Liquid refrigerant injection system for hermetic electric motor driven helical screw compressor

Claim 2

In a refrigeration system employing an electric motor driven helical screw compressor forming a part of a closed refrigeration circuit which further includes downstream of the compressor and in order, a condenser, a thermal expansion valve, and evaporator means, wherein the electric motor includes a motor housing which hermetically seals the motor from the screw compressor and which carries a fixed stator and a rotatable rotor in concentric fashion, and the screw compressor housing is provided with a liquid refrigerant bleed port opening to a closed screw compressor thread at a pressure intermediate compressor suction and discharge, the improvement comprising: means for bleeding liquid refrigerant from the high pressure side of the circuit, and delivering the liquid refrigerant to the bottom of the motor housing for gravity accumulation therein, means responsive to accumulation of liquid refrigerant within said motor housing, for causing said motor rotor in response to rotation thereof, to pick up some liquid refrigerant and distribute it to that portion of said stator lying above the accumulated refrigerant to cool the same by vaporization and to thereby maintain said liquid refrigerant at a predetermined level, determined by initial contact of said rotor with said liquid refrigerant accumulating within said motor housing, and fluid passage means coupled at one end to said injection port and opening at the other end within said housing at said predetermined level; whereby, liquid refrIgerant accumulating within said motor housing is simultaneously vaporized within said housing to cool said motor and is bled to the closed thread for injection into said compressor for cooling the screw compressor closed thread content by vaporization of said liquid refrigerant therein during compression thereof.

Claim 3

The system as claimed in claim 1, further comprising: means within said system, downstream of said compressor, for providing vaporized refrigerant at a pressure intermediate compressor suction and discharge pressure, and means for delivering said vaporized refrigerant to said motor housing for impingement on said motor stator to additionally cool said motor prior to passing from said motor housing to said compressor via said bleed port.

Claim 4

The system as claimed in claim 2, wherein said means within said system for providing vaporized refrigerant at a pressure intermediate compressor suction and discharge comprises: an economizer positioned within said system intermediate of said condenser and said thermal expansion valve, a fluid restrictor within the line leading from said condenser to said economizer for reducing pressure of the liquid refrigerant entering said economizer to cause flash gas resulting therefrom to subcool the remaining liquid refrigerant therein, resulting in creation of the vaporized refrigerant, and wherein said vapor delivering means comprises conduit means fluid coupling said economizer to said motor housing to supply the vaporized refrigerant thereto.

Claim 5

The system as claimed in claim 1, wherein: said electric motor is oriented horizontally, said rotor is spaced relative to said fixed stator to form an annular gap between the peripheries thereof, and said fluid coupling means comprises a passage leading to said bleed port and opening into said motor housing at a height corresponding to the lowermost gap position.

Claim 6

The system as claimed in claim 2, wherein: said electric motor is oriented horizontally, said rotor is spaced relative to said fixed stator to form an annular gap between the peripheries thereof, and said fluid coupling means comprises a passage leading to said bleed port and opening into said motor housing at a height corresponding to the lowermost gap position.

Claim 7

The system as claimed in claim 3, wherein: said electric motor is oriented horizontally, said rotor is spaced relative to said fixed stator to form an annular gap between the peripheries thereof, and said fluid coupling means comprises a passage leading to said bleed port and opening into said motor housing at a height corresponding to the lowermost gap position.

Claim 8

The system as claimed in claim 1, further comprising: a thermal expansion valve positioned within said circuit leading from said condenser to said motor housing for modulating the flow of liquid refrigerant between said condenser and said motor housing, and thermal energy sensing means positioned in heat transfer with respect to said means fluid coupling said bleed port to said motor housing interior and being operatively coupled to said thermal expansion valve for controlling valve operation.

Claim 9

The system as claimed in claim 7, wherein: said valve further includes means responsive to vapor pressure within said motor housing for additionally modulating said flow of liquid refrigerant therethrough.

Claim 10

In a refrigeration system employing an electric motor driven helical screw compressor forming a part of a closed refrigeration circuit which further includes downstream of the compressor and in order, a condenser, a thermal expansion valve, and evaporator means, and wherein the electric motor includes a motor housing which hermetically seals the motor from the screw compressor and which carries a fixed stator and a rotatable rotor in concentric fashion, and the screw compressor housing is provided with a liquid refrigerant bleed port opening to a closed screw compressor thread at a pressure intermediate compressor suction and discharge, the improvement comprising: means fOr bleeding liquid refrigerant from the high pressure side of the circuit, and delivering the liquid refrigerant to the bottom of the motor housing for gravity accumulation therein, means responsive to accumulation of liquid refrigerant within said motor housing to a predetermined level, for causing liquid refrigerant to impinge upon portions of said motor stator and by rotation thereof to splash against portions of the motor stator above said predetermined level for cooling by vaporization of liquid refrigerant and to maintain the level of accumulated liquid refrigerant within said housing at said predetermined level defined by initial contact of said rotor with the liquid refrigerant accumulating within said motor housing in a closed fluid passage opening at one end to liquid injection port and at the other end directly to said motor housing at said predetermined level such that simulaneously in response to accumulation of liquid refrigerant to said predetermined level, vaporized liquid refrigerant within said housing deposited on the stator above the level of accumulated liquid refrigerant causes cooling of said motor and liquid refrigerant delivered to said port through said passage cools the screw compressor closed thread content by vaporization of said liquid refrigerant therein during compression thereof.

Claim 11

In a refrigeration system employing an electric motor driven helical screw compressor forming a part of a closed refrigeration circuit which further includes downstream of the compressor and in order, a condenser, a thermal expansion valve, and evaporator means, and wherein the electric motor includes a motor housing which hermetically seals the motor from the screw compressor and which carries a fixed stator and a rotatable rotor in concentric fashion, and the screw compressor housing is provided with a liquid refrigerant bleed port opening to a closed screw compressor thread at a pressure intermediate compressor suction and discharge, the improvement comprising: means fOr bleeding liquid refrigerant from the high pressure side of the circuit, and delivering the liquid refrigerant to the bottom of the motor housing for gravity accumulation therein, means responsive to accumulation of liquid refrigerant within said motor housing to a predetermined level, for causing liquid refrigerant to impinge upon portions of said motor stator and by rotation thereof to splash against portions of the motor stator above said predetermined level for cooling by vaporization of liquid refrigerant and to maintain the level of accumulated liquid refrigerant within said housing at said predetermined level defined by initial contact of said rotor with the liquid refrigerant accumulating within said motor housing in a closed fluid passage opening at one end to liquid injection port and at the other end directly to said motor housing at said predetermined level such that simulaneously in response to accumulation of liquid refrigerant to said predetermined level, vaporized liquid refrigerant within said housing deposited on the stator above the level of accumulated liquid refrigerant causes cooling of said motor and liquid refrigerant delivered to said port through said passage cools the screw compressor closed thread content by vaporization of said liquid refrigerant therein during compression thereof.