Effect of physical properties on heat transfer and flow behavior of flat plate heat pipe with closed meandering channel composed of sintered metal porous sidewalls

This study investigates the heat transfer characteristics of a novel flat-plate heat pipe featuring a closed meandering channel with sintered porous sidewalls. Building upon previous work that used FC-72 as the working fluid, the present research explores the effects of the physical properties of the fluid on the heat transfer and flow characteristics using distilled water. In terms of thermal performance under bottom-heated conditions, FC-72 demonstrated superior heat transport performance at low heat transfer rates, whereas water exhibited enhanced performance at moderate to high heat transfer rates. Importantly, the two fluids exhibited fundamentally different flow behaviors: FC-72 induced self-excited oscillations flow within the meandering channel, whereas water was primarily driven by the vapor flow in the meandering channel and capillary-driven flow within the porous sidewalls. Consequently, despite the absence of self-excited oscillations in the meandering channel, water exhibited a better heat transport performance than FC-72 under high heat input conditions. These distinct flow mechanisms are closely linked to differences in fluid properties, particularly in the Capillary and Bond numbers. The critical diameter concept established for conventional pulsating heat pipes (PHPs) may also be applicable to heat pipes incorporating meandering channel with porous walls.