US2473384A - Apparatus for and method of returning purged inert gas to an absorption refrigerating system - Google Patents

Description

June 14, fig-'4. MONEELY 2,473,384

APPARATUS FOR AND METHOD OF RETURNING PURGED INERT GAS TO AN ABSORPTION REFRIGERATING SYSTEM Filed Jan. 13, 1948 Patented June 14, 1949 APPARATUS FOR AND METHOD OF RETURN- ING PURGED INERT GAS TO AN ABSORP-' TION REFRIGERATIN G SYSTEM Lowell McNeely, Evansville, Ind., assignor to Servel, Inc., New York, N. Y., a corporation of Delaware Application January 13, 1948, Serial No. 2,039 8 Claims. (01. 62-119) This invention relates to refrigeration and particularly to absorption refrigerating systems of the two-pressure type.

In absorption refrigerating systems of the twopressure type, particularly such systems that operate at low pressure, non-condensable gases often collect in certain parts of the system, such as in the condenser, evaporator and/or absorber, whereby the efficiency of the refrigerating system is reduced. Various means have been provided for removing. non-condensable gases from refrigerating systems, which means generally strip the system of all non-condensable gas. However, lt has been found in practice that a small amount of non-condensable gas should. be retained and circulated through the system. Noncondensable gas forms vapor nuclei in the generator or vapor expeller,- which nuclei promote quiet boiling of the refrigerant-absorbent solution and thereby reduce superheat and its ensuing noise.

It is therefore an object of this invention to provide an improved method of and apparatus for withdrawing any excess of non-condensable gas that may accumulate in a refrigerating system of the above type, while at the same time retaining and circulating a small amount of such gas in the refrigerating system.

The invention together with its objects and advantages will be more clearly understood from the following detailed description taken in connection with the accompanying drawing, in which:

Fig. 1 is a view diagrammatically illustrating a refrigerating system embodying my invention; and

Fig. 2 is an enlarged fragmentary view of certain parts shown in Fig. 1.

="For purposes of illustration, I have incorporated my inventionin a two-pressure absorption refrigerating system like that disclosed in the United States Patent to A. R. Thomas No. 2,384,- 860 granted September l8, 1945. A system of this type operates at low pressures and includes a generator or vapor expeller I0, a condenser ii, an evaporator 12 and a main absorber 13 which arev interconnected in such a manner that flow of fluid between the high and low pressure sides of the system is regulated by liquid columns. The disclosure in the aforementioned Thomas patent may be considered as being incorporated in this application, and, if desired,- reference may be made thereto for a detailed description of th refrigerating system.

The generator includes an outer shell l Within which are disposed a, plurality of vertical riser tubes- 16 having the lower ends thereof connected to receive liquid from an inlet chamber l1 and the upper ends extending into and above the bottom of a separating vessel 18. A space I 9 within shell l5 forms a chamber to which steam is supplied through a conduit 20 from a suitable source of supply, so that full length heating of the tubes I6 is efiected. A vent 2| is provided at the upper end of shell l5, and a conduit 22 is connected to the bottom part of the shell for draining condensate from the space l9.

The system operates at a partial vacuum and contains, for example, a saline refrigerant-absorbent solution, in which water is the refrigerant and lithium chloride, lithium bromide or a mixture of the two is the absorbent. When steam is supplied. through conduit 20 to space 19 at atmospheric pressure, heat is supplied to tubes l6 for expelling water vapor from solution. The residue absorption liquid is raised through tubes It by gas or vapor-lift action. The water vapor discharged from the upper ends of the tubes or risers i6 separates from the raised absorption liquid in the vessel l8 and flows through a conduit 23 into condenser H wherein the vapor is condensed. The liquid refrigerant formed in the condenser flows through a U-tube 24 into a flash chamber 25 and from the latter through a tube 26 into evaporator 41 2.

The evaporator includes a plurality of horizontal banks of tubes 21 disposed one above the other and having heat transfer fins 28 secured thereto to provide a relativel large heat transfer surface. the evaporator is divided in any suitable manner for flow through theuppermost bank of tubes For example, the dividing of liquid may be effected by a liquid distributing trough 29 into which the liquid flows from the tube 26. The liquid refrigerant flows in successively lower tubes through suitable end connections which are open to permit escape of vapor from the tubes.

The liquid refrigerant supplied to tubes 21 evaporates therein to produce a refrigerating or coolingeffect with consequent absorption of heat from the surroundings, as from a stream of air flowing over the exterior surfaces of the tubes 21 and fins 28. The vapor formed in tubes 21 passes out into end headers 30 which are connected at their lower ends to the absorber l3. Any vapor formed in flash chamber 25 passes through a conduit 3| into one of the headers The liquid refrigerant flowing to.

and mixes with vapor formed in the evaporator l2, so that disturbances in the evaporator due to vapor flashing of incoming liquid are avoided.

In absorber l3 refrigerant vapor is absorbed into-absorption liquid entering through a conduit 32. The entering absorption liquid flows into a vessel 33 in which the liquid is distributed laterally with respect to a plurality of vertically disposed pipe banks 34 arranged alongside of each other. The liquid flows from vessel 33 through conduits 35 into a plurality of liquid holders and distributors 36 which extend lengthwise of and above the uppermost branches of the pipe banks 34. Absorption liquid is siphoned over the walls of the liquid holders 38 onto the uppermost pipe sections. Absorption liquid drips or trickles from each horizontal pipe section' onto the next lower pipe section, so that all of the pipe sections are wetted with a fllm of liquid. Absorption liquid enriched in rei'rigerant flows from absorber l3 through a con duit 31, an inner group of passages in a liquid heat exchanger 38, a conduit 39, a stabilizing vessel 40, and a conduit 4i into the inlet chamber I'I oi! the generator. Water vapor is expelled from solution in the generator by heating, andthe residue absorptionliquid is raised by gas or vapor-lift action in riser tubes l6, as explained above.

The absorption liquid in vessel It, from which refrigerant has been expelled, flows through a conduit 42, an outer group of passages in liquid heat exchanger 38, and conduit 32 into the upper part of absorber l3. This circulation of absorption liquid is eflected by raising the liquid in the vertical riser tubes is by vapor-lift action, so that liquid can flow from the generator to the absorber and return from the latter to the genorator by force of gravity.

The upper part of vessel 40 is connected by a conduit 43 to vessel I 8, so that the pressure in vessel 40 is equalized with the pressure in the upper part of the generator and in the condenser. Vessel 40 is of suilicient'volume to hold the liquid differential in the system and is o! sumcient cross-sectional area that the liquid level therein does not vary appreciably, so that a substantially constant reaction head is provided for lifting liquid in the riser tubes of the generator.

The heat liberated with absorption 01' water vapor in absorber I3 is transferred to a cooling medium, such as water, which flows upward through the vertically disposed pipe banks 34. The cooling water enters the lower end of the pipe banks through a conduit 44 and leaves the upper end of the pipe banks through a conduit 45. Conduit 45 is connected to the condenser so that the same cooling water is utilized to eflect cooling of both condenser II and absorber l3. From the condenser the cooling water flows through a conduit 46 to waste, or to a cooling tower, not shown.

During operation of the refrigerating system, non-condensable gases may collect in both the high and low pressure sides of the system. The non-condensable gases collecting in the highpressure side of the system, that is, the generator Ill and condenser H, are carried to the dead or far end of the condenser in the bottom part thereof by the sweeping efi'ect of the refrigerant vapor flowing into the condenser. Since the non-condensable gases are swept to the bottom part of the condenser, the U-tube 24 is efiectively with it the nn-c0ndensable gases collecting in the condenser and generator.

The non-condensable gases in the low-pressure side of the system, that is, in the evaporator i2 and absorber I3, are carried to the bottom center part of the absorber by the sweeping action oi the refrigerant vapor entering the top of the absorber through headers 33. In order to localize the non-condensable gases in a relatively small space, such gases are withdrawn from the bottom part of absorber l3 through a conduit 50 to the top of an auxiliary absorber iii. A small portion of the absorption liquid flowing toward the upper part of absorber i3 in conduit 32 is diverted into a conduit 52. A screen 53 removes any foreign matter in the diverted liquid that would tend to clog a flow-restricting device 54, and the restricting device in turn limits the rate at which liquid is diverted into conduit 52 from the main stream of absorption liquid flowing in conduit 32. The

auxiliary absorber is provided with plates 56 over which the diverted absorption liquid flows.

While the gases withdrawn from 'the main absorber I! through conduit 50 into auxiliary absorber II are for the most part non-condensable,

these gases are not suificiently localized in the bottom oi! the main absorber and tests have shown that refrigerant vapor accompanies the non-condensable gases withdrawn from the main absorber. For this reason the gases withdrawn from absorber l3 are brought into intimate contact with the diverted absorption liquid in the auxiliary absorber 5i, whereby the refrigerant vapor accompanying the non-condensable gases is absorbed into the absorption liquid. The heat liberated with absorption of refrigerant vapor in the auxiliary absorber is transferred to a cooling medium flowing through a coil 55 connected between theinlet conduit 44 and outlet conduit of the cooling system of the main absorber. The

absorption liquid and gases both flow downwardly in intimate contact with each other in the auxiliary absorber and the gases arrive at the bottom part oi the auxiliary absorber substantially stripped of refrigerant vapor.

The liquid flowing by gravity to the bottom part of the auxiliary absorber enters the upper end of a conduit 51 until the conduit is closed with liquid and sealed from the gases in the bottom part of the auxiliary absorber. When the liquid level rises sufliciently in the upper curved or bent portion of conduit 51, the small quantity of liquid within the open end'is siphoned past the bend into the downwardly depending straight portion thereof. When liquid is siphoned from the upper curved end of conduit 51, the liquid level falls in the bottom part of the auxiliary absorber below the upper open end of conduit 51, so that non-condensable gases pass into the upper bend or curved part of this conduit. The

liquid level-in the bottom part of the auxiliary absorber again rises to close and seal the upper end of conduit 51, and, when the liquid level again rises sumciently, a small quantity of liquid is once more siphoned into the downwardly depending straight portion oi conduit 51. In this way small quantities of non-condensable gases are withdrawn from the bottom part of the auxiliary absorber and trapped between successive be referred to as a fall tube pump, is of such size that flow of liquid is not appreciably restricted,

however. the internal diameter is such that gas to retain a given amount of non-condensable gas in circulation in the system, purge pump 51 discharges absorption solution and non-condensabie gas into the top of a gas trap 58. The absorption solution flows from the lower portion of the trap through a conduit 59 into conduit 31, which latter conduit conveys absorption solution from the main absorber l3 to the inner passage of heat exchanger 38'en route to the generator. A conduit 69 connects the gas trap 58 to a purge receiver or reservoir 68. An evacuating pump 62 is connected to the purge receiver by a conduit 63. which conduit is provid d with a valve 54. The non-condensable gas collects in the upper part of trap 58 until so much gas accumulates therein that the level of absorption solution is depressed to the point at which conduit 60 opens into the trap, after which, any excess gas pumped into trap 58 passes therefrom through conduit Gil to the purge receiver 5|.

Each time the unit shuts down, the slugs of liquid in the purge pump 51 fall into the gas trap 58 and the volume of non-condensable gas trapped in the gas trap escapes upwardly throu h fall a tube 51, auxiliary absorber 5|. and conduit 50 back to the main absorber Hi. When the unit is again started up, the absorption solution tricklin chamber 25, conduit circuit includes the generator l0, vapor separator l8, conduit 23, condenser l l, U-tube 24, flash 26, evaporator i2, absorber l3, conduit 31, the inner passage of liquid heat exchanger 38, conduit 39, stabilizin vessel 40, and conduit 4| back to the generator ill. A second main circuit includes the generator Ill, vapor separator i8, conduit 42, the outer passage of liquid heat exchanger 38, conduit 32, absorber l3, conduit 31, the inner passage of gas heat exchanger 38. conduit 39, stabilizing vessel 48, and conduit 4i back to the generator Ill. The auxiliary or by-pass circuit includes the generator i0, vapor separator 18, conduit 42, the outer passage of liquid heat'exchanger 3B, conduit 32, conduit 52, auxiliary absorber 5i, purgepu'mp 51, gas trap 58, conduit 59, conduit 31, the inner passage of gas heat exchanger 38, conduit 39, stabilizing vessel 40, and conduit 4| back to the generator i0.

Having thus disclosed my invention, I wish it to beunderstood that I do not desire to be limited to the particular structure illustrated and described, for obvious modifications may occur to a person skilled in the art.

What is claimed is:

1. An absorption refrigerating system including a high and a low-pressure side, means for collecting non-condensable gas in the low-pressure side of the system, means for entraining at least a portion oithe collected non-condensable gas into absorption solution inthe low-pressure side of the system, means for withdrawing from the downward over the pipe banks 34 in the main absorber absorb or dissolve a portion of the noncondensable gas into the absorption solution, which entrained non-condensable gas is conveyed by the absorption solution from the main absorber throu h conduit 31, liquid heat exchanger 38, conduit 39. stabilizing vessel 40. and conduit 4| into the inlet chamber l1 of the generator. In the generator. the non-condensable gas forms vapor nuclei which promote quiet boiling of the refrigerant-absorbent solution and thereby re-' duce superheat and its ensuing noise. Any excess non-condensable gas that finds its way into the main absorber, beyond that picked up by absorption solution therein, is conveyed therefrom through conduit 50. auxiliary absorber 5| and fall tube 51. into the gas trap 58, as explained above. Gas trap 58 is of such size that an optimum amount of non-condensable gas is retained in the system at all times. Any excess of non-condensable gas beyond this optimum amount is conveyed through conduit 60 to the purge receiver 6i, from whence such excess gas may be exhausted from time to time by pump 62.

The refrigerating system illustrated and described herein is generally referred to as a continuous absorption refrigerating system of the two-pressure type, in that, so long as the medium which is being cooled demands refrigeration, the system operates continuously. However, when the refrigeration demands on the system are satisfied the system shuts down until such time as the demand for refrigeration is renewed. In

other words, the system operates on on periods when there is a demand for refrigeration, and on oif periods when the demand for refrigeration is satisfied. Also, the particular refrigerating system illustrated and described herein may be said to have two main circuits or paths of flow for working media and one auxiliary or by-pass circuit for flow of working media. A first main low-pressure side of the system any collected noncondensable gas beyond that entrained in the absorption solution, and a gas trap for storing the withdrawn non-condensable gas during on' periods of operation of the system, said gas trap and said withdrawing means being so connected and arranged as to return the stored non-condensable gas to the low-pressure side of the system during oif periods of operation.

2. An absorption refrigerating apparatus including a generator, a condenser, an evaporator, an absorber, conduits interconnecting said elements for flow of a refrigerating medium and an absorption solution and a by-pass for flow of absorption solution from and to the generator, said by-pass including means for withdrawing non-condensable gasesfrom the absorber during on periods of operation of the apparatus, means for storing at least a portion of the withdrawn non-condensable gases, and means including at least a portion of said by -pass for returning the stored non-condensabie gases to the absorber during each off period of operation of the apparatus.

3. An absorption refrigerating apparatus including a generator, a condenser, an evaporator, a main absorber, conduits interconnecting said elements for flow of a refrigerating medium and an absorption solution, and a by-pass for flow of absorption solution from and to the generator, said by-pass including an auxiliary absorber, a purge pump for withdrawing non-condensable gas from the main absorber through the auxiliary absorber and a gas trap for storing the withdrawn non-condensable gas, said purge pump including a tube connected between the bottom of said auxiliary absorber and the top of said gas trap, the construction and arrangement being such that during on periods of operation of the apparatus non-condensable gas is withdrawn from said main absorber through the auxiliary absorber and stored in said gas trap, whereas, during off periods auxiliary absorber to the main absorber.

4. An absorption refrigerating system including a generator, a condenser, an evaporator, an absorber and conduits interconnecting said elements for flow of a refrigerating medium and an absorption solution, and means for retaining a given amount of non-condensable gas in said system and for exhausting from the system any accumulated non-condensable gas beyond the given of operation the stored non-condensable gas is returned from said gas trap via said tube andabsorption solution,

the generator of the system wherein the entrained amount retained therein, said last-named means including a gas trap, a fall tube pump connected between said absorber and the top of said gas trap, and a purge reservoir located above and connected to a lower portion or said gas trap, the

construction and arrangement being such that during on periods of operation of said refrigerating system non-condensable gas is withdrawn from the absorber and delivered to said gas trap until a given amount of gas is accumulated in said trap, thereafter, any non-condensable gas delivered to said trap beyond the given amount is conveyed therefrom to said purge receiver, and during oil periods of operation of said refrigerating system the given amount of non-condensable gas retained in said gas trap is returned to the absorber.

5. In the art of refrigeration through 'the agency of a two-pressure absorption refrigerating system including a generator, a' condenser, an evaporator, an absorber and conduits interconnecting said elements providing main and auxiliary circuits for flow of working media therethrough, that improvement which comprises withdrawing non-condensable gas from a main circuit of said system, storing at least a portion of the withdrawn non-condensable gas out of the main circuit during operation of the refrigerating' system, and returning the stored noncondensable gas to the main working media circult each time the system shuts down.

6. In the art of refrigeration through the agency of a two-pressure absorption refrigerating system including a generator, a condenser, an evaporator, an absorber and conduits interconnecting said elements providing main and auxiliary paths for flow of working media therethrough, that improvement which comprises withdrawing non-condensable gas from the absorber of said system, storing the withdrawn noncondensable gas out ot the main paths of flow of working media during operation of the refrigerating system, and returning the stored noncondensable gas to the absorber of said system each time the system shuts down.

7. In the art of refrigeration through the agency of an absorption refrigerating system of the two-pressure type, which system includes a generator, a condenser, an evaporator, an abde'nsable gas the absorber any excess bondensable gas beyond that entrained by the gas forms vapor nuclei which promote quite boiling of the absorption solution, withdrawing from of accumulated nonabsorption solution, storing the withdrawn noncondensable gas during on periods of operation of the system, and returning the stored non-conto the absorber during of! periods of operation of the system.

8. In the art of refrigeration through the agency of an absorption refrigerating system of the two-pressure type, which system includes a generator, a condenser, an evaporator, an absorber and conduits interconnecting said elements for flow of a refrigerating medium and an absorption solution, that improvement which comprises accumulating non-condensable gas in the absorber of said system, subjecting the accumulated non-condensable gas to absorption solution whereby at least a portion of the accumulated non-condensable gas is entrained by the absorption solution, flowing the absorption solution and entrained non-condensable gas to the generator of the system wherein the entrained gas forms vapor nuclei which promote quiet boiling of the absorption solution, withdrawing from the absorber any excess of accumulated non-condensable gas beyond that entrained by the absorption solution, storing at least a portion of the withdrawn non-condensable gas during on periods of operation of the system, returning the stored noncondensable gas to the'absorber during ofi periods of operation of the system, and exhausting from the system any excess of withdrawn non-condensable gas beyond the amount stored and returned to the absorber, whereby a given amount of noncondensable gas is retained and circulated through the system.

LOWEIL McNEELY.

REFERENCES CITED UNITED STATES PATENTS Name Date Thomas Sept. 18, 1945 Number

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