A quasi two-dimensional numerical study is performed to analyze the thermo-magneto-convective transport of liquid metal around a Square cylinder in a Square duct subjected to a strong externally imposed axial magnetic field. The channel bottom wall is considered heated while the top wall is maintained at the free stream temperature keeping the cylinder adiabatic. The Reynolds and Hartmann numbers are kept in the range 0< Re £ 6000 and 0 < Ha £ 2160. The flow dynamics in the aforementioned range of parameters reveals the existence of four different regimes out of which the first three ones are similar to the classical non-MHD 2-D cylinder wakes while the fourth one is characterized by the vortices evolved from the duct side walls due to the boundary layer separation which strongly disturbs the Karman vortex street. The flow dynamics and heat transfer rate from the heated channel wall are observed to depend on the imposed magnetic field strength.With increasing magnetic field, the flow becomes stabilized resulting in a degradation in the forced convection heat transfer. A special case at a very high Reynolds numberRe = 3´104 with Ha=2160 is also considered to show the development of a Kelvin–Helmholtz-type instability that substantially affects the heat transfer rate.

The effect of thermal and solutal buoyancy induced by a discrete source of heat and mass transfer in a Square duct under the influence of magnetic field, especially at the turbulent regime for the first time is reported. Al2O3/water nanofluid is used with constant heat flux from three discrete heat sources. In the present study, the effects of Reynolds number (100 to 3000), particle volume fraction (0 to 2%) and magnetic field (Ha = 10 to 90) on the Nusselt number, pressure drop and wall temperature (at the axial and height directions) are represented graphically and discussed quantitatively. Two percent Al2O3-water nanofluid under Ha = 10 can produce 81% increase in Nusselt number with only 60% increase in pressure drop when compared to base fluid at Re = 100. Four percent enhancement in nanofluids cooling effect in the vicinity of a centre of the final heat source can be utilized in hot spots cooling.

In this paper, fully developed flow and heat transfer of viscoelastic fluid in a curved pipe with Square cross section is investigated. To that end, Criminale-Eriksen-Filbey (CEF) constitutive equation is used as viscoelastic model and heat transfer is studied at constant heat flux and in constant temperature conditions. Here, the governing equations are discrete using finite difference method. Also, staggered grids are used as mesh, and Marker and Cell method is applied for allocating the flow parameters on staggered grids. Here, the effect of the stress fields’ work of viscoelastic fluid and Brinkman number on convective heat transfer inside a curved duct is studied for the first time. Overall, the inverse effect of the first and second normal stress differences on secondary flows intensity and heat transfer is the main result of the current research.

In this article, the forced displacement heat transfer of nanofluid flow in horizontal curved tubes with a four-sided cross-section, under heat flux, was numerically simulated. A homogeneous nanofluid of aluminium oxide particles and water was used as the base fluid. Continuity, momentum and energy equations and the control volume method were used to numerically solve the flow. In this study, the effects of secondary flows, centrifugal force, and buoyancy on the flow field were considered, and the effect of the Reynolds number, volume fraction of nanoparticles and the effect of the curved surface in different geometries on the amount of heat transfer and pressure drop were investigated. The results are presented in the contour of flow and temperature parallel lines as well as Nusselt number and pressure graphs. Heat transfer and pressure drop in different concentrations of solid particles and different Reynolds numbers were compared. The results demonstrated that by increasing the volume fraction of solid particles from 0 to 5%, the heat transfer increased by up to 10% and the pressure drop increased by 100%. In addition, by increasing the Reynolds number from 100 to 900, the heat transfer and pressure drop inside the elbow increased by up to two times. According to the results, the concave surface from inside the tube has a greater effect on heat transfer than the convex surface.

Analysis of air bubbles entrainment in liquid slug body is one of the most important and complicated phenomena during slug flow regime. In the present attempt, a method is proposed for slug modeling to consider the air bubble entrainment into slug liquid body. The effect of consequences and their impact on slug behaviour to predict more accurate correlations for slug parameters is estimated and calculated.A two-fluid single pressure model is considered that is combined with population balance model for equal bubble diameter series and is solved using volume of fluid. In this regard, based on slug and hydraulic jump similarity, a correlation for air bubble entrainment rate and its mechanism is selected.This correlation is developed in the form of a user defined function code and is coupled with other models in FLUENT solver to calculate slug flow. Finally, the result of this numerical modeling is validated with the result of other numerical and experimental results in the related literature. The result is consist with the slug flow profile, entrained air bubble profile and their diameter distribution, slug mixture velocity, etc.

This numerical and experimental work aims to improve the heat transfer inside a solar thermal collector. By incorporating rectangular baffles in the middle of the distributed air passing channel at different angles of inclination (ß= 90°, ß= 180°, ß= 180° and ß= 90°). That is called the model H. These experiments were carried out in the Biskra region of Algeria in good natural conditions with an average solar radiation approximately constant I= 869 W/m2 varying from 11:30 to 14:00. After the completion of the experimental investigation, a computational fluid dynamics (CFD) model was created that matches this experimental model with the same experimental boundary conditions. In the numerical study, ANSYS Fluent 18.1 was used to conduct simulations and compare the results of the thermal and hydraulic performance of the collector. It was concluded that the effectiveness of the CFD model, meaning that the theoretical and numerical data were very close to each other for all mass flow rates. As the mass flow increased the heat transfer process increased, while the absorber plate temperature inside the collector for experimental and numerical studies decreased. Addition of baffles increased heat transfer, due to the creation of turbulent flow that leads to crack the dead thermal layers near the absorber plate, which leads to an increase in heat transfer from the absorber plate to the air.

A numerical study on steady laminar magnetohydrodynamics (MHD) mixed convection flow of an electrically conducting fluid in a vertical Square duct under the action of transverse magnetic field has been investigated. The walls of the duct are electrically non-conducting. In this study both forced and free convection flows are considered. The viscous dissipation and Joule heat are also considered in the energy equation and moreover the walls of the duct are kept at constant temperature. The governing equations of momentum, induction and energy are first transformed into dimensionless equations by using dimensionless quantities, then these are solved employing finite difference method for velocity, induced magnetic field and temperature distribution. The computed results for velocity, induced magnetic field and temperature distribution are presented graphically for different dimensionless parameters Hartmann number, Prandtl number, Grashof number and magnetic Reynolds number.

An 1D hydrodynamic model has been simulation and developed for gas hold-up and liquid circulation velocity prediction in air-lift reactors. model is based on momentum balance equations and has been adjusted to experimental data collected on a pilot plant reactor equipped with two types of gas distributors and using water as the liquid phase.The model equations described previously constitute a set of non-linear equations which are solved by an iterative procedure (v.b) (c plus). This model has also been combined with mass transfer and the kinetics of a chemical reaction to yield a complete model of the performance of a reactor.