Amir Houshang Mahmoudi

Entropy Generation Due to Natural Convection in a Partially Open Cavity with a Thin Heat Source Subjected to a Nanofluid

This article presents a numerical study of natural convection cooling of a heat source mounted inside the cavity, with special attention being paid to entropy generation. The right vertical wall is partially open and is subjected to copper–water nanofluid at a constant low temperature and pressure, while the other boundaries are assumed to be adiabatic. The governing equations have been solved using the finite volume approach, using SIMPLE algorithm on the collocated arrangement. The study has been carried out for a Rayleigh number in the range 103 < Ra < 106, and for solid volume fraction 0 <ϕ <0.05. In order to investigate the effect of the heat source and open boundary location, six different configurations are considered. The effects of Rayleigh numbers, heat source and open boundary locations on the streamlines, isotherms, local entropy generation, Nusselt number, and total entropy generation are investigated. The results indicate that when open boundary is located up, the fluid flow augments and hence the heat transfer and Nusselt number increase and total entropy generation decreases.

Combined Effect of Magnetic Field and Nanofluid Variable Properties on Heat Transfer Enhancement in Natural Convection

The current work investigated, numerically, enhancement of heat transfer in natural convection using CuO-water nanofluid in the presence of a magnetic field. The governing equations were discretized using the control volume method and solved numerically via the SIMPLE algorithm. For the case of absence of a magnetic field and for low Rayleigh number, the heat transfer was almost insensitive to the presence of nanoparticles. For moderate and high Rayleigh numbers, the presence of nanoparticles had an adverse effect on heat transfer at high volume fraction of nanoparticles. The highest reduction in heat transfer was registered for the case of Ra = 105. Contour maps are generated for the normalized Nusselt number (Nu*) to determine the optimum selection of volume fraction of nanoparticles and magnetic field that gives maximum heat transfer enhancement. The results demonstrated the effectiveness and practicality of using high values of magnetic field in enhancing heat transfer using nanofluids.

Effect of a discrete heat source location on entropy generation in mixed convective cooling of a nanofluid inside the ventilated cavity

In this paper, the effect of localised heat sources on entropy generation owing to mixed convection flow in a vented square cavity has been studied numerically. Laminar steady forced convection flow of copper–water nanofluid through the cavity has been affected by density variations as a result of heat input from a wall–mounted heat source. To investigate the effect of the heat source location, three different placement configurations of the heat source have been considered. Furthermore, to further generalise the results, three different non–uniform heat flux conditions were also examined. The entropy generation rate has been analysed for Richardson numbers 0 ≤ Ri ≤ 10 and for solid volume fraction within 0 ≤ φ ≤ 0.05. With either uniform or non–uniform wall heating, the entropy generation rate is found to be minimal when the heat source and cavity exit are on the same wall. The maximum heat transfer rate, however, corresponds to the case when the main flow is parallel to the heated wall.

Numerical modeling of ground water flow and contaminant transport in a saturated porous medium

In this paper, numerical modeling and experimental testing of the distribution of pollutants along the water flow in a porous medium is discussed. Governing equations including overall continuity, momentum and species continuity equations are derived for porous medium. The governing equations have been solved numerical using the Finite Volume Method based on collocated grids. The SIMPLE algorithm has been adopted for the pressure _ velocity linked equations. In order to validate the numerical results, experimental data from laboratory apparatus are applied and there is a good agreement among numerical results and experimental test. Finally, the main affecting parameters on the distribution and transport of pollutants porous medium were investigated. Results indicate that, the domain of pollution rises with increasing dispersion coefficient and the dispersion phenomenon overcomes on pollutant transfer. Reduction of porosity has decreased the pollutant transfer and increased velocity has result in the increasing pollutant transport phenomenon but has reduced the domain of the pollution.