Optimal Performance of an Asymmetric Quantum Harmonic Otto Engine and Refrigerator

TL;DR

This paper analyzes the efficiency and performance of an asymmetric quantum harmonic Otto engine and refrigerator, revealing conditions under which asymmetry enhances efficiency and providing analytical expressions for key performance metrics.

Contribution

It introduces analytical derivations of efficiency and performance for asymmetric quantum Otto cycles, highlighting the impact of sudden expansion and compression.

Findings

Efficiency is higher during sudden compression than sudden expansion.

Efficiency at maximum Omega function exceeds maximum work efficiency.

Fractional work loss analysis provides insights into asymmetric cycle performance.

Abstract

We study a quantum Otto cycle operating with a time-dependent harmonic oscillator as the working material. We examine the asymmetry present between the two adiabatic processes of the Otto cycle, focusing on cases of sudden expansion and sudden compression. We analytically derive the efficiency and coefficient of performance for an asymmetric Otto cycle, employing the Omega function, which represents the balance between the maximum useful energy and minimum lost energy. Notably, our findings reveal that the efficiency (coefficient of performance) of an asymmetric engine (refrigerator) is higher during the sudden compression case compared to the sudden expansion case. Furthermore, we derive the results for the maximum work efficiency and observe that efficiency at the maximum Omega function consistently exceeds the maximum work efficiency. Finally, we compute the fractional loss of work in both cases to thoroughly examine the performance of asymmetric Otto engine.