  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.
