Abstrait

CFD Investigation of Influence of Spanwise Pitch on Local Heat Transfer Distribution for In-Line Array of Impinging Jets for Medium Crossflow

Vivekananthan Karthikeyan, Ssheshan Pugazhendhi, Sai Krishnan Subramanium, Antony Aroul Raj V

Jet impingement systems provide an effective means for the enhancement of convective processes due to the high heat and mass transfer rates that can be achieved. The range of industrial applications that impinging jets are being used in is wide. In the annealing and tempering of materials, impinging jet systems are finding use in the cooling of hot metal, plastic, or glass sheets as well as in the drying of paper and fabric. Compact heat exchangers, with applications in the aeronautical or the automotive sector, often use multiple impinging jets in dense arrangements. In gas turbine applications, jet impingement has been routinely used for a long time. Because of increased thermal efficiency at high turbine inlet temperatures, many gas turbine components, such as rotor disks, turbine vanes and blades, or combustion chamber walls, are operated at temperatures well above highest allowable material limits. In order to assure durability and long operating intervals, effective cooling concepts are required for these highly loaded components.The current work involves studying of effect of spanwise jet-to-jet spacing on local heat transfer distribution due to an in-line rectangular array of confined multiple circular air jets impinging on a surface parallel to the jet plate computationally. Shear Stress Transport (SST) k-ω turbulence model is used. The flow, after impingement, is constrained to exit in two opposite directions from the confined passage formed between jet plate and target plate. Mean jet Reynolds numbers based on the nozzle exit diameter (d) covered is 10,000 and jet-to-plate spacings studied are d, 2d and 3d. Spanwise pitches considered are 2d, 4d and 6d in steps of 2d keeping the streamwise pitch at 5d. Length-to-diameter ratio of nozzles of the jet plate is 1.0. For all the configurations, the jet-plates have ten spanwise rows in streamwise direction and six jets in each spanwise row. The results obtained are validated against the experimental data available in the open literature.