to flow a second liquid on said surface, said first means being formed so that said second liquid drips from part to part of said surface, means to circulate inert gas adjacent said surface, said vessel including a wall limitingthe path of flow of inert gas adjacent said surface, said surface and wall being spaced to provide a minimum diffusion distance without bridging of liquid, said surface and wall being mutually irregular to provide turbulence, and members connected to said vessel to form a system for circulation of liquid and gas.

31.,In a refrigerating system of the kind employing an inert gas, structure providing a path of flow for inert gas including a wall, a conduit in said path of flow of inert gas connected for flow of liquid therethrough, means to cause liquid to flow on the exterior of said conduit, said conduit being formed so that liquid flowing on the exterior thereof drips from part to part of said conduit, said conduit being relatively close to said wall to provide a gap therebetween in said path of flow of inert gas without bridging of such gap by liquid flowing over the exterior of said conduit and dripping from part to part thereof, and a member on the opposite side of said conduit from said wall and relatively close to said conduit to provide a gap therebetween in said path of flow of inert gas without bridging of the last-mentioned gap by liquid flowing over said conduit and dripping from part to part thereof.

ALBERT R. THOMAS.