Numerical investigation and modeling of thermal resistance and effective thermal conductivity for two-phase thermosyphon

Heat pipe technology with latent heat has been a rising topic for various engineering applications such as electric cars and high-power computer chips. It has been studied for thermal resistance and model development as they are the key to infer effective thermal conductivity. In this article, computational fluid dynamics is investigated to look at the two-phase flow and heat transfer of a two-phase thermosyphon of which inside cannot be visualized experimentally. The Volume-of-Fluid model has been utilized as well as the Lee model. Thermal resistance tendencies are also examined for different amounts of water, heat pipe diameter, and heater power. As a result, the thermal resistance decreases when the water amount, heat pipe diameter, and heater power increase, indicating that temperature is quickly cooled down by latent heat. The thermal resistance for different conditions is modeled with a simple scaling analysis, and a good agreement is made between the model and the numerical results. Effective thermal conductivity is also calculated based on the thermal resistance results. An increase in thermal conductivity is observed as the diameter decreases, indicating the importance of an optimum thermosyphon design