This article presents the results of an experimental study of the void fraction at high pressure (80 to 140 kg/cm2) in two rectangular channels (5 × 0.2 and 5 × 0.28 cm) simulating a subchannel of a nuclear reactor plate-type fuel element. The method enabled the distribution of the local void fraction in a cross section to be measured at about 100 locations; from these local values it was possible to determine accurate mean values and to precisely quantitate the influence of the parameters: pressure, mass velocity, and heat flux. This distributions of void fractions, among the first to be determined in this range of pressures, were obtained from 120 000 systematic, individual measurements, sufficient to allow accurate interpolations in the experimental region under consideration which included subcooled conditions. These results enabled testing certain models presented in the literature. Analyses with the Bowring model, for example, are in good agreement with present experimental data at 80 kg/cm2. The purpose of this study was not to establish a new model but to furnish accurate data for verification or, if necessary, adjustment of existing models.
