Recent advances in the numerical analysis of heat pipes

Numerical simulation of heat pipes has progressed significantly in recent years. The state-of-the-art has been advanced in steady state, continuum transient, and frozen startup simulation for high, moderate, and low temperature heat pipes of conventional cylindrical and nonconventional geometries such as wing leading edges and spacecraft nosecaps. This review summarizes these advancements and discusses the important results.List of symbols A cross-sectional area of the vapor channel, m² - c specific heat, J/(kg-K) - C _p specific heat at constant pressure, J/(kg-K) - C _v specific heat at constant volume, J/(kg-K) - D vapor space diameter, m - D _v coefficient of self-diffusion, m²/s - G vapor mass flux, kg/(m²-s) - h convective heat transfer coefficient, W/(m²-K) - h _fg latent heat of evaporation, J/kg - H latent heat due to melting or freezing, J/kg - k thermal conductivity, W/(m-K) - Kn Knudsen number, /D - L total length of the heat pipe, m - L _a length of the adiabatic section, m - L _c length of the condenser, m - M molecular weight, kg/kmol - Ma Mach number, - m _i mass flux at the liquid-vapor interface, kg/(m²-s) - P pressure, N/m² - q heat flux, W/m² - Q heat input at the active evaporator, W - Q _o heat output at the condenser, W - r radial coordinate, m - R gas constant, J/(kg-K) - R _o outer pipe wall radius, m - R _u universal gas constant, J/(kmol-K) - R _v vapor space radius, m - t time, s - T temperature, K - T _i,c interfacial temperature on the continuum vapor flow side, K - T _i,r interfacial temperature on the rarefied vapor flow side, K - T _rf reference (saturation) temperature, K - T _tr transition vapor temperature, K - v radial velocity, m/s Funding for this work was provided by a joint effort of the NASA Lewis Research Center and the Thermal Technology Center of Wright Laboratory under contract No. F33615-88-C-2820