# The many avatars of Curzon-Ahlborn efficiency

## TL;DR

This paper explores the widespread appearance of the Curzon-Ahlborn efficiency formula, which predicts the maximum power efficiency of irreversible heat engines, across various models and contexts.

## Contribution

It highlights the universality and simplicity of the Curzon-Ahlborn efficiency formula in different thermodynamic models.

## Key findings

- The Curzon-Ahlborn efficiency appears in diverse models.
- The efficiency is given by the formula 1 - sqrt(Tc/Th).
- The formula's simplicity suggests a fundamental principle in thermodynamics.

## Abstract

Efficiency at maximum power output of irreversible heat engines has attracted a lot of interest in recent years. We discuss the occurance of a particularly simple and elegant formula for this efficiency in various different models. The so-called Curzon-Ahlborn efficiency is given by the square-root formula: $1-\sqrt{T_c/T_h}$, where $T_c$ and $T_h$ are the cold and hot reservoir temperatures.