Maximum efficiency of low-dissipation heat pumps at given heating load

TL;DR

This paper derives analytical bounds for the maximum efficiency of low-dissipation heat pumps operating at fixed power, providing insights into optimal performance regimes and comparisons with endoreversible models.

Contribution

It introduces a new analytical framework for maximum efficiency of low-dissipation heat pumps at fixed power, including bounds and approximations.

Findings

Derived simple formulas for efficiency bounds.

Identified parameter regimes where low-dissipation and endoreversible devices perform similarly.

Provided expressions useful for practical operation optimization.

Abstract

We derive an analytical expression for maximum efficiency at fixed power of heat pumps operating along a finite-time reverse Carnot cycle under the low-dissipation assumption. The result is cumbersome, but it implies simple formulas for tight upper and lower bounds on the maximum efficiency and various analytically tractable approximations. In general, our results qualitatively agree with those obtained earlier for endoreversible heat pumps. In fact, we identify a special parameter regime when the performance of the low-dissipation and endoreversible devices is the same. At maximum power, heat pumps operate as work to heat converters with efficiency 1. Expressions for maximum efficiency at given power can be helpful in the identification of more practical operation regimes.