Investigation on the critical heat flux in typical 5 by 5 rod bundle at conditions prototypical of PWR based on CFD methodology

The Critical Heat Flux (CHF) is crucial for the safety of power equipment working with boiling heat transfer, such as the heat exchanger and fuel assembly. The wall heat partition model with consideration for the heat transferred to the vapor can be used along with the Eulerian two-fluid model to predict the CHF. In our previous work, the model was validated to be applicable to predict the CHF in a 2 by 2 rod bundle without strong secondary flow. While strong secondary flow occurred in the reactor core due to the existence of MV (Mixing Vane) spacers. In this paper, the model was validated by the CHF experiment in a typical 5 by 5 rod bundle with 3 different types spacers under Pressurized Water Reactor (PWR) condition. The effects of secondary flow induced by MV spacers on CHF were analyzed. The CFD calculation showed good agreement against the experimental measurements with the deviation of heating power 5.06%, and the deviation of axial location 4 mm. As for the CHF location in the cross section, the result obtained by CFD calculation was on the outer rod which was consistent with the experiment, while the results by system code and subchannel codes showed CHF occurred at the inner rod.