393 publications from this institution
In this chapter, nanofluid forced and mixed convection in the presence of external forces is presented. Homogeneous model is considered for nanofluid. The effect of nanoparticle shape on the rate of heat transfer is taken into account. Final equations are derived in form of vorticity stream function. Control Volume-based Finite Element Method (CVFEM) is selected as a simulation tool. Influences of active parameters on nanofluid flow and heat transfer are examined.
The electrohydrodynamic method can be one of the most promising methods among various active techniques because of its several advantages, e.g., simplified implementation using only a transformer and electrodes. Applying an electric field leads to generation of Coulomb force. Nanofluid flow in existence of an electric field has been investigated in this chapter.
In this research, the effects of non-uniform magnetic field on the heat transfer of ferrofluid inside a T-junction are investigated. The finite volume method with the SIMPLEC algorithm is applied to simulate the effects of non-uniform magnetic field on the thermal and friction factor of ferrofluid. The ferrofluid inside T-junction is assumed single phase and laminar and constant heat flux is applied on the wall while three wires are chosen as a source of non-uniform magnetic field. This study focused on main effects of magnetic field on the flow feature and temperature distribution in the vicinity of magnetic source. Comprehensive parametric studies are performed to investigate the influence of various factors such as intensity of magnetic field and Reynolds number on the heat transfer. Obtained results show that average heat transfer of ferrofluid rises more than 64% when magnetic field is applied. In addition, the local heat transfer increases more than 200% in vicinity of the first magnetic field.
In this article, the effect of magnetic field on the Nanofluid flow inside a sinusoidal two-tube heat exchanger is investigated numerically. This study focuses on the influence of variable magnetic field in the heat transfer of heat exchanger while mixture is single phase. In this heat exchanger, the inner tube is sinusoidal and the outer tube is considered smooth. The magnetic field is established orthogonal to sinusoidal tube. The basis fluid is water with 4vol.% Nano particles (Fe3O4). In our study, Ferrofluid flows in the internal tube (sinusoidal tube) as hot fluid and air flows counter currently as cold fluid in external tube. The finite volume method with the SIMPLEC algorithm is used for handling the pressure⿿velocity coupling. The numerical results present validated data with experimentally measured data and show good agreement with measurement. The influence of the variation of different parameters like geometric shape, intensity of magnetic field non-dimensional number and Reynolds number, on heat transfer is investigated. According to obtained results, sinusoidal formation of the internal tube significantly increases the Nusselt number inside a two-tube heat exchanger. Also, magnetic field enhances diffusion of the cold boundary layer to the central parts of the inner tube for various geometric shape coefficients. Our findings show that the diffusion also elevates as the intensity of the magnetic field is increased. So, Nusselt number and heat transfer increase and this augmentation intensifies in high Reynolds number.
No abstract is provided for this article.
An investigation has been conducted to study Lorentz effect on nanomaterial behavior within a permeable space including innovative numerical technique namely CVFEM. Iron oxide has been mixed with H2O and porous domain was filled with this nanomaterial. The impacts of the flow and geometric variables on entropy generation along with the heat transfer have been examined. The simulations have been carried out with wide ranges of the magnetic force, permeability and Rayleigh numbers. The outcomes indicate that the Darcy term has inverse relationship with temperature of hot surface. Stronger convection mode and lower exergy loss appear when buoyancy forces augment. Entropy generation goes up with growth of Hartmann number.
In this study, three dimensional Al2O3-Water nanofluid flow and heat transfer features between two horizontal parallel plates in the presence of magnetic field through porous medium is scrutinized. System under consideration is rotating. Effects of thermal interfacial resistance, nanoparticle volume fraction, Brownian motion, nanoparticle size, types of nanoparticle and base fluid on thermal conductivity are considered. Also micro mixing in suspensions is taken into account while calculating viscosity. Homotopy Analysis method is employed to solve the system of ordinary differential equations, obtained by reducing original system of partial differential equations using suitable change of variables. Effects of different prevailing parameters: Reynolds number, Radiation parameter, Magnetic parameter, nanoparticle volume fraction, Eckert number, Permeability parameter, Rotation parameter and Prandtl number on Heat transfer and fluid flow are discussed. Also it is observed that the skin friction increases with increase in Reynolds number and rotation parameter but trend is reversed for nanoparticle volume fraction. The magnitude of Nusselt number rises with Reynolds number and nanoparticle volume fraction but it declines with increase of rotation parameters and Eckert number.
In this research, numerical simulation is examined for nanofluid hydrothermal treatment during solidification. Time dependent mesh has been utilized. Various shapes of CuO nanoparticles are dispersed in water. Solid fraction and isotherm contours are shown for several values of fin length, radiation parameter and shape factor. Results demonstrate that minimum solidification time has been obtained for Platelet shape. Solid faction improves with increase of radiation parameter.
In this model, heat transfer analysis of water functionalized Fe3O4 ferrofluid is performed along with the irreversibility process along a porous semi annulus. To determine the discrete behavior of the temperature distribution and ferrofluid flow inside the semi annulus, a non-Darcy approach is introduced for permeable media. To manage the movement of the powders, magnetohydrodynamic (MHD) is applied normal to the surface of semi annulus. A complex nature system of nonlinear partial differential equation (PDE's) was developed along with the constraint defined at the surface of the annulus. Mathematical expression and thermophysical properties of both liquid and nanoparticles, respectively are introduced. Structure of this model has been solved though CVFEM and obtained the outputs against the emerging parameters namely: Hartmann number Ha, Rayleigh number Ra, Darcy numbers Da. All the obtained results defining the behavior of streamlines, isotherms, entropy generation, Bejan number and exergy loss contours. Obtained results portrays that disordered in the entire mechanism is more rapid by increasing the values of Darcy number however and exergy drop reduces but it depends upon the values of Hartmann number.
In the present article Parameterized Perturbation Method (PPM) is used to obtain the solutions of momentum and heat transfer equations of non-Newtonian fluid flow in an axisymmetric channel with porous wall for turbine cooling applications. The validity of the results of PPM solution were verified by comparison with numerical results obtained using a fourth order Runge–Kutta method. These comparisons reveal that Parameterized Perturbation Method is a powerful approach for solving this problem. The analytical investigation is carried out for different governing parameters namely, Reynolds number, injection Reynolds number, Prandtl number and power law index. The results show that skin friction coefficient increases with increase of Reynolds number, especially at high Reynolds numbers. Also it can be found that Nusselt number has direct relationship with Reynolds number, Prandtl number and power law index.
Steady nanofluid convective flow in a porous cavity is investigated. Darcy and Koo–Kleinstreuer–Li (KKL) models are considered for porous media and nanofluid, respectively. The solutions of final equations are obtained by control volume-based finite element method (CVFEM). Effective parameters are CuO–water volume fraction, number of undulations, and Rayleigh and Hartmann numbers for porous medium. A correlation for Nuave is presented. Results depicted that heat transfer improvement reduces with the rise of buoyancy forces. Influence of adding nanoparticle augments with augment of Lorentz forces. Increasing Hartmann number leads to decrease in temperature gradient.
MHD forced convection of nanofluid inside a porous cavity with hot circular obstacle is presented. Lattice Boltzmann method is selected as simulation tool. Brownian motion impact is considered for nanofluid modeling. Roles of Reynolds number (Re), nanofluid volume fraction (ϕ), Darcy number (Da) and Hartmann number (Ha) are demonstrated. Results reveal that thermal plume diminishes with augment of Ha. Nusselt number improves with increase of Da,Re.
Nanofluid free convection in presence of Lorentz forces in a permeable semi annulus is simulated using Control Volume based Finite Element Method. Impact of porous media on governing equations is considered by means of Darcy law. Brownian motion impact on properties of nanofluid is taken into account using Koo-Kleinstreuer-Li (KKL) model. Important parameters are inclination angle ( ξ ) , CuO-water volume fraction ( ϕ ) , Hartmann ( Ha ) and Rayleigh ( Ra ) numbers for porous medium. A formula for Nuave is provided. Results indicated that temperature gradient detracts with enhance of Ha but it enhances with rise of ξ , Ra . Heat transfer augmentation enhances with rise of Lorentz forces.
Lattice Boltzmann Method is applied to investigate natural convection flow of a nanofluid in a concentric annulus between a cold outer square cylinder and a heated inner elliptic cylinder. In order to simulate the effective thermal conductivity and viscosity of nanofluid, Maxwell–Garnetts (MG) and Brinkman models are used, respectively. This investigation compared with other numerical methods and found to be in excellent agreement. Numerical results for the flow and heat transfer characteristics are obtained for various values of the nanoparticle volume fraction, Rayleigh numbers and eccentricity. The results show that the minimum value of enhancement of heat transfer occurs atforbut for other values of Rayleigh number it obtained at.
The problem of nanofluid hydrothermal behavior in presence of variable magnetic field is investigated analytically using Differential Transformation Method. The fluid in the enclosure is water containing different types of nanoparticles: Al2O3 and CuO. The effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation. In this model effect of Brownian motion on the effective thermal conductivity is considered. The comparison between the results from Differential Transformation Method and previous work are in well agreement which proved the capability of this method for solving such problems. The effect of the squeeze number, nanofluid volume fraction, Hartmann number and heat source parameter on flow and heat transfer is investigated. The results show that skin friction coefficient increases with increase of the squeeze number and Hartmann number but it decreases with increase of nanofluid volume fraction. Nusselt number increases with augment of nanoparticle volume fraction, Hartmann number while it decreases with increase of the squeeze number.
In this study, micropolar fluid flow in a channel subject to a chemical reaction is investigated analytically using Differential Transformation Method (DTM). The effects of Peclet numbers on the temperature and concentration profiles are determined. Also the effects of various parameters such as the Reynolds number, the coupling parameter and the spin gradient viscosity parameter on the fluid properties are determined and shown graphically. The comparison between the results from DTM and numerical method are in well agreement which proofs the capability of this method for solving such problems. Also, for both suction and injection it can be found that Reynolds number and Peclet number have direct relationship with Nusselt number and Sherwood number.
No abstract is provided for this article.
This study presents an experimental investigation into the impact of vortex generators (VGs) on the productivity of a CPVT (concentrated photovoltaic thermal) system. The CPVT system was tested using a single-axis solar tracking mechanism and a parabolic solar collector that concentrated solar radiation onto a photovoltaic thermal (PVT) module. The cooling system utilized water, and two different geometries—one without VGs and one with VGs—were tested across various flow rates to assess their influence on system performance. The CPVT system consisted of eight monocrystalline solar modules interconnected in parallel to maximize energy collection. The experiments were conducted in Najaf, Iraq, on July 27, 28, 30, 31, and August 2, 2023. Data collection was carried out at 20-min intervals from 10:20 to 14:00 on each test day. Environmental conditions were carefully monitored and recorded using precise measurement instruments. Key performance indicators, such as electrical and thermal efficiencies, were analyzed at various times throughout the day. The results revealed that enhancing the cooling of the solar cells significantly improved their power production capabilities and longevity. Given Iraq's hot climate, where temperatures can reach extreme levels, effective cooling is crucial to prevent long-term damage to the solar cells. The study found that increasing the coolant flow rate led to a significant improvement in thermal efficiency, with an average enhancement of 22.07 %. The introduction of VGs resulted in substantial gains, with average thermal efficiency increasing by 15 % and electrical efficiency by 23 %. The overall efficiencies of the CPVT systems were recorded as 64.31 % without VGs and 74.81 % with VGs, highlighting a marked improvement in performance due to the incorporation of VGs. This study emphasizes the critical role of effective thermal management in CPVT systems, particularly in hot climates, where the risk of thermal degradation is high.
