Frequency‐dependent performance of a nonideal Carnot engine

The average power output P, efficiency η′, and entropy production P_s have been determined as function of cycle frequency ν for a nonideal Carnot engine where the ratio r of the heat absorption time and heat rejection time can be varied and the heat is transferred by conduction into the working fluid. The power output has an optimum at the value r=(β/α)^1/2, where α and β are the thermal conductances of the upper and lower isotherm, respectively. The efficiency decreases and the conduction losses increase drastically with cycle frequency. The power output goes through a maximum, peaked at a frequency ν*. The efficiency can be increased without much sacrifice in power output if the engine is run below the frequency ν* (12% efficiency increase at 3% loss in power for ν=0.85ν*). The entropy production grows approximately as P_s ∼ν².