Thermal Rectification of Solid-liquid Phase Change Thermal Diode under the Effect of Supercooling

TL;DR

This study demonstrates that controlling supercooling in a solid-liquid phase change thermal diode enhances its thermal rectification performance, achieving a ratio of 2.95 and enabling persistent heat transfer asymmetry over large temperature biases.

Contribution

It introduces a supercooling-controlled thermal diode with gating functionality, providing a new approach to sustain and improve thermal rectification using supercooling effects.

Findings

Supercooling sustains heat transfer in forward direction below melting temperature.

Manual supercooling release inhibits heat transfer in reverse direction.

Thermal resistance modeling agrees with experimental results.

Abstract

Thermal rectification ratios of solid-liquid phase change thermal diodes (SL-PCTDs) are not sustainable beyond a certain temperature bias, necessitating reasonably compatible designs. Manipulating the heat transfer in the forward and reverse directions of the SL-PCTD is of great practical interest to achieve persistent performance. Herein, a SL-PCTD prototype is investigated under the supercooling effect of a phase change material (calcium chloride hexahydrate). In the forward direction, supercooling effect plays a significant role in sustaining natural convection far below the melting temperature (30 C), which leads to robust heat transfer within a temperature bias of 10-40 C. While in the reverse direction, dislodging the supercooling via manual supercooling release (MSR) within a large temperature range of 30-7 C tends to greatly inhibit heat transfer. As a consequence, thermal rectification ratio of 2.95 is achieved, which is competitively sustainable at large temperature bias compared to the SL-PCTD without supercooling effect. To address the effect of supercooling on thermal rectification comprehensively, thermal resistance approach is applied to theoretically model the SL-PCTD, which shows a good agreement with experimental data. Such a device with supercooling control in only one direction is further named as the SL-PCTD with gating functionality, where manipulating supercooling effect of phase change material opens up a feasible avenue for enabling generalized thermal diode.