Experimental and Numerical Investigation of Air Jet Impingement on Heated Cylinder

Abstract

newline The jet impingement cooling is a topic of wide spread interest and is used in many newlineengineering applications. In the present study, experimental and numerical investigation of this newlinephenomenon is carried out. The working fluid is taken as air and the target surface is considered newlineas cylinder for the present study. The experimental study predicts the heat transfer distribution newlinefrom the heated cylinder. The numerical study predicts the fluid flow distribution as well in newlineaddition to the heat transfer distribution. The numerical study is carried out by two different newlineapproaches RANS (Reynolds Averaged Navier Stokes) and LES (Large Eddy Simulation). For newlineRANS approach, various two equation turbulence models RNG k and#949;, realizable k and#949; and SST newlinek and#969; are used. The original and modified v2f four equation turbulence models are also used. newlineFor LES approach the WALE subgrid scale turbulence model is taken for numerical newlineinvestigation. Different configurations for jet impingement on cylinder are studied newlineexperimentally and numerically. newlineThe numerical study for the round jet impingement over a circular cylinder is carried newlineout by using original and modified v2f four equation turbulence model. The comparison of these newlinemodels are done with the other two equation turbulence models from the fluid flow and the newlineheat transfer point of view. To compare the performance of these turbulence models, the newlinenumerical results obtained from these turbulence models are compared with the experimental newlinedata available from the literature. The nozzle is placed orthogonally to the target surface (heated newlinecylindrical surface). The flow is assumed as the steady, incompressible, three dimensional and newlineturbulent. The spacing between the nozzle exit and the target surface ranges from 4 to 15 times newlinethe nozzle diameter. The Reynolds number based on the nozzle diameter (Red) ranges from newline23,000 to 38,800. For the fluid flow and heat transfer distribution, the modified v2f turbulence newlinemodel is found better as compared to the other turbulence models. The modified v2f turbulence newlinemodel has the least error for the numerical Nusselt number at the stagnation point and wall jet newlineregion. newlineTo study the heat transfer characteristics at the rear of the cylinder, a semi-circular newlineconfinement is used for slot jet impingement. The closed and open semi-circular confinement newlineis considered and the bottom opening angle (and#945;) ranges from 0o 120o. The Reynolds number newline(ReD) based on the cylinder diameter ranges from 30,000 90,000. The non-dimensional newlinedistance between the nozzle exit and the heated circular cylinder ranges from 4 10. The newlinenumerical results of the four turbulence models SST k and#969;, realizable k and#949;, RNG k and#949; and newlineV newlinemodified v2f are compared to the experimental results. Further, the numerical results of the newlineoriginal and the modified v2f model are compared to the experimental results. From the newlinecomparison of the numerical and the experimental results, the SST k-and#969; model is found better newlinefrom the other models. Hence, the further parametric investigation has been carried out by the newlineSST k and#969; model for h/S, ReD and and#945;. The mean Nusselt number (NumD) is found maximum at newlineh/S = 4, 6, 8 and 10 for and#945; = 70o, 60o, 100o and 90o. The ReD does not have much effect on the newlinesemi-circular confinement bottom opening angle (and#945;) for the maximum value of the mean newlineNusselt number (NumD). newlineThe slot jet impingement in the presence of flat plate is investigated experimentally and newlinenumerically. The heated cylinder is placed on flat plate. The flat plate has an effective newlinedimension as plate length (P) from heat transfer point of view. For the experimental study, the newlineparametric investigation for the heat transfer distribution (stagnation and local Nusselt number) newlineis investigated. The range of the parameters are ReD = 10,000 25,000, h/S = 4 12, S/D = newline0.072 0.108 and P/D = 0 2. The correlation for stagnation and mean Nusselt number is newlinedeveloped using regression analysis as a function of ReD, h/S, S/D and P/D. The maximum newlineerror associated with correlated value of Nustag and Num as compared to the experimental data newlineis ± 13 % and ± 25 %. The numerical study is carried out by LES. It is observed that ReD and newlineh/S does not alter the size of the attached flow region, recirculation zone and location of newlineseparation point for S/D = 0.09 and P/D = 1. The flow separation shifts towards lower angular newlinelocation of the cylinder with increase in value of P/D.