Power systems using heat from hot liquid

Claim 1

In a process for converting thermal energy to mechanical energy wherein a working fluid is pre-heated and vaporized by being passed through a heating zone in countercurrent heat exchange relation with a heating fluid, said working fluid is expanded to produce mechanical energy, and said working fluid is cooled and condensed, the improvement comprising: using as said working fluid a mixture of ingredient fluids having moderately close but essentially different boiling points such that said working fluid vaporizes over a desired range of substantially continuously increasing vaporization temperatures, wherein for a substantial increase in enthalpy of said working fluid as it passes through said heating zone there is a substantial increase in temperature of said working fluid, and the differences in temperature between said working fluid and said heating fluid at each point in said heating zone are more nearly equal than would be the differences in temperature between any of said ingredient fluids and said heating fluid at each point in said heating zone were said ingredient fluids passed individually through said heating zone in counter-current heat exchange relation with said heating fluid; maintaining substantially constant the respective compositions of said working fluid and said heating fluid throughout said heating zone; and further maintaining said heating fluid in substantially a single phase throughout said heating zone.