Experiments on Convection Heat Transfer Along a Vertical Flat Plate Between Pools with Different Temperatures

To evaluate the heat removal capability of an external water wall-type containment vessel, which is a passive system for containment cooling, thermal-hydraulic behavior in the suppression and outer pools has been examined experimentally. The following results are obtained: 1. A thermal stratification boundary, which separates the pools into an upper high-temperature region and a lower low-temperature region, is observed just below the vent outlet. 2. The natural-convection heat transfer coefficients (HTCs) for the downward and upward flows that appear inside and outside the primary containment vessel wall are measured. These values can be expressed by Nu = 0.13Ra^1/3. 3. The condensation HTCs in the presence of non-condensable gas, which affect heat transfer between the wet well and the outer pool, are measured along the long wall. The vertical variations of the condensation HTCs are within 10% of the averaged coefficients, and the averaged coefficients can be expressed by h_m = 0.43(m_a/m_s)^-0.8, where h_m (kW/m²·K is the condensation HTC and (m_a/m_s) is the mass ratio of noncon-densable gas and steam. 4. The capability for decay heat removal in the external water wall-type containment vessel for a 600-MW(electric) plant is evaluated based on these results and is found to be large enough.