Analysis of siloxane mixtures used in organic Rankine cycle with thermal stability limits

The siloxanes and their mixtures are suitable working fluids for organic Rankine cycle (ORC) systems with high-temperature heat sources. The thermal stability of siloxanes has a significant effect on the working fluid selection and cycle performance of ORCs. In this study, a thermal decomposition experimental system is designed to measure the thermal stability of octamethyltrisiloxane (MDM), and the effects of the hexamethyldisiloxane (MM) mass fraction and evaporation temperature on the net power and thermal efficiency are calculated. The results showed that the decomposition of MDM could be detected at 240℃ and had higher decomposition ratios comparing with MM. With the temperature limit, the net power and thermal efficiency are both lower than those without the evaporation temperature limit. Siloxane mixtures are the better choice for ORC systems using siloxanes as working fluids in conditions of this paper. MM/MDM (0.6/0.4) improves the net power and heat efficiency of the system by 8.1% and 1.7% respectively, comparing with that of the pure working fluids.     «

The siloxanes and their mixtures are suitable working fluids for organic Rankine cycle (ORC) systems with high-temperature heat sources. The thermal stability of siloxanes has a significant effect on the working fluid selection and cycle performance of ORCs. In this study, a thermal decomposition experimental system is designed to measure the thermal stability of octamethyltrisiloxane (MDM), and the effects of the hexamethyldisiloxane (MM) mass fraction and evaporation temperature on the net pow...     »