Discussion:
Entropy increase of Carnot engine operating on methane
Q: A Carnot engine operates on 1 kg of methane, which we shall consider to be an ideal gas. Take γ = 1.35. The ratio of the maximum volume to the minimum volume is 4 and the cycle efficiency is 25 percent. Find the entropy increase of the methane during the isothermal expansion.
γ = cp/cv
η = .25 = 1-T1/T2
Consider the definition of ds (ds = dq/T), and apply it to the isothermal expansion.
Consider how temperature and volume change for the adiabatic process and use the given information about the efficiency to get a relationship between the temperatures of the hot and cold reservoirs.