Yasushi Koito^1,*, Shoma Hitotsuya², Takamitsu Takayama², Kenta Hashimoto²

Frontiers in Heat and Mass Transfer, Vol.21, pp. 33-46, 2023, DOI:10.32604/fhmt.2023.041829

Abstract 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… More >

Yasushi Koito^a,*

Frontiers in Heat and Mass Transfer, Vol.13, pp. 1-6, 2019, DOI:10.5098/hmt.13.26

Abstract This paper describes extended numerical analyses on vapor pressure distribution in a centered-wick ultra-thin heat pipe. Analyses were conducted by using a three-dimensional model developed by the author. Numerical results were obtained changing design parameters and operating conditions of the heat pipe. Discussion was made on the heat transfer limit as well as the vapor pressure drop. Moreover, a simple method was also presented to evaluate the vapor pressure drop in the ultra-thin heat pipe. Calculated results with the simple method agreed in 10 % with the three-dimensional numerical results. More >

Yasushi Koito^*

Frontiers in Heat and Mass Transfer, Vol.16, pp. 1-6, 2021, DOI:10.5098/hmt.16.8

Abstract Numerical analyses were conducted for an ultra-thin heat pipe in which a thin wick layer was placed on the bottom. The vapor temperature drop caused by vapor flow friction was discussed for two types of the ultra-thin heat pipes with small and large widths. The numerical results were compared with those obtained for an ultra-thin heat pipe with a centered-wick structure. It was confirmed that the vapor temperature drop was reduced effectively by increasing the width of the heat pipe. Therefore, a wider ultra-thin heat pipe, that is, an ultra-thin vapor chamber is a promising option for nextgeneration thermal management. More >

Yasushi Koito^a,*

Frontiers in Heat and Mass Transfer, Vol.16, pp. 1-7, 2021, DOI:10.5098/hmt.16.1

Abstract For ultra-thin heat pipes, a centered wick structure is often used. In this study, a numerical analysis is performed on an ultra-thin heat pipe in which the wick structure’s position has deviated from the center. A 3D heat pipe model, developed by the author in a previous study, is extended, and numerical calculations are conducted to determine any differences in performance because of an off-center wick. The major findings are as follows: (1) a completely centered wick structure is recommended for optimum performance; (2) accurate central positioning of the wick structure is important in the fabrication process of ultra-thin heat… More >