Heat transfer compositions, methods and systems

The refrigerant comprising at least about 97% by weight of the following four compounds in the relative amounts set forth below:

• 38±1% by weight trifluoroiodomethane (CF3I);
• 54±1% by weight 1,1,1,2-tetrafluoropropene (HFO-1234yf);
• 5±1 by weight difluoromethane (HFC-32);
• and
• 3% by weight pentafluoroethane (HFC-125).

A method of cooling in a low or medium temperature heat transfer system comprising an evaporator, a condenser and a compressor, the process comprising the steps of

• i) condensing a refrigerant comprising at least about 97% by weight of the following four compounds, with each compound being present in the following relative percentages:
• 32.8 to 42.8% by weight trifluoroiodomethane (CF3I);
• 48 to 58% by weight 1,1,1,2-tetrafluoropropene (HFO-1234yf);
• 2 to 6% by weight difluoromethane (HFC-32);
• and
• 1 to 3.2±0.2% by pentafluoroethane (HFC-125) and
• ii) evaporating the composition in the vicinity of body or article to be cooled, wherein the evaporatoring temperature of the refrigerant in the heat transfer system is in the range of from about −40° C. to about −10° C.