Thermal stability and decomposition behavior of HFO-1234ze(E) as a working fluid in the supercritical organic Rankine cycle

The supercritical organic Rankine cycle (SORC) is a highly promising technique to recover non-utilized low-to-medium-temperature heat sources. A good thermal stability of the working fluid is crucial to create a safe SORC system. Herein, the thermal stability of a new type of working fluid, HFO-1234ze(E) (trans-1,3,3,3-tetrafluoroprop-1-ene), which is an environmentally friendly fourth-generation refrigerant, is investigated in supercritical regimes. The experimental conditions are designed for long-term reactions for 56 days at 453.15 K and 5 MPa, which represent the highest temperature and pressure, respectively, at the SORC turbine inlet. In addition, the effects of temperature, pressure, and time on the decomposition of HFO-1234ze(E) are investigated over a short experimental period of up to 24 h to propose the reaction kinetics. Decomposed gases species from HFO-1234ze(E) included difluoromethane (HFC-32), pentafluoro ethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), 1,1,1,2,2-pentafluoropropane (HFC-245fa). For extended time periods or in high-pressure and high-temperature conditions, HFO-1234ze(E) decomposes to form liquid products with weight average molecular weights in the range of 470–740 g mol–1. The decomposition of HFO-1234ze(E) can be fitted with a first-order kinetic model. Under the assumption that major decomposition occurs at the turbine inlet, the decomposition rate of HFO-1234ze(E) is found to be 0.02% per year in this study.