This paper presents a two-dimensional numerical analysis of an evaporative drying process of the porous bodies in a row, considering effects of configuration on heat and mass transfer in assembly. Drying process simulation of three rectangular porous material subject to forced convection, was carried out by employing N-S, energy and concentration equations for external air flow; along with moisture conservation and energy equations for the porous zone. Numerical predictions indicate that the first porous body encountered with flow dries faster in comparison to the others, while for next bodies average moisture contents are approximately equal in all the drying time. Moreover, it was observed that for the first body, both of top surface and opposite surface to the flow direction have equal importance in heat and mass transfer; while top surface of next bodies, have major role in drying process. Also moisture and temperature profiles of the first body have shown essential difference with the other objects. It can be concluded that no significant change in heat and mass transfer and drying rate will be achieved through the change in distance between porous bodies.

A vital challenge in fusion nuclear reactors is the heat removal through the embedded channels. Various methods have been employed to improve the reactor core cooling systems. One of the methods in this context is creating turbulence in the flow field by using the sphere packed beds. In the present study, the heat transfers in channels filled with spheres, as a technique to enhance the heat transfer coefficient, is investigated through numerical modelling. The spheres in the channel are assumed as a continuous porous media and domain coefficients are obtained by using the Ergun and the momentum conservation equations. Wall effect in porous media modelling is considered by employing the modified k-ϵ turbulent model. In comparison with the conventional numerical methods that requires high number of unstructured grid generation, the porous media numerical simulation demonstrates acceptable accuracy in obtaining flow field parameters including pressure drop and heat transfer coefficient. Meanwhile, it is concluded that a reduction of porosity results in an increase in pressure drop and heat transfer coefficient.

this paper, thermal conductivity of porous media has been modeled based onmathematical analysis in one dimensional space with micro size. First, porous modeling established on three kinds of porosity (y = 0.52, 0.68 and 0.74) and then to make analysis and calculation easy, reality assumptions were considered. With omitted radiation and convection mechanisms, we can developed one simple model as kP = kgks / (ks - y (ks - kg)). After developing the model its results for three materials cotton, fiber and sand obtained and then compared to the experimental data and the results of Maxwell model as a valid model. The results obtained for two modes of material into the holes once air and once again water. The results obtained from the model for gas fluid (air)into the holes with great accuracy. Generally, based on the terms of model, in porous media accuracy of the model was increased when the ratio of (ks / kg) was increased. At the other hand, if the bulk has much conductivity or the fluid into the hole has low conductivity, the prediction of model and its adaptation on heat behavior of the body will be better. So the uses of this model was recommended for dense porous materials

Simulation and analysis of two phase flow that crosses over tube bundles is crucial in safety analysis and design of kettle reboilers and steam generators. The geometry complexity of the tube bundle flow field increases the difficulty of the conventional numerical analysis. One of the methods to reduce the numerical calculations cost, is to use the porous media theory instead of the complete tube bundle modeling. Drag and tube bundle resistance force equations have been used in the porous media analysis. Based on available experimental results, two tube bundle arrangements have been considered. Due to existence of symmetric geometry and uniform energy source over the tube bundle, the two dimensional symmetric models has been used as well. It was observed that the predicted pressure drop in this research has acceptable adaptation with the experimental results. Meanwhile, by considering different outlet boundary conditions, calculated void fraction is compared to the experimental results and showed better accuracy than similar CFD research. It was observed that the enhancement of the tube bundle thermal power increases the void fraction in the heating area of the reboiler.

In this research, a new analytical solution of one dimensional coupled equations of moisture and heat transfer in capillary-porous body is presented. These equations are known as the Luikov system of equations. These partial differential equations are coupled and nonhomogenous, which is assumed linearly with the assumption that the coefficients of the equations are independent of space, time, and every dependent variables.In innovative method of this survey, considering the governing equations are coupled, at first , assuming that the independent equations system from each other (removal coupling), it has been resulted a public answer for equations by using the method of separation of variables. Next, the private answers will be gotten by considering coupled equations and using laplace transform method, in this survey it has been searched the effect of dimensionless coefficients such as Lu, Fo, ε concluding on the rate of heat and moisture transfer. The outcome shows the effect of Luikov number on the rate of heat and moisture transfer of capillary-porous body equations coupling. It has also been resulted the depending of phase change coefficient and this outcome has been planned in the surveys by Luikov

Stepped gabion spillways have many applications in dam structure, river engineering and soil conservation works. These types of weirs have more flexibility in respect to rigid (impervious) type and are more stable against water pressure. Energy dissipation through this weir is high due to over flow and inflow from steps, so the cost of stilling basin construction can be reduced. Flowing water through the body of weir is one of its important characteristics that make flow condition more complex. Most of the researches until now were on rigid stepped weir in large dams and there are a few studies on gabion stepped spillways. The purpose of this study is to investigate flow over and through the gabion stepped spillway body and determine energy dissipation rate. For this purpose 8 physical gabion stepped spillways with 3 different porosities 38 to 42 percent and two slopes 1:1 & 1:2 (V:H) were made and iron plate on each horizontal or vertical step was used to study the effect of step pervious on energy dissipation. Results show that at higher discharge, energy dissipation is more in pervious (gabion) spillway. In fact at higher discharge or skimming flow regime, energy dissipation divided in to over flow and inflow through the spillway body. In this situation energy dissipation through the spillway body have more effect on total energy dissipation. Thus in skimming flow regime, gabion stepped spillway will have greaterenergy dissipation. At lower discharge, energy dissipation is more in impervious stepped spillway. In this condition other rank belongs to gabion, step with vertical plate and step with horizontal plate respectively. Gabion with higher porosity had bigger energy dissipation and with increasing in discharge, their differences tend to zero. Slope decreasing from 1:1 to 1:2 causes more energy dissipation.

Lipid core plaques are the major cause of the vascular stenosis and heart attacks. Accumulation of Low-Density Lipoproteins (LDLs) across the atherosclerotic lesions، leads to the hardening of the arterial wall and causes cross sectional narrowing of the artery. Among different arterial wall models، Multilayer model gives accurate LDL concentration across the layers. In this study LDL accumulation in the four-layer carotid artery is investigated numerically. Navier-Stokes equations along with Darcy’s model for the porous regions and the convection-diffusion mass transport equation are employed. Blood considered as a Newtonian fluid and the artery’s wall is assumed to be a porous rigid medium. Due to the negligible pulsatile effect of the flow on the LDL concentration، equations are solved in the steady state condition. In this paper LDL concentration across the layers is considered under normal blood pressure to examine effects of the LDL’s size and the hypertension on the LDL accumulation. Furthermore، a comparison between normal endothelium and the leaky junction is performed. Results indicate that the normal endothelium plays a crucial role in prevention LDL accumulation in the arterial wall.

In this paper, drying of the moist object is numerically investigated in the forced convection with and without the electric field. Finite volume method is used to solve governing equations of electric, flow, temperature, and the concentration fields in flow phase, as well as the temperature and the moisture fields in the moist object. In this study, the effect of applied voltage and the arrangement of the emitting electrode are evaluated. The results indicated that in presence of electric field, the increment of the applied voltage for 18 kV to 24 kV, the mass transfer from porous object 3.78 times and power consumption 7.96 times are increased. It is also found that the drying rate is increased by decreasing the distance between the emitting and collecting electrodes. According to numerical results, the mass transfer enhancement is usually accompanied by penalty of electric energy consumption. Therefore, the specific energy consumption has been evaluated as final criterion. It is shown that the specific energy consumption of the electrohydrodynamic drying process has been remarkably affected by the changing of the emitter arrangements. Finally, an optimum arrangement has been introduced as the affordable arrangement.

The atherosclerosis disease is the most prevalent illness that occurs in large or medium size arteries. The most important consequence of this disease is creation of arterial platelets in places where in addition to artery damages; the density of materials such as low density lipoprotein (LDL) is being increased. The produced platelets not only block appropriate blood delivery to downstream fibers but also in advanced stages, rubbing or tearing platelet could bring about clot and eventually heart or brain stroke. In this research, in order to review the procedure of LDLs accumulation within lumens and arterial wall, numerical simulation of LDL particles mass transport by using several layer model and diffusion coefficient depending on shear rate are used. Arteries’ walls are assumed to be porous and rigid. In this study, Navier–Stokes equations, mass transport, and Darsi have been solved by numerical methods with regarding to non-Newtonian behavior of blood in lumens and different layers of vessel’s wall. In this article, the impacts of diffusion coefficient being constant or variable, impact of non-Newtonian behavior of blood, impact of non-Newtonian behavior of plasma and impact of blood pressure on the amount of LDL accumulation in lumen and layers of carotid artery are reviewed. The results indicate that diffusion coefficient variation in arterial lumen and non-Newtonian behavior of plasma within the arterial wall could affect significantly on LDL accumulation. In addition, increasing blood pressure not only increases LDL accumulation on interface of blood and arterial wall but also increases the accumulation within arterial wall layers and consequently the artery is more susceptible to atherosclerosis development.

Permeability is one of the most effective parameters on concrete durability. Therefore, in this paper penetration of water into concrete is studied. Although most of the researchers have considered the coefficient of permeability obtained from one dimensional Darcy’s equation, in the present paper due to movement of water in all directions, two-dimensional diffusion equation which defines penetration of fluid into a porous material has been used for first time. For this purpose, cubic concrete specimens with different W/C ratios were prepared and their permeability was measured using “Cylindrical chamber” method. In this method, applied pressures and durations of water penetration were varied. The two-dimensional equation considered, was solved using Laplace and Henkel transformations and the obtained results were compared with the “Cylindrical chamber” results. Comparison of the theoretical and experimental results showed that the average respective percentage errors calculated for the estimation of wet curve, maximum penetration depth, average penetration depth and wet surface were 23.07, 13.64, 21.41 and 1.66. The coefficients of determination between pressure magnititude and duration of water penetration, considering the variables of maximum penetration depth, average penetration depth, wet surface, penetrated volume and optimum diffusion coefficients were seen to be higher than 0.95. Furthermore, no reliable correlation was observed between the optimum diffusion coefficients and the mentioned variables.