Heat Transfer of Slug Air-Water Flow in a Slightly Upward Inclined Tube

Abstract

Abstract This paper presents a preliminary study on the heat transfer in slug air-water flow in a slightly upward inclined tube, which is a widely appeared pattern in the inclined two-phase flow regime. Local heat transfer coefficients and flow parameters have been measured for slug air-water flow in a pipe [1.097 in (2.79 cm) I.D. and L/D = 100] at slightly upward inclination angles of 2° and 5°. The heat transfer data with slug air-water flow pattern were measured under a uniform wall heat flux boundary condition. The change on the heat transfer with inclination angle compared to the horizontal case is discussed in terms of the change in the overall heat transfer coefficient with respect to the superficial gas and liquid Reynolds numbers. For these data, the superficial Reynolds number ranged from about 3700 to 28000 for the water and from about 540 to 6500 for the air. The results indicate that there is an increase in the heat transfer with only slight increases in the inclination angle. However, the amount of increase is strongly dependent on the magnitudes of superficial liquid and gas Reynolds numbers.