Comparative thermal performance evaluation between ultrathin flat plate pulsating heat pipe and graphite sheet for mobile electronic devices at various operating conditions

Highlights: • Performance comparison between flat plate PHP and graphite sheet is conducted. • An optimum PHP is determined based on the optimization of channel geometries. • Finished PHP shows 200% higher performance than graphite sheet at 90° and 0°. • Benefits of PHPs increase with increasing heat input owing to increased (dp/dT)_sat. -- Abstract: The objective of this study is to evaluate the thermal performance improvement of an ultrathin, flat plate pulsating heat pipe (PHP) against a graphite sheet for use in mobile electronic devices. Initially, the thermal performances of five PHP models with various channel designs are quantified, and an optimum PHP is selected to achieve the best performance. In the optimum PHP, the thermal performance is analyzed as a function of the heat input and condenser temperature. Finally, the finished product of the flat plate PHP is fabricated using a diffusion bonding technique. The thermal performance of the finished flat plate PHP is then compared with that of the graphite sheet based on conducted tests at the inclination angles of 90°, 0°, and −90°. The thermal resistances of the finished flat plate PHP at the inclination angles of 90° and 0° are 63% and 56%, respectively, lower than those of the graphite sheet, whereas the resistance at the inclination angle of −90° is almost the same as that of the graphite sheet.