WORKING MEDIUM FOR HEAT CYCLES, COMPOSITION FOR HEAT CYCLE SYSTEM, AND HEAT CYCLE SYSTEM

摘要

Provided are a working medium for heat cycles, a composition for a heat cycle system, and a heat cycle system, that provide a heat cycle system having high durability, excellent compatibility with a greater number of refrigerant oil varieties, and has excellent cycle performance (ability). The working medium for heat cycles, the composition for heat cycle systems, and the heat cycle system include trifluoroethylene and difluromethane, have a total trifluoroethylene and difluromethane content of more than 90% by mass of the total amount of working medium for heat cycles, and have a mass ratio, indicated by trifluoroethylene/difluromethane, of 21/79-39/61 in the working medium for heat cycles.