LawsThermo - previous index next The Laws of Thermodynamics...

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previous index next The Laws of Thermodynamics and Limits on Engine Efficiency Michael Fowler, 7/15/08 The Laws of Thermodynamics (Picture below from St. Andrews ) In 1850, Rudolph Clausius , a German physicist, created the science of thermodynamics . He was convinced by Joule’s experiments (he didn’t know about Mayer’s work at the time) that total energy , including kinetic, potential, electrical, and, importantly, heat, was conserved , he called this: The first law of thermodynamics: total energy , including heat energy, is always conserved. He explicitly assumed that heat was just the kinetic energy of the moving particles that made up a body. He was the first to make clear that Carnot’s analysis of the heat engine (the cycle) was almost right except that the “caloric fluid”, meaning heat, wasn’t actually conserved—less of it was dumped in the cold reservoir than was taken from the hot one. The difference of course was the work done (in an ideal engine). Engines at the time were so inefficient that this loss of heat energy wasn’t obvious. But abolishing the caloric fluid in favor of overall energy conservation raised another problem. The fluid theory had been highly successful in describing heat flow through solid materials, like electric current flow but with temperature gradients replacing voltage drops, different materials having different thermal conductivities, etc. ( Note : Fourier revolutionized mathematics by inventing Fourier series, his method of analyzing caloric fluid flow. In fact Kelvin used it in 1862 to estimate the rate of cooling of the earth. Kelvin’s conclusion
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LawsThermo - previous index next The Laws of Thermodynamics...

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