Date of Completion


Embargo Period



Tai-Hsi Fan, Michael Pettes, Xinyu Zhao

Field of Study

Mechanical Engineering

Open Access

Open Access


Full numerical simulation of heat pipes was performed for heat pipes under various operating conditions with a variety of working fluids including fins and nanofluid. Two and three-dimensional models were developed assuming a laminar compressible vapor core. An advanced thermal resistance network for heat pipes was used along with the numerical model to identify dominant thermal resistances. Simulations were performed on heat pipes with external channel cooling around the condenser with and without external fins to determine the impact of individual heat pipe thermal resistances. It was found that the vapor core thermal resistance is significant as the operating temperature increases. The largest thermal resistances are those corresponding to the external heat sources and sinks.

The numerical model was extended for use with nanofluid-filled heat pipes and accounted for flow in the wick; to determine the capillary limit and corresponding optimal nanoparticle concentration. A revised Merit number was proposed for nanofluid-charged heat pipes and used to quantify performance enhancements. Three nanoparticles were explored in this study Al2O3, TiO2 and CuO. The optimal nanoparticle concentration of Al2O3, TiO2 and CuO corresponding to the capillary limit for a conventional nanofluid-filled heat pipe was determined to be 25% by vol. for both Al2O3 and TiO2, and 35% for CuO. Overall, a maximum decrease in total thermal resistance was observed to be 83%, 79% and 76% for Al2O3, CuO and TiO2, respectively. Finally, a homogenous multiphase model was developed for simulation of a thermosyphon and some preliminary results were obtained for the operation of the condenser section.

Major Advisor

Amir Faghri