Thermodynamic Analysis on the Reversibility of Compressor-expander

Expander is the most important component for Organic Rankine Cycle (ORC) especially to convert low-temperature heat to power in remote areas. However, most of developing countries are still far from capability in fabricating the required expander. Thermodynamically, the expander's function can be obtained by reversing the operation of the compressor. The purpose of this study is to test the performance of a compressor reversed expander and to study its thermodynamic reversibility. The compression cycle and the expansion cycle were performed by using a scroll-type compressor, and the working fluid used for the performance test was R134a. Based on the test results, it was found that the pressure ratio, in terms of maximum-to-minimum ratio, increased in line with the increase of the evaporator temperature both in the compression and expansion cycle. The average isentropic efficiency of the expansion cycle was 77.66%, with an entropy generation rate of 0.06 W/K. It was relatively higher than that of the compression cycle, which was 30.34% of average isentropic efficiency with 1.11 W/K of entropy production rate. The results showed that the scroll-type compressor reversed expander can be used for ORC process with considerable effectiveness.