صابر یکانی مطلق

Deficiency of potable water has created many problems for human and human society, Therefore, The production of fresh water from saline water is an important issue. One of the method of production fresh water from saline water is the use of solar stills. This paper is the numerical simulation of the conventional solar stills with setting Rectangular, Triangular, Wavy barriers on the left and right walls inside the solar still. Setting barriers causes a change in the pattern of humid airflow in the solar still that it affect water productivity and convective heat transfer rate. Also, changes in the size and number of barriers cause changes it will be in the result. The continuity, momentum, energy and concentration equations are discretized by finite volume method and the results are presented as flow function and concentration and temperature contours. The simulation results show that setting wavy barriers with A=0.01(m) and N=2 at left wall and A=0.075(m) and N=5 at right wall water productivity and convective heat transfer rate can be increased by about 31% and 31.34%.

Today, the water crisis has been issued in most parts of the world and for this reason, the production of fresh and potable water is one of the most important and considerable factors to deal with endangering human health in the last few decades. Solar water stills are one of the simplest and most available tools for purifying and producing drinking water, but unfortunately, due to their low efficiency they cannot be used to produce the daily needs of water. The purpose of the research is to increase productivity and improve the performance of the traditional solar water stills by injecting nano aerosol particles and creating a magnetic field by a solenoid. To simulate the present work, the equations of continuity, momentum, energy and concentration have been solved by finite volume method and for this purpose, a numerical code in C++ language has been developed to solve the humid air flow containing magnetic nano-aerosols. The effect of the presence of magnetic nano-aerosol in the magnetic field on the humid air flow pattern inside the desalinated water and the amount of desalinated water production are investigated. The results show an increase in the amount of drinkable water production up to 238%.

In this paper, mixed convection of water-Fe3O4 magnetic nanofluid in a channel containing open cavity is studied. Buongiorno’s non-homogenous model, assuming the effect of the Brownian and thermophoresis of nanoparticles is applied for modeling of nanoparticle migration in base fluid. The Boussinesq approximation is used for free convection modeling. The governing equations are solved using finite volume method and SIMPLE algorithm, numerically. First, a comparison is made between the results of the single-phase method and the present Buongiorno’s model. Furthermore, the effect of changes in various parameters such as Reynolds number (10, 100, 300 and 600), volume fraction of nanoparticles (0.02, 0.04 and 0.06) and Richardson number (0.01, 1 and 10) on heat and nanofluid flow, have been studied in detail. The results showed that with the addition of nanoparticles, the highest increase in heat transfer occurred in the low Reynolds numbers (10.62%). Due to the dominance of thermophoresis effect, nanoparticle volume fraction is low near the hot wall. In Reynolds 10, the thermophoresis has a greater impact on the local volume fraction of nanoparticles than in high Reynolds.

In the present study, natural convection of Al2O3–water nanofluid and nano-particles local distribution inside trapezium enclosure has been investigated using non-homogenous two-phase Buongiorno’s model. The effect of the variation of trapezium enclosure inclantion angle on heat transfere, mass and momentum has been investigated. The governing equations of the problem are momentum, energy and volume fraction of nanoparticles that are solved using the finite volume method and the SIMPLE algorithm. Diffusion and convective terms are descritized using a second-order central difference and upwind schemes. The left and right walls of cavity are kept at constant temperatures Th and Tc, respectively, while the other walls are thermally insulated. Using the finite volume method and the SIMPLE algorithm, the governing equations have been discretized. Simulations have been carried out for different inclination angle( ), Rayleigh number(102≤Ra≤104) as well as particle average volume fraction (φ) ranging from 0.01 to 0.04. Results show that at low Rayleigh number for a specific particle volume fraction, with increasing the inclination angle from zero to 45 degree, the average Nusselt number (NuAve)and heat transfer decreases 81%. On the other hand, optimum results were obtained for the inclination angle of 30 degree. The Nuselt enhancement percent was obtained 5.5 compared to the square enclosure and 6.8 compared to inclination angle of 45 degrees. Results also showed a uniform distribution for nanoparticles in high Rayleigh numbers and in enclosures with different inclination angle.

Nowadays, magnetic nanofluids have drawn a lot of attention toward themselves due to various applications in different fields such as medicine and industry. In this paper, for the first time new pumping method for magnetic nanofluids and ferro-fluids is presented. Moreover, magnetic nanofluid flow inside a rectangular channel under the effect of nonuniform magnetic field of permanent magnet is investigated. Iron oxide nanoparticles which lie completely homogeneous inside the based fluid of water are used. The governing equations obtained by adding the Kelvin body force term to the Navier-Stokes equations, and the equations are discretized using finite volume method and PISO algorithm. In order to study the effective parameters in the function of the FHD micro pump, a selected ranges of nanoparticles size, volume fraction of nanoparticles, saturated magnetization, and the length and width of the magnet are studied. The results demonstrate the increase in any of the mentioned parameters leads to rise in velocity magnitude inside the channel. Change in the diameter of magnetic nanoparticles has greatest effect on the velocity magnitude inside the channel. Furthermore, vertical magnet has better performance than horizontal one in FHD micro pump.

In the present paper, three dimensional turbulent mixed convection inside the ventilated cavity is solved using by Large Eddy Simulation (LES) and the results are validated with available numerical and experimental ones. In the present work, the forced convection and free convection are due to the injected flow from ventilation system and temperature difference among floor and other walls of cavity, respectively. The effects of obstacle on flow characteristics such as velocity, temperature and turbulent kinetic energy are investigated for cavity flow containing obstacle with three different height. In continuation, effect of obstacles on coherent structures are investigated by applying the proper orthogonal decomposition (POD) algorithm on velocity fluctuation field in x direction. From the results, firstly, obstacle causes to increase the energy of coherent structures, and secondly, obstacle with large height break the coherent structures to smaller ones, but for obstacles with medium and small height dominant structures are enlarged.

In this paper, drug coated magnetic nanoparticle delivery is numerically studied. Specific part of right foot vessel connected to the abdominal aorta is considered as target tissue. Single wire is applied as magnetic source. Buongiorno’s two-phase model is modified by adding the magnetophoresis term to the volume fraction transport equation. Governing unsteady equations with ferrohydrodynamics Kelvin force as a source term is discretized with PISO based finite volume method. Effects of the location of magnetic source and magnitude of current carrying from wire (1000, 2000, 3000, 4000 and 5000 amperes) are investigated on residence time and deposition level of drug on target tissue. Diameter and volume fraction of nanoparticles are 10 nm and 0.002, respectively. From the results, location of wire should be near and upstream the target tissue. Furthermore, by using this method deposition level of drug on target tissue can be increased by 7.5 times. Best drug delivery performance is seen for current magnitude of 2000 amperes.

Equations of Large Eddy Simulation are obtained by applying low pass filter on the Navier-Stokes equations. The turbulent modeling in LES depends on the type of the filter function used. In this paper, two explicit filtering methods are compared, using a fully developed turbulent channel flow. First, it is simulated by explicit filtration method applying the smooth Laplace filter. In this case, the subfilter stress term is added to the subgrid model. Good agreements are observed in comparison with Kim's DNS results. Second, in order to consider the effects of closeness of explicit filter shape to the cut-off filter, three different filter types were used for the flow simulation. Finally, the abilities of each approach was investigated. Moreover, the regions of boundary layer being more different from each approaches are specified.