Solar energy is one of the most efficient forms of renewable energy. Solar air collectors are promising utilization of solar energy. The present study used unsteady three-dimensional Computational Fluid Dynamic (CFD) analysis to investigate the heat transfer and fluid friction in solar air collectors with smooth and v-corrugation absorber plates. The studied parameters are Reynolds number, v-corrugation height, and pitch. Three Reynolds number (500, 1000, 1500) values were used with three arrangements configuration of the v-corrugation of relative heights of 0.10, 0.16, and 0.23. Roughness pitches varied between 1.33, 1.66, and 2. By comparing the simulated thermal efficiency with the currently known experimental values, great agreement can be approved. Results show the superiority of the performance of v-corrugated collector against the traditional or smooth type. The outlet temperature obtained in case of relative roughness height = 0.23 and relative roughness pitch = 2 is 61 °C, while it is 53 °C for a smooth type. Also, a higher thermal efficiency of 46.7 % can be obtained compared to 33.01% for smooth type.
Couple stresses because of magnetic particles additives on the lubrication performance of a journal bearing system was embraced and scrutinized in the current examinations theoretically. The governing equations of Reynolds (pressure field), energy (temperature field), and heat conduction (temperature field through the solids) are coupled and solved instantaneously in term of temperature and viscosity. After these set of equation pressure is obtained, it is used to obtain the bearing characteristic. It was found that the load currying capacity and maximum pressure are increased due the employing of magnetic fluids along with the couple stresses, as well as side leakage flow and the friction coefficient are decreased. It can be also concluded that the magnetic fluids with couple stresses are better lubricant than magnetic fluid only (l _ = 0), Newtonian fluids, and couple stress fluid ( = 0).
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