Experimental and Large Eddy Simulation Study of Slot Jet Impingement Cooling from Heated Cylinder placed on Flat Plate

Abstract

The present study focuses on experimental investigation and numerical study using Large Eddy Simulation (LES) for an air impinging jet flow. The investigation is carried out for slot jet impingement on heated cylinder with provision of adiabatic flat plate beneath the heated cylinder. The parametric investigation is conducted for parameters such as Reynolds number (Re), jet to cylinder spacing (h/S), surface curvature (S/D) and plate length (P/D). They are varied as Re = 10,000 – 25,000; h/S = 4 – 12, S/D = 0.072 – 0.108 and P/D = 0.5 – 2. The Nusselt number distribution over cylinder is experimentally obtained and to understand the impact of parameters such as Re, h/S, S/D and P/D on it; the numerical results are extracted from LES. The Nusselt number improves with increasing Re and decreasing h/S, although their impacts are not same. The major influence of Re and h/S is noticeable from θ = 0o – 180o and θ = 0o – 90o; however impact of h/S is very negligible from θ = 90o – 180o. The Nusselt number increases with increasing S/D due to more air entrainment which produces higher Reynolds stress and turbulence kinetic energy. The increasing plate length (P/D) shifts flow separation at lower angular position (θ) thereby increasing recirculation zone and reducing attached flow region. The recirculation zone contributes to heat transfer improvement in that region. Hence longer plate length P/D = 2 is ideal selection of plate length compared to P/D = 0.5 and 1 as it better facilitates positioning of cylindrical food product with optimum heat transfer.