Effects of soot deposition and slot erosion on the mist film-cooling of a flat plate in the presence of upstream ramp

In the present work, the numerical analysis is conducted on the film cooling of a flat plate with the air and mist injection from a slot. The effect of soot deposition and erosion of the cooling slot has been investigated in the presence of an upstream ramp. Simulations are performed at blowing ratios, M = 1, 1.5 and 2 with the slot angles, θ = 30°, 45° and 60°. The effect of presence of upstream ramp is studied by varying ramp angles from α = 5° to 15°. The numerical study is carried out on Eulerian-Eulerian framework. Thermal phase change model based on the evaporation and condensation is used to account heat and mass transfer. It is found that the film cooling effectiveness is better for the mist injection as compared to the air injection. Soot deposition on the cooling slot has a significant influence on the film cooling effectiveness. The soot deposition is not always adversely affecting the film cooling effectiveness. Moreover, the film cooling effectiveness decreases for the eroded slot for all the investigated slot angles and ramp angles for mist injection. An increment in the film cooling effectiveness is observed for 0 < x/2w < 15 in the presence of the upstream ramp; thereafter film cooling decreases as compared to the case without the upstream ramp. The optimum slot angle to inject the mist is found to be θ = 45°

Experimental and numerical study of air-water mist jet impingement cooling on a cylinder

The paper presents the study of experimental as well as the numerical study of air-water mist jet impingement cooling over a heated cylinder in the non-boiling region. The studies are conducted for various mist loading fraction, f = 0.0025, 0.0050, 0.0075 and 0.01; Reynolds number, Remix.=8000, 10,500, 13,000 and 15,500; and surface-to-nozzle spacing, H/d = 30, 40, 50 and 60. Enhancement in the heat transfer (η) for mist jet impingement as compared to air jet impingement is obtained from experimental and numerical analysis. The numerical study also helped in understanding the distribution and tracking of droplets in the computational domain. High enhancement in the heat transfer is observed with high mist loading fraction. Also, the lowest Reynolds number yielded the highest enhancement in heat transfer with comparison to the higher Reynolds number. At various surface-to-nozzle spacing, the enhancement in heat transfer is high for low surface-to-nozzle spacing near the stagnation zone to a certain point, after which point the enhancement reverses as higher enhancement in heat transfer is observed for high surface-to-nozzle spacing. As high as 408% and 775% enhancement in the heat transfer at the stagnation point is observed for f = 0.01, Remix.= 8000and H/d = 30 during experimental and numerical analysis respectively. The correlation has been proposed to estimate the enhancement in heat transfer at the stagnation point