393 publications from this institution
A numerical analysis of Copper oxide-H2O nanomaterial hydrothermal characteristics through a duct with utilizing turbulator under constant heat flux has been carried out by means of FVM. Simulations contain the effect of width tape (b) and Reynolds number (Re). Single phase model for nanomaterial and k-ɛ for turbulence modeling have been selected. Outputs indicate that friction factor tends to decline with augment of Re. Greater Nu due to insertion of turbulator is related to swirl flow generation. Augmented convective heat transfer is obtained with inserting turbulator with higher width.
In this study, coupled equations of particle's motion in Couette fluid flow are solved by Multi-step Differential Transformation Method (Ms-DTM) considering the rotation and shear effects on lift force and neglecting gravity. The precious achievement of the present work is introducing a new, fast and efficient analytical technique for spherical particles in plane Couette fluid flow over the previous numerical and analytical results in the literature. Also, obtained values are compared with numerical solution and HPM–Pade which recently are done by Torabi et al. It is shown that presented method gives approximations with a high degree of accuracy and least computational effort for studying particle motion in Couette fluid flow without the need for any linearization, discretization or perturbation against the previous work. Also, the acceleration profiles of the particle are presented and positions of the particle in each 1s time step are depicted graphically in the current study.
In the present article, the improvement of nanofluid heat transfer inside a porous cavity by means of a non-equilibrium model in the existence of Lorentz forces has been investigated by employing control volume based finite element method. Nanofluid properties are estimated by means of Koo-Kleinstreuer-Li. The Darcy-Boussinesq approximation is utilized for the nanofluid flow. Roles of the solid-nanofluid interface heat transfer parameter Nhs, Hartmann number Ha, porosity ε, and Rayleigh number Ra were presented. Outputs demonstrate that the convective flow decreases with the rise of Nhs, but it enhances with the rise of Ra. Porosity has opposite relationship with the temperature gradient.
Turbulent flow of oil based hybrid nanofluid within an absorber tube of concentrated solar system has been evaluated in this article. To concentrate the solar irradiation, the parabolic plate has been located below the tube and variable heat flux was considered as the boundary condition of the tube. The presence of a turbulator within the circular tube causes secondary flow to increase. Both thermal (S gen,th ) and frictional (S gen,f ) components of irreversibility were reported in outputs. As Re increases, the residence time decreases and lower outlet temperature has been achieved. S gen,th decreases about 57.36% with growth of Re while S gen,f increases about 17.44 times. As the number of rows of tapes increases, the value of S gen,f enhances about 69.23% while the value of S gen,th decreases around 3.67%. Increase of pitch ratio causes S gen,th to decrease about 11.25% while frictional component increases around 76.7%.
In this study, the entropy treatment of a nanomaterial flow in the existence of Lorenz forces within a porous domain is carried out via the non-Darcy model. Fe3O4-water is the ferrofluid flowing through the porous enclosure under the magnetic force impact. Simulations for different Darcy, Rayleigh and Hartmann numbers have been reported by applying the novel numerical simulation approach of the control-volume FEM. The outputs of the simulations showed that increasing permeability makes Be to decline, boundary layer thickness enhances with a rise of Lorentz force. In the end, based on the obtained outcomes and employing curve-fitting on the plots, two precise formulas were suggested for the estimation of the Bejan number and average Nusselt number.
Latent heat thermal energy storage systems (LHTESS), which work based on energy storage and retrieval during solid–liquid phase change is used to establish balance between energy supply and demand. LHTESS stores and retrieves thermal energy during solid–liquid phase change, while in SHTESS phase change doesn’t occur during the energy storage and retrieval process. LHTESS has a lot of advantages in comparison to SHTESS; the most important one is storing a large amount of energy during phase change process, which makes the energy storage density in LHTESS much higher than SHTESS. Due to this property, LHTESS have a wide application in different cases, such as solar air dryer, HVAC systems, electronic chip cooling, and engine heat recovery. The main restriction for these systems is thermal conductivity weakness of common PCMs. In this chapter, the method of adding nanoparticles to pure PCM and making nanoenhanced phase change material (NEPCM) and using fin with suitable array are presented to accelerate solidification process. The numerical approach, which is used in this paper is standard Galerkin finite element method.
Finite volume method is employed to simulate water based nanofluid turbulent flow and entropy generation in a heat exchanger. In order to augment heat transfer rate, twisted tape turbulators insert inside the pipe. Second law analysis are presented for various values of height ratio (BR) and pitch ratio (PR) and Reynolds number (Re). Related formulas for entropy generation and Bejan number are provided. Results indicate that secondary flow increases with increasing number of revolution. Bejan number and total entropy generation augment with augment of pitch ratio. But they decreases with augment of Reynolds number and height ratio.
No abstract is provided for this article.
No abstract is provided for this article.
Purpose – The purpose of this paper is to study the effects of natural convection heat transfer in a cold outer circular enclosure containing a hot inner elliptic circular cylinder. The fluid in the enclosure is Cu-water nanofluid. The main emphasis is to find the numerical treatment for the said mathematical model. The effects of Rayleigh number, inclined angle of elliptic inner cylinder, effective of thermal conductivity and viscosity of nanofluid, volume fraction of nanoparticles on the flow and heat transfer characteristics have been examined. Design/methodology/approach – A very effective and higher order numerical scheme Control Volume-based Finite Element Method (CVFEM) is used to solve the resulting coupled equations. The numerical investigation is carried out for different governing parameters namely; the Rayleigh number, nanoparticle volume fraction and inclined angle of elliptic inner cylinder. The effective thermal conductivity and viscosity of nanofluid are calculated using the Maxwell-Garnetts (MG) and Brinkman models, respectively. Findings – The results reveal that Nusselt number increases with an increase of nanoparticle volume fraction, Rayleigh numbers and inclination angle. Also it can be found that increasing Rayleigh number leads to a decrease in heat transfer enhancement. For high Rayleigh number the minimum heat transfer enhancement ratio occurs at. Originality/value – To the best of the authors’ knowledge, no such analysis is available in the literature which can describe the natural convection heat transfer in a nanofluid filled enclosure with elliptic inner cylinder by means of CVFEM.
In this study, a three-dimensional mesoscopic simulation of magneto hydrodynamics (MHD) natural convection in a cubic cavity has been studied by new means of the Lattice Boltzmann method with double Multi-Relaxation-Time (MRT) model. In order to solve the momentum and energy equations, two different populations with various lattices have been used. This paper has been conducted for specific values of the Grashof number ( Gr = 2 × 1 0 3 _ 2 × 1 0 5 ) and Hartmann number (Ha=0–100), while the Prandtl number is fixed at Pr = 0 . 73 . The results are presented in the form of average and local Nusselt number and contours of temperature and velocity at different planes of the cavity. It was found that the double MRT-LBM method is an appropriate approach to solve the studied case. The present results also show that the increase of the Hartmann number causes the heat transfer to drop considerably. Also, the effect of Hartmann number increases by enhancing the Grashof number, as the reduction of average Nusselt number is 12% for Gr = 2 × 1 0 3 and 71% for Gr = 2 × 1 0 5 when Hartmann number increases from 0 to 100. In contrast with Hartmann number, increasing of Grashof number raises heat transfer rate and the average Nusselt number increases by more than three times by enhancing the Grashof number from 2 × 1 0 3 to 2 × 1 0 5 .
In this paper the magnetohydrodynamic (MHD) nanofluid flow and heat transfer between two horizontal plates in a rotating system is analyzed. The lower plate is a stretching sheet and the upper one is a solid permeable plate. The basic partial differential equations are reduced to ordinary differential equations which are solved numerically using the fourth-order Runge–Kutta method. Different types of nanoparticles such as copper, silver, alumina and titanium oxide with water as their base fluid have been considered. Velocity and temperature profiles as well as the skin friction coefficient and the Nusselt number are determined numerically. The influence of pertinent parameters such as nanofluid volume fraction, magnetic parameter, wall injection/suction parameter, viscosity parameter and rotation parameter on the flow and heat transfer characteristics is discussed. The results indicate that, for both suction and injection the Nusselt number has a direct relationship with the nanoparticle volume fraction. The type of nanofluid is a key factor for heat transfer enhancement. The highest values are obtained when titanium oxide is used as a nanoparticle. Also it can be found that the Nusselt number decreases with the increase of the magnetic parameter due to the presence of Lorentz forces.
No abstract is provided for this article.
In this model, a comprehensive study related to non-equilibrium model of nanomaterial is under consideration in attendance of magnetic force. Free convection effects will appear within the permeable medium by introducing the two different temperature dependent models. Radiation source is also added in energy equations. To obtain the results for system of constructed mathematical model in the form PDE, we have used CVFEM. To understand the outcomes, impacts of each parameter for stream function and isotherms are obtained. Various constrain are defined at the surface of the cavity to determine the heat transfer behavior. Impacts of buoyancy, parameter, magnetic forces, radiative factor, interface heat transfer parameter and nanoparticles’ shape on nanomaterial treatment are demonstrated. Outcomes illustrate by increasing the solid–nanofluid interface heat transfer parameter, conduction becomes more dominant while Nusselt number gradually decreases.
No abstract is provided for this article.
No abstract is provided for this article.
A theoretical and a mathematical model is presented to determine the entropy generation on electro-kinetically modulated peristaltic propulsion on the magnetized nanofluid flow through a microchannel with joule heating. The mathematical modeling is based on the energy, momentum, continuity, and entropy equation in the Cartesian coordinate system. The effects of viscous dissipation, heat absorption, magnetic field, and electrokinetic body force are also taken into account. The electric field terms are helpful to model the electrical potential terms by means of Poisson–Boltzmann equations, ionic Nernst–Planck equation, and Debye length approximation. A perturbation method has been applied to solve the coupled nonlinear partial differential equations and a series solution is obtained up to second order. The physical behavior of all the governing parameters is discussed for pressure rise, velocity profile, entropy profile, and temperature profile.
