Operational characteristics of single particle heat engines and refrigerators with time asymmetric protocol

TL;DR

This paper investigates the operation of single particle heat engines and refrigerators driven by a time asymmetric protocol, revealing irreversibility, non-achievable Carnot efficiency, and complex phase behavior.

Contribution

It introduces a detailed analysis of a single particle system with a time asymmetric driving protocol, highlighting irreversibility and unique phase diagram features.

Findings

System operates irreversibly even in quasistatic limit

Carnot efficiency and COP are not achievable due to irreversibility

Phase diagrams are sensitive to protocol asymmetry and show counterintuitive features

Abstract

We have studied the single particle heat engine and refrigerator driven by time asymmetric protocol of finite duration. Our system consists of a particle in a harmonic trap with time-periodic strength that drives the particle cyclically between two baths. Each cycle consists of two isothermal steps at different temperatures and two adiabatic steps connecting them. The system works in irreversible mode of operation even in the quasistatic regime. This is indicated by finite entropy production even in the large cycle time limit. Consequently, Carnot efficiency for heat engine or Carnot Co-efficient of performance (COP) for refrigerators are not achievable. We further analysed the phase diagram of heat engines and refrigerators. They are sensitive to time-asymmetry of the protocol. Phase diagram shows several interesting features, often counterintuitive. The distribution of stochastic efficiency and COP is broad and exhibits power law tails.