US2729071A - Two fluid refrigeration system - Google Patents

Description

Jan. 3, 1956 L. F. WHITNEY TWO FLUID REFRIGERATION SYSTEM Original Filed Oct. 4, 1949 I5 Sheets-Sheet 1 Janeway Jan. 3, 1956 l.. F. WHITNEY Y 2,729,67

TWO FLUID REFRIGERATION SYSTEM Original Filed Oct. 4, 1949 3 Sheets-Sheet '2 frame/far Jan. 3, 1956 l.. F. WHITNEY 2,729,071

Two FLUID REFRIGERATION SYSTEM Original Filed Oct. 4, 1949 3 Sheets-Sheet 3 L, mmJZ/W/wm f Il @i United States Patent* TWO FLUID REFRIGERATEON SYSTEM Lyman F. Whitney, Boston, Mass., assigner, by mesne assignments, to Stator Company, a'corporation of Massachusetts original application october 4, 1949, sensi No. 119,4s9,

now Patent No. 2,678,548, dated May 18, 1954. Digignd this application March 19, 1953, Serial No.

4 Claims. (Cl. 62-126) This invention relates to refrigeration apparatus of the type shown in United States Patent Nos. l,76l,55l and 2,180,447, and more particularly to improved evaporator for such systems.

Conventional refrigerating apparatus embodies an evaporator disposed in heat transfer relation to the cooling and/or freezing compartment and which contains a refrigerant, the vapors of which are pumped from the evaporator, condensed, and the condensate then returned to the evaporator. Non-aqueous refrigerants having high vapor pressures evaporate freely throughout the liquid mass by boiling, agitating the liquid mass and bringing it in contact with vapor. Thus any portieri of the liquid mass located so as to receive heat from the space to be refrigerated can absorb that heat continuously by ebullition. The same is not true of aqueous and other refrigerants having low volatility, for at the low temperatures required by present-day refrigeration their vapor pressures are so low that inthe absence of dissolved gases no bubbles will ordinarily form below the free surface of `the liquid unless Athe latter becomes substantially superheated. Thus the mass is not agitated by boiling, and the free surface gets all the cooling, which is not readily communicated elsewhere due to the low heattransmissivity of quiescent liquids. Hence, the coldest portion of the evaporator is that adjacent to the line of contact between liquid and vapor, which affords a limited area for cooling an adequate refrigeration space.- Enough copper, `'aluminum or other good heat-conductor to distribute the cooling effect would be bulky, expensive and generallyimpractical. l

vAlthough the trouble could theoretically be remedied by introducingthe condensed refrigerant at a point close to the top of the evaporator so as to trickle down the evaporator walls in a thin film, as a practical matter this method encounters certain diiiiculties including a need for precise levelling to spread the how to all sides of the evaporator. Relatively slight mislevelling tends to ood one portion of the walls and leave the rest dry.

The difficulty is aggravated by the need of a dissolved volatile antifreeze. An ideal substance for this purpose would vaporize with the water in unchanged proportions (azeotropic solution), but such solutions are not very common at any specified temperature and pressure, and the antifreeze must meet so many other requirements (such as thermal stability; non-reactivity with water,

iron or mercury; non-emulsifying tendency, etc.) that only a rough approximation to the desired volatility has yet been achieved. Too volatile a substance would cause prohibitive difiiculty by failure to condense fully with the water vapor, blocking the condenser with accumulated A vapor and causing the pressure to rise too high for the overcome the aforementioned diliiculties and to providev "ice asystem effective to insure adequate 'evaporation of refrigerant with little superheating, and to distribute the cooling effect throughout an extensive refrigerationspace and control its temperature, without requiring relatively costly, heavy or bulky apparatus. Y

A more specific object is to provide an efiicient heat conveyor to absorb heat from a substantial frozen food space and deliver it at a higher gravitational level to the restricted region where the aqueous refrigerant can absorb said heat by evaporation.

A Vfurther object is to provide an improved purging system which is designed so as to insure continuous removal of extraneous gases from the system without danger of becoming sludge-bound;

Further objects relate to various features of construction and will be apparent from a consideration of the following disclosure.

ln accordance with the present invention i provide a refrigerating apparatus or system which includes a ompartment having therein an enclosed evaporator or ooler containing a normally liquid primary refrigerant, such as water containing a suitable antifreeze agent, spaced below the upper wall of the evaporator, so as to provide a liquid-vapor interface. Disposed within the evaporator is a portion of an enclosure adjacent to the liquid-vapor interface so as to transfer heat thereto, and another portion of the enclosure is disposed outside the evaporator and at a level below'the liquid-vapor interface but in heat transfer relation to the storage compartment so as to receive heat therefrom. This enclosure contains a fluid or secondary refrigerant having a vapor pressure greater than water or the primary refrigerant in the evaporator and is normally under such pressure as will cause it to circulate through the enclosure in response to a temperature dierentialr between the liquid-vapor interface and the interior of the compartment by reason of the secondary fluid receiving heat from the storage compartment which results in vaporization, the vapors being conducted to the part of the enclosure at or adjacent to the liquid-vapor interface where they give up their latent heat of vaporization by condensation, the condensate then returning by gravity to the lower part of the enclosure. The secondary refrigerant preferably consists of a halogenated parafiin such as a chloroiiuoro derivative of methane or ethane sold under the trade name Freon.

The enclosure containing the secondary iiuid or refrigerant may be in the form of a housing in telescoping relation to the evaporator and in heat-transfer relation to the maincompartment; or it may be in the form of a coil, a conduit or other enclosure having a part in heattransfer relation to the liquid-vapor interface andanother part in heat-transfer relation to the main compartment and at a level below the liquid-vapor interface, as shown in the accompanying drawings which illustrate different embodiments of the invention as applied to a modern i domestic refrigerator.

In the drawings:

Fig. l is a diagrammatic View of a complete refrigeray modified purger connections.

Referring to Fig. 1, the refrigerating system shown therein comprises a boiler 1 havinga suitable heater such as a gas burner assembly 2 anda draft-inducing iiue 3, only a portion of which is shown. Mercury vapor passes atentd Jan. 3, 1956 from the boiler 1 through a riser 5 to the branches 5a and 5b which are connected, respectively, to the interconnected rst and second stage aspirators 6a and 6b of a multiple stage ejector. The rst stage aspirator 6a is connected by a vapor duct Sto my improved cooler or evaporator 11 (hereinafter more fully described) which contains a body of aqueous refrigerant containing a suitable antifreeze agent. Vapor is drawn through the duct 8 to'the mixing chamber of the first stage aspirator and the mixed propellant mercury vapor and the refrigerant vapors are passed through the aspirator where the refrigerant is compressed and the mercury is condensed.

The condensed mercury flows from the first stage aspirator into a drain 1 4 while the compressed vapor passes through a duct 15 to the second stage aspirator 6b into which a second stream of mercury vapor flows from the line 5b, this latter propellant stream causing a further compression of the refrigerant vapor in the second stage aspirator. Drains 27 and 27a receive the condensed mercury from the second stage aspirator and the two drains 27 and 27a join the drain i4 at 28 and 28a, respectively, the drain 14 being connected to an inclined drain line 31 which is normally filled with mercury. The compressed refrigerant passes upwardly from the second stage aspirator through duct 29 to the refrigerant condenser 30. The condenser 30 may be of any suitable form and is here shown as being disposed within a water tank or reservoir T, as in Patent No. 2,174,302, granted September 26, 1939, to which reference may be had for a more detailed description of the system.

A chamber or drum 32 is preferably located at the end of the condenser 30 remote from the inlet of the pipe 29, and one end of a pipe 39 communicates with the chamber 32 so as to receive noncondensable gases therefrom. The lower portion of this chamber is connected with a drain or refrigerant return pipe 34 through which the condensed refrigerant passes on its way back to the cooler 11.

The lower end of return pipe 34 is connected with the upper end of the inclined drain line 31 and also with a vertically extending double bend, having legs 40 and 4l through which condensed refrigerant standing in line 34 pushes through the mercury at its junction with leg 40 and pipe 34, and thus makes its way back to the cooler 11. The junction 43 of the lower end of the drains 31 and 14 is connected with an upwardly inclined spill-over line 42 which is connected with the line 39 at 60, which connection determines the normal mercury level L of the system.

The lower end of the leg 41. is connected to the intermediate portion of a vertical capillary tube 45, the upper and lower ends of which are respectively connected with inlet and outlet openings at the top and bottom of the cooler 11, as hereinafter more fully explained. The parts 41 and 45 provide a vapor lift, as more fully explained in the copending application of Eastman A. Weaver, Serial No. 60,881, filed November 19, 1948, now Patent No. 2,633,007, granted March 31, 1953.

The lower end of cooler 11 is provided with a sludge drain 46 connected to the central part of a drum 48, the upper end of which is connected by a line 50 with a mercury return pipe and boiler feed 52, and the lower end of the drum is connected by a line 54 with the return line 52 at a level slightly higher than the junction of drain 46 and drum 4S. The upper end of this return line 52 is hooked so as to connect in at the top of vapor duct 8, and its lower end is connected to the inlet of boiler 1. With this construction and arrangement of parts, mercury and mercury sludge (an emulsion of mercury in the aqueous refrigerant) accumulating in the lower part of the cooler 11 ow through drain 46 into drum 4S where they are subjected to the action of the low pressure in duct 3. Hence the emulsion or sludge is broken up by evaporation of the aqueous component and the mercury is returned to the boiler through line 52.

As above noted, and as shown Amore clearly in Fig. 5, the spill-over line 42 and lower end of line 39 are connected at so as to provide a purger comprising a mercury pump in which drops or slugs of mercuryrun down a capillary tube 62, trapping noncondensable gases drawn from chamber 32 and compressing them to more than atmospheric pressure. The lower end of tube 62 is connected with an inclined fitting or pipe line 64, the upper end of which is provided with a vent cap 66 open to the atmosphere and the lower end of which is connected to a return branch 68 which in turn is connected with the return line 52. With this construction and arrangement the parts 62, 64 and 68 providea trap for the mercury whichpermits the entrapped gases carried down and compressed by the mercury to rise in the line 64 and escape through vent cap 66, while the mercury returns through lines 68 and 52 to the boiler 1.

The parts 62, 64, etc. are disposed in relatively close proximity to the riser 5 and are enclosed by suitable insulating material within the contines of broken line A (Fig. l) so that they are normally maintained at a temperature above 212 F., thereby preventing an accumulation of mercury sludge in any part of the purger system.

Both the aspirators 6a and 6b are provided with cooling jackets interconnected by the duct 70, the rst stage aspirator 6a having a cooling line or riser 71 connected with a condenser 72 within the tank T which has the usual pump-out connection SS, cold water supply line 86, and hot water discharge line 87, as in Patent No. 2,174,302. The Water in tank T is thus heated by the condensation of the primary refrigerant and the cooling fluid which absorbs a major portion of the heat of condensation from the mercury vapors.

Referring to Figs 2 to 4, the cooler 11 comprises a hollow inner housing 101 and a hollow outer housing 102, the inner housing 101 having a bottom wall consisting of a Fiat inner plate 104 (Fig. 4) and a corrugated outer plate 105. The plates 104 and 105 extend upwardly to form the inner and outer side walls 106 and 107 of the housing 101 (Fig. 3), and their top and end edge portions are sealed together so that the plates 104 and 1.05 define an enclosure which receives a secondary iiuid such as Freon, it being noted that passages in both the bottom and side walls defined by the corrugations or reinforcing grooves intercommunicate with one another.

The housing 102 is generally similar to the housing 101 in that it comprises inner and outer plates 1.10 and 1.11 formed with reinforcing dimples 112 which maintain them in properly spaced relation. These plates are shaped to provide a hollow, roof-like top wall 115 and hollow depending walls 116 and 117 intercommunicating with each other. The enclosure or outer housing thus dened by the inner and outer walls and 11.1 receives the primary aqueous refrigerant which is normally at a level below the vapor duct outlet 118 and above the junction of tube 45 with arm 41 so as to provide at all times a liquid-vapor interface. The construction and arrangement of parts are such that the outer side wall of the inner housing 101 is-in direct heat transfer relation to the inner side walls of the outer housing so that vapors of the secondary uid in the upper part of the side walls of the inner housing quickly transfer their latent heat to that portion of the inner side walls of the outer housing contiguous or adjacent to the liquid-vapor interface which, of course, has a relatively great heat-absorbing capacity. Thus, vapors of the secondary fluid transfer their latent heat to the primary refrigerant which is constantly being vaporized and ultimately the latent heat of the latter is transferred to the water in tank T along with the heat transferred from the fluid in the cooling jackets.

The telescoping housings 101 and 102 provide a storage compartment for receiving foods or articles to be stored, and the front may be provided with the usual doors (not shown) through which access to the interior may be had. I use a vapor lift in this embodiment similar to that disclosed in the copending application of Eastman A. Weaver, Serial No. 60,881, filed November 19, 1948, now Patent No. 2,633,007, granted March 31, 1953. To this end the inner plate 110 of the housing 102 is formed `vith a central trough 120, the bottom wall of which in clines from rear to front, as shown in Fig. 4. The outer plate or wall 111 is formed with an inlet opening 122 adjacent to the rear of the trough and the upper or delivery end of capillary tube 45 communicates with the opening so as to deliver liquid refrigerant to the trough. The lower end of tube 45 is connected to the rear bottom wall of the outer housing adjacent to its connection with the sludge drain 46.

The lower end of the trough 120 is connected with a J-tube 125 which provides a mercury trap operative to hold back the aqueous refrigerant in the trough and at the same time permit stray particles of mercury to pass therethrough to the bottom of the outer housing and then into the drain 46. All or part of the wetted sloping top surface of wall 110 is preferably roughened as by Sandblasting or otherwise formed with capillary rugosities effective to increase the liquid-vapor interface and distribute refrigerant overflowing from trough 120 over the maximum area, as in my copending application, Serial No. 36,932, now Patent No. 2,562,652, granted Iuly 31, 1951.

In operation the vapor lift carries refrigerant from both the lower part of the outer housing and the return line 34 to the trough 120 where it overflows onto the rugose surface of the wall 110 and forms additional liquid-vapor interface by trickling down the inner side walls where appreciable vaporization takes place from the extended liquid-vapor interface thus formed. Since the inner side walls of the outer housing are in heat-transfer relation to the outer side wall of the inner housing, the latent heat of the secondary refrigerant is readily transferred to the primary refrigerant and hence the overall efficiency and capacity of the system is greatly increased.

In the embodiment shown in Figs. 1 and 5, the purging outlets 32 and 32a are connected at the low points of the condenscrs because air is, in general, heavier than the aqueous refrigerant vapor. If, due to contained antifreeze vapors or for other reason the refrigerant vapor is the heavier, then the connection should be at a high point remote from the vapor inlet, as shown in Figs. 6 and 7, wherein the same or similar reference characters as used in Fig. 1 are employed to designate the same or corresponding parts. In any case the condensed refrigerant is drawn from the condenser through the return 34 which is connected at or close to the lowest point of the condenser.

The present application is a division of my copending application, Serial No. 119,489, filed October 4, 1949, now United States Patent No. 2,678,548, granted May 18, 1954.

I claim:

1. Refrigerating apparatus comprising a compartment having a housing formed with spaced inner and outer top and side walls providing an enclosure, a primary liquid refrigerant disposed within said enclosure so as to provide a liquid-vapor interface in heat transfer relation to the interior of said compartment between its upper and lower parts, a second enclosure formed with spaced inner and outer side walls, the side walls of one enclosure being disposed in close thermal contact with the side walls of the other enclosure so that the upper part of the second enclosure is in heat transfer relation to at least a part of said liquid-vapor interface, and a secondary refrigerant within said second enclosure said secondary refrigerant having a vapor pressure greater than that of the primary refrigerant and adapted to reux in response to a temperature differential between said liquid-vapor interface and the lower part of said second enclosure, thereby transferring heat from the latter to said interface.

2. Refrigerating apparatus comprising a compartment having a housing formed with spaced inner and outer top and side walls providing an enclosure, the top wall slanting from its intermediate portion toward the side walls, a

primary liquid refrigerant within said enclosure at a level below the upper part of said walls so as to provide a liquid-vapor interface in heat transfer relation to the interior of said compartment between its upper and lower parts, a vapor duct connected to said enclosure above said level, a condensate return connected to said enclosure so as to deliver condensate to the upper part of the inner top wall, a second enclosure having spaced inner and outer side walls in telescopic relation to those of the first enclosure so that the upper part of the second enclosure is in heat transfer relation to at least a part of said liquidvapor interface and its lower part in heat transfer relation to the lower part of said compartment, and a secondary fluid within said second enclosure, said secondary refrigerant having a vapor pressure greater than that of the primary refrigerant and adapted to reflux in response to a temperature differential between said liquid-vapor interface and the lower part of said second enclosure, thereby transferring heat from the latter to said interface.

3. Refrigerating apparatus comprising a compartment having a housing formed with spaced inner and outer top and side walls providing an enclosure, the top wall slanting from its intermediate portion toward the side walls, a primary liquid refrigerant within said enclosure at a level below the upper part of said walls so as to provide a liquid-vapor interface. in heat-transfer relation to the upper part of said enclosure, a vapor duct connected to said enclosure above said level, a condensate return connected to said enclosure so as to deliver condensate to the upper part of the inner top wall, the inner surface of said inner top wall being formed with capillary rugosities effective to distribute refrigerant delivered by saidcondensate return over an extended area of its surface, a second enclosure having spaced inner and outer side walls in close juxtaposition to those of the first enclosure so that the upper part of the second enclosure is in heat transfer relation to at least a part of said liquid-vapor interface, and a secondary refrigerant within said second enclosure having a vapor pressure greater than that of the primary refrigerant and adapted to reflux in response to a temperature differential between said liquid-vapor interface and the lower part of said second enclosure, thereby transferring heat from the latter to said interface.

4. Refrigerating apparatus comprising a compartment having a housing formed with spaced inner and outer top and side walls providing an enclosure, a primary liquid refrigerant disposed within said enclosure so as to provide a liquid-vapor interface in heat transfer relation to the interior of said compartment, an upper portion of said top and side walls being formed with capillary rugosities, a second enclosure formed with spaced inner and outer side walls, the side walls of` one enclosure being disposed in close thermal Contact with the side walls of the other en.- closure so that the upper part of the second enclosure is in heat transfer relation to at least a part of said liquidvapor interface, and a secondary refrigerant within said second enclosure, said secondary refrigerant having a vapor pressure greater than that of the primary refrigerant and adapted to reflux in response to a temperature differential between said liquid-vapor interface and the lower part of said second enclosure, thereby transferring heat from the latter to said interface.

References Cited inthe kfile of this patent UNITED STATES PATENTS 1,798,951 Munters Mar. 31, 1931 1,942,458 Taylor Ian. 9, 1934 1,979,617 Heidman Nov. 6, 1934 2,003,414 Allyne June 4, 1935 2,075,438 Heitman Mar. 30, 1937 2,174,303 Whitney Sept. 26, 1939 2,175,419 Whitney Oct. 10, 1939 2,261,682 Hedlund Nov. 4, 1941

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