USRE21599E - A schwarz - Google Patents

Description

Oct. 15, 1940- A. SCHWARZ PROCESS OF AND APPARATUS FOR REFRIGERATION Sheets-Sheet 1 Original Filed April 18, 1930 HTTZZENEYTS Oct. 15, 1940.

Original Filed April 18, 1930 A. SCHWARZ rnocass OF AND APPARATUS FOR REFRIGERATION 2 Sheets-Sheet 2 Reirsued Oct. 15. 1940 UNITED STATES PATENT OFFICE PROCESS OF AND APPARATUS FOR REFRIGERATION August Schwarz, Chicago, IIL

20Claims.

The present invention relates generally to an improved process of and apparatus for refrigeration, and has reference more particularly to a novel process of refrigeration embodying the use of carbon dioxide (CO2) as the refrigerant. In certain respects, the' present invention is an improvement of that disclosed in my copending application Serial Number 429,176, filed February 17, 1939.

One of the objects of the present invention re-.

sides in a novel process of refrigeration in which carbon dioxide as the refrigerant is condensed and cooled by means of cold brine having approximately zero Fahrenheit so that very low condenser pressure, resulting in an exceptionally low temperature of vaporization by low suction pressure, will be obtained.

Other objects reside in the provision of a new and improved process of refrigeration which comprises two stages for liquefying and vaporizing the refrigerant to produce low temperatures by low condensing and suction pressures, and in the preferred form of which the low temperature refrigerant is carbon dioxide. and the refrigerating medium for condensing the carbon dioxide is vaporized ammonia.

Further objects are to provide a novel refrigerating plant which may be utilized to accomplish the foregoing objects, and which comprises an ar rangement of pipes and valves, for connecting the various operating units, adjustable at will to produce selectively any one of a plurality of systems, for example, 1) a two stage system' adapted to operate at different pressures, and (2) a single stage system in which the evaporator is adapted to be connected in a closed circuit with either a water cooled condenser or a brine cooled condenser, and (3) a split stage system wherein the water cooled condenser may be connected with the brine or gas cooled condenser and wherein the brine or gas cooled condenser unit functions as an evaporator.

Another object of my invention is to provide a refrigeration system employing carbon dioxide, or a similar refrigerant, having a brine cooled or a gas cooled condenser wherein the system operates with a lesser amount of refrigerant, which would not condense under atmospheric condition and wherein the refrigerant gas in the condenser is cooled by cold brine or gas and the carbon dioxide gas is only partly liquefledor densified. under low pressure, and whereby said partly liquefied or densitled gasis expanded down to approximately atmospheric pressure or by creating a vacuum on the low side of the system.

Another object of the invention is in providing a low temperature condensing and cooling apparatus wherein the heat absorbing surface of the refrigerant evaporating passage is approximately twenty-five per cent greater'than the heat transfer surface of the condenser passage.

Other objects and advantages will become apparent as the description proceeds.

In the accompanying drawings- Figure l is a plan view of a plant embodying the principles of the invention.

Figure 2 is a horizontal sectional view of a combination evaporator and condenser shown in plan in Figure 1.

Figure 3 is a sectional view along the line 3-3 of Figure 2.

Figure 4 is a horizontal sectional view through an evaporator, shown in plan in Figure 1, and

Figure 5 is a horizontal sectional view through a condenser shown in plan in Figure 1.

In the plant according to the present invention a condenser I2 is provided through which a refrigerant is forced by pressure exerted by a compressor I4.

The refrigerant flows from said compressor through a pipe line 45 in which valves 51 and 50 are located and into a header 20 of condenser I2. The condenser I2 (see Figure 5) has a pair of header tanks 21 and 28 and a plurality of condenser tubes 29 connecting said two header tanks. 30

These tubes extend through the space 30 in the condenser I2. The liquefied refrigerant flows from the header tank 21 through pipes 46 and BI and an expansion valve 02 into a combination evaporator and condenser II. This refrigerator unit I I (see Figures 2 and 3) consists of evaporating tubes I1 connecting oppositely arranged header tanks 2| and 22.

From the header tank 22', the refrigerant vapor is drawn oil by the compressor 14 through pipes 11 and 44, and in said pipe line a plurality of shutoff valves 56, 10,19 and 80 are provided. In this manner the circuit of the refrigerant is closed.

The condenser I2 of this first refrigerating system is cooled by means of fresh water which is forced by a pump 36 into the space 30 in the condenser I2 through the pipe I08. From the space 30, the fresh water is drained off through a pipe I09. Suitable valves 9 and I20 are interposed respectively in the pipes I00 and I09. This condenser I 2 may be of any suitable construction.

An exaporator I0 (see Figure 4) is provided, having two oppositely located header tanks 24 and 25 which are connected with each other by means of a plurality of refrigerating tubes 23, extending 55 arranged and extend at right angles between the evaporator tubes II as shown clearly in the Figures 2 and 3, the condenser tubes connecting two header tanks I! and 20. Free passages are arranged in said unit for introducing and withdrawing a fluid medium, said medium being in contact with said condenser and evaporating tubes, if desired. coils or coils and tubes may be arranged in said unit, and the construction of said unit may be in the form of a shell or housins.

The refrigerant used in the second evaporator system is CO2. and this refrigerant leaves the condenser tubes l6 and the header tank 20 in the liquid condition through pipes 88 and 48, and flows through an expansion valve 84 into the evaporator tubes 23. From here the refrigerant vapor is drawn of! through pipes 40, 65 and 86 by a compressor N, which recompresses and forces the refrigerant through a pipe line 61 into the header tank I 9 and back into the CO: condenser tubes li.

The above shows clearly that in the plant according to the present invention, two refrigerating stages are present, and that the CO2 in the condenser tubes I8 is cooled by means of the evaporator tubes l I, that is, the refrigerant of the first refrigerating stage. It will be noted that the unit II has a larger cooling surface than condensing surface, thus especially adapting the unit for low temperature operation, whereby heat transfer is accomplished without excessive condensing surface. Within the broad concept of the invention, any suitable refrigerant or refrigerants may be used in the two stages. If carbon dioxide is used as the refrigerant in both stages, the pressure in the first stage will be normally high, but the pressure in the second stage will be exceptionally low. Carbon dioxide is .safe in use, and hence desirable as a refrigerant on shipboard. If ammonia is used as the refrigerant in the two stages, the pressure in the second stage will be exceptionally low. The use of ammonia in the first and carbon dioxide in the second stage has the advantage that less power will be required with greater emciency in the present split stage system, using ammonia in the first stage and carbon dioxide in the second stage, than in a single stage high pressure carbon dioxide system, in which the condenser is cooled by fresh water.

It will be understood that the pressure in the second stage CO: condenser is subject to control by varying either the temperature or the amount of refrigerant therein. Thus, it is possible to operate the second stage condenser at a pressure higher or lower than from 300 to 350 pounds at a given temperature, for example 0 l-"., by respectively increasing or decreasing the amount of carbon dioxide employed.

Also, the operating pressure of the second stage condenser may be reduced below or increased above the aforementioned pressure range by respectively decreasing or increasing the temperature in the condenser. Obviously, the operating pressure may also be changed by varying both the temperature and the amount of carbon dioxide employed, that is to say, that a pressure approximately from 100 to 500 pounds may be maintained in the CO: condenser at a given temperature.

Before starting the second refrigerating system in which CO: is used as a refrigerant. the CO: in the condenser tubes II in the combination tank will be cooled down to about zero Fahrenheit by the refrigerant in the evaporating tubes ll of the first refrigerating system. It

will be understood that both systems may be started at the same time if desired. If desired, a brine solution may be present in the space surrounding the evaporator tubes l1 and the condenser tubes I! in the tank II and may be circulated in said space by means of a brine pump 85 and. a pipe line 84. Suitable valves ll and ll are arranged in the pipe lines .84 at opposite sides of the unit ll.

If the pressure in the cm condenser originally is 900 pounds at a temperature 'of about "15 degrees above zero Fahrenheit, this pressure will be reduced to about 300 to 350 pounds when the above mentioned temperature of zero Fahrenheit is Obtfilllflly That means that the pressure will be reduced about 66 percent when the second refrigerating system is started. and the liquid C0: will leave the condenser pipes Ii at approximately this temperature, and will enter the evaporator Ill at about the same temperature.

In this evaporator, the liquid CO: is vaporized and is then drawn off and recompressed by the compressor l5. Since this CO: enters the evaporator at a very low temperature, and evaporates at a still lower temperature, the suction pressure will be correspondingly low, so that the object of the invention is obtained, namely: Low temperature is produced by low condenser and suc-' tion pressure.

On account of the heat created by compression of the CO: and the heat absorbed by the housing or unit II, and the necessity of maintaining a temperature below the liquefaction temperature of the CO: and to permit heat transfer without excemive condenser surface in the CO2 condenser, the flrst refrigerating system has to have a capacity about 25 percent higher than the second one, and in addition to the 25 percent higher capacity mentioned, provision must be made for any additional load which may be carried by the first system, and for that reason the first stage refrigerating system must be provided with refrigerating tubes or coils having a greater heat absorbing capacity than the refrigerating tubes or coils of the second system (if tubes or'coils are employed) and the refrigerating tubes If .in the CO: condenser are placed closer together and are more in number than the condenser tubes or coils l6.

By a pump 35, any suitable heat carrying medium may be forced through Pipes I03, I04, the CO1 evaporator space 28 and a pipe I" to a cooling room (not shown). From the cooling room, this medium may be returned through pipes llll and llll to the pump 35. The flow of the heat carrying medium is controlled by valves I'll to H5 and I23.

Extremely low temperatures may be produced by reducing the pressure on the low side of the CO2 system down to approximately atmospheric pressure or to a vacuum by employing the absorption method.

If desired, the tank ll may be eliminated and the fresh water cooled condenser I! may be connected directly with the CO: evaporator by means of the pipes 46, 41, 48, and expansion valve 64.

The refrigerant gas in the evaporator 13 will then be drawn oil and recompressed by the compressor i4 through the pipes 40, 85, I4, 43 and 44, and will be returned to the fresh water cooled condenser through the pipe 45. In this case the liquid refrigerant would enter the evaporator ill at a higher temperature than described before. and in consequence, the suction pressure would be correspondingly higher. Thus, the plant may be converted at will into a single stage system.

The plant may also be operated as a single stage system with the unit II as a condenser. In this event, brine may be utilized as the cooling medium. The fresh water cooled condenser H with the compressor i 4 canbe disconnected by closing valves 55, 56, 80 and 83.

If the fresh water cooled condenser i2 is to be used in connection with the refrigerating tubes II in the tank II, the valves 51 and 58 in the pipe line 45, valves 58 and 83 in the pipes 48 and II, the valves Oil, 19 and I! in the pipe line 11 and the valve 86 in the pipe line 44 must be open. At the same time, valves ill and ii inthe pipe 41 and a valve 55 in the pipe 43 must be closed. To connect the C: evaporator l0 with the condenser tubes I8 in tank ii, valves 50, ii, 68, [0, II, 12, 13', 62 and 83 in the pipes 40, 85, 68, 61, Cl and 48 must be open. When. however, the fresh water cooled condenser I2 is to be connected directly with the CO: evaporator,

'the valves 83, I3, 80 and 18 must be closed while the valves 59, 80, Si, 82, 83, 50, 5|, 6!, I6, 15, 54, 55 and 56 have to be open.

It will be evident that I have provided a refrigerating system which may be adjusted for use in different ways and which therefore is adapted to satisfy widely varying demands. Thus, the entire plant, including both stages, may be employed. In this event, brine may or may not be used in the refrigerator and condenser unit II. If brine is used in the unit II, it will be available at the temperature prevailing in the unit for use in the cooling room (not shown). Assuming that brine is circulated through the refrigerator ill, brine at two different temperatures will be available from separate sources, namely, from the units Ill and II, respectively.

If the refrigeration requirements drop to such a point that the full capacity of the entire plant or system is not needed, the plant may be converted into any one of a plurality of single stage systems of varying capacity. For example, one single stage system may include the evaporator ill, the compressor I5, the condenser tubes ii in the unit ii and the expansion valve 64, connected in series in the order named, and utilizing either brine or fresh water as the condensing medium in the space I8 about the tubes It. It will be understood that when brine is used as the condensing medium, it ,will be obtained from an outside source at a suitably low temperature.

As an alternative expedient, another single stage system comprises the refrigerator Hi, the compressor I4, the fresh water cooled condenser l2 and the expansion valve 64, connected in series in the order named. v

As a still further expedient, a third single stage system may include the tubes H in the unit II as refrigerating tubes in contact with brine or any other fluid medium to be cooled, the comprmsor l4, the fresh water cooled condenser i2 and the expansion valve 82, connected in series in the order named, preferably with ammonia as the refrigerant.

Thus, the refrigerating plant by reason of its convertibility at will into any one of a plurality of single and double stage systems, has a flexible capacity adapted to satisfy widely varying refrigeration demands. When the refrigeration demands are small, it would be wasteful to operate the entire plant at its maximum capacity, and

- hence one of the various single stage systems, best suited to the particular demand, would be emp yed.

Having described my invention and how the same is to be used, I claim as new, and desire to secure by Letters Patent:

1. In a two stage refrigerating system and method of producing low temperatures by low condenser and suction pressures two refrigerating systems adapted to cooperate with each other, the condenser of the first system being cooled by fresh water. a combination evaporator and condenser unit consisting of a closed housing containing the refrigerating tubes or coils of the first and the condenser tubes or coils of the second system with brine passages therebetween, a by-path connecting the pipe line, leading from the fresh water cooled condenser, to the pipe conducting the liquid of low boiling point from the condenser tubes of the second system to the evaporator of the same system, a second by-path connecting the suction line of the first system with the suction line of the second system, a valve adapted to prevent the entrance of the refrigerant into the evaporator tubes of the first system, another valve arranged in the suction line of the first system before the junction of said line with the second by-path, a third valve inserted in the suction line of the second system right behind the junction of the second by-path with said line, a fourth valve in the pipe conducting the liquid refrigerant of low boiling point to the evaporator of the second system and located between the outlet of the condenser of the second system and the first by-path and a valve in each of said by-paths.

2. A refrigerating system comprising, in com- I binati'on, a primary system having an evaporator, a compressor, a suction conduit connecting said evaporator to said compressor, a fresh water cooled condenser connected to said compressor, an expansion valve'connected to discharge into said evaporator, a discharge conduit connecting said condenser to said expansion valve, a secondary system having a second evaporator, a second compressor, a second suction conduit connecting said second evaporator to said second compressor, a second condenser connected to said second compressor, said second condenser and said first mentioned evaporator being arranged in heat exchange relation for the transfer of heat from the former to the latter, a second expansion valve discharging into said second evaporator, a second discharge conduit connecting said second condenser to said second expansion valve, a valve controlled connection between the second condenser and said second discharge conduit, a bypass conduit includinga control valve leading from said second suction conduit at a point between said second evaporator and said second mentioned compressor to said first mentioned suction conduit, and a by-pass conduit including a control valve leading from said first mentioned discharge conduit to said second discharge conduit.

3. A refrigerating system comprising, in combination, a primary system having an evaporator, a compressor, a suction conduit connecting said evaporator to said conpressor, a fresh water cooled condenser connected to said compressor,

an expansion valve connected to discharge into said evaporator, and a discharge conduit connecting said condenser to said expansion valve, a secondary system having a second evaporator, a second compressor, a second suction conduit connecting said second evaporator to said second compressor, a second condenser connected to said second compressor, said second condenser and said first mentioned evaporator being arranged in heat exchange relation for the transfer of heat from the former to the latter, a second expansion valve discharging into said second evaporator. and a second discharge conduit "connecting said second condenser to said second expansion valve. a by-pass conduit including a control valve for connecting said two suction conduits, and a bypass conduit including a control valve for connecting said two discharge conduits.

4. A refrigerating systerncomprising, in combination, a primary system having an evaporator, a compressor, a suction conduit connecting said evaporator to said compressor, a fresh water cooled condenser connected to said compressor, an expansion valve connected to discharge into said evaporator, and a discharge conduit connecting said condenser to said expansion valve, a secondary system having a second evaporator, a second compressor, a second suction conduit connecting said second evaporator to, said second compressor, a second condenser connected to said second compressor, said second condenser and said first mentioned evaporator being arranged for the transfer of heat from the former to the latter, a second expansion valve discharging into said second evaporator, and a second discharge conduit connecting said semnd condenser to said second expansion valve, a by-pass conduit including a control valve for connecting said two suction conduits, a control valve in said second suction conduit between said -by-pass conduit and said second compressor, a by-pass discharge conduit including a control valve for connecting said discharge conduits, and a control valve in said second discharge conduit between said second condenser and said by-pass discharge conduit.

5. A refrigerating system comprising, in combination, an evaporator, an expansion valve discharging to said evaporator, and two separate refrigerant paths connected between the outlet of said evaporator and the inlet of said valve, said paths being selectively available, one path including a compressor and a brine and gas cooled condenser, the other path including a compressor and a water cooled condenser, and two separate paths arranged in said brine and gas cooled condenser, means for leading brine to and away from one of said separate paths, and means for leading a refrigerant to and away from the other of said separate paths.

6. A refrigerating system comprising, in combination, a primary single stage system including afirst evaporator, a compressor, a condenser, and an expansion valve connected in series in the order named, a second single stage system including a second evaporator, a compressor, a second condenser and an expansion valve connected in series in the order named, said first evaporator and said second condenser being arranged in a single unit in heat exchange relation, means for circulating a fluid medium through said unit to effect a heat exchange therebetween and to cool the fluid medium to a low temperature for outside use, and means for circulating a fluid medium through said second evaporator to cool' it to a low temperature, said systems being operable Jointly,

or one or the other may be operated single, by leading a fluid medium to be cooled through said unit in connection with said first or primary system, or'by leading a fluid medium through said unit to cool the condenser of the second system.

'7. A refrigerating system comprising, in combination, a compressor, a condenser, the inlet of said condenser being connected to the discharge of said compressor, a refrigerating element connected to the discharge of said condenser, an expansion valve interposed between said condenser and said element, the discharge of said element being connected to the inlet of said compressor, a second compressor, a second condenser having a housing for enclosing said refrigerating element, said second condenser being connected to the discharge of said second compressor, a refrigerator or evaporator connected to the discharge ends of said condensers, a valve controlled by-pass be tween the outlet of the first mentioned condenser and the outlet of the second mentioned condenser whereby the refrigerant from said condensers may becommingled and expanded into said refrigerator or evaporator, an expansion valve at the inlet of said refrigerator or evaporator, and valve controlled means connecting the discharge of said refrigerator or evaporator to said compressors.

8. A low temperature condenser and cooler comprising, in combination, a housing defining a chamber, condenser and cooler means defining a closed passage or passages extending through said chamber, means adapted to lead a medium to be condensed and cooled or a liquid to be cooled through said passage or passages, a refrigerating element or elements defining a closed passage or passages extending through said chamber and adapted to expand and evaporate a refrigerant therein to abstract heat from said first mentioned passage or passages, and means for leading cold brine through said chamber, said brine and said vaporized refrigerant being employed singly or jointly to abstract heat from said medium passing through said condenser and cooler means.

9. A refrigerating system comprising, in combination, a first system and a second system, each including a compressor, a condenser, an expansion valve and an evaporator connected in a closed circuit in the order named, a heat exchange in which the evaporator of the first sys tem and said condenser of the second system are located and defining therewith a combination evaporator and condenser unit, means for leading a fluid medium to be cooled through said unit, said first system having a much greater heat absorbing capacity than said second system so as to remove the heat of the second system and also to remove heat from the medium passing through said unit.

10. In a refrigerating apparatus, a combined evaporator and condenser comprising a single closed housing defining a chamber, two opposed headers respectively at two opposite walls of said housing and having means for introducing and withdrawing a refrigerant, a plurality of rows of spaced condenser tubes connectingsaid headers and extending through said chamber, two opposed headers respectively at two other opposite walls of said housing and having means for expanding a refrigerant into one of said last mentioned headers, and aplurality ofrows of spaced refrigerating tubes connecting said last mentioned headers and extending through said pressing,

chamber, and means for introducing and withdrawing brine from said chamber.

11. A two stage refrigerating system consisting of two refrigerating systems, each system comprising a compressor, a condenser, an expansion valve and an evaporator arranged in the order named to form two closed refrigerating cycles, the first system employing-a refrigerant of high boiling point and the second plant employing a refrigerant of low boiling point, the evaporator of one system and the condenser of the other system being arranged in a single closed shell or housing to constitute a combined evaporator and condenser unit having a free passage or passages for a fluid medium therethrough, valve controlled connections whereby one of said systems may be disconnected from the other system and said combined evaporator and condenser unit then made to function merely as an evaporator unit, and means whereby a fluid medium to be cooled is circulated through the free passage or passages in said unit.

12. In a two stage refrigerating system, a combined evaporator and condenser unit consisting of a closed housing provided with two sets of elements arranged in heat exchange relation and having free passages'therebetween, the element of one set being a refrigerating element of one stage and the element of the other set being a condenser element of the other stage, the refrigerating element of one stage having a greater heat absorbing capacity than the condenser element of the second stage and also having a greater heat absorbing capacity than the evaporating element of the second stage, and means 7 for circulating a fluid medium through said passages in contact with both sets of elements and for conveying the fluid medium to and away from said housing.

13. The process of producing low temperature without vacuum operation which consists in comcondensing, expanding and vaporizing a volatile refrigerant in one path in a continuous cycle, circulating a refrigerant of low boiling point in a second path in a. continuous cycle, and with the vaporizing portion of the first path in heat exchange relation with the condensing portion of the second path, utilizing the low temperature of the vaporized refrigerant in the first path to greatly reduce the pressure and temperature of the refrigerant on the high side of the second path, maintaining the low pressure and low temperature on the high side of the second path during operation, thereby greatly reducing the power required in said second path, expanding and vaporizing the low temperature refrigerant of relatively low pressure by a correcycle, circulating a refrigerant of low boiling point in a second path in a continuous cycle and with the vaporizing portion of the first path in heat exchange relation with the condensing portion of the second path, utilizing the low tempermedium in conta :t with the heat exchange POrtions of the two paths, and utilizing the medium for outside use.

15. In a combination condensing and refrigerating apparatus, a closed housing defining a chamber provided with a passage adapted to receive a refrigerant gas to be condensedand cooled to a low temperature, and a refrigerant cooling medium receiving passage for vaporizing a refrigerant therein, and a third passage adopted for introducing and withdrawing a fluid medium to-be heated or cooled in direct contact with said other two passages, the last mentioned passage having a much greater heat absorbing surface than the condenser passage heat transfer surface, either two of said three mentioned passages may be operated independently.

16. A refrigerating system comprising, in combination, an evaporator, an expansion valve discharging into said evaporator, and two separate refrigerant paths connected between the outlet of said evaporator and the inlet of said valve, said paths being selectively available either singly or jointly,'one path including a compressor and a water cooled condenser, the other path including a compressor and a low temperature brine or gas cooled condenser.

17. In a two-stage split stage system, having a compressor and a condenser, a conduit connecting said compressor and said condenser, a secondary condenser, a liquid discharge conduit connecting said condenser and said gas cooled condenser, an expansion valve inserted in said discharge conduit to supply refrigerant to-said gas cooled condenser through said valve, an exhaust conduit opening from said gas cooled condenser, and connected to the inlet of said compressor to draw off the vaporized refrigerant and return the same to the first mentioned condenser, an evaporator, a liquid discharge conduit opening from said gas cooled condenser and connected to said evaporator, an expansion valve inserted in said last mentioned discharge conduit to supply refrigerant to said evaporator through said valve, a conduit connecting the discharge of said evaporator and the gas cooled condenser, a compressor inserted in said last mentioned conduit to draw on the vaporized refrigerant and return the same to the gas cooled condenser, a valve controlled branch conduit opening from said first mentioned liquid discharge conduit, and a valve controlled branch exhaust conduit in said first mentioned exhaust conduit.

18.. A refrigerating apparatus comprising, in combination, a housing defining a chamber therein, a plurality of closed passages arranged in said shell or housing and including said chamber, one of said closed passages being adapted to expand and vaporize a'refrigerant therein, another of said passages being adapted for leading cold brine therethrough, still another of said passages being adapted for leading a gaseous medium to be condensed or a liquid to be cooled therethrough, said vaporized refrigerant and said cold brine may be employed singly or jointly to abstract heat fromsaidgaseousmediumorfromsaidliquid.

19. A split stage refrigerating system for producing low and moderate refrigeration temperatures. consisting of two independent refrigerating systems cooperating with each other, said systerns permitting the use of diilerent refrigerants. the condenser element of one system and the refrigerating element of the other system being arranged in heat exchange relation ina heat exchange unit having a free fluid passage therethrough, and means for leading a fluid medium to be heated or cooled in heat exchange relation with said elements to and away from said unit, either one of said system when desired may be operated as an independent refrigerating system to do useful refrigerating work.

20. In a refrigerating apparatus 'of' the character described, a closed housing provided with a plurality of independent passages for condensing a refrigerant and for vaporizing a refrigerant and to receive a fluid to be heated or cooled, each of said passages having separate inlets and outlets whereby diilerent refrigerants and a medium to be heated or cooled may beeonveyed through said independent passages and in heat exchange relation with each other, the vaporizing passage being of greater capacity than the condenser passage.

AUGUST SCHWARZ.

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