US2715818A

US2715818A - Absorption refrigeration

Info

Publication number: US2715818A
Application number: US263731A
Authority: US
Inventors: Carl T Ashby; Charles A Miller
Original assignee: Servel Inc
Current assignee: Servel Inc
Priority date: 1951-12-28
Filing date: 1951-12-28
Publication date: 1955-08-23
Anticipated expiration: 1972-08-23

Description

Aug. 23, 1955 c. T. ASHBY ET AL 2,715,813

ABSORPTION REFRIGERATION I 1 Filed Dec. 28, 1951 Rs 6404 Z'As/wy (194 925.; i Ma /P W (Ill United rates Patent @ffice 2,715,818 Patented Aug. 23, 1955 ABSORPTION REFRIGERATION Carl T. Ashby and Charles A. Miller, Evansville, Ind.,

assignors to Servel, Inc., New York, N. Y., a corporation of Delaware Application December 23, 1951, Serial No. 263,731

Claims. (Cl. 62-119.5)

Our invention relates to refrigerating systems of the absorption type wherein an inert gas is used to maintain an equal total pressure throughout the system and more particularly to refrigerating systems of this type wherein a quantity of inert gas is held in reserve in a normally inactive part of the system under normal operating conditions which reserved gas is conveyed to an active part of the system to increase the total pressure therein under abnormal operating conditions.

In refrigerating systems of the above type it is common practice to provide a vent connection between active and normally inactive gas circuits, which vent may or may not include a separate vessel for holding a reserve quantity of inert gas out of circulation. Heretofore, this vent has been constructed in a manner that the inactive gas circuit is open at all times for flow of inert gas between the active and normally inactive gas circuits with the result that, under certain conditions of operation, inert gas may be short circuited from the active gas circuit through the vent and back to the active circuit.

This short circuiting may, for example, occur in absorption refrigerating systems of the air cooled type wherein the condenser is formed with two condensate drains leading from different sections thereof to different portions of the evaporator. When such a system operates under normal room temperature, say up to 80 F., all of the refrigerant vapor supplied by the generator is condensed in the first section of the condenser and the resulting liquid refrigerant fiows from this section of the condenser to the evaporator. Under these conditions the second section of the condenser, the vent line between this condenser section and the active gas circuit and the second drain between the condenser and the evaporator will be filled with inert gas weak in refrigerant Vapor.

Now then, with an increase in room temperature, say to 100 F., all of the refrigerant vapor furnished by the generator cannot be condensed in the first section of the condenser, therefore, ammonia vapor will pass into the second section of the condenser displacing the mixture of inert gas and refrigerant vapor therefrom and through the vent into the active gas circuit thereby raising the total pressure in the system with the result that refrigerant vapor begins to condense in the second section of the condenser. However, since the vent conduit, filled with a mixture of inert gas and refrigerant vapor, is in open communication with the second section of the condenser, and since the vapor pressure of refrigerant in this mixture is relatively low, the liquid refrigerant draining from the second section of the condenser will not reach the evaporator but will evaporate and diffuse into the inert gas in the second drain thereby setting up a short circuit through the second drain and the vent conduit to the active gas circuit.

An object of our invention is to prevent short circuiting of inert gas between the active and normally inactive inert gas circuits of a refrigerating system of the above type.

The above and other objects and advantages of our invention will be more fully understood from the following description taken in conjunction with the accompanying drawing in which:

Fig. l is a more or less schematic illustration of a refrigerating apparatus embodying our invention; and

Fig. 2 is a detail section of a part of the apparatus illustrated in Fig. 1.

Referring now to Fig. 1 of the drawing, our improved refrigerating system includes generally, a generator assembly 10, an air cooled condenser 11, a gas storage vessel 12, an evaporator 13, a gas heat exchanger 14, an air cooled absorber 15, a liquid heat exchanger 16, an analyzer 17 and conduits interconnecting said elements to provide circuits for flow of a refrigerating medium, an absorption solution and an inert pressure-equalizing gas. The system is charged, for example, with a refrigerant-absorbent solution wherein ammonia is the refrigerant and water the absorbent, and wherein hydrogen is the inert pressure-equalizing gas.

The generator 10 includes a pump chamber 18, a weak solution chamber 19 and a flue 20, which flue passes through the pump chamber and the weak solution chamber. Suitable means, such as a gas burner 21, is provided for heating the generator. A separating vessel 22 is connected to the upper part of the weak solution chamber 19. A vapor-lift pump 23 leads from the upper part of the pump chamber 18 and is connected to the upper end of the separating vessel 22 above the uppermost part of the weak solution chamber 19. The separating vessel 22 is connected by a conduit 24 to the lower portion of the analyzer 17, and the upper portion of the analyzer is connected by a conduit 25 to the inlet end of the condenser 11. An air cooled rectifier 26 is provided in the conduit 25.

The condenser 11 is formed of a lower section 11*- and an upper section 11 The evaporator 13 is formed of a lower section 13 and an upper section 13 The lower section 11 of the condenser is connected by a conduit 27 to the lower section 13 of the evaporator. This conduit, which forms a liquid trap between the condenser and the evaporator, is provided with a refrigerant precooler in the form of a coil 28 that is wrapped around and placed in thermal contact with the upper portion of the gas heat exchanger 14. A conduit 29 connects the outlet of section 11 of the condenser to the inlet of section 11*, and a conduit 30, in the form of a liquid trap, connects the outlet of section 11 of the condenser to the upper section 13* of the evaporator.

The weak solution chamber 19 of the generator is connected by a conduit 31, an inner pasage 32 of the liquid heat exchanger 16, and a conduit 33 to an uppermost section 15 of the absorber. A conduit 34 connects the outlet end of section 15 of the absorber to the next lower section 15' thereof. The lower portion of the absorber is connected by an absorber vessel 35, a conduit 36, an outer passage 37 of the liquid heat exchanger, a conduit 38, the analyzer 17, and a conduit 39 to the pump chamber 18 of the generator.

The upper part of the absorber is connected by a conduit 40, an outer passage 41 of the gas heat exchanger and a conduit 42 to the inert gas inlet end of section 13 of the evaporator. The inert gas outlet end of the evaporator section 13 is connected by a conduit 43 to the inert gas inlet end of the evaporator section 13 and the outlet end of this evaporator section is connected by a conduit 44, an inner passage 45 of the gas heat exchanger, a conduit 46, and the absorber vessel to the lower end of the absorber. A drain conduit 47 connects the lower part of the evaporator section '13 with the inner passage of the gas heat exchanger. Also, so that condensate may drain from the outer gas heat exchanger 14.

passage of the gas heat exchanger into conduit 46, the

' upper end of conduit 46 extends into and is slightly smaller 5 than the lower end of the conduit which forms the inner passage 45 of the gas heat exchanger.

Corning .now to the present invention we connect the upper part of the gas storage vessel 12 to the conduit 30 leading from the outlet of the condenser section 11 by a vent conduit 48. A second conduit 49 connects the lower part of the storage vessel 12 to a horizontal portion of the conduit46 between the gas heat exchanger 14 and the absorber vessel 35. As shown in Fig. 2, the

vent conduit 49 includes an enlargedportion 50, and the lower part of this conduit is submerged in a sump or trap 52 arranged in the horizontal portion of the conduit 46.

Our invention has been illustrated anddescribed in connection with a refrigerating apparatus wherein a separate'storage vessel (vessel 12) is used to hold hydrogen in reserve under normal operating conditions. However, the storage vessel, as such, may be omitted, in which case the section 11 of the condenser and the

vent conduits

48 and 49 would be constructed'and arranged so as to hold hydrogen in reserve under normal operating conditions.

The operation of the system in general is as follows:

Heat is. applied to the generator 10 by the gas burner 21. The generator contains a solution of refrigerant medium in absorption liquid, for example, ammonia dissolved in water. With heat applied to the generator, refrigerant vapor .is expelled from solution the pump chamber 18, which vapor lifts absorption solution through a the vapor-lift 23 into theupper portion of the separating vessel 22, from whence the absorption solution flows into the weak solution chamber 19 wherein additionalheat is applied to the solution in this chamber and additional refrigerant vapor is expelled therefrom. The refrigerant vapor from the vapor-lift 23 and from the weak solution chamber 19fiows from the upper portion of the vessel 22'through the conduit 24 into and through the analyzer 17 in counterflow relation with strong refrigerantabsorbent solution, which latter solution flows through the conduit 38. into the the opposite end of the analyzer. From the analyzer the refrigerant vapor flows through the conduit 25 and the rectifier 26 into the inletof section 11 of the condenser.

Assuming that the system is operating under normal temperature conditions and that the first condenser section .11? has sutlicient condensing surface so that all of the refrigerant vapors from the generator are condensed in this section of the condenser. Under these conditions conduit 29, the condenser section 11*, conduit 30, conduit 48, the gas storage vessel 12 and vent conduitr49 will be filled with a mixture of hydrogen weak in ammonia vapor, and the fiuid in these elements will stand more or less dormant; The refrigerant vapor in the con- 5 denser section 11 condenses to liquid, giving up its heat of condensation to air flowing over this condenser section, and the liquid refrigerant flows through conduit 27 and the precooler 28 into the upper part of section 13 of the evaporator. In passing through the precooler, the liquidrefrigerant is cooled by transfer of heat therefrom to cold rich gas passing through the upper portion of the Inert gas weak in refrigerant flows through conduit 42 into the gas inlet end of section 13 of the evaporator, Wherefore the-liquid refrigerant evaporates and dilfuses into the inert gas producing the desired refrigerating effect. The partially enriched inert gas flows from section 13 ofthe evaporator through conduit 43 into section 13 of the evaporator and from there, assuming that no liquid refrigerant is being conveyed to this section of the evaporator, the partially enriched inert gas flows through conduit 44, the inner passage 45 of the gas heat exchanger, conduit 46, and the absorber vessel 35 into the lower portionof the absorber.

Absorption solution weak in refrigerant is conveyed 7 of inert gas and refrigerant vapor, wherefore the refrigerant vapor is absorbed in the absorption solution. The

inert gas stripped of refrigerant vapor flows from the upper part of the absorber through conduit 40, the outer passage 41 of the gas heat exchanger and conduit 42 back to section 13*? of the evaporator.

The absorption solution enriched in refrigerant vapor flows from the lower portion of the absorber into the absorber vessel 35, and from there theenriched absorption solution flows through conduit 36, the outer passage 37 of the liquid heat exchanger, and conduit'38 into the upper portion of the analyzer 17. In the analyzer, the enriched absorption solution flows in countercurrent relation with refrigerant vapor en route from the generator.

From the analyzer, the rich absorpto the condenser. tion solution flows through conduit 39 into the pump chamber 18, wherein refrigerant vapor is expelled from solution and the absorption solution is lifted through the vapor-lift pump 23 into the separating vessel 22 of the generator, as explained above. Weak absorption solution flows from the lower portion of the weak solution chamber 19 through conduit 31, the inner passage 32 of the liquid heat exchanger, and conduit 33 back to the upper portion 15* of the absorber.

Referring now with more particularity to the present invention, the vessel 12, usually referred to as a pressure vessel, provides for a reserve quantity of hydrogen, which upon increase in ambient temperature is displaced by uncondensed ammonia vapor which flows from the condenser section 11 through conduit 48 into the vessel 12, forcing the hydrogen through vent conduit 49 and into the 'active gas circuit. Displacement of the hydrogen from storage in the vessel 12. into the active gas circuit is accompanied by a rise in total, pressure in the system 7 so that all of the ammonia vapor supplied to the condenser is condensed therein and refrigeration continues under the high ambient temperature conditions.

The control function of submerging the lower end ofv vent conduit 49 in the sump 52 may probably be best understood by first considering what would happen if the vent conduit 49 were not submerged in the sump 52. Assuming high ambient temperature conditions, all of the ammonia vapor supplied by the generator will not be condensed in the section 11 of the condenser. Under these conditions, ammonia vapor will pass through conduit 29 into section 11* of the condenser. Since the trap in conduit 30 between section 11 of the condenser andsection 13 of the evaporator is filled witha mixture of inert gas weak in refrigerant rather than with liquid refrigerant, a short circuit will be established between section 13 of the evaporator and the absorber by way of conduit 30, conduit 48, storage vessel 12, vent conduit 49, conduit 46 and the absorber vessel 35. Now then, as the total pressure in the system is, 'raised by the displacement of hydrogen from the storage vessel 12 into the active gas circuit, ammonia vapor will condense into liquid ammonia in section 11 of the condenser and drain therefrom into conduit, 30. However, since conduit 39 is filled with inert gas weak in refrigerant, the partial pressure of ammonia vapor' in this conduit will be relatively low and the liquid re- 7 frigerant that flows into this conduit will evaporate therein and the mixture of inert gas and refrigerant vapor produced thereby will flow therefrom to the absorber by way of the short circuit path just described.

With our invention, however, by submerging the lower 7 portion of the vent conduit 49 in liquid in the sump 52, short circuiting of gas between the evaporator and the absorber is prevented and refrigerant vapor condensed in the section 11 of the condenser will soon fill the trap in conduit 30 and flow therethrough into section 13 of the evaporator wherein the liquid refrigerant evaporates and diffuses into the partially enriched gas flowing therethrough from section 13 of the evaporator. It is necessary, however, for vent conduit 49 to also function in reverse. In other Words, with a return to normal operating conditions the pressure in the condenser will fall below that of the evaporator and absorber, and an equalizing effect will take place through vent conduit 49. Therefore, it is imperative that this vent conduit be submerged a fixed and constant amount. This is accomplished by placing the sump 52 in the horizontal portion of conduit 46 and using condensate from the gas heat exchanger which drains back to the absorber vessel 35 through the pipe 46 to keep the sump filled to a predetermined level. When the above mentioned pressure equalization occurs, liquid in the sump 52 will be drawn up into vent pipe 49 until this liquid reaches the enlarged portion 50 of the vent pipe where the slug of liquid will break and allow the gas to pass up through the vent pipe 49 into the pressure vessel 12. The liquid will then fall back into the sump 52.

While we have illustrated and described but one embodiment of our invention, it obviously may take other forms and be variously applied within the scope of the following claims.

What is claimed is:

1. A refrigerating system including a generator, a condenser, an evaporator, an absorber, means for supplying vaporous refrigerant to said condenser, means for conveying liquid refrigerant from said condenser to said evaporator, means for supplying absorption liquid to said absorber, means forming a circuit for circulating an inert gas between and through said evaporator and absorber, a vent conduit between said condenser and said inert gas circuit, and a connecting conduit between said vent conduit and said evaporator, said vent conduit having means therein arranged to accumulate liquid refrigerant from said evaporator to block and unblock flow of inert gas through said vent conduit responsive to a change in operating conditions within the system.

2. A refrigerating system including a generator, a condenser including a first and a second section, an evaporator including a first and a second section, an absorber and conduits interconnecting said elements and forming therewith a first circuit for flow of a refrigerating medium, a second circuit for flow of an inert pressure equalizing gas and a third circuit for flow of an absorption solution, said conduits including a first conduit connecting the first section of the condenser to the first section of the evaporator for flow of liquid refrigerant therethrongh and a second conduit connecting the second section of the condenser to the second section of the evaporator for flow of liquid refrigerant therethrough, a vent conduit connected for flow of inert gas between the refrigerating medium circuit and the inert gas circuit, and means communicating with the vent conduit and the inert gas circuit for blocking and unblocking flow of inert gas through said second conduit responsive to a change in operating conditions within the system, said means including a liquid trap connected to one of said evaporator sections for receiving liquid therefrom to fill the trap.

3. A refrigerating system as set forth in claim 2 in which said liquid trap is formed in said inert gas circuit.

4. A refrigerating system as set forth in claim 2 in which said liquid trap is formed in said inert gas circuit and in which one end of said vent conduit is submerged in liquid in said trap.

5. That improvement in the art of refrigeration by the aid of an absorption refrigerating system which comprises circulating a refrigerant through a main circuit, circulating a pressure equalizing gas through an auxiliary circuit which coincides in part with said main circuit, liquefying refrigerant at a point in said main circuit under normal conditions, passing a portion of said refrigerant beyond said point in the main circuit without being liquefied under abnormal conditions, storing excess pressure equalizing gas in said system in a third circuit which coincides in part with said auxiliary circuit, displacing the stored pressure equalizing gas into said auxiliary circuit under abnormal conditions by uncondensed refrigerant from said main circuit, blocking circulation of pressure equalizing gas in said third circuit by an accumulation of excess liquid refrigerant flowing from a point of vaporization in said main circuit, and unblocking circulation of inert gas in said third circuit responsive to an operating condition within the system.

References Cited in the file of this patent UNITED STATES PATENTS 2,069,865 Ullstrand Feb. 9, 1937 2,136,600 Ullstrand Nov. 15, 1938 2,252,791 Ullstrand Aug. 19, 1941 2,306,199 Ullstrand Dec. 22, 1942 2,402,416 Kogel June 18, 1946 2,484,669 Backstrom Oct. 11, 1949