US2377319A

US2377319A - Refrigeration

Info

Publication number: US2377319A
Application number: US435491A
Authority: US
Inventors: George A Brace
Original assignee: Hoover Co
Current assignee: Hoover Co
Priority date: 1942-03-20
Filing date: 1942-03-20
Publication date: 1945-06-05
Anticipated expiration: 1962-06-05

Description

June 5, 1945. G. A. BRACE 2,377,319

REFRIGERATION Filed March 20, 1942 2 Sheets-Sheet l l llll|||| IH IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII (Ill 7 I I /Z E ||IY|Ill|Illllll||||lIIHIIIII IIIIIIIIIIIII Illlllll g Aw INVENTOR I BY 'M W ATTORNEY G. A. BRACE 2,377,319

June 5, 1945.

REFRIGERATION Filed March 20, 1942 2 Sheets-Sheet 2 fizzy-3 6601512 A. Braqe 5 ATTORNEY Patented June 5, 1945 REFRIGERATION George A. Brace, Takoma Park, D. 0., assignor to The Hoover Company, North Canton, Ohio, a

corporation of Ohio Application March 20, 1942, Serial No. 435,491

12 Claims.

This invention relates to refrigeration and more particularly to an improvement in intermittent absorption refrigerating machines of the type which use a solid absorbent, such as strontium chloride, and a refrigerant such as ammonia. In this type of absorption machine the absorbergenerator is alternately heated to drive the refrigerant from the absorbent and cooled to reabsorb the refrigerant in the absorbent. The condenser is usually spaced to one side or above the absorbergenerator and the parts of the apparatus are otherwise suitably arranged for assembly with a domestic refrigerator cabinet.

In such an apparatus during the heating period the vapor driven from the absorbent in the ab sorber-generator passes through a conduit leading to the condenser. Some of these vapors are inevitably condensed in this conduit and flow back to the absorber-generator in liquid form. The above is especially true in air cooled machines to which this invention relates. At the start of the absorption period in such machines, sudden cooling of the absorber-generator causes a rapid decrease of the internal pressure at this point, with the result that liquid refrigerant in the condenser is carried back into the absorber-generator.

It has been found that the absorbing ability of the absorbent material is greatly impaired, if not in fact destroyed, wherever contacted by liquid refrigerant. Accordingly, it is of paramount importance to take efiective measures for safeguarding the absorbent against contact by the liquid at any time. Certain attempts to deal with the foregoing problem have been proposed but have proven inadequate, untrustworthy and of limited value.

It is accordingly an object of the present inventiorn to provide an intermittent absorption refrigerator so designed and constructed that it is impossible for liquid refrigerant to return to the absorber-generator at any time and under any condition or position of the refrigerator whether in an operative or inoperative condition. More specifically, it is an object to provide means in the vapor conduit leading from the absorberenerator designed to collect and trap liquid refrigerant flowing toward the absorber-generator until such time as it can be vaporized.

Another object is to collect liquid refrigerant condensing in the vapor conduit leading from the absorber-generator during the heating period thereof, and utilizing waste heat to vaporize the same whereby to increase the emciency of the sorbent by the liquid.

apparatus while preventing damage to the ab- Another object is to trap liquid refrigerant flowing toward the absorber-generator from the condenser at the beginning of a cooling period.

Still another object is to so construct a liquid trap that liquid cannot flow to the absorber-generator regardless of the position of the apparatus during shipment or other handling.

A further object of the invention is to provide a novel and more eflicient method of producing refrigeration.

Other objects and advantages of this invention will become apparent as the description proceeds when taken in connection with the accompanying drawings in which:

Figure 1 is a diagrammatic representation of an intermittent absorption machine with this invention applied thereto;

Figure 2 is a vertical sectional view of the absorber-generator according to this invention; and

Figure 3 is a cross sectional view of the absorber generator of Figure 2 taken on line 3-3 of 2 and 3 comprises an outer cylindrical wall l6, an'intermediate cylindrical wall l8, and an iimer' cylindrical wall 20. The inner cylindrical wall 2|! has indentedportions 2| whichcontact with the intermediate cylindrical wall [8 for a purpose to be described hereinafter. The outer cylindrical wall l6 and the intermediate cylindrical wall l8 are connected at the ends by end walls 22 welded thereto to form an absorbent medium chamber which is divided into a plurality of small chambers by plates 24 secured in good heat conducting relationship to the intermediate wall I8. Each of the plates 24 has a plurality of openings 26 therein.

As shown in Figure 2, tube 20 forming the heating chamber extends above both the cooling and.

the absorbent chambers for some distance. Secured to the. extended portion of this tube is a chamber 28 of sufilcient size to hold the maximum quantity of liquid refrigerant which would ever be present in vapor conduit l0 during any normal or abnormal condition of the apparatus.

A conduit 2! extends from the absorbent chamber to a point adjacent the uppermost portion of chamber ll and provides a passage for the free flow of refrigerant vapor to or from the absorbergenerator. As will be obvious from Figure 2, the relationship of chamber 28 and conduit 29 is such that any liquid flowing downwardly through vapor conduit l collects in chamber 28 and is trapped therein. If the upper end of conduit 29 terminates adjacent the heating chamber wall 20, and if the left hand side of chamber 28 is made larger than presently shown in Figure 2, as is preferable, it is impossible for liquid to return to the absorbent chamber regardless of the position in which the apparatus may be placed during shipment or other handling.

The intermediate wall l8 extends above the outer annular wall It and is bent inwardly at 10 and welded to the inner cylindrical wall 20.

. wall and the intermediate wall i 8 forms a cooling chamber or heat exchange device of an indirect cooling circuit for the absorber-generator A. The entire absorber-generator, including the liquid trap, is suitably enclosed in heat insulating material to reduce heat losses to a minimum.

The inner annular wall 20 may form a combustion flue for the absorber-generator A when a liquid or gaseous fuel burner is used or, as shown in Figure 1, may form the housing for a suitable electric'heating element 32. The struck out portions II of the inner cylindrical wall which contact with the intermediate cylindrical wall I! form a good thermal path for transferring heat from the heating element 32 to the solid absorbent in the annular chamber between the outer cylindrical wall l8 and the intermediate cylindrical wall l8 during the heating period, and for cooling the absorber-generator uniformly throughout its height during the cooling period. This later function is facilitated by indentations II which divide the annular cooling chamber into vapor lift pumps by means of which the cooling liquid is continually circulated to the upper part of the chamber by rising bubbles of vaporizing cooling liquid.

The upper end of the annular space between the walls is and 20 is connected by conduit 34 to the upper end of the secondary condenser 38. The secondary condenser 36 has a continuous downward slope throughout and leads to a reservoir 3|. The reservoir 38 is connected by conduit M to a valve chamber 42. The valve chamber 42 is connected by conduit 44 to the lower end of the space between the annular walls l8 and 20. The valve 48 is designed to be operated by a1 snap acting device 48 of any suitable construct on.

The conduits Ill of the evaporator E extend downwardly from the bottom of the receiving chamber II and are in direct thermal contact with the ice freezing chamber 5 I. From the lower ends of the conduits 50 extend conduits 52 which are bent backwardly and forwardly in the form of a sinuous coil having a continuous upward slope and enter the receiving chamber l4 above the point of connection of the conduits 50.

A thermostatic bulb 56 contacts the outer surface of the absorber-generator A and is connected by a capillary tube 58 to a bellows 60 which upon expansion and contraction is adapted to operate the snap acting device 48. The bulb ll, tube 58 and bellows 60 are filled with a sui able thermally responsive fluid so that the bellows M will expand and contract upon variations in temperature of the bulb II as is well known in the art. A snap acting switch I! of any suitable construction is positioned to be actuated by the snap acting device 48.

A thermostatic bulb 64 in thermal contact with the freezing chamber ii is connected by a capillary tube 88 to a bellows I. The bulb i4, tube 60 and bellows 68 are filled with a suitable vaporizable fluid so that the bellows 68 will expand and contract upon variations in temperature of the ice freezing chamber 5| as is well known in the art. Upon expansion and contraction the bellows BI is adapted to actuate a snap acting device III which in turn operates the valve 12 in the conduit 40 and an electric switch 14.

One side of the power line is connected to one side of the switch 14. The other side of the switch 14 is connected by a-suitable conductor, as shown. to one of the contacts of switch 62. The other contact of switch 82 is connected by a suitable conductor to one side of the heating element 32, the other side of which is connected to the other side of the power line.

The absorber-generator A is charged with a suitable solid absorbent such as strontium chloride and a refrigerant such as ammonia, while the indirect cooling system is charged with a vaporizable medium such as methyl chloride. all-as is well known in the art. When strontium chloride absorbs ammonia, addition compounds, such as SrCln.lNHa, SrClaZNHh, SrClzANH: and SlCl2.8NH3 are formed. As the addition compounds are formed, strontium chloride expands and when 8 molecules of ammonia have been absorbed for every molecule of strontium chloride, it will occupy a volume of approximately 2% times its original volume.

Preferably sumcient strontium chloride is charged into the absorber-generator, that the walls thereof will remain under pressure due to the expanded strontium chloride even at the end of the generating period of the absorber-generator. When the absorber-generator is fully charged with ammonia, its walls will of course be under a greater pressure due to the expanded absorbent. s

The indirect cooling circuit for the absorbergenerator A is suitably charged with a vaporizable liquid such as methyl chloride. The

pressure within the indirect cooling circuit when using methyl chloride is relatively low; hence, the snap acting device 48 may be led into the interior of the valve chamber 42 through a suitable flexible ioint I6.

As shown in Figure 1, the bellows 8B is in an expanded position with the result that the valve 12 is open and the switch 14 is closed. The switch 82 is set so that electricity will be conducted to the heating element 32 of the absorber-generator A which will be heated. The bellows BI is contracted with the result that the snap acting device 48 will be positioned to the left and the valve ll will be closed.

With the control set as in Figure 1 the heating of the absorber-generator A by the heating element will drive refrigerant vapor from the solid absorbent contained therein. This refrigerant vapor will pass by the conduit 29, chamber 28 and conduit II to the condenser C where it will condense and the heat of condensation will be carried away by air flowing over the heat reiectingilns mounted on the tubes in the absorber-generator A some of the refrigerant vapor may condense in the conduit I and flowi'.

backwardly toward the absorber-generator Ar? This is particularly true at the beginning of the heating period at which time conduit I0 is cold and consequently serves as a fairly efilcient con denser. However, by reason of the construction hereinabove described, liquid condensed in conduit cannot reach the absorber-generator, but instead becomes trapped in chamber 26. After a short" period of operation, trap 28 will become heated by waste heat not absorbed by the absorber-generator proper. As a result, the liquid will vaporize and pass to the condenser and the evaporator where it is available to produce refrigeration at a later time. Thus, the liquid is automatically removed from the trap as it collects without expense and by the use of waste heat.

During the heating of the generator-absorber A the small amount of auxiliary cooling fluid which may remain in the space between the cylinders I8 and of the generator-absorber A will quickly vaporize and flow by conduit 34 into tne secondary condenser 36. The air flowing over the fins in the condenser 36 will carry away the heat of condensation of the auxiliary fluid whereby it will condense and flow downwardly through the tubes of the condenser 36 into the reservoir 38. This liquid auxiliary cooling fluid cannot return to the absorber-generator A at this time because the valve 45 is closed.

As soon as the refrigerant has been liberated from the absorbent in the absorber-generator A, the temperature of the absorber-generator A will rise abruptly even though the heat applied to the absorber-generator A remains constant. This comes about by reason of the fact that so long as refrigerant is being driven from the solid absorbent the heat supplied thereto is utilized to vaporize the refrigerant, but after the refrigerant is vaporized. the heat supplied quickly raises the temperatures of the absorber-generator to a much higher value.

This raised temperature will cause the liquid in the bulb 56 to operate bellows 60, and push the snap acting device 48 to the right. As the snap acting device 48 moves to the right, it will operate switch 62 to de-energize the heating element 32 and to open the valve 46.

The indirect cooling system is charged with suflicient auxiliary cooling medium, so that the reservoir 38 will always contain cooling medium in liquid form. When the control operates to open the valve 46, the liquid in the reservoir 38 will be dumped into the space between the walls l8 and 20 of the absorber-generator A. Since the absorber-generator A is hot at this time the -auxiliary cooling fluid will be quickly vaporized evaporator E will begin. The vapor so formed will return to the absorber-generator A through conduit l2, condenser C, conduit l0, chamber 28 and conduit 29.

At the end of the generating period, some liquid refrigerant is likely to be present in condenser C, and possibly in conduit l6. Since, immediately upon the termination of the generating period, cooling liquid is admitted to the cooling compartment of the absorber-generator, both the temperature and the internal pressure of the absorber-generator decreases abruptly. As a consequence, there is a flow of vapor through the condenser in the direction of the absorber-generator of sufllcient magnitude to carry the liquid refrigerant with it. However, trap 28 separates the liquid from the vapor and retains it while permitting the vapor to continue to the absorbergenerator where it is absorbed.

Due to the much lower internal pressure existing during the cooling period, liquid collecting in the trap readily vaporizes and mingles with the main stream of returning vapor.

As absorption proceeds in the absorber-generator A, the heat of absorption is transferred to the auxiliary cooling fluid in the space between the walls l6 and 20, This vaporizes the auxiliary liquid and this vapor flows to the secondary condenser 36 by conduit 34. The vapor is condensed and the heat of condensation is carried away by air flowing over the heat rejecting fins on the condenser 36. The tubes of the condenser 36 have a continuous downward slope and the liquid auxiliary cooling fluid returns to the reservoir 36 to be returned in due time to the space between the walls l8 and 20 for further cooling action.

When all of the refrigerant in the evaporator E is evaporated, absorption will cease in the absorbeli=geherator A with the result that no more heat will be generated therein and its temperature will be lowered to substantially room temperature by the circulating cooling medium. This will cause the fluid in the bulb 56 to contract suiflciently to collapse the bellows 60 and to shift the snap acting device 46 to the left. In this regard it is to be noted that the bellows 66 and snap acting device 46 are set so that the snap acting device will be moved to the left at the highest room temperature liable to be encountered so as to assure that the unit will always be returned to the generating period under any operating conditions.

The valve in the chamber 42 will be closed so that the cooling medium cannot flow to the absorber-generator A through the conduit 44, and the switch 62 will be closed so as to energize the heating element 32. The fluid in the cooling pocket of the absorber-generator A will be quickly vaporized therein by the heat supplied by the heating element 32, and the vapor will pass to the condenser 36 where it will be liquefied and flow to the receiver 36 for subsequent use in producing refrigeration.

The absorber-generator A will thus automatically operate alternately on an absorption and a generating period as the temperature thereof rises and falls without the necessity of providing any additional control. In the particular application of the invention herein disclosed by way 01 illustration, the bulb 64, bellows 68, switch 14 and valve 12 are so designed and adjusted that the temperature of the evaporator E will not fail to a value below that desired in a domestic refrigerator. It will of course be understood that in other applications of the invention,

thermostat

64, 66, valve 12, switch 14 could be omitted. In this event the apparatus would operate automatically under the control of

thermostat

56, 60, as will be readily apparent.

When the temperature of the freezing chamber 6i goes to a desired low value, which may be appreciably below the average temperature of the food storage space of a domestic refrigerator, the bulb M will operate to collapse the bellows I and operate to close the valve 12 and open the switch ll. This will operate to de-energiae the heating element 32 if the system is on the heating period and to close the valve 12 to stop the flow of cooling fluid if the absorber-generator is on the absorption period.

If the absorber-generator A is on the absorption period, the liquid cooling medium in the space between the walls II and 20 will soon vaporize due to the heat of absorption and will pass through the secondary condenser 30 where it will be condensed. Since the tubes of the secondary condenser I. slope towards the reservoir 88, this condensed liquid cannot return to the coolin space of the absorber-generator A but will flow to the reservoir ll and be trapped out of circuit by the closed valve II. When the absorption of refrigerant vapor in the absorber-generator ceases, no more liquid refrigerant will evaporate in the evaporator. Thereafter the temperature of the air in the storage space will slowly rise until the control bellows ll again acts to open the valve 12 and to close the switch ll. The unit will then continue to operate alternately on the absorption and generating periods as previously described.

While the invention has been shown and described as applied to an intermittent absorption machine having a single absorber-generator, it is to be understood that it is equally applicable to one having two absorber generators operating a1- ternately and two evaporators operating alternately to provide continuous refrigeration.

From the foregoing it can be seen that this invention provides a novel intermittent absorption refrigerating machine in which th absorbent is protected against contact by liquid refrigerant at all times and under all conditions and on all positions of the machine.

Any refrigerant which may collect in the conduit leading from the absorber generator to the condenser during the generating period will be trapped in the vessel 28 where it is vaporized by waste heat. Any liquid refrigerant which may be carried toward the absorber-generator by returning refrigerant vapor at the start of the absorption period will likewise be trapped in the vessel 28 and vaporized.

While I have shown but a single embodiment of my invention, it is to be understood that this embodiment is to be taken as illustrative only and not in a limiting sense, I do not wish to be limited to the particular arrangement shown and described but to include all equivalent variations thereof except as limited by the scope of the claims.

I claim:

1. An intermittent absorption refrigerating machine including an absorber-generator having an absorbent receiving chamber charged with a refrigerant and an absorbent the absorbing characteristics of which are subject to impairment if the same is contacted by liquid refrigerant, a condenser above said absorber-generator, a conduit leading from said absorber-generator to said condenser, a heating tube for said absorber-generator, and a liquid trap in said conduit above said absorber-generator in direct heat exchange relationship with said heating tube and connected to said absorbent receiving chamber by an upwardly extending vapor conduit.

2. An intermittent absorption refrigerating machine including an absorber-generator, a condenser, a conduit leading from said absorbergenerator to said condenser, a heating tube for said absorber-generator, an indirect cooling circuit for said absorber-generator having a heat exchange chamber surrounding said heating tube and a liquid trap in said conduit in heat exchange relationship with said heating tube above said heat exchange chamber.

3. An absorber-generator for an intermittent absorption refrigerator comprising, means providing a heating chamber, a heat exchange chamber surrounding said heating chamber, means for connecting said heat exchange chamber to a source of cooling fluid, an absorbent receiving chamber surrounding said heat exchange chamber, and aliquid trap communicating with said absorbent receiving chamber constructed to prevent liquid which may collect therein from nowing to the absorber-generator, said trap surrounding said heating chamber and being in direct heat exchange relationship therewith.

4. An absorber-generator for an intermittent absorption refrigerator comprising a cylindrical heating chamber, means cooperating with said chamber to form a cylindrical heat exchange chamber surrounding said heating chamber, means for connecting said heat exchange chamber to a source of cooling fluid, and means forming an absorbent receiving chamber surrounding said heat exchange chamber, said heating chamber having a plurality of spaced apart indentations therein extending into said heat exchange chamber and forming with the inner wall of said absorbent receiving chamber a plurality of fluid passages at an angle to the horizontal.

5. An intermittent absorption refrigeration machine including an absorber-generator, a condenser, a conduit leading from said absorbergenerator to said condenser, a heating chamber for said absorber-generator, an indirect cooling circuit for said absorber-generator including a heat exchange chamber surrounding said heating chamber, an absorbent receiving chamber surrounding said heat exchange chamber and a liquid storage chamber in said conduit above said heat exchange chamber in heat exchange relationship with said heating tube.

6. An intermittent absorption refrigerating machine as described in the preceding claim characterized in that said heating chamber has indentations therein extending into said heat exchange chamber and cooperating therewith to provide narrow elongated fluid passages.

7. An absorber-generator for an intermittent absorption refrigerating machine comprising a cylindrical heating tube, an annular heat exchange chamber surrounding said heating tube, means for connecting said eat exchange chamber to a source of cooling'fluid, an annular absorption receiving chamber surrounding said heat exchange chamber, an annular liquid trap above said heat exchange chamber surrounding said heating tube and in direct heat exchange relationship therewith and a vapor duct connected to said absorbent receiving chamber and said liquid trap.

8. An absorber-generator for an intermittent absorption refrigerating machine comprising a cylindrical heating tube, an annular heat exchange chamber surrounding said heatlng tube, means for connecting said heat exchange chamber to a source of cooling fluid, an annular absorbent receiving chamber surrounding said heat exchange chamber, an annular liquid trap above said heat exchange chamber surrounding said heating tube and in direct heat exchange relationship therewith and a vapor duct connecting said absorbent receiving chamber and said liquid trap, said heating tube having indentations therein extending into said annular heat exchange chamber into heat exchange relationship with the inner wall of said absorbent receiving chamber.

9. An intermittent absorption refrigerating machine including an absorber-generator having an absorbent receiving chamber charged with a refrigerant and an absorbent, the absorbing characteristics of which are subject to impairment if the same is contacted by liquid refrigerant, a condenser, a heating tube for said absorber-generator, and a liquid trap insaid conduit in direct heat exchange relationship with said heating tube and connected to said absorbent-receiving chamber by a vapor conduit, said trap being so constructed and arranged as to hold all of theliquid refrigerant with which the machine is charged regardless of the position in which the machine is placed.

- 10. An absorber-generator for an intermittent absorption refrigerating machine comprising a cylindrical heating tube, an annular heat exchange chamber surrounding said heating tube, an annular absorption receiving chamber surrounding said heat exchange chamber, an annular liquid trap above said heat exchange chamber surrounding said heating tube and in direct heat exchange relationship therewith and a vapor duct connecting said absorbent-receiving chamber and said liquid trap, said trap being so constructed and arranged as to hold all of the liquid refrigerant with which the machine is charged regardless of the position in which it may be placed.

11. An absorber-generator for an intermittent absorption refrigerating machine comprising a cylindrical heating tube, an annular heat exchange chamber surrounding said heating tube and connected to a cooling circuit, an annular absorbent-receiving chamber surrounding said heat exchange chamber, an annular liquid trap above said heat exchange chamber surrounding said heating tube and in direct heat exchange relationship therewith and a vapor duct connecting said absorbent-receiving chamber and said liquid trap, and said absorber-generator, trap and connecting vapor duct being imbedded in insulation.

12.An intermittent absorption refrigerating machine including an absorber-generator having an absorbent-receiving chamber charged with a refrigerant and an absorbent, the absorbing characteristics of which are subject to impairment if the same is contacted by liquid refrigerant, a condenser, a conduit leading from said absorber.- generator to said condenser, a heating tube for said, absorber-generator and'a/liquid trap in said conduit in direct heat exchange relationship with said heating tube and connected to said absorbent-receiving chamber by an upwardly extending vapor conduit, said absorber-generator, liquid trap and connecting vapor conduit being imbedded in insulation.

GEO. A. BRACE.