Pool Boiling Heat Transfer of Tube Array Having Inclined Upper Tube and Horizontal Lower One

The convective effects due to the fluid flow and the rising bubbles are the major influencing factors. One of the key parameters is the inclination angle of the heated surfaces. Many researchers had in the past generations investigated the effects of the orientation of a heated surface for the various combinations of geometries and liquids. The increase in the heat flux of the lower tube and the decrease of the inclination angle increases the heat transfer of the upper tube. Since the lower tube was also inclined as the upper one, the tube array used in Kang's study maintains equal spacing through the inclination angles. If the lower tube maintains as horizontal and the upper one is inclined, the effect of the flow on pool boiling heat transfer will be different. An experimental study is performed to investigate the combined effects of an inclination angle of the upper tube and the heat flux of the lower one on pool boiling heat transfer of the upper one. Through the study, two smooth stainless steel tubes of 19mm diameter and 400mm length are tested in the water at atmospheric pressure. Through the heat fluxes, the increase of the inclination angle eventually decreases heat transfer coefficients because the affected region by the bubbly flow from the lower tube becomes reducing.