The Effect of Secondary Slow on Droplets Behavior in Gas-Liquid Mixing Process Downstream of a Curved Duct

Abstract

Experimental and numerical investigations are carried out on water injection in a humidification process of air traveling steadily through the curved part with a constant cross-section. A principal aim is to study the flow behavior through the curved duct and the generation of secondary flow. The effect of bend angle on the development of secondary flow and flow structure intensities and enhancement of the heat and mass transfer downstream the curved duct. Moreover, the influence of the mixing process between liquid and gas in an air humidification process was examined. Experiments were performed with an average air velocity range from (2.5 to 5 m/s) while keeping the water injection rate of (19 kg/h) through (50) cm square wind tunnel includes three bend angles of (45º, 90ºand 135º) along with three sets of nozzle tilt angles of (-45º, 0º and 45º) to the axial flow direction. The study also implies a numerical analysis using ANSYS FLUENT 2019 R3 with the turbulent model of RNG using (k-ε). Experimental results showed that the optimum operating condition (greater extent of cooling and humiliation) was obtained with a bend angle of 135º at axial water injection, i.e., 0º nozzle tilt angle at the lowest air velocity of 2.5 m/s. This could be attributed to the strong identical vortices developed and better droplet distribution across the duct, and more time available for heat exchange between water droplets and the air stream. The maximum reduction in treated air temperature was 28 %, with 219% in the relative humidity of the air stream. This condition gave corresponding cooling effectiveness of 58%.