[en] For example, in steam generators in a nuclear power plant, when porous corrosion product adheres to the heat transfer surface, boiling occurs within this porous layer. The boiling phenomena have been studied by introducing fine particles and water between two parallel plates, and heating on both sides. In the porous bed thus formed, several different layers were created: a capillary layer, a cracked layer with horizontal cracks, and a chimney layer with vertical channels. Underneath these layers, the bed becomes dry. An analysis is presented to calculate the heights of these layers. The height of the capillary layer decreases in inverse proportion to the square roof of the heat flux on sides. The height of the cracked layer is small as compared with other layers. The height of the chimney layer has a maximal value in relation to the size of bed-forming particles. (Mori, K.)