Experimental implementation of finite-time Carnot cycle

TL;DR

This paper experimentally demonstrates a finite-time Carnot cycle using dry air, confirming a tradeoff between power and efficiency, and achieving efficiency close to half of the Carnot limit at maximum power.

Contribution

The study provides the first experimental verification of the power-efficiency tradeoff in finite-time Carnot cycles with real working substances.

Findings

Efficiency at maximum power is approximately half of the Carnot efficiency.

Experimental results align with theoretical predictions of finite-time thermodynamics.

The setup offers a new platform for studying nonequilibrium thermodynamic processes.

Abstract

The Carnot cycle is a prototype of ideal heat engine to draw mechanical energy from the heat flux between two thermal baths with the maximum efficiency, dubbed as the Carnot efficiency $\eta_{\mathrm{C}}$. Such efficiency can only be reached by thermodynamical equilibrium processes with infinite time, accompanied unavoidably with vanishing power - energy output per unit time. In real-world applications, the quest to acquire high power leads to an open question whether a fundamental maximum efficiency exists for finite-time heat engines with given power. We experimentally implement a finite-time Carnot cycle with sealed dry air as working substance and verify the existence of a tradeoff relation between power and efficiency. Efficiency up to $(0.524\pm0.034)\eta_{\mathrm{C}}$ is reached for the engine to generate the maximum power, consistent with the theoretical prediction $\eta_{\mathrm{C}}/2$. Our results shall provide a new platform for studying finite-time thermodynamics consisting of nonequilibrium processes.