Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

We conducted boiling flow experiments and measured the void fraction in a 3 x 3 rod bundle with a spacer grid using high resolution X-ray computed tomography. We focused on the effects of mass and heat flux on the void fraction downstream of the spacer. We found that the void fraction increases as the
flow passes through the vanes and then decreases downstream until 𝑍 ≈ 4𝐷ℎ , and then increases again. In addition, we found that the mixing vanes cause a local increase in void fraction even at low heat flux or high mass flux, and that the arrangement of the vanes influences the size and location of the high and low void content regions. We also found that the effect of heat flux on the relative void fraction is more noticeable at high mass flux than at low mass flux. Furthermore, the experimental database obtained in this study can be used to validate CFD simulations.