Cooling by heating a nanodroplet - proof of concept

TL;DR

This paper provides the first empirical evidence, via molecular dynamics simulations, confirming the theoretically predicted phenomenon where heating a nanodroplet causes its interior temperature to initially decrease, demonstrating the effect beyond the inertia-free limit.

Contribution

It offers the first experimental proof of the cooling-by-heating effect in a nanodroplet, extending the understanding beyond the quasi-elastic, inertia-free assumptions.

Findings

The effect occurs even when inertia is significant.

Simulations confirm the temperature decrease inside the droplet upon surface heating.

The phenomenon persists in a supercooled Lennard-Jones droplet.

Abstract

Recently [3] predicted the existence of an intriguing new phenomenon. It was shown that if temperature is suddenly raised at the surface of a sphere the temperature in the interior initially decreases. The authors of [3] gave a thorough analysis explaining the physics leading to this remarkable effect. They linked the existence of the phenomenon to the subtle thermomechanical coupling between displacement and temperature in a sphere that is able to expand freely and showed that the effect is expected to be largest close to the glasstransition temperature of the perturbed material. The prediction was based on the assumption of quasi-elasticity where the sample is much smaller than the wavelength of acoustic waves at frequencies of relevance. Being in the inertia free limit they could ignore the acceleration term in the thermoviscoelastic equations of motion. Here we give the first empirical proof of existence of the effect by performing molecular dynamics simulations of a supercooled Kob-Andersen binary mixture of Lennard-Jones particles forming a droplet consisting of 500.000 particles. We show that the phenomenon is real even when inertia cannot be disregarded.