Experimental study on forced convection heat transfer of a nanofluid in a heat exchanger filled partially porous materia
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Experimental study on forced convection heat transfer of a nanofluid in a heat exchanger filled partially porous material Mehdi Salari1 · Mohammad Reza Assari1,2 · Ashkan Ghafouri3 · Nader Pourmahmoud4 Received: 1 April 2020 / Accepted: 9 September 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Heat transfer of MgO-EG nanofluid flowing in a double tube heat exchanger with an inner tube containing a partial porous material under laminar and turbulent flows was investigated experimentally. The MgO nanoparticles with 20 nm of size were added to the EG to made the working fluid with a concentration of 0–1 vol%. The copper metal foam was used to create a partial porous medium in the inner tube. The Nusselt number and friction factor were reported as a function of the Reynolds number, using the measurement of the temperatures and pressure drop of flows inside the tube. The accuracy of the empirical results was also validated using the presented theoretical formulas in the literature. The results showed a considerable increase in the Nusselt number by employing the nanofluid and porous media. Using porous media resulted in an increase in the effectiveness of nanoparticles in improving heat transfer. The results indicated a significant increase in the performance evaluation criteria (PEC) parameter. The highest PEC was 1.19 for 1.0% concentration of nanoparticles. The effect of porous material porosity on the EPC was also investigated. The results showed that by decreasing the porosity, the PEC increased. The Nusselt number was very sensitive to porosity variations. Therefore, using partial porous media is suggested to improve the thermal performance of heat exchanger in industrial applications. New correlations are proposed to predict the Nusselt number and friction factor for empty tubes and tubes containing partial porous media. Keywords Nanofluid · Metal foam · Nusselt number · Friction factor · Heat exchanger List of symbols cP Specific heat capacity at constant pressure (J kg−1 K−1) d Diameter (m) f Friction factor k Conductive heat transfer coefficient (W m−1 K−1) L Length (m) h Convective heat transfer coefficient (W m−2 K−1) Nu Nusselt number (= hd/k) * Mohammad Reza Assari [email protected]; [email protected] * Ashkan Ghafouri [email protected] 1
Department of Mechanical Engineering, Dezful Branch, Islamic Azad University, Dezful, Iran
2
Department of Mechanical Engineering, Jundi- Shapur University of Technology, Dezful, Iran
3
Department of Mechanical Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran
4
Department of Mechanical Engineering, Urmia University, Urmia, Iran
P Pressure (pa) p Surface perimeter Pr Prandtl number (= νf/αf) q″ Heat flux (W m−2) Re Reynolds number (= ρVd/μ) R Radius s Thickness T Temperature (°C) U Uncertainty Greek symbols α Fluid thermal diffusivity (m2 s−1) μ Dynamic viscosity (N s m−2) ν Kinematic viscosity (m2 s−1) ρ Density (kg m−3) φ Nanoparticle volume fraction Subscripts f Base fluid o Out i In m Mean
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