A process for transferring heat from a heat generating source to a heat transfer fluid, comprising contacting the heat generating source with a heat transfer fluid for a time sufficient to effect heat transfer between the source and the fluid, wherein the heat transfer fluid comprises polytrimethylene homo- or copolyether glycol where at least about 50 mole percent of the repeating units are trimethylene ether units. In preferred embodiments the polytrimethylene homo- or copolyether glycol is selected from the group consisting of (i) polytrimethylene ether glycol, (ii) poly(trimethylene-ethylene ether)glycol, and (iii) random polytrimethylene ether ester.