Integration of Organic Rankine Cycle and Scroll Expander Models for Effective Design and Performance Using Organic Working Fluids

This paper presents the organic Rankine cycle performance comparison of several working fluids with low global warming potential and low ozone depletion potential at several heat source temperatures. At an evaporating temperature of 80°C, maximum first law efficiency of 5.8% was achieved with ammonia, while at 145°C and 180°C, diethyl ether provides the maximum cycle efficiencies of 11.4% and 13% respectively. For the best operating conditions of the ORC model, a suitable two-stage scroll geometry was modeled and its performance was evaluated. Stage I and stage II scroll geometries with volume ratios of 5.3 each were modeled for the supply conditions of 180°C and 2.6 MPa. The geometries provided a combined shaft work of 8.7 kW at combined expander efficiency of 89% accounting for the losses due to the leakage in the expander.