| abstract |
Provided are a composition for a heat cycle system having good lubricating properties including a working medium for the heat cycle having a low global warming potential that can be substituted for R410A, and a heat cycle system using this composition. A composition for a heat cycle system including a working medium for the heat cycle including 1,2-difluoroethylene, oxygen-containing synthetic oil (ester refrigeration oil, ether refrigeration oil, or the like), and refrigeration oil such as hydrocarbon refrigeration oil or the like, and a heat cycle system using this composition for a heat cycle system. |