Influence of alkane working fluid decomposition on supercritical organic Rankine cycle systems

The supercritical Organic Rankine Cycle (ORC) develops rapidly due to its low exergy loss, high thermal efficiency and high work output. The thermal stability of working fluid is the major limitation when selecting the working fluid for high temperature heat sources (150-350 °C). The influence mechanisms of the working fluid decomposition are important considerations when evaluating the thermal stability for ORCs. This study analyzed the influence of alkane working fluid decomposition on ORCs with n-pentane as the test fluid. The compositions of the gaseous and solid products were confirmed by experiments. The experiments and ORC system model were designed to analyze the different influence mechanisms of gaseous and solid products on the ORCs. The results showed that the main influence is the condensation pressure rise caused by non-condensable gases in gaseous decomposition products. Studies on methods for predicting the long-term thermal stability are also significant and merit further work.