Numerical modeling of flow structure and heat transfer in a mist turbulent flow downstream of a pipe sudden expansion

Abstract

Turbulent droplet-laden flow downstream of a sudden pipe expansion is numerically studied using Eulerian two-fluid model. The model is used to investigate the effect of droplet evaporation on the particle dispersion and on the gas phase turbulence modification. Turbulence suppression in the case of evaporating droplets is hardly observed near the wall, and the level of turbulence tends to the corresponding value for the single-phase flow regime. In the flow core, where evaporation is insignificant, a decrease in the level of gas turbulence (to 20% as compared to a single-phase flow) can be observed. The maximal effect of droplet evaporation is obtained in the wall region of the tube. A considerable increase in the maximal value of heat transfer on adding the evaporating droplets to the separated flow is shown (more than 2-folds as compared to the single-phase flow at a small value of droplet mass concentration of ML1 ≤ 0.05). The addition of the solid non-evaporating particles causes a slight increase in the maximum value of heat transfer in the case of small particles and a decrease in heat transfer in the case of large particles.