TRAC-PF1 assessment on direct-contact condensation in horizontal countercurrent stratified flow

The condensation in countercurrent stratified two-phase flow is one of the important phenomena for safety analyses of nuclear reactors. The physical benchmark problem on the direct-contact condensation under the horizontal countercurrent stratified flow was analysed using the TRAC-PF1 one-dimensional model. The experimental data provided in the problem was obtained by observing flow conditions in the rectangular test section which had inlets for superheated steam at one end and subcooled water at the other end. The heat transfer model of TRAC-PF1 depends on the liquid-side condition, and the condensation rate was overpredicted though the interfacial heat transfer area was underpredicted. The interfacial area therefore was fixed to be the same as the area of test section and the Kim's empirical correlation was implemented to the code. Power coefficients were modified so as to obtain the good agreement between experimental and calculated results. The capability of TRAC-PF1 in predicting the condensation rate under the horizontal countercurrent stratified flow was enhanced due to the modification. (author)