Experimental Investigation of the Effect of Surface Inclination Angle on Saturated Pool Film Boiling Heat Transfer in Transient Regime

In order to examine the effect of surface inclination angle on saturated pool film boiling heat transfer in transient regime, an experimental study was carried out. The experiments were performed through a cylindrical rod, made up of brass 20 mm in diameter and 75 mm in length, placed at six inclination angles about the vertical (from 0 to 50 degrees) under atmospheric pressure. The test specimen heated at high temperatures was immersed in a distilled water pool at saturated condition. Temperature of the specimen during the cooling process was recorded using a K-type thermocouple embedded at the center of the specimen. In the experiments, the pool film boiling was observed for each inclination angle. In the film boiling region, the heat transfer coefficients were calculated by means of a lumped parameter method. The experimental results showed that the heat transfer coefficient increased as the inclination angle increased. In addition, to predict the Nusselt number, an empirical formula including the inclination angle as well as the Grashof, Prandtl, and Jakob numbers was developed, and good agreement between the predicted and experimental data for the vapor Nusselt numbers was observed.