VALIDATION OF DIRECT CONTACT CONDENSATION CFD MODELS AGAINST CONDENSATION POOL EXPERIMENT

An experiment related to steam discharge into sub-cooled water was carried out with a scaled down condensation pool test facility at Lappeenranta University of Technology. The vertical blowdown pipe was submerged by 1.81 m and thermally insulated. Condensation took place only at the steam-water interface near the pipe outlet. Since very low steam flow rates (1.0...1.5 g/s) were used, the steamwater interface remained steady close to the pipe outlet. Several quasi-steady intervals suitable for the validation of direct contact condensation models can be found from the experiment data. Simulations with the Hughes-Duffey based DCC model of the NEPTUNE CFD code indicated two orders of magnitude higher condensation rates than the experiment. This overestimation was reduced by one order of magnitude by decreasing the numerical truncation parameter and by disabling the residual droplet handling. By implementing the DNS-based model of Lakehal et al. (2008) the heat transfer coefficient reached the same order of magnitude as indicated by experiments. More stable transfer rate values were also attained. However, uncertainties prevail in the experimental and simulation results as the presence of non-condensables, which has a significant suppressing effect on condensation, has not been taken into account. The work was accomplished in the framework of the EU/NURESIM project.