Evaporation Heat Transfer Characteristics from a Sintered Powder Wick Structure Sandwiched between Two Solid Walls

An ultra-thin flattened heat pipe has been developed with a centered wick structure. This structure is essential to make the heat pipe thinner. However, the centered wick structure reduces the evaporation and condensation surface areas of the wick structure because it is sandwiched between heat pipe walls. In this study, because detailed discussion has not been made, heat transfer experiments were conducted for the wick structure sandwiched between two solid walls. This study focused on the evaporation heat transfer characteristics from the sandwiched wick structure. The experiments were conducted with three wick structures, that is, strip-shaped sintered copper powders with thicknesses of 0.5, 1.0, and 1.5 mm. Water was used as working fluid. The capillary pumping performance, that is, the liquid lifting velocities of the three wick structures were the same. The experimental results of the three wick structures were compared regarding the relation between the evaporation heat transfer rate and the superheat of the working fluid. The heat transfer experiments were also conducted when one of the solid walls was removed from the wick structure. It was confirmed that even if the wick structure was sandwiched between the solid walls, sufficient evaporation of the working fluid occurred from the thin sides of the wick structure.