The removal of the non-return valve from the refrigeration system with a twin screw compressor is realizable by fitting a non-reversing clutch to the prime mover to restrain the reverse rotation of the compressor following shut down. Utilizing a suite of computer programs developed by the authors, the influence of the non-return valve is examined; gas torques under normal running condition and on shut down are calculated and compared. The results suggest that the use of the non-reversing clutch results in a decrease in energy consumption and an increase in system COP. The shut down torque may have a peak value considerably higher than the normal driving torque, thus care must be taken with the choice or design of the clutch.
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