Patent CA-2310871-A1 (CA)
Title: Capacity control of compressors
Inventor: VAISMAN IGOR
IPC: F04C18/344
Filed: 2000-06-06
Abstract: The present invention is directed to a method of reducing cooling capacity in a rotary vane compressor in such a way that the power requirement to drive the rotor is reduced to the same extent (or close to) as capacity is reduced. In an aspect of the invention this is accomplished without any impact on compressor efficiency at regular mode. In another aspect, this is accomplished without excessive complexity or low reliability.      The present invention provides for a rotary vane compressor comprising a rotor, a stator, and vanes placed in slots spaced apart about the rotor. The stator is provided with an inlet and an outlet and a compression region therebetween. The rotor rotates in a forward direction past the inlet through the compression region and then past the outlet thereby to transport gas from the inlet to the outlet. Two adjacent vanes, the rotor and a wall portion of the stator in the compression region define a compressor chamber. The stator is shaped to compress gas in the compressor chamber when gas travels from the inlet to the outlet. An economizer port is located in the compression region at a point where the port is in communication with the compression chamber after it has been closed for compression. A valve is associated with the economizer port, the valve body being formed from a part of the stator body. The seat of the valve in the closed position is shaped to be contiguous with the wall portion of the stator. The integrity of the whole compressor is maintained and compressor cycle efficiency is improved since there is no additional volume of passages attached to the compressor chamber and associated with the economizer port. In an opened position the valve provides communication between the compression chamber and the economizer port.      In yet another aspect of the invention there is provided a refrigeration system comprising a main circuit, an economizer circuit, and a bypass circuit. The main circuit comprises, in a closed loop, a rotary compressor, a condenser unit, an expansion device, an evaporator unit, connecting piping and appropriate refrigeration control.      The rotary compressor includes an inlet, an outlet, a compression region therebetween, an economizer port located in the compression region at a point where the port is in communication with the compression chamber after it has been closed for compression, and a variable flow valve associated with the economizer port. The economizer circuit includes a first solenoid valve, an additional expansion device and an economizing heat exchanger and is connected to the economizer port. The economizing heat exchanger provides thermal contact between refrigerant in the main circuit after the condenser unit and evaporating refrigerant in the economizer circuit after the additional expansion device. The bypass circuit has a second solenoid valve located between the economizer port and the suction side of the compressor. The valves, a control system, and a transducer, reading parameters associated with a system capacity demand, are wired in an electrical circuit. The control system activates the valves based on the capacity demand.