Effect of aspect ratio on the flow and heat transfer characteristics of mist/steam in rectangular ribbed channels |
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| Authors: | Tieyu Gao Junxiong Zeng Jun Li Jianying Gong |
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| Affiliation: | 1. School of Energy and Power Engineering, Institute of Turbomachinery, Xi’an Jiaotong University, Xi’an, China;2. Key Laboratory of Thermal-Fluid Science and Engineering, Ministry of Education, Xi’an Jiaotong University, Xi’an, China |
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| Abstract: | The effects of Reynolds number from 10,000 to 80,000, mist mass ratios from 1 to 6%, and droplet sizes from 5 to 20?µm on flow and heat transfer behaviors of mist/steam in rectangular channels with various aspect ratios of 1/4, 1/2, 1/1, 2/1, and the rib angle of 60° are numerically studied in this paper. Additionally, secondary flow distribution in the four ribbed channels and its effect on heat transfer are analyzed in detail. The 3D steady Reynolds-averaged Navier–Stokes equations with a SST k-ω turbulent model are solved by using ANSYS CFX. The CFD model has been verified by the experimental data for steam-only case with a good agreement. The results indicate that similar secondary flow pattern can be observed in the four ribbed channel except for the size of main secondary flow; the heat transfer augmentation of mist/steam raises as Reynolds number and mist mass ratio increase; a peak value of average Nu is obtained in the case of 15?µm mist among all the sizes of droplets. The friction coefficient decays with increase of Reynolds number and mist mass ratio but is insensitive to droplet sizes. The case of AR?=?1/2 obtains the best thermal performance in mist/steam cooling channels. |
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