True nature of the Curzon-Ahlborn efficiency

TL;DR

This paper challenges the universal status of the Curzon-Ahlborn efficiency, showing it is specific to nonlinear heat engines and providing a generalized formula for efficiency at maximum power.

Contribution

It redefines the understanding of the Curzon-Ahlborn efficiency by linking it to nonlinear heat engines and deriving a broader efficiency expression.

Findings

Curzon-Ahlborn efficiency is not universal.

Derived a generalized efficiency formula.

Linked efficiency to nonlinear heat engine models.

Abstract

The Curzon-Ahlborn efficiency has long served as the definite upper bound for the thermal efficiency at maximum output power, and has thus shaped the development of finite-time thermodynamics. In this paper, we repeal the ruling consensus according to which it has a genuine universal character that can be derived from linear irreversible thermodynamics. We demonstrate that the Curzon-Ahlborn efficiency should instead properly be associated with a particular case of nonlinear heat engines, and we derive a generalized expression for the efficiency at maximum power beyond the restrictive case of linear models.