Carrier Corporation

David N Shaw

Erric L Heitmann

Edward A Huenniger

Arthur G Mensing

Loss of oil due to oil feedback is prevented in a screw compressor in a refrigeration application due to low capacity operation. The apparent suction temperature is compared to the temperature of the water exiting the evaporator to determine the apparent superheat and the loading is increased upon the apparent superheat reaching a predetermined level. Upon sensing a predetermined difference, an electronic slide valve block is initiated to prevent further unloading and loading may be initiated in a fixed amount, incrementally or on a pulsed basis.

Electronic slide valve block

Oil laden refrigerant is supplied tangentially into an oil separator for a primary removal of oil and then into a coalescer for a secondary removal of oil. Flow between the oil separator and coalescer is controlled by a valve so as to insure that a rapid build up of pressure takes place in the sump to insure adequate lubrication to the compressor.

Oil separator

A refrigeration system includes a rack or bank of compressors located in parallel and feeding a common condenser. Liquid refrigerant from the condenser is supplied to a plurality of evaporators located in parallel and feeding a common suction manifold. The suction manifold is connected to the compressors and contains a valve for selectively isolating one or more compressors and evaporators whereby the isolated compressor acts as a satellite compressor and the isolated evaporators are operated at a lower temperature than the other evaporators.

Refrigeration temperature control system

A thermally protected heater element is located in an oil sump such that it is normally located beneath the surface of the oil whereby the oil is heated and acts as a heat sink relative to the heater element. If the oil level drops below the heater element, the thermal protection disables the heater element and the compressor whereby the location of the heater element defines the nominal minimum oil level.

Combined oil heater and level sensor

An economizer is connected to a fluid line connecting the booster compressor and high stage compressor of a refrigeration system at a point downstream of the bypass for unloading the booster compressor. The economizer flow controls the discharge temperature of the second stage and, in addition, coacts with the bypassing of the booster compressor such that all of the flow supplied to the high stage is at system suction pressure when the bypass is fully open. When the booster compressor is fully unloaded and the unloading valve is fully open, the booster compressor is shut off and bypass flow for unloading reverses direction to permit flow from the condenser to the second stage past the shut off booster compressor.

Unloading system for two compressors

The slide valve and the slide stop of a screw compressor are infinitely positionable over their range of movement. Movement is achieved by fluid pressure acting across an actuating piston in combination with the fluid pressure acting on the slide valve and slide stop plus a spring bias.

Capacity volume ratio control for twin screw compressors

An economizer is connected to a fluid line connecting the first and second stages of a compressor at a point downstream of the bypass for unloading the first stage. The economizer flow controls the discharge temperature of the second stage and, in addition, coacts with the bypassing of the first stage such that all of the flow supplied to the second stage is at system suction pressure when the bypass is fully open.

Unloading system for two-stage compressors

Gaseous refrigerant is supplied from a flash tank economizer to cool the motor of a hermetic or semi-hermetic compressor when there is a sufficient flow available. When the flow becomes too small, liquid refrigerant is supplied to the shell of the compressor for cooling the motor.

Evaporator feed system with flash cooled motor

In a compressor of the type in which there is a movable trapped volume such as a screw or scroll type of compressor the trapped volume moves into and out of fluid contact with one or more valves. The valve(s) can provide fluid communication between the trapped volume and either suction for unloading or discharge for V.sub.i control.

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Manlius, NY, United States of America

David N Shaw