Numerical Simulation of a Cylindrical Heat Pipe and Performance Study

Heat Pipes are passive devices used for transferring heat from a heat source to a heat sink with very small difference in temperature. They have three main sections namely the evaporator, adiabatic section and the condenser. In construction terms, they have three parts, the metal container, the porous wick region which lines the container from inside and the hollow flow chamber. Heat pipe performance is governed by several parameters such as the geometry, dimensions, working fluid, wick and container materials etc. In this study numerical simulation method was used to analyze the performance of the heat pipe. A numerical model based on Navier stokes equation, Energy equation and conjugate heat transfer was developed using COMSOL Multiphysics package. The top wall temperature profile obtained was validated with experimental results, and further the absolute thermal resistance was calculated. A sensitivity study was carried out to study the performance dependency of heat pipe on four parameters namely, porosity, condenser evaporator lengths, radius of heat pipe and the heat input, in terms of the absolute thermal resistance. The results showed that absolute thermal resistance varied directly with respect to porosity of the wick, and inversely in case of radius of the heat pipe. The absolute thermal resistance was maximum in case of equal condenser and evaporator lengths. Interestingly the absolute thermal resistance did not vary with the applied heat rate, demonstrating the practicality in using absolute thermal resistance as a performance characteristic parameter.