Numerical study of free surface jet impingement on orthogonal surface

Abstract

Numerical study is carried out to investigate hydrodynamic structures and heat transfer characteristics of vertical free surface liquid jet impingement on a horizontal flat plate. Different turbulent models (k−ϵ,k−ω,v2f) are compared to predict velocity field of the free surface jet, and the most suitable turbulence model is identified for prediction of flow physics of free surface jet impingement. A parametric study is performed to investigate the effect of Reynolds number (20000−60000), nozzle to plate spacing, H/d (0.5−2), and nozzle exit diameter (10.9, 15, and 23 mm) on the hydrodynamics, turbulence and heat transfer. The paper focuses on the underlying physics for jet impingement in the case of the lower jet to plate spacing, H/d (0.5−2). It was found that v2f turbulence model predicts flow field reasonably well compared to other turbulent models (k−ϵ and k−ω). Liquid jet radius before the impact and liquid film thickness after the impact have been examined. Velocity field, pressure and shear stress distribution on the flat plate are presented for free surface jet impingement. Further, turbulence intensity variation is examined and its effect on heat transfer is discussed. Jet to plate spacing, H/d=0.5 resulted in around 20% higher Nusselt number compared to H/d ≥ 1 cases; and it is identified that a higher momentum before impact, compared to H/d ≥ 1, is the driving factor. Transition to turbulence is observed for higher Reynolds number and is explained by analyzing the variation in turbulence intensity along the flow streams of the free surface jet.