Flat Miniature Heat Pipe With Composite Fibre Wick Structure for Cooling of Mobile Handheld Devices

Abstract

Heat pipe is a very reliable and efficient two phase heat transfer device that has been extensively investigated for applications in electronic cooling. In the past, different types of heat pipe have been developed for specific as well as general applications. With the development in technology and trend towards miniaturization, thermal control of electronic devices with compact structure and concentrated heat sources has really become a challenge. Miniature heat pipes can be considered as potential candidates to address these issues. In the present paper, experimental investigation of the Flat Miniature Heat Pipe (FMHP), with the characteristic thickness of 1.5 mm and new type of composite fibre wick structure (FB-G), has been done for the thermal management of the mobile handheld devices. The so called composite fibre structure consists of combination of copper fibres and axial grooves as a capillary wick along the inner wall of the heat pipe. The design configuration of the experimental FMHP comprised of L-shaped flat heat pipe with rectangular cross section (1.5 mm × 8 mm) and heat transfer length of 100 mm. The body of FMHP was made of copper with pure deionised water as the working fluid. FMHP was easily able to transfer required heat fluxes in the range of 1–6 W/cm2 given by mobile-handheld chipset. Thermal resistance of the heat pipe from evaporator to the condenser surface came out to be in the range of 0.25–0.45 °C/W. In order to highlight the performance of the FMHP with composite fibre wick, thermal resistance was compared to different prototypes with screen mesh and axial grooves. It can be concluded from the outcomes of the investigation that the composite fibre wick structure provides an optimum capillary head and permeability for better heat transfer capabilities and minimal end to end temperature gradient than the conventional type of wick structures. FMHPs with composite fibre wicks will find prospective applications in the cooling of the compact handheld devices like Palm PC, mobile phones and digital diaries.