Experimental analysis and simulation of passive flexible heat transfer device

Modern day foldable electronic devices with high heat dissipation rates poses a challenge to conventional air-cooling techniques in attaining the necessary cooling efficacy. The present study addresses the challenges faced by existing Flexible Heat Pipe (FHP), namely non-condensable gas penetration and out-gassing. These challenges are instrumental in compromising the long-term reliability of these devices. This paper presents the performance characterisation of a novel Flexible Heat Transfer Device (FHTD) that can cater to the flexible thermal management needs of futuristic electronic devices. Heat load varying from 4 W to 24 W, typical range pertaining to laptops and other foldable e-devices at different bending angles of 0, 45 degrees , and 90 degrees is chosen for the study. Variations in temperature at different cross-sections, effective thermal conductivity and thermal resistances as a function of heat load are reported in the current work. Numerical investigations to elucidate the heat transfer dynamics are presented using COMSOL Multiphysics software and the results are validated with experiments. Under steady-state operating conditions, the minimum thermal resistance of an FHTD at a heat load of 24 W is found to be 1.3 K/W and a maximum effective thermal conductivity of 2683 W/mK is reported for a 90 degrees bending angle. The effective thermal conductivity of FHTD is 6.7 times higher than similar flexible heat transfer devices like copper thermal straps.