An Experimental Investigation on Thermal Performance of Ultra-Thin Heat Pipes with Superhydrophilic Copper Braids

Abstract

This study investigated the thermal performance of ultra-thin heat pipes (UTHPs). The total thickness of the heat pipe was 1 mm and the novel wick structure was copper braids modified to be superhydrophilic with higher capillary ability. This paper is divided into three parts, each focusing on the effect on the heat transfer performance of UTHPs, including the wettability of the wick, the filling ratio (FR), and the variation of sectional lengths. The experimental results indicate that the superhydrophilic wick structure improves the thermal performance of UTHPs, and that the FR of 16.4% results in the best thermal performance of UTHPs. Furthermore, the sectional lengths affect both the thermal resistance and the maximum heat transport capacity. The results indicate that the thermal resistance of UTHPs increases for longer adiabatic lengths but slightly decreases for longer condenser and evaporator lengths. However, because the maximum heat transport capacity is influenced by the effective length of the heat pipe, it is degraded when the adiabatic length or the condenser and evaporator length increases. An UTHP of 55-mm effective length with superhydrophilic copper braids yields thermal resistance around 0.3 $°\mathrm{C}$/W and the best heat transport capacity of 26.3 W.

Acknowledgments

The authors gratefully acknowledge funding support from the Ministry of Science and Technology, MOST (Project Nos. MOST 105-2221-E-002-107-MY3).

Additional information

Notes on contributors

Hui-Chung Cheng

Hui-Chung Cheng received a Bachelor degree in Mechanical Engineering from National Chiao Tung University in 2015 and is now pursuing PhD from MEMS Thermal Control Lab of National Taiwan University. His main research interests include heat transfer and fluid flow in micro scales.

Te-Hsuan Chen

Te-Hsuan Chen received a Master degree in Mechanical Engineering from National Taiwan University in 2019. Her main research interests include heat transfer and fluid flow in micro scales.

Hsu-Sheng Huang

Hsu-Sheng Huang received a Master degree in Mechanical Engineering from National Taiwan University in 2018. His main research interests include heat transfer and fluid flow in micro scales.

Ping-Hei Chen

Ping-Hei Chen received the BS degree in Mechanical Engineering from National Taiwan University in 1980. He then received the MS and PhD degrees from the University of Minnesota in 1984 and 1988, respectively. Since 1988, he had been an Associate Professor in the Department of Mechanical Engineering at National Taiwan University. He was promoted to the full Professor at 1996, then served as the vice-Chairman for two years, and Chairman for three years at Department of Mechanical Engineering in National Taiwan University. His current research interests are MEMS, biochips, diamond film wafer, nanotechnology, thermal and fluid control in MEMS, and packaging for optical devices and IC. He has published more than 60 academic journal papers, 90 conference papers, and ten patents, and three textbooks. He is a member of ASME, CSME, CIE, CIAA, and CMEMSS.