3×3ロッドバンドルにおけるフラッディング状態での流動特性

抄録

Experiments on countercurrent flows of air and water in a 3×3 rod bundle were carried out, and countercurrent flow limitation (CCFL), pressure gradients dP/dz and void fractions α were measured under flooding conditions. Flooding with smooth and thin liquid film occurred at the top when the gas volume flux J_G was small, whereas flooding with rough and thick liquid film took place at the bottom for medium and large J_G. This behavior was similar to flooding in a vertical pipe. CCFL characteristics were expressed by Kutateladze parameters and agreed with those for the upper tie plates in BWR fuel bundles. The volume flux J_L of falling water in the bundle was larger than J_L in a vertical pipe, but it was smaller than J_L through horizontal perforated plates without rods. α under flooding conditions were lower than α under stagnant water (J_L = 0) conditions in the region of J_G > 4 m/s. The wall friction and interfacial friction factors were obtained from the data and discussed.