US2321929A - Absorption refrigeration system - Google Patents

Description

WR. M qmms ABSjORPTION REFRIGERATION SYSTEM [i u 0 N G M a- VNN m P 2 E WM m m Mi H w A T ofi jgml Filed June 13-; 193 9 STRONG AQUA PUMP I TO RECEIV ER CONDENSER.

GENERATOR SU EGE. DRUM HEADER.

STEAM 3nventor attorneys con ENSATE HEADER,

generator was large.

Patented June 15, 1943 ABSORPTION REFRIGERATION SYSTEM Walter R. McGinnis, York, Pa., assignor to Yon-h Ice Machinery Corporation, York, Pa., a corporation oi Delaware 1942, Serial No. 444,072

11 Claims. (or. 52- 119) in the generator prevents rapid adjustment to This invention relates to refrigeration systems of the absorption type utilizing a volatile refrigerant such as ammonia and a volatile solvent such as water. More particularly, it relates to an improved generator for use in such systems.

The present application is a division of my parent application Serial No. 278,949, filed June 13, 1939, now Patent No. 2,287,441. While it is preferably employed with systems of the type disclosed in that application, it is useful in absorption systems of types other than the one illustrated. This disclosure is intended to be read with that understanding.

The system described in the above application is an improvement on prior art systems in that among other changes it substitutes for the usual analyzer-dehydrator combination a bubble tower having a lateral connection for strong aqua return, and an anhydrous ammonia connection 1;- application June 13, 1939', Serial No. 278,949. Divided and this application May 22,

changing load conditions.

The present invention aimsto improve the circulation caused by thermal action and to supplement it by positive circulating means which is efiective under all load conditions and under all temperature differentials. Systems embodying generators of the improved type employing positive circulation avoid the disadvantages of prior systems, and are characterized by their flexibility and by their ability to adjust themselves to different conditions and different loadsby mere change in steam flow without unbalancing'the system.

For purposes of illustration the improved type of generator will be described as applied to a system of the type disclosed in the above parent v application without, however, limitation to use in systems oi" that type. In the drawing:

near the top. This arrangement has been found Fig. 1 is a flow sheet showin e ain of the to be particularly eflicient in producing substan- Systems of this type are, therefore, characterized by simplified structure, flexibility of operation, low steam consumption and substantialfreedom from purging operations. The gas leaving the generator is cooled to approximate the condensing temperature, and the ammonia gas is dehydrated to a much greater degree than has been possible with apparatus of the prior art. The liquid anhydrous ammonia condenses the, water vapor out of the ammonia gas and in so doing is completely re-evaporated and re-enters the condenser from the top of the bubble tower. The strong aqua feed to the bubble tower. performs'the function of desuperheating the vapors passing upwardly through the tower from the generator.

- In the prior art it was customary to use a shell and tube generator in which the aqua surrounded the tubes and the heating medium passed through the tubes. The circulation of the aqua in contact with the tubes was simply that caused by ebullition, and because this circulation was of low velocity, the heat transfer rate was low. For this reason it was necessary to use a large shelland a large heating surface with the attendant result that the charge of aqua'ammonia in the Such a generator, whilerather inefiicient, is reasonably satisfactory at uniform loads, but it is particularly inefilcient on essential elements of a refrigeration'system of the absorption type utilizing the generator of the present invention; and

Fig. 2 is a sectional view through one of the heating elements of the generator.-

In Fig. 1 the generator G is shown in an ab sorption system. The system includes a bubble tower T, a heat exchanger 8, a strong aqua pump 1, and a condenser C which delivers substantially anhydrous ammonia. to a receiver in the usual manner. The absorber, receiver and evaporator are not shown. The strong aqua tank 6 is arranged to receive strong aqua from the absorber and deliver it to the strong aqua pump whence it passes through the exchanger 8 in heat exchanging relation with the weak aqua delivered to the exchanger from the generator G. It is i3 from the tower T alone, or in conjunction with return line 26 through the by-pass valve 39. The drum has a vapor outlet l4 connected to the bottom chamber of the tower, and a weak aqua outlet l5 which delivers weak aqua to an absorber through exchanger 8. Connected to the surge drum 9 in parallel relation with one another are a plurality ofv heater units or calandrias preferablyof the shell and tube type, adapted to be appliedwith a heating medium such as changing loads because the large charge of aqua steam from a header l6.

Each of these calandrias comprises a shell or casing l1 having a top header l8 connected by,

a horizontal tube to the drum} and a bottom header I! connected through a pipe 2| to a vertical pipe 22 leading into the bottom of the surge drum. The headers are connected by riser tubes 23. The arrangement is such that the ammonia-water solution in the surge drum may circulate from the 'drum downwardly through pipes 22, horizontally through pipes 2| and headers l9 and up through riser tubes 23 to the top headers l3 and back to the surge drum. Steam supplied through'the header l6 passes into the casings l1 and when condensed flows out to a common condensate return header 25. The heat delivered by this steam and controllable by valves 26 induces a thermal circulation through each calandria by thermo-siphon action, and also by the gas lift resulting when the ammonia gas rises through the tubes after being driven from the water. This action is a marked improvement over prior art arrangements where the heating medium passed through the tubes which were submerged in the aqua.

In addition. to the thermal circulation, positive pressure circulation is provided for. The strong aqua from pump I is delivered to a header 23 and thence to each of a plurality of pipes 2i. The pressure of the pump is augmented by placing in each of these pipes 2| a jet typ circulator or ejector comprising a restricted throat 21 controllable by a valve 23. The .valve 23 controls the flow of strong aqua under pressure to nozzle 3| which directs a jet into the throat 21 and thus positivelyinduces aqua circulation through the calandria regardless oftemperature condi tions. It will be understood that although three calandrias are shown, it is possible according to the present invention to use any desired number of these units or to use one of these units alone,

according to the amount oi aqua to be circulated and heated. ejectors and to rely upon the pressure of the pump alone, or even to omit this connection and rely solely upon the thermal circulation in small installations.

It is also practicable to omit the The liquid level in surge drum 9 is above the upper tube sheets of the calandrias and cross baiiles 32 partially segregate different portionsof the drums associated with the various calandrias. These baifles 32 also serve to restrict longitudinal flow of aqua in the surge drum. with the arrangement shown, the concentration of the adjusted so as to secure proper and uniform circulation through each heater, thereby securing high heat transfer rates in each heater.

It will be understood that the flow of steam to each of the calandrias may be controlled individually by the control valves 26. The drip valves 84 are normally wide open, condensate line 25 being connected to a suitable steam trap, not shown. Similarly, the electors may be controlled by manipulation of the valves 28 to proportion the circulation through the various heaters or calandrias to control the heat transfer rates as above suggested.

The end of the surge drum 9 adjacent the weak aqua discharge Ii embodies a liquid level responsive float disposed in a chamber 33 having a connection 35 to the top 01. the surge drum and a similar connection ll to the bottom of that drum. The float serves to control the supply of air under pressure from pipe 33 to the pneumatic motor which controls valve II. In this way, the liquid level float in chamber ,33 regulates the amount of strong aqua which is returned to the generator from the absorber, and maintains the aqua in the surge drum at a proper level. An initial or approximate adjustment is made by the manually controlled valves l2 and 39.

The ejectors associated with the individual heaters being supplied directly with strong aqua under pressure from pump I insure direct and positive circulation of the aqua up through the heaters regardless of the temperature diflerentials which would normally have to be relied upon to produce adequate thermal circulation. This arrangement for the first time insures adequate circulation in the heater at low temperatures and during slight changes of load, and hence substantially improves the flexibility, economy, and responsiveness of any system to which this improved type oi generator is applied.

What is claimed is:

1. In an absorption refrigeration system of the ammonia-water type, a source oi strong aqua under pressure; a generator comprising a surge drum and a plurality of aqua heating units of the surface type connected in parallel relation with one another to the surge drum; means connected to said strong aqua source for causing circulation of the aqua in said heating units; a heat source for supplying said parallel heating units; and a connection for withdrawing weak aqua from the surge drum.

2. In an absorption refrigeration system of the ammonia-water type, a source of strong aqua under pressure; a generator comprising a surge drum connected to said source and a shell and tube structure having two headers, one connected to the low portion of said drum and the other toa higher portion of the drum, and at least one interposed riser tube; means for heating said shell and tube structure to cause thermal circulation of aqua from one 01' said headers to the other through said tube and said surge drum; and means for delivering said aqua under pressure from said source to the bottom of said shell and tube structure and causing it to augment the aqua flow therein.

3. In an absorption refrigeration system .0 the ammonia-water type, a source of strong aqua under pressure a generator comprising a surge drum connected to said source and a shell and tube structure having two headers one connected to the low portion of said drum and the other to a higher portion of the drum, and riser tubes connecting said headers; means for heating said shell and tube structure to cause circulation of aqua from one of said headers to the other through said tubes and said surge drum; and

weak aqua respectively; a plurality of spaced transverse segregating baiiies mounted in said 8. In an absorption refrigeration system ofthe ammonia-water type, a source of strong aqua drum so as to ailord limited liquid flow past said baiiies; a plurality of aqua heaters connected in parallel circuits with said drum, said heaters comprising inlet headers connected to the bottom of said drum, and outlet headers connected to higher portions of said drum and riser tubes connecting said headers; means for supplying heating fluid to said heaters to induce aqua circulation between said headers and through the spaces in said drumbetween said bailles; and ejector means disposed in the inlet to each bottom header and connected to said strong aqua source for stimulating the circulation of liquid and vapor in said heaters. V 1 g 5. In an absorption refrigeration system of the ammonia-water type, a source of strong aqua under pressure; a generator comprising a surge drum, a heater connected to said surge drum, and means for supplying heating medium to said heate to cause circulation of aqua between said heater and said drum; and means connected between said source of strong aqua and the lower portion of said heater for assisting circulation of aqua through the heater.

6. -In an absorption refrigerating system of the ammonia-water type, a source of strong aqua under pressure; a generator comprising a substantially horizontal surge drum having a weak aqua d scharge connection, transverse baiiies extending across the lower part of said drum at intervals, and an ofltake for gaseous ammonia; a plurality of surface type heaters arranged to afford rising paths for the heated liquid, succesammonia-water type, a source of strong aqua under pressure; a generator comprising a surge drum connected to said source and a shell and tube structure having two headers one connected to the low portion of said drum and the other to a higher portion of the drum, and riser tubes consive heaters serving successive inter-.baflie intervals and each having a supply connection leading from the bottom of the drum to the lower' end of the heater, and a discharge connection leading from the upper end of'the heater to the drum approximately at the level of the tops of the battles; and means for supplying heating mediam to said heaters.

7, In an absorption refrigerating system of the Y .ing across the lowerpart of said drum at inter-.--

vals. and an oii'take for gaseous ammonia; a pin rality of surface type heaters arranged to aflord rising paths for the heated liquid, successive-heaters serving successive inter-baiiie intervals and each having a supply connection leading from the bottom of the drum to the lower end of the heater, and.a discharge connection leading from the upper end of the heater to'the drum approxi mateiy at the. level of the tops of the baiiies; jet type circulators' interposed in the supply connections to the heaters: and connections for conducting strong aqua from said source to said circulators and thence through said heaters to said drum.

necting. said headers; means for heating said shell and tube structure to cause circulation of aqua from one of said headers to the other through said tubes and said. surge drum; and

.means connecting the bottom header of said shell and tube structure to said source of strong aqua for assisting the upward flow of aqua through said riser tubes.

10. In an absorption refrigeration system of the ammonia-water type. a generator comprising a surge drum; means for supplying strong aqua to sa d drum and discharging weak aqua from said drum; a heater for said drum and havin spaced top and bottom headers; means connecting the top header to the upper part of said drum and the lower heade tothe bottom of said drum; a plural ty of riser tubes connecting said headers;

' and means for supplying heating medium into thermal contact with said riser tubes to cause header and upwardly through said riser tubes to spaced top and bottom headers; means connect-- ing the top header to the upper part of said drum and the lower header to the bottom of said drum; aplurality ofriser tubes connecting said headers;

means for delivering heating medium into heat exchanging relation with said riser tubes to cause circulation of aqua from said drum to said lower header and upwardly through said riser tubes;

' and means connecting said strong aqua supply means to the aqua circuit to assist the action of the heating medium in causing flow oi! aqua through said drum, said headers and said riser 7 tubes.

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