Performance of Oil-Injected Scroll Compressors for Helium Refrigerators

Abstract

In recent years there arises growing demand of helium liquefaction refrigerators for the magnetic resonance imaging systems, magnetically levitated vehicles and other systems using superconducting magnet. From this background, a small size, scroll type of hermetic helium compressor capable of compressing helium gas to the pressure ratio of 20 in a single stage is developed. Main features of this compressor are as follows.
1) Discharge capacity can be varied from 7 to 20 Nm³/h by changing driving motor frequency from 30 to 80 Hz.
2) The overall adiabatic efficiency showed 72%∼79% under the pressure ratio range of 11∼20 at 60 Hz using oil injection cooling device.