HEAT TRANSFER COMPOSITIONS AND METHODS
Compositions, methods and systems which comprise or utilize a multi-component mixture comprising: (a) from about 10% to about 35% by weight of HFC-32; (b) from about 10% to about 35% by weight of HFC-125; (c) from about 20% to about 50% by weight of HFO-1234ze, HFO-1234yf and combinations of these; (d) from about 15% to about 35% by weight of HFC-134a; and optionally (e) up to about 10% by weight of CF3I and up to about 5% by weight of HFCO-1233ze, with the weight percent being based on the total of the components (a)-(e) in the composition
1 . A heat transfer composition comprising: (a) from about 10% to about 35% by weight of HFC-32; (b) from about 10% to about 35% by weight of HFC-125; (c) from about 20% to about 50% by weight of HFO-1234ze, HFO-1234yf and combinations of these; (d) from about 15% to about 35% by weight of HFC-134a, with the weight percent being based on the total of the components (a)-(c) in the composition.
2 . The heat transfer composition of claim 1 comprising (a) from about 10% to about 30% by weight of HFC-32; and (b) from about 10% to about 30% by weight of HFC-125.
3 . The heat transfer composition of claim 1 wherein said HFO-1234ze comprises trans-HFO-1234ze.
4 . The heat transfer composition of claim 1 having a weight ratio of HFC-32:HFC-125 of from about 0.9:1.2 to about 1.2:0.9.
5 . The heat transfer composition of claim 1 comprising HFO-1234ze and HFO-1234yf.
6 . The heat transfer composition of claim 9 having a weight ratio of HFO-1234ze:HFO-1234yf of from about 5:1 to about 3:1.
7 . A method of replacing an existing heat transfer fluid contained in heat transfer system comprising removing at least a portion of said existing heat transfer fluid from said system, said existing heat transfer fluid being HFC-404A and replacing at least a portion of said existing heat transfer fluid by introducing into said system a heat transfer composition comprising: (a) from about 10% to about 30% by weight of HFC-32; (b) from about 10% to about 30% by weight of HFC-125; (c) from about 20% to about 50% by weight of HFO-1234ze, HFO-1234yf and combinations of these; (d) from about 15% to about 35% by weight of HFC-134a, with the weight percent being based on the total of the components (a)-(c) in the composition.
8 . The method of claim 7 wherein said heat transfer composition comprises (a) from about 10% to about 30% by weight of HFC-32; and (b) from about 10% to about 30% by weight of HFC-125.
9 . A heat transfer system comprising a compressor, a condenser and an evaporator in fluid communication, and a heat transfer composition in said system, said heat transfer composition comprising: (a) from about 10% to about 30% by weight of HFC-32; (b) from about 10% to about 30% by weight of HFC-125; (c) from about 20% to about 50% by weight of HFO-1234ze, HFO-1234yf and combinations of these; (d) from about 15% to about 35% by weight of HFC-134a, with the weight percent being based on the total of the components (a)-(c) in the composition, said condenser having an operating temperature of from about 35° C. to about 45° C.
10 . The heat transfer system of claim 9 wherein said evaporator has an operating temperature of from about −40° C. up to less than about −15° C.
11 . The heat transfer system of claim 9 wherein said evaporator has an operating temperature of from about −35° C. to about −25° C.