کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
647631 1457186 2011 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Natural convection heat transfer of nanofluids in annular spaces between horizontal concentric cylinders
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی جریان سیال و فرایندهای انتقال
پیش نمایش صفحه اول مقاله
Natural convection heat transfer of nanofluids in annular spaces between horizontal concentric cylinders
چکیده انگلیسی

Natural convection heat transfer of nanofluids in annular spaces between long horizontal concentric cylinders maintained at different uniform temperatures is investigated theoretically. The main idea upon which the present work is based is that nanofluids behave more like single-phase fluids rather than like conventional solid–liquid mixtures. This assumption implies that all the convective heat transfer correlations available in the literature for single-phase flows can be extended to nanoparticle suspensions, provided that the thermophysical properties appearing in them are the nanofluid effective properties calculated at the reference temperature. In this connection, two empirical equations, based on a wide variety of experimental data reported in the literature, are used for the evaluation of the nanofluid effective thermal conductivity and dynamic viscosity. Conversely, the other effective properties are computed by the traditional mixing theory. The heat transfer enhancement that derives from the dispersion of nano-sized solid particles into the base liquid is calculated for different operating conditions, nanoparticle diameters, and combinations of solid and liquid phases. The fundamental result obtained is the existence of an optimal particle loading for maximum heat transfer. In particular, for any assigned combination of suspended nanoparticles and base liquid, it is found that the optimal volume fraction increases as the nanofluid average temperature increases and the nanoparticle size decreases.


► An optimal particle loading for maximum heat transfer is found to exist.
► The optimal particle loading increases as the nanofluid temperature increases.
► The optimal particle loading increases as the nanoparticle diameter decreases.
► The liquid phase affects the optimal particle loading much more than the solid phase.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Applied Thermal Engineering - Volume 31, Issues 17–18, December 2011, Pages 4055–4063
نویسندگان
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