William John Macquorn Rankine (5.07.1820-24.11.1872) was a Scottish engineer and physicist, one of the creators of technical thermodynamics, and a Fellow of the Royal Societies of Edinburgh (1850) and London (1853). He was born in Edinburgh. He studied at the University of Edinburgh. From 1838 he worked in surveying and harbour construction. From 1855 he was lecturer and then professor at the University of Glasgow.
His work was in thermodynamics, the theory of heat engines, molecular physics, the theory of elasticity and the study of vibrations. In 1849, independently of R. Clausius, he obtained the general equations of thermodynamics expressing the relations between heat and mechanical energy. He studied the thermodynamic properties of gases and water vapour (1850) and drew up tables of water vapour that came into wide use. He concluded that saturated water vapour must partly condense on expansion and become supersaturated on compression. He built (1859) a complete theory of the steam engine and in particular developed (independently of Clausius) the ideal thermodynamic cycle of a steam engine (the Rankine–Clausius cycle). He introduced a number of terms: “potential energy”, “adiabatic and isothermal processes” and “adiabat”. He laid the foundations of the theory of the regenerative process for caloric engines running on heated air and, independently of W. Thomson and Clausius, gave a formula for the efficiency of a steam engine in terms of the temperatures of the heater and the cooler. For calculating double-expansion steam engines he proposed a method of constructing the cycle, called “Rankinising”. He was one of the first to understand the importance of atomism for the foundation of the laws of heat; in 1850 he proposed a vortex model of the atom, and he tried to give (1865) a foundation for the second law of thermodynamics.
He was the author of the first work on technical thermodynamics (“A Manual of the Steam Engine”, 1859), which went through about 20 reprintings in England alone. The founder of energetics.