Hydrodynamics and thermal performance of turbulent falling films through horizontal tube bundles

Abstract

Turbulent falling films are commonly encountered in the practical operations of most falling film applications, but the relevant numerical study is very scarce. The hydrodynamics and thermal performance of falling films in horizontal tube bundles under the turbulent regime were numerically investigated in this study. The calculation ranges are: film Reynolds number from 3505 to 8034, heat flux of 47.3 kWm−2, inlet liquid temperature of 46 °C, tube diameter of 19.0 mm and liquid distributor height of 6.4 mm. Based on the results of the present numerical model, the Standard k-ω model is more suitable in reproducing the falling film heat transfer profile, as the present numerical model accurately predicted the turbulent falling film heat transfer characteristics. There are various hydrodynamics depending on the bundle arrangement and flow regime, including splashing, bridging, gas entrainment, Coanda effect, and liquid film thickness. The triangular bundle provides the highest heat transfer coefficient, but the square bundle provides the poorest one, and the square and rotated-triangular tube bundles behave the largest and smallest bundle effect, respectively. The bundle effect is generally independent of film Reynolds number, liquid feeder height and tube spacing.