Numerical investigation of effect of fill ratio and inclination angle on a thermosiphon heat pipe thermal performance

Abstract

Computational Fluid Dynamic (CFD) modelling of a heat pipe is a powerful tool that can be used to investigate the complex physical phenomena of the evaporation and condensation phase change processes inside thermosiphon heat pipes. In this work, a new CFD simulation of two phase flow inside thermosiphon heat pipe is carried out to investigate the effect of fill ratio (ratio of liquid volume to the evaporator volume) and inclination angle on its thermal performance in terms of temperature distribution and thermal resistance using FLUENT (ANSYS 15). Results of the CFD simulation were compared to published experimental data showing good agreement with maximum deviation of 4.2% and 8.1% for temperature distribution and thermal resistance, respectively. In addition, numerical results of inclination angle were also compared with experimental data in terms of thermal resistance giving maximum deviation of 1.3%. Using the validated CFD modelling, results showed that at low fill ratio and low inclination angle, there was a significant increase in the evaporator temperature. Regarding the thermal resistance, a fill ratio of 65% and inclination angle of 90° produced the lowest thermal resistance for all the heat input values used. Also, as heat input increases, the effect of the fill ratio and inclination angle becomes more significant.