Forced convective subcooled boiling: comparison between one-dimension al models and a new data bank for freon 12 boiling simulating pwr conditions

摘要

For many years, the design of Pressure Water Reactors (PWRs) has induced a large amount of thermal-hydraulic studies. To get a better understanding of boiling crisis, it is necessary to perform a comprehensive approach of the whole range of local phenomena involved in boiling. In addition, any investigation has to account for the specificity of PWR thermal-hydraulic conditions, i.e. water at pressures up to 15 MPa, heat fluxes of about 1 MW/m~2 and mass velocities from 1 to 5.10~3 kg/s/m~2. CEA has developed local measuring technique for Freon 12 as a simulating fluid, built a specific test section and completed a data base. The technology of optical probe sensors was improved in order to obtain detailed measurements with sensor tips of 10 mum in diameter. The tests were performed on the DEBORA loop at CEA/Grenoble with Freon 12 as a cooling fluid. Measurements of bubble diameters, bubble center densities, phase velocities, phase temperatures, void fractions, interfacial areas have been conducted in subcooled boiling. It is hoped that this data base will permit models to be developed for describing boiling phenomena in PWR conditions.