Geometrical characteristics of screw refrigeration compressor under part-load conditions

On the basis of the operating feature of screw compressors, the critical angles of the working chamber in different processes were determined under part-load conditions. A model was established to calculate the effective by-pass area and radial discharge area at a certain rotation angle of the male rotor under various part-load conditions. The influences of key design parameters on the geometrical characteristics of a screw refrigeration compressor under part-load conditions were investigated, such as the slide stop length and slide valve installation position relative to the cylinder. The results show that, in order to improve the performance of screw refrigeration compressors under part-load conditions, the fixed type slide stop with 20%-25% of the rotor length should be adopted for a fixed external pressure ratio while the moveable type should be applied for variable external pressure ratios. Moreover, the slide valve installation angles relative to the cylinder should be as large as possible in the installation space.