Heat and lost work in irreversible cycles: the two sides of the same coin

TL;DR

This paper explores the relationship between heat, lost work, and entropy generation in irreversible cycles, proposing a conceptual model that clarifies their interconnected roles and challenges traditional diagram-based assessments.

Contribution

It introduces a new conceptual model using Carnot cycles to better understand irreversibility, heat, and lost work, emphasizing their connection through entropy generation.

Findings

Heat and lost work are two sides of the same coin, representing entropy generation.

Traditional cycle diagrams are insufficient to determine lost work.

The model enhances understanding of irreversibility for educational purposes.

Abstract

We discussed the criterion for usefully comparing an irreversible cycle with a reversible one, and show that the lost work cannot be determined by the usual cycle diagrams, contrary to what has been found in the literature. To better understand the lost work concept and its role in entropy generation, we present a conceptual model that uses Carnot cycles to describe thermal and mechanical irreversibility, which also instructively reveals that heat and lost work are the two sides of the same coin, this coin being the entropy generation. This study, addressing issues that are virtually absent from the literature, is expected to be not only relevant from a scientific standpoint but also useful for physics teachers and students.