Effect of mesh wick thickness on thermal performance of cylindrical heat pipes

Heat pipes are passive heat transfer devices capable of transferring large amount of heat isothermally based on boiling-condensation principles. These devices can have the potential usage in intense heat dissipation/transferring applications such as in Nuclear, Solar thermal systems, cooling of electronic equipment, air-conditioning systems, etc. In heat pipes the working fluid gets vaporised at the evaporator by absorbing heat and rejects it at the condenser and hence condensed. The condensate reaches the evaporator end by the capillary pumping of the wick material along with or without the assistance of gravity. The function of the mesh wick is thus to do this liquid cycling process inside the heat pipe. So wick thickness and filling ratio seems to be crucial factors for determining the heat transfer capability of heat pipes. In the present work, the thermal performance of DI water heat pipes was experimentally analysed in terms of thermal resistance and equivalent thermal conductivity by varying the wick thickness at 2, 4 and 8 layers and also at varying filling ratios at 70, 90 and 110 %. The effect of tilt angle and heat flux levels on heat pipe operation are also investigated. The optimised values of tilt angle, filling ratio, wick layers for the given heat flux range is obtained for minimum thermal resistance. The results from this research would be useful in designing mesh wick heat pipe based thermal systems.