US1991188A - Solvent for absorption refrigeration plants - Google Patents

Description

Patented Feb. 12, 1935 SOLVENT FOR ABSORPTION REFRIGERA- TION PLANTS Glenn F. Zellhoefer, Bloomington, 111.

No Drawing.

Application December 27, 1932, Serial No. 648,991

I 6 Claims. (01. 252-5) The present invention relates generally to refrigerant materials for automatic refrigerators and particularly to the type of refrigerant material for the so-called two-fluid machines, wherein there is a solvent material adapted to remain liquid through-out the operation of the refrigerator, and a refrigerant material adapted to have a liquid and a vapor phase in the cycles of operation, and adapted to be dissolved in the solvent.

Numerous refrigerants and numerous solvents are known and numerous combinations of these are known.

The present invention is directed to a new solvent material and to the combination thereof with well-known refrigerant material.

One object of the invention is the use of monochlzornaphthalene as a solvent for a refrigeran Another object of the invention is the use of monochlomaphthalene and methyl chloride in combination.

An example of an apparatus in which the new materials have been successfully employed is described in my copending applications Serial No. 473,486 filed August 6, 1930, allowed July-14, 1932.

Briefly described, the apparatus specifically referred to comprises a still in which amixture of solventand refrigerant is heated to vaporize the refrigerant from the solution, a condenser wherein the vapor is condensed to a liquid state, an evaporator wherein the liquid is vaporized at reduced pressure, such evaporator being the efiective cooling 'means, such as coils, in the apparatus, and an absorber in which vapors containing added heat units are again dissolved in the solvent. Suitable heat exchanging and circulation means are included, and automatic controls may be provided.

The particular characteristics of such machines are that the still operates at temperatures well above normal temperatures against which the refrigeration acts, such for example at 210 F. to 250 F.; and that the cooling unit operates at temperatures much lower than normaLsuchas from 5 F. to 40 F. Various parts of the ap paratus differ in the prevailing pressures as well as temperatures and both pressure and temperature determine the physical state of the free refrigerant, whether gaseous or liquid, and determine the solubility relations between the refrigerant and the solvent. It is therefore very important that the solvent and the refrigerant be physically adapted for use as individual materials in certain places and for certainfuncfactors tions, and that they be mutually adapted for certain functions when they are in combination. Other qualities not essential to refrigeration, but pertinent to practical usage control or limit the choice of solvent or refrigerant, such as ,5 odor, viscosity, heat capacity, boiling point, freezing point, volatility, chemical stability, reactivity, corrosive action, infiammability, toxicity, etc.

In the following description the particular ad- 10 vantages and merits of methyl chloride and of chlomaphthalene and of their combination will become apparent as they are discussed with relation to these various important commercial Monochlornaphthaleae.'l'hroughout this description the material may be referred to as chlomaphthalene, although there are two distinct chemical; forms of it known as the alpha form and the beta form. They are generally similar but diiler in some respects. The invention may employeither form, butin some cases operating conditions may not permit using the beta form exclusively. Both forms boil above 480 F. at. atmospheric pressure which is far ,above the operating temperatures ordinarily contemplated. Hence the volatility at the operating temperatures is much less than with solvents having a lower boiling point. This is important in limiting the amount of solvent which vaporizes with the refrigerant and accompanies it in its-journey through the cooling means. The alpha type is liquid at all temperatures normally encountered in apparatus, and whatever small amount gets into the cooling means remains. liquid and does not clog the apparatus; However, the beta type freezes at about 133 F. This material might asily freeze solid in the cooling means or in some other part of the apparatus where temperatures lower than about 133 40 F. are encountered. The presence of refrigerant material with the wandering quantity of 1 The chlomaphthalenes have a specific heat of about 0.282 which is low, water. being a standard of 1. This means that in a heat condition it contains a proportionately less quantity of heat units than if it were water. The quantity of heat to be transferred to and from the solvent is therefore much less, and the transfer is more quickly effected than if it were water. Smaller heat exchangers are thus permitted.

The chlornaphthalenes are chemically stable at temperatures up to 450 F. and over, and hence are highly stable at 250 F. and under, as encountered in refrigeration apparatus. In addition, they are non-reactive with available refrigerant materials suitable as solutes therein for refrigeration purposes, including methyl chloride,

which I specifically prefer. In connection with chemical reactivity, the question of inflammability must be considered, in the event of accident or leakage. The flash point for the chlornaphthalenes is much higher than the temperatures encountered in the apparatus.

In the event of leakage, or in handling the material in production of apparatus, the toxicity and odor are of importance. Chlornaphthalenes are essentially non-toxic. They are quite odorless, but tend to be slightly pungent at temperatures well above those encountered in refrigeration apparatus.

For practical and mechanical considerations it W is advantageous that the chlornaphthalenes are not corrosive towards iron, brass, copper, and bronze, and are inert of themselves, and to such metals, in the presence of air and water. Consequently, cast iron parts and flexible tubing may be employed in apparatus designed for use with them.

Methyl chloride-This material is a gas or vapor at ordinary temperatures, and is subject to liquefaction by increased pressure and by lowered temperature. It is highly soluble in-the chlornaphthalenes. Its refrigerant qualities apart from the chlornaphthalenes are well known. It is essentially odorless, and only slightly toxic. It-is non-corrosive towards iron, brass, copper and bronze, and non-reactive with chlornaphthalene. It is diflicultly inflammable.

Combination of chlornaphthalene and methyl chloride-The chlomaphthalenes have a high solvent capacity for methyl chloride, and the heat of solution is very low. This results izrthe advantage that only a relatively small amount of heat need be dissipated from the absorber, and returned in the still. This contributes to high thermal efficiency in using the combination.

Apparatus of the two-fluid type may have a rectifier unit which treats the vapors from the still to remove solvent therefrom and return it to the still. The high volatility of the new solvent,

and the great difference in volatility between the solvent and refrigerant of this specific combination lessens the amount of solvent in the vapors, and hence the amount of heat exchange in the rectifier. Again this contributes to high thermal efliciency. v

In common use of the combination, the pressure on the high side maybe from '75 to 100 pounds per square inch and on the low-side from 6 to 28 pounds per square inch. These figures are merely exemplary of the range of pressure change and are not by any means to be considered as limits. The properties of the refrigerant, as related .to the solvent, permit circulation through the cooling unit of a large amount of refrigerant per unit weight of solvent. The following tables express these relativeproperties under some of the prevailing conditions, and may be useful to those skilled in the art in applying this mixture to specific refrigeration units.

Solubility of methyl chloride in chlornaphthalene at 75 temperature and at the pressure as indicated Pounds of methyl chlo- Pressure rideperpoundofchlornaphthalene Solubility of methyl chloride and chlornaphtha- Zene at 90 pounds pressure and the temperature 7 indicated Pounds of methyl ch10- Tempem' ridepetpoundofchlo'rtum naphthalene 210 F. 092 220 F. 078 230 F. .008 240 F. .058 250 F .052 200 F .052

It is well known :that there are other common refrigerants generally similar to and useful like methyl chloride, and that they can be used like methyl chloride in a variety of solvents. Because chlornaphthalene has way specific advantages and properties in combination with methyl chloride, it will offer the same order of advantage with other refrigerants which have the same order of difference in properties or with mixtures of suitable refrigerant material. The specific solubility relations for refrigerant material, other" than methyl chloride, may vary somewhat with corresponding changes in thermal efflciency. Accordingly the present invention contemplateschlornaphthalene as a new solvent, and the speciflc combination of methyl chloride and chlornaphthalene. The proportions in which the solvent and refrigerant are used will, of course, depend entirely upon the type of apparatus employed, and also upon the particular design.

While I prefer alpha chlornaphthalene, it is to be understood thatwhatever form the chlornaphthalene has, the refrigerant mixture consists only of that material as the solvent, and a suitable refrigerant material, preferably a single substance such as methyl chloride. It is further to be understood that if the materials are adulterated by the substitution of other solvent or refrigerant material in such a manner as to retain the substantial benefits and advantages of the unadulterated combination, then the adulterated composition is intended to fall within the scope of the appended claims. q L

What I claim is:

1. A refrigerant mixture for the absorption type of refrigeration apparatus consisting of alpha chlornaphthalene as a solvent, and methyl-chlo ride as a refrigerant. r

2. A refrigerant mixture for the absorption type of refrigeration apparatus consisting of a non-freezing mixture of alpha and beta chlornaphthalenes as a solvent, and methyl chloride as a refrigerant.

'3. A refrigerant mixture for the absorption mixture of a major portion of alpha chlomaphthalene and a minor portion of beta chlomaphthalene as a solvent, and methyl chloride as a refrigerant.

4. A refrigerant mixture for the absorption type of refrigeration apparatus consisting of alpha chlornaphthalene as a solvent, and a highly volatile refrigerant soluble in said solvent.

5. A refrigerant mixture for the absorption type of refrigeration apparatus consisting of a non-freezing mixture of alpha and beta chlornaphthalenes as a solvent, and. a highly volatile refrigerant soluble in said solvent.

6. A refrigerant mixture for the absorption type of refrigeration apparatus consisting of a mixture of a major portion of alpha chlornaphthalene and a minor portion of beta chlornaphthalene as a solvent, and a highly volatile refrigerant soluble in said solvent.

GLENN F. ZELLHOEFER.