The OpenFOAM-based GeN-Foam solver has recently been extended to allow simulating water boiling based on a porous-medium approach. This paper describes such extension and preliminarily validates it based on the OECD/NRC PSBT benchmark. Three benchmark exercises are included: steady-state single sub-channel exercise; steady-state rod bundle exercise; and transient rod bundle exercise. Model sensitivity analysis is conducted, with a simple empirical turbulent model that is developed and calibrated to account for the mixing effect caused by the interaction of the two phases. The calculated results are compared with the experimental data, and most of the predictions fall within the & PLUSMN; 2 & sigma;exp error bar. The results indicate that the solver can simulate water boiling heat transfer process and predict void fraction distribution accurately, at least for the cases of the PSBT benchmark.