Modeling an efficient Brownian heat engine

TL;DR

This paper investigates how subdividing the potential barrier in a Brownian heat engine affects its efficiency and performance, revealing that smaller subdivisions optimize velocity and efficiency but cannot reach Carnot limits due to irreversibility.

Contribution

It introduces a model showing that subdividing the potential barrier enhances performance metrics and analytically demonstrates the limits imposed by irreversibility on efficiency.

Findings

Maximum velocity and efficiency occur with subdivided barriers.

Efficiency cannot reach Carnot efficiency due to irreversible heat flow.

Coefficient of performance of the refrigerator is always below Carnot limit.

Abstract

We discuss the effect of subdividing the ratchet potential on the performance of a tiny Brownian heat engine that is modeled as a Brownian particle hopping in a viscous medium in a sawtooth potential (with or without load) assisted by alternately placed hot and cold heat baths along its path. We show that the velocity, the efficiency and the coefficient of performance of the refrigerator maximize when the sawtooth potential is subdivided into series of smaller connected barrier series. When the engine operates quasistatically, we analytically show that the efficiency of the engine can not approach the Carnot efficiency and, the coefficient of performance of the refrigerator is always less than the Carnot refrigerator due to the irreversible heat flow via the kinetic energy.