Heat transfer optimization of grooved heat pipes

An extensive experimental investigation on heat transfer of grooved heat pipes has been conducted in order to determine the primary factors affecting the heat transfer performance. Several heat pipes composed from five different grooved tubes were fabricated and tested. Results show that the groove dimensions, the working fluid wetting characteristics, as well as the charging amount significantly affect the effective thermal conductivity of grooved heat pipes. It is found that when the surface is chemically treated, the contact angle can be reduced, which enhances the evaporating heat transfer coefficient and significantly increases the effective thermal conductivity of the grooved heat pipe investigated here. A manufacturing process to fabricate the grooved heat pipes was developed, which can be employed in the mass production. In order to predict the heat transfer performance, a theoretical analysis was conducted. The model includes the thin film evaporation in the evaporator and film condensation in the evaporation. Although the prediction is not agreeable well with the experimental data, the model provides an insight into the mechanisms of phase-change heat transfer in a grooved heat pipe and it will help design the highly efficient grooved heat pipe.