Papers by Author: Ghanbar Ali Sheikhzadeh

Abstract: The present research studies on the effect of nanoparticles on polymeric coatings and heat transfer in them. For this purpose, three different weight percentage of nanozirconium oxide (1, 3 and 5%) were added to polyurethane resin and applied on metallic plates. To determine the radiation heat transfer coefficients, emissivity coefficient and thermography of the samples along a region of long wavelengths (IR) were measured. The results showed that by adding zirconium oxide nanoparticles to the polyurethane resin, the absorption and emissivity coefficient of coating in all three samples were improved compared to the coating without nanoparticles.

Abstract: Mixed convection of Cu-water nanofluid in a lid-driven square cavity with a heat source embedded in the bottom wall is studied numerically. The governing equations together with the respective boundary conditions are solved numerically using the finite volume method and the SIMPLER algorithm. The computations are performed for various Richardson numbers (), heat source length () and volume fraction of the nanoparticles (). It is observed from the results that the average Nusselt number is increased by increasing the Richardson number and the volume fraction of the nanoparticles. Moreover, the maximum temperature at the heat source surface decreases by increasing the Richardson number and the volume fraction of the nanoparticles.

Abstract: Numerical simulation of natural convection heat transfer in the presence of a magnetic field is analyzed in a non-isothermally heated square enclosure. The left wall is heated and cooled with a sinusoidal heat source and the right wall is cooled isothermally. The horizontal walls of the enclosure are adiabatic. The effects of Rayleigh number (Ra = 104, 105 and 106), Hartmann number (Ha = 0, 25, 50 and 100) and amplitude of sinusoidal function (n = 0.25, 0.5 and 1) on temperature and flow fields are analyzed. It is observed that the rate of heat transfer is decreased with increasing the Hartmann number; it is also decreased when decreasing the amplitude of sinusoidal function.

Abstract: In this study, the buoyancy-driven fluid flow and heat transfer in a differentially-heated rectangular cavity filled with the TiO₂-water nanofluid is investigated numerically. The left and the top walls of the cavity are maintained at constant temperatures T_h and T_c, respectively, with T_h > T_c. The enclosure’s right and bottom walls are kept insulated. The governing equations are discretized using the finite volume method. A proper upwinding scheme is employed to obtain stabilized solutions for high Rayleigh numbers. Using the developed code, a parametric study is undertaken, and the effects of pertinent parameters, such as, the Rayleigh number, the aspect ratio of the cavity and the volume fraction of the nanoparticles on the fluid flow and heat transfer inside the cavity are investigated. It is observed from the results that by increasing the volume fraction of the nanoparticles, the mean Nusselt number of the hot wall increases for the shallow cavities; while, the reverse trend occurs for the tall cavities. Moreover, the heat transfer enhancement utilizing nanofluid is more effective at Ra = 10³.

Abstract: In this work, the mixed convention of air inside a rectangular cavity with moving cold sidewalls is studied numerically. A constant flux heat source is attached to the bottom wall of the cavity. A thin thermal shield is located at a specific distance above the heat source. The governing equations are solved using appropriate numerical methods. A parametric study has been conducted and the effects of heat source length, its location and the shield distance from the source on the heat transfer have been investigated. The results show that the heat dissipation increases as the heat source and the shield are moved up to a certain distance towards either sidewall. However, moving them beyond this limiting distance results in the reduction of heat dissipation. It is shown that the presence of shield results in the reduction of the heat transfer coefficient. However, for the normalized distance of the shield from the heat source greater than , the shield’s effect on the reduction of the heat transfer coefficient is less than.

Abstract: Numerical study of natural convection heat transfer inside a differentially heated square enclosure with adiabatic horizontal walls and vertical isothermal walls is investigated. Two insulated ribs are symmetrically located on horizontal walls. The governing non-linear equations are solved in a two-dimensional domain using a control volume method and the SIMPLER algorithm for the velocity–pressure coupling is employed. The results will be presented in forms of streamlines, isotherms and Nusselt number for Rayleigh number 106. It is shown that for small rib height the isotherms indicate the laminar boundary regime with high temperature gradient near the bottom of the hot surface and the top of cold one. However, as rib height increases this boundary layer is vanished. Also it is found that as the length and height of the ribs increase the mean Nusselt number decreases.