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

Experimental and numerical study on the heat transfer of a flat plate impinged by air-water mist jet

The present work focuses on the experimental and numerical investigation of air-water mist jet impingement heat transfer from a heated flat plate. The heated flat plate is constructed from a 25μm Stainless steel-304 foil, and the temperature distribution on the plate is recorded with the help of Infrared Thermography. The detailed experimental parametric study is performed for a varied range of parameters such as plate heat flux (4000−16500 W/m2), mist loading fraction (0−1.5%), Reynolds number of air-jet (4500−8800) and plate-to-nozzle distance (20−40). The temperature distribution over the heated flat plate is used to evaluate the effect of the above parameters on the local and average heat transfer coefficient and Nusselt number. A two-phase, stochastically dispersed mist droplets in air-jet is modeled based on Eulerian-Langragian approach for the numerical study. Heat transfer from the droplets and the liquid film formation over the heated surface and its evaporation is modelled in the numerical study. The present numerical results are found to be in good agreement with the experimental results. An increase in the heat transfer rate with an increase in the mist loading fraction and Reynolds number is reported. Also, the heat transfer rate decreases with an increase in the plate-to-nozzle distance. A maximum increment of 132% in the average Nusselt number is reported during both the experimental and numerical analysis, whereas 275% and 281% increment for the local Nusselt number at the stagnation point is reported during the experimental and numerical analysis as compared to the air jet impingement, respectively. Further, correlations are proposed for local and average increment in the Nusselt number in terms of Reynolds number, plate-to-nozzle distance, and mist loading fraction