Experimental study of a sliding vane expander in a micro-scale ORC system for utilizing low-grade heat

Abstract

In the other study of the authors, the sliding vane expander, was developed successfully. It was workable satisfactorily and provided an acceptable performance for a certain working condition. In this present study, performance of the sliding vane expander with a wider range of operating conditions is observed and examined. The boiler temperature is varied from 70 to 90°C while the condensation temperature is varied between 34 to 42°C. This range of condensation temperature is consistent with hot climate such as Thailand. The results show that at the boiler temperature of 90°C and condensation temperature of 34°C, torque of the expander increases with a decrease in the rotational speed. The shaft power and efficiency initially increase with a decrease in the rotational speed until reaching the optimal point. Later, they decrease as the rotational speed continue to decrease. The optimal point indicates the highest possible shaft power and efficiency at which the expander is able to produce for one particular operating condition. It is also found that an increase of condensation temperature and decrease in boiler temperature cause the optimal point of shaft power and efficiency reducing. The mass flow rate increases with rotational speed. At identical rotational speed, a decrease in the boiler temperature results in a decrease of torque, shaft power, mass flow rate, and efficiency. An increase of the condenser temperature causes a decrease of torque, shaft power, and efficiency. Meanwhile, the mass flow rate is kept constant. The maximum power output of 185W and efficiency of 1.57% are obtained at the 4,100 rpm.