Effects of Inclination Angle on Pool Boiling Heat Transfer of Near Horizontal Tubes

Pool boiling heat transfer has been studied for the past decades to guarantee the inherent safety of industrial systems. Recently, a passive type heat exchanger has been adopted in nuclear power plants to meet safety functions in case of no power supply. Many researchers have investigated the inclined surface for the various combinations of geometries and liquids as listed in Table 1. Many researchers have investigated the effect of inclination angle on pool boiling heat transfer along with the effects of pressure and fluid properties for the past decades. The present study is aimed at the identification of the effect of the inclination angle on pool boiling heat transfer of nearly horizontal tubes. To identify the effect of the inclination angle on pool boiling heat transfer of a nearly horizontal tube three tubes having L/ D = 21.05, 28.42, and 5.91, respectively, were studied. As the value of L / D increases, the effect of the inclination angle is increasing. The increase of the inclination angle is increasing or decreasing the heat transfer depending on the L / D value. However, the ratio of hb / hb, is converging to 1 as the heat flux increases. The mechanisms of liquid agitation, bubble coalescence, and the length of bubble traveling along the tube surface were considered as the major factors for heat transfer.