US2139996A - Cooling system for compressors - Google Patents

Description

Dec, 13, 1938. B. M BUCHANAN 2,139,996

I COOLING SYSTEM FOR COMPRESSORS Filed June 5, 1956 INVENTOR Lzsu: anBuu-munu' BY ATTOR EY STATES 2,139,998 coomve SYSTEM non oonmmzssons Leslie B. M. Buchanan, Springfield, Mesa, assignor to Westinghouse Electric & Manufacturing Company, East Pittsb of Pennsylvania urgh, Pa, a corporation Application June 5, 1936, Serial No. 83,617

6 Claims. (01.230-208) My invention relates to cooling systems for motor driven compressor mechanisms of the hermetically-sealed type and has for an object to provide an improved system.

A further object of my invention is to provide an improved cooling system for apparatus of this kind wherein a heat exchanging fluid such as, for example, lubricant is circulated over the apparatus for cooling the same.

A further object of the invention is to effect a reduction in the operating temperature of conventional mechanisms of this kind without increasing the amount of lubricant that is circulated.

A still further object of my invention is to provide an improved system for cooling the resiliently mounted, hermetically sealed motor compressor unit of a refrigerating machine.

These and other objects are eflected by my inventionas will be apparent from the following description and claims taken in connection with the accompanying drawing, forming a part of this application, in which: I v Fig. 1 is a vertical sectional view of a hermetically sealed motor driven compressor employing my novel system of cooling;

Fig. 2 is a diagrammatic view of a conventional oil cooling system for a motor driven compressor mechanism with oil temperatures indicated thereon;

Fig. 3 is a view similar to Fig. 2 but including my improved oil cooling system and having oil temperatures indicated thereon; and,

Fig. 41s a view of a novel pump structure which may form a part of my improved cooling system. Y

Heretofore, it has been the practice to cool the hermetically sealed motor compressor units of -firefrigerating machines, and particularly resiliently mounted units of this kind, by passing oil in heat exchanging relation therewith. The oil heated by the unit then drains to a sump and is withdrawn therefrom by a pump. A portion of,

Means are provided for withdrawing cooled oil from the sump and conveying it to the motor compressor unit where it performs its cooling action. In circulating the oil in :this manner,

I am enabled to operate the unit at a lower temperature than is possible with the prior method of circulation and without increasing the total quantity of oil that is circulated per unit of time. In the drawing, Figs. 2 and 3 disclose, respectively, a method of circulation employed heretofore and my improved system of circulaton. Temperatures oi the oil at various stages of its circulation are indicated on these views. Further reference to these figures will be made hereinafter. r

Referring now to Fig. 1 of the drawing, I show my improved cooling system applied to a hermetically sealed refrigeratingmachine which includes a compressor Iii driven by an electric motor I 6 having a shaft Q, the motor and compressor being enclosed by' a casing structure I2. As shown, the motor II and compressor III define a unit structure with the compressor superim-' posed upon and carried by the-motor II,-. but it will be understood that the invention is equally applicable to units wherein the compressor is disposed beneath the motor. .Furthermore, it

is equally applicable to units employing motors and compressors of the horizontal type. The hermetic casing l2 may include a base member I3 and a shell I4 secured thereto. Suitable means, such as, for example, a cooling coil Ila may be employed for abstracting heat from the shell I4 in a well understood manner. It will be obvious that the casing may be cooled in any other suitable manner, such as, by radiation to the ambient atmosphere. 1 I

My invention may be applied to units that are directly connected to. the enclosing, shell, but it is particularly adaptable to units which are resiliently supported therein. Accordingly, I show resilient members orsprings I5 supportedby the casing structure I2 for carrying the motor II and compressor l0. Any suitable means for attaching theusprings I5 to the casing I2 may be employed such as, for example, lugs l6 secured to the shell I. Lugs I! may be formed on the motor II for attachment to the opposite ends of the springs I5. With this arrangement, vibrations originating'in motor I I and compressor III are dampened by thesprings I5 and are not transmitted to the casing l2, whereby quiet operation is obtained. I I

Compressed refrigerant is delivered to a condenser IO by means of a conduit I9 which passes through the casing I2 as shown. The evaporator of the refrigerating system is shown at 2| and connects with the condenser l8 through a suitable pressure reducingdevice 22. -A conduit 23' conducts vaporized refrigerant from the evaporator 2| to the interior of the casing 82 from which it is withdrawn by the compressor I0 and compressed. By admitting cool vapor from the' evaporator to the interior of the casing, advantage is taken of the cooling action thereof.

Heat generated by the motor and compressor i0 is abstracted by passing a heat exchange medium, such as the lubricating oil, in heat exchanging relation with the motor and compressor. The oil is subsequently passed over the interior surface of the shell H for cooling and the heat abstracted therefrom by the shell is conducted to its cooling coil l4a, or radiated to the ambient atmosphere. The bottom portion of the casing |2 defines a sump 24 for the cooled oil that drains by gravity from the interior surface of the shell |4.

In accordance with my invention, I provide a pair of pumps 25 and 26 beneath the compressor and motor and, preferably, driven by the shaft 9. The pumps 25 and 26 may have a common casing 21 divided into a pair of pump chambers 28 and 29. A receptacle 3| is disposed beneath the motor for receiving'heated oil which drains by gravity from the compressor l0 and motor H. The receptacle 3| and pump casing 21 are preferably carried by the motor II and, as shown, the receptacle 3| is secured to a frame member 320i the motor H and the pump casing 21 is fixed to the receptacle 3|.

The lower pump 25 operates to circulate cooled oil from the sump 24 through a conduit 33 which extends upwardly and terminates above the motor and adjacent to'the compressor l0. Cool oil discharged by the conduit 33 is diffused over the compressor I0 and motor for the abstraction of heat therefrom. The pump 25 draws oil from the sump 24 through an opening 34 that is formed in the casing 21 and preferably submerged in the pool of oil.

The upper pump 26 has an inlet'passage 35 communicating with the receptacle 3| through which heated oil is drawn prior to its discharge through a conduit 36 which extends upwardly and terminates adjacent the top of the shell I4. Heated oil discharged by the conduit 36 flows radially over the inside surface of the top of the shell and thence downwardly toward the sump 24 in a cylindrical film within the side walls of the casing. Cooling of the oil is effected during this passage by the relatively cool walls of the casing l4. A bafiie 31 may be disposed between the discharge ends of the conduits 33 and 36 for preventing mixture of oil which maybe splashed during discharge and for preventing heated oil from dropping to the motor or compressor.

In Fig. 2, I have diagrammatically shown the cooling system for hermetically sealed refrigerating systems employed heretofore with temperatures indicated thereon. The numeral 4| indicates a motor compressor mechanism of the type shown in Fig. 1 and driving a single pump 42. The pump 42 draws oil from the sump 43 and discharges approximately half of it over the casing and a second half over the unit 4|. The heated oil' drops to the sump 43 where it mixes with the cooled oil draining from the casing walls. In the following comparison, I am assuming that one gallon of oil is delivered to the casing and one gallon to the mechanism 4|, per unit of time. Fig. 3 diagrammatically illustrates my improved system shown in Fig. 1 with oil temperatures shown thereon. I am assuming that each pump 25 and 26 is pumping one gallon of oil per unit of time over the motor mechanism and the casing, respectively. There is, therefore, one gallon of oil circulated over the motor mechanisms and one gallon over the casing in each case.

I am assuming an average shell temperature of 150 in both cases, which indicates that the watts or B. t. u. input to the shell is the same in both cases. I am, furthermore, assuming a 20 temperature rise in the oil passing over the motor mechanism due to the heat abstracted therefrom. It will be apparent from Figs. 2 and 3 that I obtain a 20 cooler motor mechanism than is obtained by the oil cooling system used heretofore. This is due to the fact that a lower temperature oil is available in the sump for circulation to the.

motor mechanism. In the prior system, the oil cooled by the casing is mixed with the relatively hot oil drained from the motor mechanism so that the resultant temperature is higher than the temperature of the cooled oil. In my improved system, this mixing is obviated by circulating all of the heated oil to the casing for cooling and passing all of the cooled oil withdrawn from the sump to the motor mechanism.

It will be apparent that the differential between the motor and the shell in Fig. 2 is greater than in Fig. 3, although the shell temperatures are the same, the motor temperature in fig. 2 being at a higher value for the same shell temperature than the motor of Fig. 3. When the load is increased by the same amount on the motors shown in Figs. 2 and 3, the temperatures of the two shells will increase by substantially the same amount and the amount of heat removed therefrom will also increase. However, assuming that the safe operating temperatures of the two motors are the same, then for a given increase in load and with the same shell temperatures, the motor of Fig. 2 will rise above the safe operating temperature before the motor of Fig. 3 because of the greater temperature differential between the shell and the motor in the arrangement shown in Fig. 2. Obviously, the shell temperature for a given load in either case depends on the temperature of the cooling fluid surrounding the shell. From the two disclosed methods of heat removal, it will be apparent, therefore, that a greater load can be car- 'ried by the motor of Fig. 3 than by the motor of Fig. 2 without exceeding a safe' operating temperature.

Fig. 4 shows an arrangement of circulating the warm and cool oil in a single pump structure of the centrifugal type. The pump includes a casing 5| having opposed volutes 52 and 53 and a single runner 54 which may be driven by the shaft 9. Opposed inlet ports for the hot and cool oil are shown at 55 and 56, respectively. Conduits 51 and 58 may connect, respectively, with the receptacle 3| and sump 24 of the apparatus shown in Fig. 1.

nism wherein the operating temperature is maintained at a relatively low value and wherein relatively large overloads may be carried without seriously overheating the motor. I have, during this description, referred to the heat transfer medium as oil, but it will be understood that other media may be employed. Furthermore, I have shown a refrigerating machine wherein the casing defines a chamber communicating with the suction conduit leading from the evaporator, but it is to be understood that this is shown by way of example and that this chamber may conneat to other portions of the refrigerant circuit or may be isolated from the circuit completely.

While I have shown my invention in two forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications'without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is: 1. In a coolingsystem the combination of ,a compressor, a motor for driving the same, a casing for housing the motor and compressor and having a sump formed therein for collecting lubricant drained by gravity from the casing, a receptacle disposed beneath the motor for collecting lubricant drained by gravity from the motor, a pump for conveying the heated lubricant in the receptacle in heat exchanging relation with the casing, and a second pump for conveying the cooled lubricant in the sump to the motor and compressor for cooling the same.

2. In a cooling system, the combination of a substantially vertical motor, a compressor driven thereby, a hermetic casing for housing the motor and compressor and including a lubricant sump disposed at the bottom thereof, a receptacle arranged beneath the motor and compressor for collecting heated lubricant discharged therefrom, means for passing the heated lubricant in the receptacle in heat exchanging relation with the casing whereby the lubricant is cooled as it drains by gravity to the sump, and means for conveying the cooled lubricant from the sump to the motor and compressor for cooling the same.

3. The combination as claimed in claim 2 having resilient means for supporting the motor and compressor and carried by the casing.

4. In a cooling system for a refrigerating machine, the combination of a substantially vertical motor, a compressor driven thereby, a hermetic casing structure for housing the motor and'compressor, resilient means carried by the casing structure and supporting the motor and compressor, means defining a sump withinthe casing structure for cooled lubricant, a receptacle carried by the motor for collecting heated lubri-.

cant discharged by the motor and compressor, means driven by the motor for conveying heated lubricant from the receptacle in heat exchanging relation with the casing structure for cooling thereby, and means driven by the motor forconveying cooled lubricant from the sump to the motor and compressor for cooling the'same.

5. In a cooling system for a refrigerating machine, the combination of a substantially vertical motor, a refrigerant compressor superimposed on the motor and driven thereby, a hermetic casing structure enclosing said motor and compressor and defining a cooling surface for lubricant, said casing having a sump formed therein for collecting lubricant cooled by the casing, resilient means carried by the casing structure and supporting the motor, a receptacle carried by the motor for collecting lubricant heated thereby, means driven by the motor for conveying heated lubricant from the receptacle in-heat exchanging relation with the casing and a second means for co veying cooled lubricant from the sump in heat exchanging relation with the motor.

6. In a cooling system for a refrigerating machine, the combination of a compressor, a motor for driving the same, a casing for housing the motor and compressor and defining a cooling surface for a heat exchanging medium, said casing having a sump formed therein for the cooled medium, a receptacle disposed beneath the motor and compressor for receiving heated'medium discharged thereby, a single pump structure having first and second inlet passages therein communicating, respectively, with said sump and re-

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