Building an irreversible Carnot-like heat engine with an overdamped harmonic oscillator

TL;DR

This paper investigates a non-equilibrium Carnot-like cycle using an overdamped colloidal harmonic oscillator, optimizing power output and demonstrating near-Curzon-Ahlborn efficiency across various temperature ratios.

Contribution

It introduces a novel irreversible heat engine cycle with a harmonic oscillator, analyzing its efficiency and power optimization in the overdamped regime.

Findings

Maximum power efficiency close to Curzon-Ahlborn bound

Cycle operates irreversibly at finite rates

Optimal parameters depend on bath temperature ratio

Abstract

We analyse non-equilibrium Carnot-like cycles built with a colloidal particle in a harmonic trap, which is immersed in a fluid that acts as a heat bath. Our analysis is carried out in the overdamped regime. The cycle comprises four branches: two isothermal processes and two \textit{locally} adiabatic ones. In the latter, both the temperature of the bath and the stiffness of the harmonic trap vary in time, but in such a way that the average heat vanishes for all times. All branches are swept at a finite rate and, therefore, the corresponding processes are irreversible, not quasi-static. Specifically, we are interested in optimising the heat engine to deliver the maximum power and characterising the corresponding values of the physical parameters. The efficiency at maximum power is shown to be very close to the Curzon-Ahlborn bound over the whole range of the ratio of temperatures of the two thermal baths, pointing to the near optimality of the proposed protocol.