Effect of heat load fluctuation on heat transport characteristics of three-dimensional pulsating heat pipe

Abstract

Heat transport characteristics of three-dimensional pulsating heat pipe (3D-PHP) have been investigated experimentally. The 3D-PHP consists of 20 tubes and heating block made of copper. The 3D-PHP has 2 layers of 5 turn flow paths (10 tubes) and the layers are interconnected. The operational orientation of 3D-PHP was bottom heat. The bottom of heating block was heated by a ceramic heater. Copper tubes that played a role of heat dissipation fin were cooled by air flow. Fluorinert FC-72 was used as the working fluid and filling ratio was 50 % of the channel volume. The 3D-PHP was tested for various air velocity and heat load. Heat load increased by 10 W to 100 W and decreased by 100 W to 10 W. It was found that the thermal resistance at decreased heat load was lower than that at increased heat load for the same heat load when the heat load was lower than the start-up heat load. On the other hand, when heat input was higher than the start-up heat load, the thermal resistance at decreased heat load were approximately as same as that at increased heat load for the same heat load. Those were confirmed for all cooling air velocities within the scope of this study.

Keywords

• three-dimensional pulsating heat pipe
• thermal resistance
• heat load
• start-up
• hysteresis