Abstract
The flow instabilities were investigated for the heated pipe flow in a natural circulation experimentally and numerically. In the experiments, three types of flow instabilities were observed. The first one was a nonperiodic bubbly flow fluctuation at a low inlet temperature. The second was a periodic slag flow oscillation. The last was a sudden boiling at a high inlet temperature and a low inlet flow speed. The one dimensional numerical simulation was also performed under the assumptions of the homogeneous two-phase flow and the thermodynamic equilibrium. The oscillating solutions and the diverging solutions were obtained and it is considered that they correspond to the slag flow oscillation and the sudden boiling in the experiment, respectively. The numerical results agree well with the experimental ones qualitatively and quantitatively except the period of the slag flow oscillation.
