Composite Materials
Ali Akbar Azemati; Hossain Khorasanizadeh; Behzad Shirkavand Hadavand; Ghanbar Ali Sheikhzadeh
Abstract
One of the ways to waste energy in buildings is wasting it from the walls. For this reason, insulating materials are used to prevent the loss of energy in buildings. Typically, common insulations are high thickness and thin coatings are used less. The purpose of this research is to introduce nanocomposite ...
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One of the ways to waste energy in buildings is wasting it from the walls. For this reason, insulating materials are used to prevent the loss of energy in buildings. Typically, common insulations are high thickness and thin coatings are used less. The purpose of this research is to introduce nanocomposite thin polymer coatings and its effect on thermal conductivity. For achieving this, chemically modified nano zirconium oxide and nano aluminum oxide in three different weight percentages (1, 3, and 5%) were used in polyurethane matrix for preparing nanocomposite coatings. To study thermal conductivity, the metallic plates are coated with prepared nanocomposites and the thermal conductivity of the samples was measured. The results show that by adding zirconium oxide and aluminum oxide nanoparticles in polyurethane matrix, the thermal conductivity of coatings in all three weight percentages compared to the coating without nanoparticles, decreased. The lowest thermal conductivity was found for 5% nano aluminum oxide composition, which, compared to the conductivity of the pure polyurethane resin, has decreased about 40% that leading to a decrease in the surface heat flux.
Computational Fluid Dynamics (CFD)
Ghanbarali Sheikhzadeh; Mahdi Mollamahdi; Mahmoud Abbaszadeh
Abstract
In this study, the momentum and energy equations of laminar flow of a non-Newtonian fluid are solved in an axisymmetric porous channel using the least square and Galerkin methods. The bottom plate is heated by an external hot gas, and a coolant fluid is injected into the channel from the upper plate. ...
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In this study, the momentum and energy equations of laminar flow of a non-Newtonian fluid are solved in an axisymmetric porous channel using the least square and Galerkin methods. The bottom plate is heated by an external hot gas, and a coolant fluid is injected into the channel from the upper plate. The arising nonlinear coupled partial differential equations are reduced to a set of coupled nonlinear ordinary differential equations using stream function.These equations can be solved using the different numerical method. The numerical solution is conducted using fourth order Rung-Kutta method. With comparing the results obtained from the analytical and numerical methods, a good adaptation can be seen between them. It can also be observed that the results of the Galerkin method have further conformity with the numerical results and the Galerkin method is simpler than the least square method and requires fewer computations. The effects of Reynolds number, Prandtl number and power law index of non-Newtonian fluid is examined on flow field and heat transfer. The results show that Nusselt number increases by increasing Reynolds number, Prandtl number, and power law index.
