Browsing by Author "Mahdy,O.S."

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Thermal performance of nanofluid natural convection magneto-hydrodynamics within a chamber equipped with a hot block
(Elsevier B.V., 2024) Mahdy,O.S.; Ali,A.B.M.; Mahdi,M.S.; Jasim,D.J.; Kazemi-Varnamkhasti,H.; Goli,M.; Baghaei,S.
In this study, flow and free convection thermal performance within a chamber in the presence of a permanent magnetic field are simulated. Boussinesq approximation and the Lorentz force equation are used for the density variation in free convection, and the magnetic field, respectively. The steady-state, two-dimensional, and incompressible governing equations are simulated using the Semi-Implicit Method for Pressure Linked Equations (SIMPLE). The present study is simulated for different Rayleigh numbers (Ra) corresponding to the situation where the conduction mechanism was predominant (Ra = 100) and the convection heat transfer was predominant (Ra = 105). Also, different intensities of the magnetic field (0 ≤ Ha ≤ 40) and different directions of the magnetic field along with the effects of three different nanoparticles Ag, Cu, and Al2O3 are given. The present study showed that in the case of the dominant convection mechanism, the presence of the magnetohydrodynamics (MHD) condition decreases the Nusselt number (Nu). However, if the conduction is predominant, the applied magnetic field improves the average Nu number. The optimum state for the magnetic field strength was found in the low Rayleigh number. The presence of nanoparticles also intensifies the magnetic field effects. In the high Rayleigh number, the heat transfer rate reduces by 13.5% with the increase of the Hartmann number. © 2024 The Author(s)
Citation Count: 0
Using design of experiment via the linear model of analysis of variance to predict the thermal conductivity of Al2O3/ethylene glycol-water hybrid nanofluid
(Elsevier B.V., 2024) Jasim,D.J.; Salahshour, Soheıl; Qali,D.J.; Mahdy,O.S.; Salahshour,S.; Eftekhari,S.A.
In this paper, the thermal conductivity (knf) of the Al2O3/Ethylene Glycol -Water nanofluid is measured. MATLAB software is used to fit a nonlinear function, and the analysis of variance (ANOVA) is implemented to determine the effect of temperature and volume fraction of nanoparticles (φ) on extracting the residuals and knf. In the experimental part, various combinations of temperatures (from 30 to 60 °C) and volume fractions (fromφ = 0.15 up to 1.3%) are examined, and then the obtained data are analyzed using MINITAB software. The results show that the knf is highly dependent on φ and less dependent on temperature. By changing the φ from 0.15 to 1.3%, the thermal conductivity increases around 40%. In contrast, increasing the temperature from 30 to 60 °C will increase the knf by almost 10%. Also, the results show that the thermal conductivity slope is lower at φ < 0.75%, and this rate increases drastically for higher volume fractions. The obtained results, especially the fitting function, are useful for designing and optimizing systems using nanofluids as a working fluid in heat exchangers or energy systems. © 2024