US2855766A - Absorption refrigerating units and refrigerators - Google Patents

Description

Oct. 14, 1958 T. M. ELFVING ETAL 2,355,766

' ABSORPTION REFRIGERATING UNITS AND REFRIGERATORS Filed May 2s. 1952 THORE M. ELFvlNG, LARS B. CHRISTENSEN United States Patent Thore M. Elfving and Lars Bendix San Mateo, Calif.

Application May 23, 1952, Serial No. 289,481 4 Claims. (Cl. 62-493) Christensen,

This invention relates to absorption refrigerating units and to refrigerators, `especially domestic refrigerators, provided with absorption refrigerating units of the continuously operating type comprising three partly coinciding fluid cycles, viz. a closed circuit of gaseous refrigerant expelled by heat from a liquid in which it was absorbed and thereupon liquefied in a condenser and evaporated in an evaporator to be subsequently re-absorbed in the aforementioned liquid, another closed circuit performed by the said absorbing liquid driven by a thermos'yphonic pump through a boiler and the above-mentioned absorber with adjoining liquid vessel, and a third closed circuit performed by an inert gas through the absorber and the evaporator under the influence of the difference in specific weight of the gas leaving the evaporator enriched with gaseous refrigerant and the poor gas leaving the absorber, the evaporator being located at a suitably higher level than the absorber.

This gas circulation circuit includes a heat exchanger between the branches of the circuit which to a great extent reducesloss of refrigeration capacity by intercepting a part of the heat transferred with the inert gas from the absorber to the evaporator,

A main object of'this invention is to further reduce heat transferwith the inert gas from the absorber to the evaporator in order to increase the refrigerating capacity and the efficiency of the apparatus.

Another object of the invention is to improve the utilization of the remaining cooling capacity of the gas mixture leaving the evaporator by conducting it inside the current of inert gas to the evaporator.

Another object of the invention is to avoid condensation on the conduits connecting the evaporator withy the other components of the unit, so as to avoid undesired drip of water condensed from the atmosphere, rust formation, and loss in refrigerating capacity.

Other objects and features of the invention will appear from the following description.

In refrigerating systems of the above type the total driving force of the gravitational inert gas circulation and the total vgas iiow resistance of the inert -gas circulation circuit should be correlated in such a manner that the volume of inert gas passing through the evaporator per time unit is at least sufficient for evaporating the liquid refrigerant at a rate corresponding to the desired refrigerationy capacity of the evaporator. The equilibrium of the amount of circulating inert gas and the amount of evaporated refrigerant for a certain refrigeration capacity varies both with the evaporator temperature and with the absorber conditions, but it is also to a great extent depending upon the distribution of the `flow resistance in Athe gas circuit. i i

This invention provides for such a distribution of the gas circulation resistance in the inert gas circuit that the resistance of the gas heat exchanger comprises at least 75% ofthe total iiow resistance in said circuit. This .comparatively high resistance of the heat exchanger is ice according to the invention utilized for providing an improved efficiency of the heat exchanger by increasing the heat vtransmission properties of the heat exchanger surfaces.

The heat transmission coeliicient between a gas current and a metal surface rises with increasing velocity of the gas current which corresponds to a higher oW resistance from a certain gas volume.

By allowing a comparatively large resistance in the gas heat exchanger in an absorption refrigerating system according to this invention it has been shown that the overall eiliciency of the apparatus can be considerably increased.

The invention is illustrated in the accompanying drawing which gives a diagrammatic representation of the principal components of an absorption refrigeration unit according to the invention and the general arrangement thereof.

The unit comprises an evaporator 1, supposed to be mounted in conventional manner in a heat insulated food storage space of a refrigerator cabinet not shown. One heat insulating wall of said storage space is indicated generally at 2() in the drawing and separates the storage space from a suitable apparatus compartment preferably accomodating the remaining components of the unit.

The evaporator 1 is connected through the gas heat exchanger 3 to the absorber 2 and to the upper part of the liquid vessel 8 in which the rich solution (absorption liquid laden with absorbed gaseous refrigerant) is accumulated.

Moreover, the unit comprises in the ordinary manner a liquid heat exchanger 15 and the thermosyfonic pump 10 associated with the boiler 12 which is connected by way of a rectifier 17 to the condenser 18.

, The operation of this unit is conventional and proceeds as follows:

The rich solution of gaseous refrigerant (ammonia) in absorption liquid (Water) is supplied by gravity by way of the pipe 9 forming the inner part of the liquid heat exchangerlS to the thermosyphonic pump 10 and by means of heat supplied to the boiler inner-tube 13 raised through the riser pipe 11 to the top of the boiler 12. The inner-tube 13 may be heated electrically or by any other means such as one or more burners for gaseous or liquid fuel and the heat supply may be controlled manually or preferably automatically in the usual manner.

The poor solution `hows by gravity from the boiler through the pipe 14 and the outer part of the liquid heat exchanger and pipe 16 to the upper end of the absorber 2, d own through the absorber, and eventually back to the liquid vessel 8 enriched with refrigerant absorbed in the absorber. i i

The gaseous refrigerant expelled by heat in the pump and the boiler is conducted through the pipe 17, in which absorption liquid vapour condenses and flows back to the boiler, to the condenser 18 which comprises one or more finned or gilled air cooled tubes in which the gaseous refrigerant condenses and flows in liquid l state through pipe 6, jacket 5 and pipe 7 to the evaporator 1. v

A circulation of inert gas (hydrogen) is maintained vthrough the absorber, the evaporator, and the upper part of the liquid vessel 8 due to the above mentioned difference in specific weight of the circulating gas and the elevated position of the evaporator as against the absorber.

For further information, the arrows in the drawing indicate the dierent directions of the currents in thecomplete apparatus, fully drawn arrows indicate liquid currents, while dotted arrows indicate gas currents. The pipe 19 is a pressure equalising conduit between the upper end of the condenser and the upper part of the vessel 8.

In a particular example the evaporator consists of a coil of 3%" steel tubing having a total length of 7'; the absorber 2 consists of a coil of l steel tubing having a total length of 11'; in this example both the evaporator and the absorber had approximately windings; the driving force of the inert gas circuit is determined by an average height difference of approximately 1 between the evaporator coil and the absorber coil.

The gas heat exchanger 4 is of the coaxial-pipe type having a total length of 3%', and with the following di rnensions; inner tube (4): 7/16 inner diameter by 0.04 wall thickness; outer tube (3): 3/4 inner diameter.

Thus, according to this invention the major part of the gas flow resistance in the inert gas circuit is located in the gas heat .exchanger which in this example takes approximately 75% of the available driving force at normal operating conditions, while the resistance in the evaporator is only and the resistance in the absorber approximately 10%.

The flow resistance in the gas heat exchanger should be evenly distributed along the heat transmission surfaces, since the gas velocity in every part of the heat exchanger should be as large as possible. Further, it is a `special advantage for a heat exchanger made on the principle in question that it is so designed that the cold gas from the evaporator is conducted through the inner pipe 4 of the exchanger in order fully to utilize the cold contained therein for cooling down the hot gas from the absorber.

Another important feature of the invention is ernbodied in the above mentioned jacket 5 through which the comparatively hot liquid refrigerant is passed on its way from the condenser to the evaporator in heat exchanging relationship with the conduits of the inert gas circuit. This arrangement serves the double purpose of cooling the liquid refrigerant and thus enabling a lower evaporator temperature to be attained, and of intercepting the cold led away from the evaporator by conduction through the metal of the conduits to the surroundings so as to reduce cold losses and prevent condensation of humidity from the ambient atmosphere upon cold metal parts outside the heat insulating walls of the storage space.

The jacket 5 should extend at least over the stretch of the conduits 3 and 4 which extends through the heat insulating wall and should preferably cover that part of the outer surface of the gas heat exchanger outside said heat insulating Wall which would otherwise under normal operating and atmospheric conditions attain a temperature below the dew point of the atmosphere.

It is to be understood that the above example and the various embodiments of the individual components 'thereof are only given by way of example and should not be construed in a limiting sense.

For instance, any type of absorber than the above described plain comparatively wide tube may be employed with equal success provided that the gas ow resistance and the gas velocity therein are small as compared with the resistance and velocity in the gas heat exchanger and that the surface areas available for absorption and cooling purposes resp. are satisfactory.

Likewise, the condenser 18 may be of any suitable design, which also applies to the boiler, the pump, the liquid heat exchanger and the gas heat exchanger, provided that the latter should be of a highly etlicient type and utilize the major part of the gravitational driving force .0f ythe inert gas circuit.

Well known details such as boiler, pump, and liquid heat exchanger insulation, and means for maintaining a forced or natural draft of cooling air through and/ or past absorber, rectifier, and condenser have been omitted in the interest of brevity.

l claim:

l. An absorption refrigerating unit comprising, in combination, a boiler, a condenser, an evaporator, an absorber, and a therrnosyphonic pump connected in series to form a refrigerant circuit, said boiler, said absorber, and said pump also being connected in series with a liquid receiver to form a second circuit for an absorbing liquid, said evaporator having a gas supply pipe and a return gas flow pipe and being disposed at a higher level than said absorber and being connected in series therewith to form a gravity-actuated circulation system for an inert gas, the return gas flow pipe from the evaporator being dispo-sed inside the gas supply pipe to the evaporator for at least a substantial portion of its length whereby to form therewith an internally cold gas heat exchanger, the gas flow resistance of said gas heat exchanger being substantially evenly distributed throughout the length of the exchanger and representing the major portion of the gas ow resistance of the entire inert gas circulation system.

2. An absorption refrigerating unit as claimed in claim l, further characterized in that the total gas flow resist ance of the gas heat exchanger is at least of the gas ilow resistance of the entire inert gas circulation system.

3. A refrigerator comprising an absorption refrigerating unit having a boiler, a condenser, an evaporator arranged separately in a heat-insulated storage space, an absorber and a thermosyphonic pump connected in series to form a refrigerant circuit, said boiler, absorber, and pump being also connected in series with a liquid vessel to form a further circuit for an absorbing liquid, said evaporator eing ,arranged at a higher level than said absorber and connected in series therewith to form a gravity-operated circulation system for an inert gas, a return gas flow pipe from the evaporator extending inside a gas supply pipe thereto for at least a considerable part of its length so as to form therewith a gas heat exchanger embodying at least the major part of the total gas flow resistance of the inert gas circulation system and extending through a heat insulated wall of the storage space, a jacket enclosing at least that part of said gas heat exchanger which extends through said heat insulated wall' and forming part of a conduit for supplying liquid refrigerant to the evaporator.

4. A refrigerator as claimed in claim 3 further characterized in that said jacket extends at least over that part of said gas heat exchanger which during normal operation Would otherwise attain a surface temperature below the dew point of the ambient atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS 2,229,697 Grubb Ian. 28, 1941 2,284,691 Strandberg June 2, 1942 2,321,113 Taylor June 8, 1943 2,489,752 Coons Nov. 29, 1949 2,490,401 Bergholm Dec. 6, 1949 2,598,240 Edel May 27, 1952 2,641,003 Edel June 9, 1953 2,648,204 Grubb Aug. ll, 1953 2,663,159 Ullstrand Dec. 22, 1953 FOREIGN PATENTS 927,190 France Oct. 22, 1947 637,510 Great Britain May 24, 1950 UNITED ASTATES PATENT QFFICE CERTIFICATE 0F CURRECTION Patent No. 2,855,766 l October 14, 19;.585 There M. Elfving et al It is hereby Certified that error appears in the above numbered patent4 requiring correction and that the said Letters Patent should read as cora rested below.

In the grant, lines l, 2, and 3, for "Thore M. Eli'ving and Lars Bendix Christensen, of San Mateo, California," read There M, Elfving, of San Mateo, California, and Lars Bendix Christensen, of Kidhoj, Bagsveerd, Denmark, n; in the heading to the 'printed specification, lines 4 and 5, for Thore M Elving and Lars Bendix Christensen, San Mateo, Calif.n read Thore M.' Elfving, San Mateo, Califo and Lars Bendix Christensen, Kidhoj, Bagsveerd, Denmark Signed and sealed this 3rd day of March 1959.,

(SEAL) Attest:

KARL H AXLINE y ROBERT c. wATsoN tte'ting Officer Conmissioner of Patents

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