Thermal performance assessment of a flat-plate solar collector considering porous media, hybrid nanofluid and magnetic f
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Thermal performance assessment of a flat‑plate solar collector considering porous media, hybrid nanofluid and magnetic field effects Seyed Pooya Aghili Yegane1 · Alibakhsh Kasaeian1 Received: 24 February 2020 / Accepted: 15 April 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract In this work, a numerical study of thermal performance enhancement of a flat plate solar collector has been presented. The collector channel is completely filled with porous media, and the Darcy–Brinkman model is used to characterize the flow field of hybrid nanofluid inside this region. Due to the existence of a uniform magnetic field, the effect of the force applied by the field on the momentum equation is considered. In addition, since the LTNE condition has been used, to describe the thermal field, two-equation model is employed. The flow has been assumed fully developed from hydro-dynamically and thermally aspects. The conservation equations of momentum and energy solved numerically. The results have been compared with previous studies, and a good agreement between them has been observed. Eventually, the effects of key parameters of hybrid nanofluid and porous media on the velocity and temperature distributions, Nusselt number, friction factor, and collector’s comprehensive performance have been scrutinized. The outcomes demonstrate that from heat transfer standpoint, in a constant volume fraction of nanoparticles, the mixture of copper and alumina with equal volume fraction works better than pure alumina nanoparticles, and there is no significant difference with pure copper nanoparticles. The results show that when the pore density changes from 5 PPI to 40 PPI, the collector comprehensive performance ratio in the porosity of 0.85 is equal to 0.445, while it is 0.487 in the porosity of 0.95. This ratio, in the Hartman numbers of 0 and 120, is equal to 0.274 and 0.655, respectively. Moreover, comprehensive performance of the collector is an inverse function of pore density, the porosity and Hartman number. Keywords Flat plate solar collector · Hybrid nanofluid · Thermal performance · Porous media · Magnetic field List of symbols ( ) asf Specific surface area m−1 B Magnetic field strength (T) cp Specific heat (J kg−1 K−1) Da Darcy number df Fiber diameter of metal foam (m) dp Pore diameter of metal foam (m) f Friction factor H Collector channel height (m) hsf Local convective heat-transfer coefficient (W m−2 K−1) Ha Hartmann number k Thermal conductivity (W m−1 K−1) K Permeability (m2) L Collector channel length (m) * Alibakhsh Kasaeian [email protected] 1
Faculty of New Sciences and Technologies, University of Tehran, Tehran, Iran
Nu Nusselt number p Pressure (Pa) P Dimensionless pressure Pr Prandtl number q Solar heat flux (W m−2) Re Reynolds number T Temperature (K) u Velocity component along x-direction (m s−1) u0 Inlet velocity (m s−1) U Dimensionless axial velocity x, y Cartesian coordinates (m) Y Dimensionless y coordinate Greek symbols 𝜀 Porosity 𝜔 Pore density (PPI) σ Electrical conductivit
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