Critical heat flux in a rod bundle cooled by forced flow of steam-water mixture under steady-state and transient conditions

Techniques and results were described of an investigation on critical heat exchange in rod assemblies with uniform and cosinusoidal heat transfers along the rod length under stationary and emergency decrease of coolant flow rate at the assembly inlet. The study was performed for operating conditions of WWER reactors. Experiments were carried out with four assemblies, heated lengths 1000, 1800 and 2500 mm. Three assemblies had longitudinally uniform heat transfer, and one stepwise heat emission, maximum in the middle (imitation of cosinusoidal heat emission). Tests on assemblies with longitudinally uniform heat emission were run under 105-190 atm, mass velocities 530-3230 kg/m2sec, relative inlet enthalpies from -0.9 to -0.02 and relative outlet enthalpies from -0.18 to 0.68. Tests on assemblies with cosinusoidal heat emission were run under 105 and 170 atm, mass velocities 510-2000 kg/m2sec, relative inlet enthalpies from -0.39 to -0.06, and relative outlet enthalpies from 0.15 to 0.74. The final data were compared with those of other authors