Two Dimensional simulation of nucleation pool boiling and investigation of phase change mechanism at low heat fluxes

At the present study, nucleation pool boiling of the saturated refrigerant R-245fa on the horizontal tube at pressure of 123.8 kPa and temperature of 20°C under different heat fluxes (18-27 kW/m2) has been simulated numerically and the details of the flow are investigated. Numerical simulation is carried out based on the volume of fluid model with piecewise linear interface construction method, without pre-determined bubbles by Lee phase change model and surface tension model of continuum surface force. The importance of this study and the numerical model, in addition to its industrial applications at nuclear reactors and flooded evaporators, is the model validation at predicting boiling portion of forced falling or climbing flows on horizontal tubes or bundle of tubes. The heat transfer coefficient of the present model, in comparison with the experimental data at two heat fluxes of 18 and 24 kW/m2 and the results of pool boiling Cooper correlation at heat fluxes of 18-27 kW/m2 has the maximum error of 6.67% and 8.64%, respectively. In addition, at this study, bubble nucleation and its departure from the tube wall and superheated liquid beside the wall, liquid and bubble temperature and modality of fluid movement due to the generated bubbles around the tube have been studied.