US2120559A - Absorption refrigeration - Google Patents

Description

' refrigerating apparatus.

Patented June 14, 1938 ABSORPTION REFRIGERATION Burgess H. Jennings, Bethlehem, Pa., assignor to The Philadelphia, and Reading Coal and Iron Company, Philadelphia, Pa., a corporation of Pennsylvania No Drawing. Application April 20, 1937,

Serial No. 137,929

9 Claims.

Ihis invention relates to absorption refrigeration, and is particularly concerned with solvent material for refrigerants in absorption type refrigerating apparatus.

As is known to those acquainted with the art of absorption refrigeration a solvent material is used to absorb a refrigerant vapor in one phase of operation of the machine, while in another phase the refrigerant is driven off from the solvent material because of heat supplied to the solvent mixture. The refrigerant driven off is condensed to liquid, and by suitable means may accomplish refrigeration when it subsequently vaporizes. The refrigerant vapor is then again absorbed by the solvent and the cycle repeats itself. In the two-fluid type of machine, mechanical means is required to circulate the refrigerant against the different pressures of thesystem, and only the refrigerant and its vapor and the solvent, with very small quantities of the vapor of the latter, are present in the machine. In the three-fiuid type of machine an inert gas, which is always gas, is also present and is used to keep the pressure throughout the machine essentially constant. The inert gas is not essentially soluble in the refrigerant or solvent of the machine.

The operation of two-fluid and three-fluid absorption refrigeration apparatus is well known to those skilled in the art, so that no detailed description of such apparatus need here be given. It may be briefly noted that such apparatus comprises a generator or still in which the solvent mixture is heated and the refrigerant driven off as a vapor, a condenser in which the refrigerant vapor is condensed to a liquid state, an evaporator in which the refrigerant liquid is vaporized at reduced pressure, and extracts heat from the medium which is to be cooled, and an absorber in which the refrigerant vapor containing, heat withdrawn from the refrigerated medium is again dissolved in the solvent.

A refrigerant solvent must meet satisfactorily widely varying special conditions in absorption In the first place, in the generator or still, temperatures of from 200 to 270 F. are commonly employed. The characteristics of the solvent should be such that in this temperature range the refrigerant in solution can, to a great extent, be removed and pass off as a gas into the condensing part of the unit. Condenser and generator pressures are essential- 1y equivalent. Furthermore, the solvent in the absorber of the unit should be capable of absorbing an appreciable quantity of the refrigerant at customary absorber temperatures of from F. to about 110 F. The absorber pressure is essentially equivalent to that of the refrigerant evaporator, which operates at'temperatures that may vary over a wide range but are customarily 5 between 0 F. and 50 F.

It will be seen from the foregoing discussion that the solvent must be able to fulfill-its functions under varying temperatures and pressures.

In addition, its freezing point should preferably 0 not be over about 10 F. It should have a viscosity preferably not substantially higher than 10 centipoises at 68 F. It must also be chemically stable at temperatures below 270 F., par

ticularly in regard to the common metals used 15 in refrigeration machine construction. It must not form permanent chemical compounds with the refrigerants used. Its specific heat should be low for the greatest efficiency. It should be capable of absorbing refrigerant at F. absorber temperature and at the evaporator pressure maintained, and should be capable of losing at 230 F. and at the condenser pressure maintained, enough refrigerant to allow each pound of absorbent circulated a reasonable car- 25 rying capacity. Its minimum boiling temperature should be about 240 (preferably above 260 F.) at atmospheric pressure.

I have discovered that tetrahydronaphthalene (also known as tetralin) effectively meets the requirements of a solvent in absorption refrigeration. Particularly I have found that this substance is a desirable solvent for the refrigerant methyl chloride under the conditions prevailing in absorption type refrigerating systems. In ad- 5' peratures not greatly in excess of F. The

critical temperature value should usually not be lower than F. vaporization must be readily I possible at the pressures for which the system is 50 designed at temperatures as low as 0 for conventional refrigeration, and usually somewhat below 50 F. for air conditioning work.

It may be noted in passing that many refrigerants are in the vacuum region during evaporation and in some of them even during condensation, but that many others may operate in both regions or altogether in the positive pressure region. The atmospheric boiling point of a substance is thus not necessarily an index of its suitability as a refrigerant because of the possibility of operating in the vacuum region.

However, atmospheric boiling points above 120 F. do not usually represent good refrigerants.

The chemical tetrahydronaphthalene to which I refer has the empirical formula C1oH12, consisting structurally of two'carbon rings constituting naphthalene, one of the rings being completely hydrogenated (except for the double bond common to the two rings), and the other ring unchanged. This structural formula may be illustrated as follows:

The chemical is a rather stable liquid, boiling at about 206 C. and freezing at about 25 C. It is practically non-toxic.

My invention also includes decahydronaphthalene (known also as decalin) which is suitable and satisfactory as a solvent for-absorption refrigeration. This chemical, the boiling point of which is about C. and the melting point about 10 C., has the empirical formula CmCia, and structurally consists of two carbon rings constituting naphthalene both of which are completely hydrogenated. This formula may be illustrated as follows:

o-o I /m in\ I claim:

1. A refrigerant mixture for absorption refrigerators, said mixture comprising a hydrogenated naphthalene as a solvent and a volatile chemically stable refrigerant soluble in said solvent.

2. A refrigerant mixture for absorption refrigeratprs, said mixture comprising a hydrogenated naphthalene as a solvent and a volatile. chemically-stable, halogenated .hydrocarbon refrigerant soluble in said solvent.

3. A refrigerant mixture for absorption refrigerators, said mixture comprising a hydrogenated naphthalene having at least two double bonds replaced by hydrogen atoms as asolvent and a volatile chemically stable halogenated hydrocarbon refrigerant soluble in said solvent.

4. A refrigerant mixture for absorption refrigerators, said mixture comprising tetrahydronaphthalene as a solvent and a volatile chemically stable refrigerant soluble in said solvent.

5. A refrigerant mixture for absorption refrigerators, said mixture comprising decahyd'ronaphthalene as a solvent and a volatile chemically stable refrigerant soluble in said solvent.

6. A refrigerant mixture for absorption refrigerators, said mixture comprising methyl chloride as the refrigerant and a hydrogenated naphthalene as'the refrigerant solvent.

7. A-refrigerant mixture for absorption refrigerators, comprising a hydrogenated naphthalene as a solvent and a volatile, chemicallystable, halogenated aliphatic hydrocarbon refrigerant soluble in said solvent.

8. A refrigerant mixture for absorption refrigerators, comprising a hydrogenated naphthalene as a solvent and a volatile, chemically- 'stable, halogenated hydrocarbon'refrigerant having not more than two carbon atoms soluble in said solvent.

9. A refrigerant mixture for absorption refrigerators, comprising a hydrogenated naphthalene as a solvent and a volatile, chemicallystable, halogenated methane refrigerant solub in said solvent.

' BURGESS H. JENNINGS.