US3581515A - Absorption refrigeration system and method of operation thereof - Google Patents

Abstract

An absorption refrigeration system and a method of operating the same. The system includes a generator, a condenser, an evaporator, an absorber and a reservoir in circuit with each other. Conduit means has two legs through one of which a pressure-equalizing gas circulates in refrigerant-enriched state and through the other of which the same gas circulates in refrigerant-poor state. The refrigerant contained in the reservoir is contacted exclusively with the pressure-equalizing gas in the refrigerant-poor state to prevent the formation of layers of different refrigerant concentration in the refrigerant contained in the reservoir.

Description

[ l l I l ited States Patent Inventor Hans Stierlin Rainweg l5, Schlieren (Katen, Zurich, Switzerland Appl. No. 870,645 Filed Oct. 6, I969 Patented June 1, 1971 Priority Oct. 4, 1968 Switzerland 14889/68 ABSORPTION REFRIGERATION SYSTEM AND METHOD OF OPERATION THEREOF 10 Claims, 2 Drawing Figs.

U.S. Cl 62/110, 62/1 10, 62/490 Int. Cl. F25b 15/04 Field of Search 62/ 101 [56] References Cited UNITED STATES PATENTS 3,516,264 6/1970 Stierlin t. 62/101 Primary Examiner-william F. O'Dea Assistant Examiner-P. D. Ferguson AtlorneyMichael S. Striker ABSTRACT: An absorption refrigeration system and a method of operating the same. The system includes a generator, a condenser, an evaporator, an. absorber and a reservoir in circuit with each other. Conduit means has two legs through one of which a pressure-equalizing gas circulates in refrigerant-enriched state and through the other of which the same gas circulates in refrigerant-poor state. The refrigerant contained in the reservoir is contacted exclusively with the pressure-equalizing gas in the refrigerant-poor state to prevent the formation of layers of different refrigerant concentration in the refrigerant contained in the reservoir.

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ABSORPTION REFRIGERATION SYSTEM AND METHOD OF OPERATION THEREOF BACKGROUND OF THE INVENTION The present invention relates to an absorption refrigeration system utilizing a pressure equalizing gas, as well as a method of operating the system.

Absorption refrigeration systems of this type usually use ammonia as the refrigerant, water as the solvent, hydrogen as the pressure equalizing auxiliary gas and natrium chromate as a corrosion inhibitor. However, other substances and com binations thereof are also possible and used in some systems. Systems of this type are well known, and one such system is clearly described in Swiss Pat. No. 357,419 to which reference may be had for background information. In a system of the type disclosed in the aforementioned Swiss patent the entire quantity of liquid refrigerant contained in the reservoir system is constantly turned over by the pumping arrangement provided. Such conventional systems therefore do not have the problems with which the present invention is specifically concerned, and which it seeks to overcome.

In particular, in absorption refrigeration systems of improved efficiency, that is systems whose operating efficiency is improved as compared with that disclosed in the aforementioned Swiss patent, and which are of the type for instance disclosed in copending U.S. application Ser. No. 731,218, now U.S. Pat. No. 3,516,264 there exists the danger that layers of different concentration are formed in the refrigerant contained in the reservoir system. This is highly undesirable for various reasons, including the fact that the formation of such layers increases the danger of corrosion in the system, tends to withdraw refrigerant from circulation, and presents other problems known to those skilled in the art.

The danger of formation of such layers of different concentration results from the fact that in systems of the type under discussion the'surface of the liquid refrigerant contained in the reservoir system is in contact with the pressure equalizing gas which is enriched with refrigerant vapor and thus can constantly absorb such vapor. On the other hand, all condensate obtained from the gas circulatory system is conveyed into the reservoir and, because that quantity of the condensate which is in contact with the gas enriched with refrigerant vapors, is relatively rich in refrigerant and therefore constantly adds refrigerant to the refrigerant solution contained in the reservoir, refrigerant is constantly withdrawn from circulation. In addition, the condensate flow contains little or no anticorrosive inhibitor. Unless special measures are taken, fonnation of pronounced layers occurs in the concentration of the inhibitor, either in form of a decrease of the concentration of the inhibitor in the upper part of the reservoir or in an excessive concentration and fall-out of the inhibitor at other points of the system.

SUMMARY OF THE INVENTION It is, accordingly, an object of the present invention to over come the aforementioned disadvantages.

A more particular object of the present invention is to avoid the formation of layers of different concentration in the refrigerant component contained in the reservoir system of the type under discussion.

A further object of the invention is to provide a system capable of carrying out the novel method.

In pursuance of the above objects, and of others which will become apparent hereafter, one feature of the invention resides in a method of operating an absorption refrigeration system including a generator component, a condenser component, an evaporator component, an absorber component, a refrigerant reservoir component and conduit means connecting said components in circuit with each other and having two legs through one of which an auxiliary pressure-equalizing gas circulates in refrigerant-rich state and through the other of which said auxiliary gas circulates in refrigerant-poor state. According to the present invention the method of operating such system comprises the step of contacting the refrigerant in the reservoir component exclusively with the auxiliary gas in refrigerant-poor state to thereby prevent the formation of layers of different refrigerant concentration in the refrigerant contained in the reservoir component.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic illustration of an absorption refrigeration system according to the prior art; and

FIG. 2 is a view similar to FIG. I but illustrating a system according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS It is emphasized that FIG. 1 illustrates an absorption refrigeration system which is already known in the prior art, and which is shown to facilitate understanding and explanation of the present invention.-

The system shown in FIG. 1 utilizes a pressure equalizing gas and mainly comprises a generator 1 in which the refrigerant vapor is developed from the refrigerant solution fed into the generator. The refrigerant vapor passes through a vapor conduit 2 into a condenser 3 wherein the refrigerant vapor condenses. The condensate thus developed flows through the condensate conduit 5 into an evaporator 7 wherein the condensate is warmed and evaporates. From the evaporator 7 a conduit 9 leads to the heat exchanger 11 in which the ammonia-rich gas passing through the conduit 9 is heated up by heat exchange with the ammonia-poor gas passing through the heat exchanger 1.1 so as to cool the am monia-poor gas as well as the condensate in the conduit 5.

At its lower end the conduit 9 communicates with the main reservoir 13 which is filled to a predetermined level 36 with medium concentrated solution, it being understood that the level in the reservoir 13 determines the operating liquid level of the system. The gas which passes through the conduit 9 into the reservoir 13 flows from the latter into an absorber 15 in which the largest part of the refrigerant vapor is dissolved in the poor solution flowing in countercurrent direction to the refrigerant vapor through the absorber 15. The remainder of the gas passes in upward direction through the conduit 17 to the evaporator 7. A conduit I25 connects the reservoir 13 with the aspirating container 123 for equalizing purposes.

Arranged at the lower part of the absorber 15, immediately adjacent the end thereof, is a conduit section whereas a liquid-conducting conduit section 117 carries the enriched solution from the absorber 15 to the generator 1. Such a system is described in detail in the aforementioned U.S. Pat. No. 3,516,264.

After the vapor has been generated in the generator 1, the cooled poor solution returns through the conduit 109 into the upper part of the absorber 15. The conduit portion 115 serves to prevent return flow of the liquid from the absorber 15 into the reservoir, because it serves to back up the liquid flowing through the absorber, accomplishing this ahead of the conduit portion 117 so that the total quantity of liquid passes through this conduit portion 117 to the generator.

The reservoir 13 contains a refrigerant solution which includes a substance acting as an inhibitor for corrosion preven tive purposes, for instance natrium chromate. In order to provide the necessary corrosion protection to the liquid in the aspirating vessel 123 also, the latter is connected via the conduit 125 with the reservoir 13, to provide for concentration equalization. This makes it possible for the density of the solution in the vessel 123 and below the opening 205 of the equalizing conduit 125 in the reservoir 13 to be approximately equal.

However, above the inlet 205 it is possible in this construction for a layer-type concentration differential to develop. This occurs under certain operating conditions. The enriched pressure-equalizing gas which flows through the conduit 9 over the liquid level 36, has an NH concentration of approximately 60percent by volume. If the device is in a room of 25 C. temperature, then the liquid level 36 assumes an NH; equalization concentration of approximately SOpercent by volume. However, the liquid in the reservoir 13 has a much lower concentration of approximately 25percent. The result is a strong layering in upward direction because the solution having a higher NH concentration is lighter than that having a lower concentration. This is further accelerated by the incoming condensate which flows at least intermittently into the reservoir 13 through the conduit 9. This condensate also has approximately 50 percent by weight concentration and in addition contains no inhibitor. The result is that over a period of time there develops in the upper portion of the reservoir 13 a layer composed of a solution which is very rich in NH and which contains no inhibitor. If now the system is moved into a space having a higher temperature, for instance 35 C., then the solution'in the upper part of the reservoir 13 evaporates and refrigerant vapor enters the circulation of pressure equalizing gas in undesired manner.

These problems are avoided with the construction and method according to the present invention, the construction being shown in FIG. 2. The problems in question adversely influence both the life and the operational efficiency of the system and it is therefore important that they be overcome.

The embodiment illustrated in FIG. 2 and showing the system according to the present invention, is shown utilizing the same reference numerals as in FIG. 1 for the identical components. In this embodiment, however, the refrigerantrich or enriched pressure equalizing gas which flows through the conduit 9 coming from the evaporator, circulates not through the reservoir 13 but instead is circulated directly to the absorber 15 without first passing over and in contact with the liquid surface 36 in the reservoir 13. In this manner the liquid surface 36 is prevented from absorbing refrigerant vapor from the gas. Furthermore, the overflow quantity which passes through the conduit 9 is not fed into the reservoir 13.

In the system illustrated in FIG. 2 the liquid surface 36 in the reservoir 13 communicates only indirectly with the refrigerant-poor gas through a conduit 202, which poor gas passes through the conduit 17, that is without directly contacting the liquid surface 36. The pressure-equalizing gas which is in dynamic balance with the liquid surface 36, is now heavier under normal operating conditions than the refrigerant-poor pressure equalizing gas which passes through the conduit 17 so that normally absorption does not take place. It is emphasized, however, that it is also possible to have the refrigerant-poor pressure equalizing gas contact the liquid surface 36 directly, if desired, in that the absorber 15 is connected with the reservoir 13 in the manner illustrated in FIG. 2 in broken lines.

A conduit section 217 corresponding to the one identified with reference numeral 117 in FIG. 1 is connected with the absorber 15 at the lowest end thereof which communicates directly with the upright conduit 9 through which the refrigerant-rich pressure equalizing gas circulates. Thus, the development of stagnating-liquid areas is avoided. The condensate quantity which is separated in the conduit 17, is in equilibrium with the refrigerant-poor gas and therefore is poor in its content of refrigerant and heavier than the liquid in the reservoir 13. This condensate thus passes into the lower portion of the reservoir 13 whereby an admixture of the total quantity of liquid in the reservoir 13 occurs and the development of layers of solutions of different concentration of refrigerant and/or anticorrosive inhibitor is avoided.

Under extraordinary operating conditions, for instance when the output of cold is reduced or if the room temperature is changed, or under other similar circumstances, the refrigerant-poor gas will have a higher concentration of refrigerant at the upper end of the absorber 15 than corresponds to the equilibrium concentration at the surface 36 in the reservoir 13. In this case the higher specific weight of the refrigerant-poor gas-but which is in this case richer than is otherwise the casecauses the gas to descend through the conduit 202 to the liquid surface 36 in the reservoir 13, which liquid surface 36 absorbs a portion of the refrigerant vapor. Thereupon, the now poorer gas rises again through the same conduit 202, which therefore must have a certain minimum diameter, and reenters the main gas circulation. Thus, refrigerant vapor is removed from the main circulation in this manner until such time as a new equilibrium condition has been reached.

If, however, the main circulation has too low a content of refrigerant for reasons connected with other changes in operating conditions, then no refrigerant can enter into the circulation in the mannerjust described. The reason for this is that as soon as refrigerant from the reservoir 13 enters by evaporation into the gas passing through the conduit 17, this gas becomes heavier than the gas at the upper end of the absorber 15 and therefore rests on the liquid surface 36 in the reservoir 13, with the result that evaporation immediately terminates. The arrangement in FIG. 2 therefore permits only withdrawal of refrigerant from the main circulation but no restoration of such refrigerant. In conjunction with the surface of the liquid in the reservoir 13, and with the main circulation, the conduit 202 in effect serves as a trap for the refrigerant.

It is emphasized that the withdrawal of refrigerant from the pressure-equalizing auxiliary gas circulation through the conduits 9 and 17, which occurs frequently, is desirable. It is necessary, in order to assure that constant circulation takes place in the concentration equalization conduit which in turn is necessary for maintaining uniform concentration of the inhibitor in the reservoir 13; this conduit 125 will always supply some refrigerant to the circulation. As a result of the arrangement which hasjust been described above there is provided an automatic readjustment of the equilibrium of refrigerant in the main circulation, even if operating conditions change.

Under normal circumstances the novel method and apparatus described in FIG. 2 prevent shift and changes in the concentration, and therefore prevent the development of layers of liquids having different concentrations in the reservoir 13. Under extraordinary operating circumstances, for instance in the aforementioned absorption in the reservoir 13, the concentration of inhibitor in the main circulation may briefly rise to some extent. This results in a danger of crystallization of inhibitor, particularly in the lower half of the absorber 15. Such crystallization is harmless as long as no summation of such incidents occurs. This is prevented by avoiding the development of dead water zones, and by providing conduits which are intermittently flushed by liquid flowing through in order to dissolve and flush away crystallized inhibitor. In order to provide proper functioning of the device described with reference to FIG. 2, the occurrence of such dead water zones-that is zones where water or liquid can collect and stagnateand the existence of conduit sections which are not at least intermittently flushed with liquid, must be avoided under all circumstances, for instance in the manner illustrated at reference numeral 206 in FIG. 2.

It should still be emphasized that the expression reservoir as employed herein includes not only the receptacle 13 but also tubes or conduits which may be used instead of the receptacle 13 for the designated purpose.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of applications differing from the types described above.

While the invention has been illustrated and described as embodied in an absorption refrigeration system, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

I claim:

1. In a method of'operating an absorption refrigeration system including a generator component, a condenser component, an evaporator component, an absorber component, a refrigerant reservoir component and conduit means connecting said components in circuit with each other and having two legs through one of which an auxiliary pressure-equalizing gas circulates in refrigerant-rich state and through the other of which said auxiliary gas circulates in refrigerant-poor state, the step of contacting the liquid surface of refrigerant in said reservoir component exclusively with said auxiliary gas in refrigerant-poor state to thereby prevent the formation of layers of different refrigerant concentration in the refrigerant contained in said reservoir component.

2. In a method as defined in claim 1, wherein said step comprises contacting said refrigerant directly with said auxiliary gas in refrigerant-poor state.

3. In method as defined in claim 1, wherein said step comprises exposing said refrigerant indirectly to communication with said auxiliary gas in refrigerant-poor state.

4. In a method as defined in claim 1; and comprising the step of causing movement of refrigerant carried by said gas exclusively in direction towards the upper exposed surface of the refrigerant in said reservoir.

5. In a method as defined in claim I, said absorber having a lower inlet for said auxiliary gas in refrigerant-rich state, and an upper outlet from which said auxiliary gas issued in refrigerant-poor state; and further comprising the step of at least intermittent flushing with liquid of said absorber and associated portions of said conduit means at least in the region of said lower inlet.

6. In an absorption refrigeration equalizing gas, the combination of a generator for producing from a refrigerant solution fed into the generator a refrigerant vapor; a condenser downstream of said generator; a vapor conduit connection said generator with said condenser for system with a pressure feeding refrigerant vapor produced in said generator into said condenser; an evaporator connected with said condenser for evaporating the condensate received from said condenser; a reservoir adapted to be filled to a predetermined level with refrigerant solution and connected with said evaporator; an absorber communicating at one end with said reservoir above the level of solution therein and at the other end with said evaporator; and conduit means, including a first conduit communicating with said absorber and said evaporator and carrying said equalizing gas in refrigerant-vapor enriched state, and a second conduit communicating with said absorber and said reservoir and carrying said equalizing gas in refrigerant-vapor poor state, so that the liquid surface of refrigerant solution in said reservoir is contacted only by said equalizing gas in refrigerant-vapor poor state to thereby prevent the formation of layers of different refrigerant concentration in the refrigerant solution contained in said reservoir.

7. In an absorption refrigeration system as defined in claim 6, wherein condensate flows from said absorber into said reservoir in contact with said equalizing gas in refrigerantvapor poor state, so that said condensate is prevented at least from absorbing significant quantities of refrigerant vapor in termediate said absorber and said reservoir.

8. ln an absorption refrigeration system as defined in claim 6; and further comprising conducting means for conducting condensate from said absorber to said. generator.

9. in an absorption refrigeration system as defined in claim 6, wherein said first conduit is at least substantially vertical.

10. In an absorption refrigeration system as defined in claim 9, said one end being the lower end of said absorber; and further comprising an additional conduit connecting said first conduit with said one end of said absorber so as to connect the former with the latter while serving to drain away condensate originating in said absorber.

Claims (10)

1. In a method of operating an absorption refrigeration system including a generator component, a condenser component, an evaporator component, an absorber component, a refrigerant reservoir component and conduit means connecting said components in circuit with each other and having two legs through one of which an auxiliary pressure-equalizing gas circulates in refrigerant-rich state and through the other of which said auxiliary gas circulates in refrigerant-poor state, the step of contacting the liquid surface of refrigerant in said reservoir component exclusively with said auxiliary gas in refrigerant-poor state to thereby prevent the formation of layers of different refrigerant concentration in the refrigerant contained in said reservoir component.

2. In a method as defined in claim 1, wherein said step comprises contacting said refrigerant directly with said auxiliary gas in refrigerant-poor state.

3. In method as defined in claim 1, wherein said step comprises exposing said refrigerant indirectly to communication with said auxiliary gas in refrigerant-poor state.

4. In a method as defined in claim 1; and comprising the step of causing movement of refrigerant carried by said gas exclusively in direction towards the upper exposed surface of the refrigerant in said reservoir.

5. In a method as defined in claim 1, said absorber having a lower inlet for said auxiliary gas in refrigerant-rich state, and an upper outlet from which said auxiliary gas issued in refrigerant-poor state; and further comprising the step of at least intermittent flushing with liquid of said absorber and associated portions of said conduit means at least in the region of said lower inlet.

6. In an absorption refrigeration system with a pressure equalizing gas, the combination of a generator for producing from a refrigerant solution fed into the generator a refrigerant vapor; a condenser downstream of said generator; a vapor conduit connection said generator with said condenser for feeding refrigerant vapor produced in said generatOr into said condenser; an evaporator connected with said condenser for evaporating the condensate received from said condenser; a reservoir adapted to be filled to a predetermined level with refrigerant solution and connected with said evaporator; an absorber communicating at one end with said reservoir above the level of solution therein and at the other end with said evaporator; and conduit means, including a first conduit communicating with said absorber and said evaporator and carrying said equalizing gas in refrigerant-vapor enriched state, and a second conduit communicating with said absorber and said reservoir and carrying said equalizing gas in refrigerant-vapor poor state, so that the liquid surface of refrigerant solution in said reservoir is contacted only by said equalizing gas in refrigerant-vapor poor state to thereby prevent the formation of layers of different refrigerant concentration in the refrigerant solution contained in said reservoir.

7. In an absorption refrigeration system as defined in claim 6, wherein condensate flows from said absorber into said reservoir in contact with said equalizing gas in refrigerant-vapor poor state, so that said condensate is prevented at least from absorbing significant quantities of refrigerant vapor intermediate said absorber and said reservoir.

8. In an absorption refrigeration system as defined in claim 6; and further comprising conducting means for conducting condensate from said absorber to said generator.

9. In an absorption refrigeration system as defined in claim 6, wherein said first conduit is at least substantially vertical.

10. In an absorption refrigeration system as defined in claim 9, said one end being the lower end of said absorber; and further comprising an additional conduit connecting said first conduit with said one end of said absorber so as to connect the former with the latter while serving to drain away condensate originating in said absorber.

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