Specific power bound of real heat engines

Abstract Industrial heat engine optimization usually takes the form of determining minimum heat exchanger area per unit net power or minimum cost per unit net power rather than the form of maximum efficiency. A specific power, power per unit total heat exchanger surface area, is adopted to be the objective function for engine optimization in this paper. Specific power output of an irreversible heat engine coupled with its heat source and sink is analyzed. When time is explicitly considered in the energy exchanges between the engine and its surroundings, it is found that there is an upper bound on the specific power output of the engine. This bound can guide the evaluation of existing real heat engines or influence the design of future heat engines.