Performance Analysis of Low-temperature Organic Rankine Cycle Using HFO Working Fluids and Single Screw Expander

orc2019 Tracking Number 38

The organic Rankine cycle(ORC) is a popular technology used in waste heat recovery and medium-low-temperature heat utilization. In the field of low-temperature heat utilization, the net work output and thermal efficiency are two critical evaluation indicators of ORC system due to the low grade of heat source. Nowadays, as environmentally friendly working fluids, hydrofluoroolefins (HFOs) have attracted more and more attention. Moreover, as a novel expander, single-screw expander also becomes research focus. Compared with other type expander, one of the advantages of single-screw configuration is that it can conduct a vapour-liquid wet expansion. In order to use this advantage, an ORC using single-screw expander and R1234yf and R1234ze, two popular HFO working fluids, was established. Net work output is the critical evaluation indicator for open type heat source. While thermal efficiency is the one for closed type heat source. Heat exchange load of condenser is the critical indicator for calculating the cost of condenser that greatly influences the cost and economic performance of entire ORC system. Therefore, three indicators, namely net work output, themal efficiency, and heat exchange load of expander, were used to analyze the performance of an ORC system using HFO working fluid and single-screw expander. Through calculation and analysis, it can be seen that compared with the traditional cycle process, the ORC system which uses single-screw expander and undergoes a vapour-liquid wet expansion can obtain a higher thermal efficiency, more net work output, and smaller heat exchange load of condenser.