HEAT TRANSFER AND PERFORMANCE CHARACTERISTICS OF VARIABLE CAPACITY ROTARY COMPRESSORS USING BY-PASS METHOD

摘要

In this paper, variable capacity rotary compressors using By-pass method are investigated. Performance of the instrumented compressor is tested and temperatures at various locations of the compressor are measured. Through the comparison of characteristics between full and part load operations, possibility of capacity control using By-pass method is verified, and some issues at part load operation are clarified. Decrease of motor efficiency, suction gas heating due to the by-passed gas of high temperature, and resistance of gas flow in the by-pass line are main reasons for the decrease in performance at part load operations. For improvement of performance at part load operations, cooling of the by-passed suction gas is carried out and the increment of the performance is proportional to the decrease of suction gas temperature by cooling of the by-passed gas. Variation of the by-passed gas flow rate using needle valve is also carried out, but the effect appears to be very tiny.