The Second Law of Thermodynamics and Entropy-Decreasing Processes With $^4$He Superflows

TL;DR

This paper reviews a quantum exception to the second law of thermodynamics involving $^4$He superflows, discussing their entropy properties and potential to realize entropy-decreasing processes in thermal environments.

Contribution

It highlights the entropy-carrying nature of $^4$He superflows and proposes using superflow loops to achieve entropy-decreasing processes, challenging traditional thermodynamic understanding.

Findings

Superflows carry entropy in thermal environments.

Heterogeneous superflow loops can realize entropy-decreasing processes.

Heat content of superflows depends unusually on flow velocity.

Abstract

We review on a recently proposed quantum exception to the second law of thermodynamics. We emphasize that $^4$He superflows, like any other forms of flows, shall carry entropy or heat in a thermal environment. Following that, one can use a heterogeneous $^4$He superflow loop to realize entropy-decreasing processes. We also mention that the heat content of a superflow has an unusual dependence on flow velocity, which is an important factor contributing to the entropy-decreasing processes.