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Ali Akbar Abbasian Arani,Ali Akbar Azemati,Mohammad Rezaee,Behzad Shirkavand Hadavand 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.5
Natural convection in enclosures containing nanofluids is important in physical and environmental applications. Different models for conduction have been developed because of the importance of this phenomenon in natural convection in enclosures. In this study, effects of conduction models of Chon, Corcione, Khanafer, and Koo and Kleinstreuer on the natural convection inside a trapezoidal enclosure with hot and cold walls are evaluated numerically. The enclosure contains Al 2 O 3 -water nanofluid with variable properties. Effects of the conduction models on fluid flow, natural convection, variations in volume fraction, and diameter of nanoparticles in the models, as well as the variations in the Rayleigh number, are examined. Results show that at Rayleigh numbers of 10 5 and 10 6 , the maximum and minimum values of the average Nusselt number are obtained using the models of Khanafer and Chon, respectively. In all models, the average Nusselt number presents upward and downward trends when the volume fraction of nanoparticles increases but decreases when the diameter of the nanoparticles increases. At Ra = 10 5 in all models, as the volume fraction of nanoparticles increases, the nanofluid provides a higher average Nusselt number compared with the base fluid. By contrast, at Ra = 10 6 , at volume fractions larger than 0.01 and using the model of Chon, the average Nusselt number of the nanofluid is lower compared with that of the base fluid.
Ali Akbar Abbasian Arani,Mehrdad Kazemi 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.10
Fluid flow, heat transfer and entropy generation inside triangular enclosure equipped with rotational obstacle filled with nanofluid were analyzed numerically by finite difference method and SIMPELR algorithm. Five cases for apex angle, swirling circle radios and spine velocity, swirling circle radios and positions and five cases for wavy wall domain and amplitude were simulated. Although α = 20 has higher average Nusslet number, α = 30 has chosen as optimum apex angle due to meet to geometry problem in next step of optimization process. Optimum wavy wall according to average Nusselt number is constructed with A = 0.05 and D = 1.45π. Radius equal to 0.1 and position equal to 3 has been obtained as optimum geometry between multiple choices. Maximum Nusselt number and entropy generation deal with blades shapes and followed by bricks, platelets and cylinder shapes for nanoparticle volume fraction of between 0.5 and 5 and Rayleigh numbers from 10 3 and 10 6 .