Annular flow experiments in rod bundles with spacers Original Research Article

Measurements of pressure drop, film flow rate and film thickness have been made on a special test section modelling the four subchannels between ten fuel rods in a LWR geometry. Tests were carried out with air/water at 2.5–3-bar (a). Measurements were made with and without spacer grids inserted in the channel. In the former case, the measurements were made upstream and downstream of the spacers. In the case without spacers, the results show similar trends to data from tubular geometries with a similar hydraulic diameter. The two spacers tested both showed similar pressure losses. There was an increase in film flow rate and film thickness downstream of the ULTRAFLOW spacer. For a conventional egg-crate spacer there was a small change, with in some cases a decrease in film flow rate.