Experimental study and Large Eddy Simulation of slot jet impingement cooling from heated cylinder placed on flat plate

The present study focuses on the experimental investigation and numerical study using Large Eddy Simulation (LES) for an air-impinging jet. The investigation is carried out for slot jet impingement on the heated cylinder with an 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 a 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 however their impacts are different. The major influence of Re and h/S is noticeable from theta = 0 degrees-180 degrees and theta = 0 degrees-90 degrees; however, the impact of h/S is negligible from theta = 90 degrees-180 degrees. The Nusselt number gets enhanced 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 a lower angular position (theta), thereby increasing the recirculation zone and reducing the attached flow region. The recirculation zone contributes to heat transfer improvement in that region. Hence, a longer plate length P/D = 2 is an ideal selection compared to P/D = 0.5 and 1 as it better facilitates the positioning of cylindrical food products with optimum heat transfer. Further, correlations are proposed for stagnation and average Nusselt numbers in terms of Re, h/S, S/D and P/D.