Effects of geometric arrangement on pool boiling heat exchange in the tubular bundle

Abstract

Examination of bubble nucleation and detachment mechanisms in tubular pool boiling is important for designing passive heat exchangers in nuclear power plants. This study investigated the heat transfer characteristics of pool boiling in deionized water using an experimental method combined with a simulation approach. Based on the change in the experimental conditions, a prediction model of the heat transfer coefficient was constructed, and the model was verified using experimental data with a maximum error of 13%. The effects of different inclination angles and lower tubes (two rods: the upper and lower tubes) on the boiling heat transfer, wall temperature uniformity, and bubble departure diameter of the tubular bundle pool were studied. The results showed that an increase in the heat flux of the lower tube and a decrease in the inclination angle increased the heat transfer coefficient of the upper tube. The main reason for the enhanced heat transfer in the upper tube was the convective flow and liquid stirring caused by the rising bubbles in the lower tube. The boiling process changed from natural convection to forced convection, which strengthened the heat transfer in the upper tube. Finally, the simulation was verified using the volume of fluid (VOF) and Lee phase change model, and the results agreed with the experimental results (within 10% of the maximum error).