Modeling for Fluid Flow and Heat Transfer in Closed Loop Pulsating Heat Pipe

Numerical modeling of multi-turn closed-loop pulsating heat pipe (CLPHP) is presented in this paper for ethanol as a working fluid. Modeling is carried out for 1-mm and 2-mm ID PHP for different numbers of turns, different orientations, and at constant wall temperature boundary conditions. Momentum and heat transfer variations with time are investigated numerically solving the one-dimensional governing equations for vapor bubble and liquid plugs. Evaporation and condensation take place by heat transfer through liquid film present around the vapor bubble. The code takes into account the realistic phenomena such as vapor bubble generation, liquid plug merging, and superheating of vapor bubbles above its saturation temperature. During the merging of liquid plugs, a time-step adaptive scheme is implemented and this minimum time-step was found to be 10⁻⁷ s. Nature of flow is investigated by momentum variation plot. Model results are compared with the experimental results from literature for nine different cases. Maximum variation in heat transfer for all these cases is found to be below ±34%.