有限長の垂直円柱まわりの過渡膜沸騰熱伝達に関する研究 (第3報) : 新伝熱整理式

概要

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The film boiling heat transfer from a vertically placed cylinder of finite-length was analyzed to predict the overall heat transfer rate around the cylinder in terms of boiling curve. The overall heat transfer rate around the cylinder was determined by taking into account every convective heat transfer on the bottom, side and top surfaces of the cylinder. The local heat transfer rate on the bottom surface was analyzed by the method similar to that developed by the authors for a downward-facing horizontal circular plate. For the vertical lateral surface of the cylinder, Bromley's model and the vapor-film-unit model presented by Nishio and Ohtake were introduced. Bromley's model is effective for the smooth interface, while the vapor-film-unit model is effective for the wavy interface. Bromley's model was modified to accommodate the continuity of the vapor flow rate at the lower end of the side wall, where the vapor film had a finite thickness due to the vapor inflow out of the bottom surface. Berenson's model was adopted on the top surface. The effects of length and diameter of the cylinder on the overall heat transfer rate were discussed in terms of boiling curve. The new prediction method was compared with the experimental data obtained by the authors.