Clapeyron's Graph FIGURE 20-5 The Carnot cycle Heat In a cyo the cycle for the Carnot engine Isothermal begins at point a on this Pl expansion diagram (1)The gas is first panded isothermally, with addition of heat @), along path ab at temperature TH. (2)Next d→ the gas expands adiabatically Adiabatic Adiabatic from b to c-no heat is exchanged, compression lexpansion but the temperature drops to TL (3) B)The gas is then compressed at co stant temperature Ti, path c to d d 0=0 and heat e. flows out. (4)Finally the gas is compressed adiabatically. path da, back to its original state. No Carnot engine actually exists, but as a theoretical engine it played c→d Isothermal Important role in the development of thermodynamics compression
Clapeyron’s Graph
High Clausius, dea temperature, TH Engine Ow temperature, FIGURE 20-1 Schematic diagram of energy transfers for a heat engine
Clausius’ Idea
Clausius statement Not possible Q
Clausius statement Not possible
SECOND LAW OF THERMODYNAMICS (Kelvin-Planck statement h gh temperature leHI Engine FIGURE 20-4 Schematic diagram of a hypothetical perfect heat engine in which all the heat input would be used to do work
Clausius' ideas 热力学第一定律 8Q=du sW =dU t pdv
Q = dU + W = dU + pdV 热力学第一定律 Clausius’ ideas