US2768511A - Motor compressor cooling in refrigerating apparatus - Google Patents

Description

Oct. 30, 1956 MOODY 2,768,511

MOTOR COMPRESSOR COOLING IN REFRIGERATING APPARATUS Filed March 21, 1955 IN V EN TOR.

ARTHUR M G. MOODY VMu/A" 41%.

A TTORNE YS United States Patent MOTOR COMPRESSQR COOLING IN REFRIGERA'IING APPARATUS Arthur M. G. Moody, La Crosse, Wis., assignor to The Trane Company, La Crosse, Wis, a corporation of Wisconsin Application March 21, 1955, Serial No. 495L487 4 Claims. (Cl. 62117.8)

This invention relates to refrigerating apparatus of the type including a motor-compressor assembly, and particularly to apparatus in which the motor and com pressor are housed in a sealed unit.

It is an object of this invention to provide means for cooling the motor using the refrigerant of the apparatus as a heat exchange medium.

It is another object of the invention to provide fans on the motor shaft for causing a circulation of refrigerant gas in a closed circuit over the heat producing elements of the motor to cool said elements, then through a heat exchanger to remove heat from the refrigerant gas.

It is another object of the invention to provide passageways in the motor casing to conduct refrigerant gas in two streams to the ends of the motor to flow first over the bearings and with each stream then separating into two streams one of which flows over the stator winding and the other of which flows through the gap and outwardly through passageways in the stator.

Other objects and advantages of the invention will appear as the specification proceeds to describe the invention with reference to the accompanying drawin in which Figure 1 is a partly diagrammatic view of the refrigoration apparatus of my invention.

Figure 2 is a cross-sectional view of the motor-compressor assembly taken on an axial plane.

Referring now to Figure 1, an electric motor has at one end a first compressor stage 12 and at the other end a second compressor stage 14. A cross-over pipe 16 conducts gas from the discharge of the first stage 12 to the inlet of the second stage 14. The gas discharged from the second stage 14 flows through a pipe 18 to a condenser Ztl. The condenser 20 may be of the shelland-tube type in which cooling Water flows through the tubing 22 and the refrigerant is in the shell outside the tubes. Refrigerant liquid condensed in condenser 24? flows by gravity through pipe 23 to a float chamber 24. Float 26 in float chamber 24- opens and closes to control the flow of refrigerant liquid to an evaporator 28 which is also of'the shell-and-tube type in which the secondary refrigerant liquid such as water or brine flows through the tubing 3% and the refrigerant is in the shell outside the tubing 30. The secondary refrigerant liquid circulates between the evaporator 23 and the cooling load served by the refrigeration apparatus to transfer heat from the load to the evaporator 28. In removing heat from the secondary refrigerant, the refrigerant in the evaporator 23 boils forming gas which passes through the liquid eliminator 32 and thence into the suction pipe 34 to the inlet of the first stage compressor 12.

The motor 1% has a fluid tight casing 35 secured in fluid tight relationship to compressor housings 12 and 14. A motor frame 38 is supported in said fluid tight casing 35 by a pair of rings 40 and 41 which divide the annular space between motor frame 38 and said fluid tight easing into a central chamber 42 and end chambers croo r 44 and 46. Motor frame 38 has bearings 48 and 50 which rotatably support a shaft 36. Shaft 36 extends at one end into compressor housing 12 and has impeller 52 secured thereto. The other end of shaft 36 extends into housing 14 and has impeller 54 secured thereto. The ends of the shaft 30 fit closely in the back plates 13 and 35 of the respective compressor housings 12 and 14 to substantially prevent any flow of gas between the casing 35 and the compressor housings 12 and 14. A stator 56 is secured to the motor frame 38. Stator 56 has the usual windings 58. A plurality of radial passageways 60 extend through the stator 56. A rotor 62 is mounted on shaft 36 to rotate therewith. Rotor 62 rotates within stator 56 and has an outside diameter slightly less than the inside diameter of the stator 56 to provide a gap between the rotor 62 and stator 56. Fans 64 and 66 are mounted on shaft 36 to rotate therewith. Shrouds 6S and 79 direct the gas into the fans 64 and 66. A duct 72 has a heat exchanger 74 mounted therein. Duct '72 is connected to receive gas from central chamber 42. A housing 76 surrounds duct 72 and provides passageways 78 and with duct 72 for the gas leaving the heat exchanger 7 5 to flow to the end chambers 44 and respectively. Heat exchanger 74 has tubes 82 for conducting fluid from a supply header 34 to a discharge header 36. Supply header is connected by pipe 83; to condenser to receive liquid refrigerant from condenser Zil. A valve is interposed in pipe 5?; to control the flow of liquid therethrough. if desired valve 9?! may be of the thermostatic type in which a temperature sensing bulb is mounted in the gas stream leaving the discharge header 86. Discharge header is connected by pipe 92 to the condenser 2d. The liquid rcfrigerant flowing upwardly in tubes 32 receive heat from the gas flowing over the outside surface of the tubes and is evaporated. The evaporated refrigerant gas flows to the condenser 2i") through pipe 92. The refrigerant in the pipe 88, the tubes 82, and the pipe 92 flows by gravity, because the liquid in pipe 88 is more dense than the gas in pipe 92 and tubes 82.

The refrigerant gas flowing over the outside of tubes 82 of the heat exchanger 74 is cooled and flows through passageways 78 and 30 to end chambers 44 and 46 respectively. From end chambers 44 and 46 the gas flows over the bearings 4-8 and 5t removing heat therefrom. The gas then flows through the fans 64 and 66. The gas leaving each fan divides into two streams. One stream flows over the windings 58 to remove heat therefrom and it then flows into the central chamber 42. The other stream flows into the gap between the stator and rotor 62 and thence outwardly through passageways 6% into the central chamber 42. In passing through the gap and the passageways 60 the gas removes heat from both the rotor and the stator. The gas collected in central chamber 42 flows again through the heat exchanger 74 which removes heat from the gas prior to its recirculation through the motor.

It is thus seen that the heat is effectively transferred from the areas in the motor at which it is generated to the refrigeration system served by the compressor.

While the apparatus disclosed and described herein constitutes a preferred form of the invention, yet it will be understood that the apparatus is capable of alteration without departing from the scope or spirit of the invention, and that all modifications that fall within the scope of the appended claims are intended to be included herein.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In refrigerating apparatus, the combination of an evaporator for vaporizing refrigerant, a condenser for liquefying refrigerant, a compressor for circulating refrigerant through said evaporator and said condenser, a motor for driving said compressor, a fluid tight casing enclosing said motor and compressor, a shaft and rotor assembly rotatably mounted in said motor, a heat exchanger in said fluid tight casing, a fan secured to said shaft and rotor assembly for circulating refrigerant gas from said motor through said heat exchanger and back to said motor, said heat exchanger having fluid passageways, a first conduit between said condenser and said fluid passageways for conducting liquid refrigerant from said condenser to said fluid passageways and a second conduit between said fluid passageways and said condenser for conducting refrigerant gas from said fluid passageways to said condenser.

2. In refrigerating apparatus, the combination of an evaporator for vaporizing refrigerant, a condenser for liquefying refrigerant, a centrifugal compressor for circulating refrigerant through said evaporator and said condenser, a casing in fluid tight connection with said centrifugal compressor, a motor frame in said casing and spaced with respect to said casing, partitions between said motor frame and said casing dividing the space therebetween into a central chamber and two end chambers, a stator secured to said frame and having radial passageways therein communicating with said central chamber, bearings secured to each end of the frame, a shaft and rotor assembly rotatably mounted in said bearings, said shaft and rotor assembly extending into said compressor, an impeller in said centrifugal compressor, said impeller being secured to said shaft and rotor assembly, fan means secured to said shaft and rotor assembly for moving gas from said end chambers into said radial passageways and thence into said central chamber, a duct extending from said central chamber to said end chambers for conducting gas from said central chamber to said end chambers, a heat exchanger in said duct, fluid passageways in said heat exchanger, a first conduit between said condenser and said fluid passageways for conducting liquid refrigerant from said condenser to said fluid passageways and a second conduit between said fluid passageways and said condenser for conducting refrigerant gas from said fluid passageways to said condenser.

3. In refrigerating apparatus, the combination of an evaporator for vaporizing refrigerant, a condenser for liquefying refrigerant, a centrifugal compressor having an inlet connected to receive refrigerant from said evaporator and a discharge chamber connected to transmit refrigerant to said condenser, a substantially annular motor casing secured in fluid tight engagement with said compressor, a motor frame in said substantially annular motor casing, annular rings between said motor frame and said motor casing to support said motor frame in said motor casing, said annular rings being arranged to divide the annular space between said motor frame and said motor easing into a central chamber and two end chambers, a stator mounted in said motor frame opposite said central chamber, said stator having radial passageways communicating with said central chamber bearings in each end of the motor frame, a shaft and rotor assembly rotatably mounted in said bearings, said shaft and rotor assembly extending into said compressor, an impeller in said centrifugal compressor, said impeller being secured to said shaft and motor assembly, fans secured to said shaft and rotor assembly for moving the refrigerant gas from said end chambers through the gap between said stator and rotor and outwardly through the radial passageways of said stator into the central chamber, a duct extending from said central chamber to said end chambers for conducting gas from said central chamber to said end chambers, a heat exchanger in said duct, said heat exchanger having first fluid passageways through which the gas flows in moving from said central chamber to said end chambers, said heat exchanger having second fluid passageways, a first conduit between said condenser and said second fluid passageways for conducting refrigerant liquid from said condenser to said second fluid passageways and a second conduit between said second fluid passageways and said condenser for conducting refrigerant gas from said fluid passageways to said condenser.

4. in refrigerating apparatus, the combination of an evaporator for vaporizing refrigerant, a condenser for liquefying refrigerant, a centrifugal compressor housing, a motor housing in fluid tight connection with said centrifugal compressor housing, means for conducting refrigerant from said centrifugal compressor housing to said condenser, means for conducting refrigerant from said condenser to said evaporator, means for conducting refrigerant from said evaporator to said compressor housing, a motor stator in said motor housing, a shaft and rotor assembly rotatably mounted in said motor stator and extending into said centrifugal compressor housing, a centrifugal impeller mounted in said centrifugal compressor housing and being nonrotatably secured to said shaft and rotor assembly for moving gas in a closed circuit from said evaporator to said centrifugal compressor, thence to said condenser and thence to said evaporator, a heat exchanger in fluid communication with said motor housing, a fan secured to said shaft and rotor assembly for circulating gas over said motor stator, said shaft and rotor assembly, and said heat exchanger, said heat exchanger having fluid passageways, a first conduit between said condenser and the fluid passageways of said heat exchanger for conducting liquid refrigerant from said condenser to the fluid passageways of said heat exchanger and a second conduit between the fluid passageways of said heat exchanger and said condenser for conducting refrigerant gas from the fluid passageways of said heat exchanger to said condenser.

References Cited in the file of this patent UNITED STATES PATENTS 1,448,700 Seidner Mar. 13, 1923 1,451,577 Jantzen Apr. 10, 1923 1,652,134 Thompson Dec. 6, 1927 2,177,827 Hintze Oct. 31, 1939 2,249,882 Buchanan July 22, 1941 2,306,632 McCormack Dec. 29, 1942

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