An experimental study of natural convection in a volumetrically heated spherical pool bounded on top with a rigid wall

Abstract

Flooding of the reactor cavity is being considered as a cooling strategy to prevent vessel thermal failure in the case of severe core damage accidents in which relocation of core material into lower vessel head occurs. A recent study carried out at UCLA showed that the flooding of cavity could indeed be a viable option. However, one important factor contributing to uncertainty in that study was the internal natural convection heat transfer coefficient. In the present work, experiments were conducted to examine natural convection heat transfer in internally heated hemispherical pools with external cooling. In the experiments, Freon-113 contained in a Pyrex bell jar, was used as a test liquid and the vessel was cooled from the outside with water. The pool was bounded with a rigid wall at the top, and was heated with a 750 W magnetron taken from a conventional microwave oven. The vessel inner wall temperature was not held constant and varied from the stagnation point to the equator. A series of chromel alumel thermocouples was used to measure the pool and wall temperatures at different locations.Experiments were performed for pools with nearly insulated and cold rigid walls at the top. The depth of the pool was varied parametrically. Both local and average heat transfer coefficients based on maximum pool temperature were obtained. The results have been compared with the correlations obtained for pools with free surface.