Numerical case study and modeling for spreading thermal resistance and effective thermal conductivity for flat heat pipe

Flat heat pipe, vapor chamber, thermal ground plane, and heat spreader have been emerging topics for various thermal applications such as electric battery packs and high-power computer chips. In this study, computational fluid dynamics is used to model the effective thermal conductivity of a vapor chamber and thermal ground plane. From various literature, simulation conditions are obtained for different flat heat pipe geometries. With the commercial code Fluent (Ansys Inc.), 4,800 cases have been used to examine the spreading thermal resistance tendencies for the different heat sink areas, heat source area, thickness, and heat transfer coefficient. In conclusion, the effective thermal conductivity increases when the thickness decreases or the heat sink area becomes greater with the same spreading thermal resistance value. In particular, the modified model of spreading thermal resistance is proposed for a better accuracy targeting various effective thermal conductivity, based on the original analytical model. A good agreement with a better accuracy is found between the model and the numerical results. This study will be able to provide the thermal system guideline for flat heat pipes.