Experiments and Analyses on Heat Transfer Characteristics from a Solid Wall to a Strip-Shaped Wick Structure

Centered or striped wick structures have been used to develop ultrathin heat pipes. Differing from traditional heat pipes, the centered or striped wick structures leave noncontact container surfaces with the wick structure. In this study, experiments and numerical analyses were conducted to investigate the influence of these noncontact surfaces. In the experiments, a strip-shaped wick structure was placed vertically, the top was sandwiched between wider rods and the bottom was immersed in a working fluid. The rod width was greater than the wick width; thus, noncontact surfaces were left between the rod and the wick structure. The heat was applied from the rod to the wick structure, and the evaporation heat transfer characteristics of the working fluid from the wick structure were evaluated. Water was used as the working fluid. The experiments were conducted by varying the rod and wick widths. The experimental results were obtained when the wick structures were placed separately. In the numerical analyses, the temperature and heat flux distributions in the rod were obtained. From the experimental and numerical results, it was confirmed that the noncontact surfaces caused the heat flux in the rod near both surfaces of the wick structure to concentrate, which increased the evaporation thermal resistance of the wick structure. A reduction in the noncontact surface area by increasing the wick width was found to be effective in decreasing the evaporation thermal resistance and increasing the maximum heat transfer rate of the wick structure. The separation of the wick structure increased the evaporation surface area. However, its effectiveness was limited when the heat transfer rate was small.