The effect of confinement on the flow and turbulent heat transfer in a mist impinging jet

摘要

Numerical study of the effect of confinement on a flow structure and heat transfer in an impinging mist jets with low mass fraction of droplets (ML1 ≤1%) were presented. The turbulent mist jet is issued from a pipe and strikes into the center of the flat heated plate. Mathematical model is based on the steady-state RANS equations for the two-phase flow in Euler/Euler approach. Predictions were performed for the distances between the nozzle and the target plate x/(2R) = 0.5-10 and the initial droplets size (d1 =5-100 urn) at the varied Reynolds number based on the nozzle diameter, Re = (1.3-8) x 104. Addition of droplets causes significant increase of heat transfer intensity in the vicinity of the jet stagnation point compared with the one-phase air impinging jet. The presence of the confinement upper surface decreases the wall friction and heat transfer rate, but the change of friction and heat transfer coefficients in the stagnation point is insignificant. The effect of confinement on the heat transfer is observed only in very small nozzle-to-plate distances (H/(2R) < 0.5) both in single-phase and mist impinging jets.