Comparison between numerical simulation and on-orbit experiment of oscillating heat pipes

•We developed a numerical model for reproducing the phenomena inside OHP.•The model was validated using on-orbit experimental data from JAXA.•The OHP can start when liquid slugs exist in the heating section.•Initial vapor-liquid distributions do not affect steady state performance.•The OHP has startup difficulty when liquid slugs localize in the cooling section. This study investigated the startup behavior of Oscillating Heat Pipes (OHPs) by comparing numerical simulation and on-orbit experimental data. Previous studies suggested that initial vapor-liquid distribution affects startup behavior. However, they provided no experimental evidence to validate this hypothesis because experimentally reproducing and specifying initial vapor-liquid distribution in OHPs is virtually impossible. Thus, a numerical approach is necessary to generate the initial vapor-liquid distribution and to understand the internal thermofluid behavior of OHPs. In this study, a one-dimensional numerical model of an OHP with check valves was first developed. Then, the model was compared with data from an on-orbit experiment. Finally, simulation of OHP startup behavior with several types of initial vapor-liquid distributions showed that OHP startup difficulty is due to localization of liquids in the cooling section.