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دانلود رایکان مقاله انگلیسی ISI با موضوع هبود انتقال حرارت همرفت طبیعی در حلقه متحد المرکز افقی

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بهبود انتقال حرارت همرفت طبیعی در حلقه متحد المرکز افقی با استفاده از نانوسیالات

عنوان انگلیسی مقاله:

Natural convection heat transfer enhancement in horizontal concentric annuli using nanofluids

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2. Problem description and governing equations

Due to geometrical symmetry, Fig. 1, only one half of the annulus is simulated. The annulus between the two cylinders is filled with water based nanofluid. Four types of nanoparticles (Al2O3, Cu, Ag, and TiO2) are investigated. It was assumed that the flow is steady, and that the base fluid and the nanoparticles are in thermal equilibrium and no slip occurs between them. Thermo-physical properties of the nanofluid are assumed to be constant except for the density variation, which is approximated by the Boussinesq model. The thermo-physical properties of the base fluid and the different types of nanoparticles as well as air which were used for code validation are given in Table 1. The inner cylinder surface is maintained at a constant temperature Ti which is higher than the outer cylinder temperature To. The governing equations for the laminar natural convection in terms of stream function-vorticity formulation are the vorticity equation, the energy equation, and the kinematics equation respectively: