US2199123A - Refrigerating apparatus and method - Google Patents

Description

Apr-i130, 1940. F. WHITNEY I REFRIGERATING APPARATUS AND METHOD Filed May 11, 1958 Patented Apr., 30, 1940 REFBIGER-ATING APPARATUS AND METHOD Lyman F. Whitney, Cambridge, Mass., assignor to Comstock & Wescott, Inc., Cambridge, Mass,

- men STATES PATENT OFFICE,

a corporation of I Massachusetts Application May 11, 1938, Serial No. 207,267

(ores-115) 14 Claims.

Ihis invention relates 'to an improved refrigerating apparatus of the general type disclosed in United States Patent No. 1,761,551 to Eastman A. Weaver and in my United States Patent No. 1,756,802. An improved system of this general character is also disclosed in my copending application Serial No. 171,325, filed October 27, 1937.

Refrigerating systems of the type disclosed in the above-identified patents employ a heavy pro- 10 pellant fluid having a high boiling point, e. g., mercury. Propellant vapor passing through an aspirator assembly entrains refrigerant vapor, compressing and pumping the same to a condenser. In order to permit relatively high pump- 5 ing efliciency and in order to permitpressure'differences within the system readily to be balanced by liquid columns, such a system preferably operates at relatively low pressures. As disclosed in the above-identified patents, water may be employed as the refrigerant and the pressure within the cooler may be of the'order of 4 mm. of mercury absolute, while the pressure within the refrigerant condenser may be of the order of 100 mm. absolute atv 125 F. It is to be noted that all 95 pressures hereinrecited are in millimeters of mercury. It is also desirable to employ a refrigerant, such as water, which has a low molecular weight so that shook losses in the aspirator may be relav 49 point and which affords vapor pressures, comparable to those of water, as well as affording a low effective or averagemolecular weight in the aspirator. Such characteristics are not possessed by conventional refrigerants, and I have found that well known anti-freeze agents such as methmay freeze before becoming mixed with the antifreeze ingredient. Furthermore, such materials, due to tipping of the apparatus or for other reasons, may pass out of theevaporator and become lodged'in traps remote from the cooler, tending to clog such portions of the'system and causing the freezing point of the solution in the cooler to rise. --I. prefer to employ an aqueous solution of a suitable anti-freeze agent or agents with water which, however, will meet the above requiremerits and which will afford a relatively stable solution under all operating conditions and which Y may be substantially immiscible with the pro'-' pellant, e. g., mercury; In so far as I am aware,

all anti-freeze agents meeting these requirements have molecular weights substantially higher than that of water. agents, when circulating with water vapor through the aspirator, tend to increase the shock losses.

in the aspirator. While it is desirable to have an anti-freeze agent included in the condensate returning to the cooler,'I have found that it may not be necessary to have as large a proportion of suchan agent in the returning condensate as in the copler itself in order to prevent freezing.

Accordingly the present invention affords a refrigerant, including an-anti-freeze agent of higher molecular weight-than water, which circulates through the aspirator with the water vapor but which occurs in less concentration in the vapor yl alcohol, when added to water, are generally objectionable-due to undesirably high vapor pressures and/or molecular weights.

-Non-volatileanti-freeze materials, such as salt,

so are objectionablefol-severalreasons.- Such materials tend to reduce-the vapor pressure-in the cooler; they may cause corrosion of the steel walls of the system; they do not circulate with the refrigerant in its vapor phase, so that the 55 condensed refrigerant returning to the cooler mixture passing through the aspirator than in the cooler itself. Thus the average or eflective molecular weight of the refrigerant vapor passing through the aspirator may more closely approach the, low molecular weight of water itself and shock losses are kept relatively low. The solutions of certain liquids such as methyl cellosolve (the mono methyl ether of ethylene glycol) morpholine, ethylene diamine, and ethyl-cellosolve (the mono ethyl ether of ethylene glycol) in water in general answer these requirements.

Accordingly such anti-freeze Solutions containing a-substantial .percentage of ethylene diamine, however, tend to attack conventional steel. Accordingly the refrigerant preferably does not include a large percentage of ethylene diamine, when the system has walls provided ,with surfaces of ordinary steel. If the system is provided with a refrigerant circuit having resistant surfaces, as disclosed in myi copending application Serial No. 207,269, filed on even date herewith, ethylene'diamine may be satisfactorily employed in relatively large proportions. As a matter of fact, ethylene diamine is advantageous since it impedes the formation of undesirable sludge by the mercury and refrigerant, which sometimes tends to collect in a system of this character. The characteristics of such a sludge are described in detail in my first above-identified application, which also discloses means for breaking up such sludge.

Morp'holine also tends to act as a sludge inhibitor, but morpholine in solution with water for some reason involves certain operating discrepancies which tend to reduce the operating efficiency of the system.

Methyl cellosolve is generally satisfactory as an anti-freeze agent, but tends to increase the tendency toward sludge formation. I prefer, however, to employ an aqueous solution having an anti-freeze ingredient, all or the'major portion of which consists of methyl cellosolve, but

which may include minor proportions of ethylene diamine and/or of morpholine, thus tending to impede sludge formation. When such a refrigerant is employed, the system preferably is provided with means to separate the sludge into mercury and refrigerant in the general manner taught in' my above-identified copending application Serial No. 171,325.

While ethyl cellosolve in general has properties comparable to those of methyl cellosolve and may be substituted inwhole or in part therefor, I prefer to employ methyl cellosolve, since the molecular weight of the latter is somewhat lower.

In the accompanying drawing:

Fig. 1 is a diagrammatic view of a simple refrigerating system of the type in which the presentinvention may be incorporated; and

Fig. 2 is a view, on a larger scale, of a portion of the system shown in Fig. 1. g

In general the principles of the present invention may be employed to advantage in a lowpressure refrigerating system of the general typedisclosedin the above-identified patents and in the above-identified application. Such a system is provided with a boiler I which may contain a body of liquid mercury and which is connected by a riser pipe 2 to an aspirator nozzle 3, the latter being arranged to emit mercury vapor at high velocity into. a mixing chamber 4 which receives refrigerant vapor from the cooler 6 through a vapor duct 5. The mixed vapors pass'to a funnel I having heat radiating fins l where the refrigerant is compressed and propellant is condensed. Condensed propellant passes from the funnel into a drain 8 while the refrigerant vapor passes through a duct 9 to the refrigerant condenser Hl. The duct 9 preferably is disposed adjoining warm parts of the system and is provided with internal fins in the general manner taught in the copending application of William E. Whitney, Serial No. 171,301, filed October 10, 1937. The refrigerant condenser I0 is arrangedso that condensate may flow into a chamber ll provided with an outlet drain l2.

The chamber II is also connected to a gas-receiving duct l3 which is arranged to supply noncondensable gases to a purger. H of the type disclosed in my copending application Serial No.

167,402, filed October 5, 1937. This purger includes a drop tube l of restricted diameter, which receives condensed mercury in the form of separate drops or globules. The mercury globules fall through this tube and compress the gases which are exhausted to the atmosphere through a mercury body l6 arranged in a vat I! at the lower part of the purger. The mercury rises in a return duct 23 disposed above the drop tube l5 and is received by a pipe 25 containing a pressure balancing column of the mercury and serving as a boiler return pipe.

The lower part of the drain 8 may be connected to two upwardly extending pipes, one pipe 21 being connected to the upper part of the purger to supply mercury thereto, and the other pipe 23 inclining upwardly to a connection with the refrigerant return pipe l2 which extends downwardly from the condenser Hi. The inclined pipe 28 extends above this connection and is provided with an upwardly extending continuation 26, the upper part of which is above the level of the liquid refrigerant in the cooler 6 and is connected to a downwardly extended pipe section 30. The lower part of the latter is connected to a duct 3| which is in turn connected to the lower part of the cooler 6.

Duct'3l forms one leg of a trap 33, the oppo'-.

site leg of which is provided by a drum 36. A drain 34 receives mercury which condenses in the mixing chamber 4 and supplies the same to the lower part of the drum. The upper part of drum 36 is connected by a tube 40 to the upper part of cooler 6. The drain 34 is provided with a spill-over connection with a pipe 31, the-lower part of which provides one leg of -a, trap 38, the opposite leg of which is connected to the mercury return pipe 25. When mercury fills the trap 33 to the level with the connection of drain 34 with pipe 31, the mercury spills over into this pipe.

The level of the mercury in the trap assembly at the lower end of the return pipe I2 is determined by the height of the spill-over connection between pipe 21 and the purger, the mercury tending to stand at this level in this trap assembly, as indicated by the dot and dash line,

when the system is not in operation. During op- Condensed refrigerant in pipe 12 tends to de-- press the mercury in the lower part of this pipe, piling up so that it passes through the trap provided by the lower part of pipe 12 and by pipe 26,

thus rising through the latter and spilling over into the pipe 30. -The refrigerant collecting in the latter depresses the mercury in the lower part of pipe 30 and rises through the pipe 3| to the cooler. Such a trap arrangement and the action of the same under different operating conditions are more fully disclosed and claimed in the first above-identified application.

When relatively heavy sludge drains from the cooler 6 into the pipe 3|, this sludge may depress the mercury in trap 33 and'p'ass through the latter into the upper part of drum 36. This sludge is .then exposed to the suction of the aspirator assembly through the pipes 40 and 5.

Thus, as more fully disclosed in the first above-- identified application. this suction is effective in drawing refrigerant from the sludge or in drying the sludge, so that the mercury coalesces and retums to the lower part of the system in the normal manner.

It will be understood that Fi 1 is a diagrammatic showing and that in practice the parts may bemore compactly arranged. For example, in practice the drum 36 preferably is substantially nearer to cooler 6 so that the mercury capacity of the system may be kept relatively low. Fig.2 affords a more accurate showing of the preferred arrangement of the cooler 6, the drum 36 and related parts, the parts in this figure being designated by reference numerals similar to those used in Fig. 1.

The cooler 6 preferably contains a body of liquid refrigerant substantially to the level of the dotted line. This refrigerant preferably is arranged to permit the operation of the cooler at a temperature substantially below 32 F. For

this purpose preferably a volatile anti-freeze agent may be employed in solution with water.

There are many characteristics which are desirable in such a solution. For example, it is desirable to approximate the characteristics of water but to provide a lower freezing point, the

solution at low temperatures having approximately the characteristics of supercooled water. Thus, the anti-freeze agent should not unduly increase the molecular weight of the refrigerant vapor which is being pumped by the propellant vapor, while occurring 'sufliciently in the refrigerant vapor so that the condensed refrigerant will not readily freeze in the return pipe or pipes extending from the refrigerant condenser to the cooler. The average molecular weight. of the vapor passing through the aspirator should preferably be less than 30. The solution'must not have a tendency to form sludge which cannot be overcomeby practical. expedients, such as are disclosed herein. Furthermore, the solution must be of a'character which does not appreciably attack the material of the walls of the system. The

anti-freeze agent should mix with or go into solution withwater. ,It'should not decompose at a temperature as high as 300 C. It must be normally immiscible with mercury and should not react with mercury even at high temperatures. Furthermore, the pressure in the refrigerant condenser at agiven temperature should not be materially higher when an anti-freeze solution is employed than isthe case when water alone is employed as the refrigerant.

Methyl cellosolve substantially answersthese requirements, as does ethylene diamine, but if the latter is employed in substantial quantities, it

tends to attack the walls of a conventional steel system. Therefore, in such a system I prefer to use methyl cellosolve alone with water'or with a small admixture of ethylene diamine, the latter preferably not being over of the weight of the solution. For example, if cooler temperatures of the order of F. are desired, a solution of 30% by weight of methyl cellosolve and 70%- by weight of water may be employed. While the molecular weight of methyl cellosolve is greater than that of water, it does not vaporize in the cooler as readily as does the water, so that the proportion of themethyl cellosolve in the refrigerant vapor which is being pumped by the propellant does not unduly increase the shock lossesduring aspiration. 'On the other hand,

suflicient methyl cellosolve vapor is intermingled with the water vapor passing to the refrigerant condenser to impede freezing in the return pipe 7 In order to permit good pumping emciency, the vapor pressure in the condenser should be kept relatively low, while the vapor pressurein the 'cooler should not be greatly lower than that of supercooled water. Morpholine solutions are not as satisfactory inthe latter respect as are solutions of methyl collosolve or of ethylene diamine (or mixture of the same) in water. However, small quantities of .morpholine may be included in the solution if desired, the morpholine tending to impede the formation of rust or scale when a conventional steel system is employed For example, 2% or 3% by weight of the solution may comprise morpholine without substantially affecting operating efficiency.

The use of methyl cellosolve, as commercially obtained, for an anti-freeze agent increases the tendency 'of deleterious sludge to form in the system. However, such sludge may drain from the cooler, passing through trap 33 to the drum 36, where the sludge is broken up. Furthermore, the heating of pipe 9 and the provision of fins therein aid in the prevention of sludge formation. In practice the proportions of methyl cellosolve and water employed in the refrigerant liquid depend upon the temperature which is de-- sired in the cooler,'more of the'anti-freze agent Y obviously being employed when it is desired to operate at 'lower'temperatures.

Ethylene diamine, in contrast to the commercially available methyl cellosolve, actually impedes sludge formation; A small percentage of the ethylene diamine may be employed satisfactorily in a conventional, steel system, replacing some of the methyl cellosolve, thus somewhat impeding the tendency toward sludge formation;

for example, 5% or less of ethylene diamine might be employed rather than a corresponding quantity of the methyl cellosolve. Such a mixture, for example, might comprise 310% by weight of water, 28% by weight of methyl cellosolve, and 2% by weight of ethylene-diamine. Such a solution as well as a solution of 30% methylcellosolve and water will provide refrigerant vapor with an average molecular weight of less than 30, so that high shock losses during aspiration are avoided.

The presentinvention affords a system of the class described with a refrigerant that may provide a freezing point in the cooler below 25 F. and that will liquefy in the condenser at a pressure of less than 130 mm., when'the condenser temperature is at least Thus the yapor pressure ofqthe condensate returning to the cooler isalso less than mm. The vapor pres-v sure of the anti-freeze ingredient, when separated from the water of the condensate preferably maybe between 20. and '70 mm. at 125 F. Furthermore, the aspirator need only increase the pressure of the refrigerant by an amount less than 130 mm. when pumping the refrigerant from the cooler to the condenser. Since such a refrigerant may have an'eifective or average molecular weight of less than 30, shock losses during aspiration may be kept relatively low. Furthermore, the returning refrigerant. although it may have a higher freezing point than that of the refrigerant in the cooler, still has a freezing point below 32 F. The difference in temperature between 32 F. and the freezing point of the condensate preferably may be at least one-fifth the difference between 32 F. and the-freezing point of the solution in the cooler. These requirements are. particularly satisfactorily met by a solution of water and an anti-freeze agent in and equivalents which fall within the scope of the appended claims.

I claim:

1. Refrigerating apparatus comprising a refrigerant circuit including a cooler and a condenser, a propellant circuit including a vaporizer and a part in common with said refrigerant circuit wherein refrigerant vapor from the cooler is entrained in a stream of propellant vapor from the vaporizer, said cooler containing an aqueous refrigerant solution comprising water and a volatile anti-freeze agent, said refrigerant having a freezing point in the cooler below 25 F., the concentration of the agent in the vapor passing through said common part being les than in the liquid refrigerant in the cooler, the conden'sate returning from the condenser to the cooler having a freezing point below 32 and the anti-freeze agent, when separated from the water of this condensate, having a vapor pressure above 20 mm.- absolute at 125 F.

2. Refrigerating apparatus comprising a refrigerant circuit including a cooler and a condenser, a propellant circuit including a vaporizer and a part in common with said refrigerant circuit wherein refrigerant vapor from the cooler is entrained in a stream of propellant vapor from the vaporizer, said cooler containing an aqueous refrigerant solution comprising water and a volatile anti-freeze agent, said solution having a freezing point in the cooler below 25 F., the concentration of the agent in the vapor passing through said common part being less than in the liquid refrigerant in the cooler, the average mo- .lecular weight of the refrigerant vapor flowing through the commn part of the circuit being less than 30, the condensate returning from the condenser to the cooler having a freezing point below 32 F., the anti-freeze agent, when separated from the water of this condensate, having a vapor pressure above 20 mm. absolute at'125 F.

3. Method of refrigeration comprising entraining refrigerant vapor from a body of liquid refrigerant in a stream of propellant vapor, thus causing evaporation of the refrigerant from said liquid body at a temperature below, 25 F.,- and which is at least 125 F., thus effecting the condensation of the refrigerant at a temperature above room temperature, and directing the resulting condensate back to the cooler at a tem perature below 32 F. by an amount which is at least one-fifth of the difference between 32 F.

'and the freezing point of said liquid body.

4. Refrigerant apparatus comprising a refrigerant circuit including a cooler and a condenser,

- a propellantcircuit including a vaporizer and a vaporizer, said cooler containing a body of liquid refrigerant, said refrigerant having a freezing point below 25 F., the refrigerant vapor passing through the common part of said circuits having an average molecular weight less than 30, the difference between the pressure in the cooler at 25 F. and the pressure in the condenser at F. being less than mm. whereby the refrigerant may be readily pumped through a low pressure range in order to effect refrigeration, the condensate returning from the condenser to the cooler having a freezing point below 32 F., the anti-freeze agent, when separated from the water ofthis condensate, having a vapor pressure above 20 mm. and less than 70 mm. abso lute at 125 F.

5. Refrigerating apparatus comprising a refrigerant circuit including a cooler and a condenser, a propellantcircuit including a vaporizer and a partin common with said refrigerant circuit where refrigerant vapor from the cooler is entrained in a stream of propellant vapor from the vaporizer, said cooler containing a body of liquid refrigerant in the form of a solution comprising water and comprising one of the group consisting of mono methyl ether of ethylene glycol, mono ethyl ether of ethylene glycol, morpholine, and ethylene diamine.

6. Refrigerating apparatus comprising a refrigerant circuit including a cooler and a condenser, a propellant circuit including a vaporizer and a part in common with said refrigerant circuit where refrigerant vapor from the cooler is entrained in a stream of propellant vapor from the vaporizer, said cooler containing an aqueous refrigerant which has a freezing point below 25" F. and which includes an anti-freeze agent having a minor percentage of ethylene diamine therein.

'7. Refrigerating apparatus comprising a refrigerant circuit including a cooler and a condenser, a propellant circuit including a vaporizer and a part in common with said refrigerant circuit where refrigerant vapor from the cooler is entrained in astream of propellant vapor from the vaporizer, said cooler containing an aqueous 25 F., the refrigerant in the condenser having a freezing point below 32 F., the difierence between the vapor pressure of the refrigerant in the cooler'and the vapor pressure of the refrigerant in the condenser being less than 130 mm., when the difference between the temperatures of the cooler and ofthe condenser is over 100 F., the, difference between 32 F. and the freezing point of the condensate returning from the condenser to the cooler being at least one-fifth of the difference between 32 F. and the" freezing point of the refrigerant in the cooler.

9. Refrigerating apparatus comprising a refrigerant circuit including a cooler and a condenser, a propellant circuit including a vaporizer and a part in common with said refrigerant circuit wherein refrigerant vapor from the cooler is entrained in a stream of propellant vapor from the vaporizer, said cooler containing an aqueous '70 mm. absolute at 125 F.

10. Refrigerating apparatus comprising a refrigerant circuit including a, cooler. and acondenser, a propellant circuit includinga vaporizer and a part in common with said refrigerant circuit wherein refrigerant vapor from the cooler is entrained in astream of propellant vapor from the vaporizer, said cooler, containing an aqueous refrigerant which has a freezing point belowv 25 F., said refrigerant comprising water and an antifreeze agent which is soluble in water, the

vapor pressure of the condensate returning to the cooler from the condenser being less than 130 mm. absolute at 125 F., the antifreeze agent in the condensate having a vapor pressure between 20 and '10 mm. absolute at 125 F'., the concentration of the agent in the vapor passing through said common part being less than in the liquid refrigerant in the cooler.

11. Refrigerating apparatus comprising a refrigerant circuit including a cooler and a condenser, 'a propellant circuit including a mercurycontaining vaporizer and a part in common with said refrigerant circuit where refrigerant vapor from the cooler is entrained in a'stream of mer-' curyvapor from the vaporizer, said cooler containing an aqueous refrigerant solution including a volatile anti-freeze agent, the major portion of. which comprises one of the group consisting of mono methyl ether of ethylene glycol and mono ethyl ether of ethyleneglycol.

l2. Refrigerating apparatus comprising frigerant circuit including a denser, a mercury circuit including avaporizer and a part in common with said refrigerant cirarebooler and a concuit wherein refrigerant vapor from the cooler is entrained in a stream of mercury vapor from the vaporizer, said cooler containing a body of refrigerant which has a freezing point below 25 F., the vapor pressure of the condensate returning from the condenser to the cooler being less than 130 mm. absolute at 125 F., the average molecular weight of the refrigerant vapor flowing through the common part of the circuit being less than 30, said refrigerant body including an electrolytic sludge inhibitor.

13.Refrigerating' apparatus comprising a refrigerant circuit including a cooler and a condenser, a mercury circuit including a vaporizer and a part in common with said refrigerant circuit wherein refrigerant vapor from the cooler is entrained in a stream of mercury vapor from:

the vaporizen'said cooler containing a body of a refrigerant which has a freezing point below 25 F., the vapor pressure of the condensate returning from the condenser to the cooler being less than 130 mm. absolute at 125 F., the average,moieoular weight of the refrigerant vapor flowing through the common part of the circuit being less than 30, said refrigerant body including a sludge inhibitor in the form of a volatile alkaline electrolyte.

14. Refrigerating apparatus comprising a refrig'erant 'circuit including a cooler and a condenser; a mercury circuit including a vaporizer and a part in common with said refrigerant circuit wherein refrigerant vapor from the cooler is entrained in a stream of mercury vapor from the vaporizer, said cooler containing a body of refrigerant which has a freezing point below 25--F., the vapor pressure of the' condensate returning from the condenser to the cooler being less than 130 mm. absolute at 125 F., the average molecular weight of the refrigerant vapor flowing through the common part of the circuit being less than 30, said refrigerant body including a sludge inhibitor in the form of an organic amine.

LYMAN-F. WHITNEY.

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