Experimental characterization of autonomous heat engine based on minimal dynamical-system model

TL;DR

This paper experimentally investigates a low-temperature-differential Stirling engine, demonstrating that its complex autonomous heat engine dynamics can be effectively modeled with a simple two-degree-of-freedom dynamical system, advancing nonequilibrium thermodynamics.

Contribution

It introduces a minimal dynamical model with two degrees of freedom to describe the engine's behavior, simplifying the understanding of autonomous heat engines.

Findings

Engine dynamics are quantitatively described by a minimal model.

The model introduces the concept of a thermodynamic pendulum driven by a force.

Experimental results validate the model's accuracy.

Abstract

The autonomous heat engine is a model system of autonomous nonequilibrium systems like biological cells, exploiting nonequilibrium flow for operations. As the Carnot engine has essentially contributed to the equilibrium thermodynamics, autonomous heat engine is expected to play a critical role in the challenge of constructing nonequilibrium thermodynamics. However, the high complexity of the engine involving an intricate coupling among heat, gas flow, and mechanics has prevented simple modeling. Here, we experimentally characterized the nonequilibrium dynamics and thermodynamics of a low-temperature-differential Stirling engine, which is a model autonomous heat engine. Our experiments demonstrated that the core engine dynamics are quantitatively described by a minimal dynamical model with only two degrees of freedom. The model proposes a novel concept that illustrates the engine as a thermodynamic pendulum driven by a thermodynamic force. This work will open a new approach to explore the nonequilibrium thermodynamics of autonomous systems based on a simple dynamical system.