Optimal Endoreversible Heat Engines with Polytropic Branches

Abstract

Endoreversible engine cycles with two adiabatic and two heat transfer branches are in-vestigated and optimized for maximum work output. The heat transfer branches are described as general polytropic processes which include common standard branches, like isotherms, isobars and isometrics, as special cases. The study considers the finite heat capacity of the working fluid and the finite-time character of the heat transfer processes, determines the optimal allocation of branch times, and derives analytic expressions for the maximized work output. The efficiency at maximum work is found to coincide with the Curzon-Ahlborn efficiency for endoreversible Carnot engines and does not depend on design parameters of the engine if the degree of the polytropic processes is equal in both heat transfer branches.

Keywords

• endoreversible, finite-time thermodynamics, optimization, polytropic, heat engine