Heat transfer process and fluid flow in a solar chimney used for natural ventilation are investigated numerically in the present work. Solar chimney was tested by selecting different positions of absorber namely: at the back side, front side, and at the middle of the air gap. CFD analysis based on finite volume method is used to predict the thermal performance, and air flow in two dimensional solar chimney under unsteady state condition, to identify the effect of different parameters such as solar radiation. Results show that a solar chimney with absorber at the middle of the air gap gives better ventilation performance. A comparison between the numerical and previous experimental results shows fair agreement.
In this work, A new strategy for enhancing the efficiency of dye sensitized solar cells (DSSC) by doping foreign ion and co- doping TiO2 / Fe and Cu (38 nm ) was prepared by sol-gel method and successfully used as a photoanode for (DSSC). The samples were characterized by using X-ray diffraction ( XRD) is used to calculate grain size, before and after Fe, Cu- doping and co- doping. Glass coating process with a thin layer on (Fluorine doped tin oxide) FTO glass by using doctor Blade technique .The optimum thickness utilized for TiO2 paste is (15μm) on a conductive glass. The best experimental results for doping and co- doping TiO2 with additive Copper (II) nitrate Cu (NO3)2 as improved it was VOC=0.6 V, ISC=1.92 mA, Imax=1.8 mA and Vmax=
... Show MoreAnalyzing the impacts of Cattaneo-Christov flux, bioconvective Raleigh number and cross diffusion effects in electrically conducting micropolar fluid through a paraboloid revolution is assessed in this work. Non-dimensional equations are solved numerically using shooting technique with an aid of Matlab software. The impact of various parameters on velocity, temperature and concentration are discussed in detail and presented graphically. Harman number and micro rotation parameters are found and have an increasing influence on shear stress. The vertical velocity increases at free stream and the horizontal velocity increases near the surface when Grb increases, which follows the opposite trend for accumulation of Rb. T
... Show MoreThis research aims to find how three different types of mouthwashes affect the depth of artificial white spot lesions. Teeth with various depths of white spot lesions were immersed in either splat mouthwash, Biorepair mouthwash, Sensodyne mouthwash, or artificial saliva (control)twice daily for one minute for 4 weeks and 8 weeks at 37°C. After this immersion procedure, lesion depth was measured using a diagnosed pen score. A one-way analysis of variance, Dunnett T3 and Tukey's post hoc α = .05 were used to analyze the testing data. Splat mouthwash enhanced the WSL remineralization and made the lowest ΔF compared with other mouthwashes in shallow and deep enamel after 4 and 8 weeks of treatment. In the repair groups, after 4 weeks
... Show MoreIn this paper, Pentacene based-organic field effect transistors (OFETs) by using different layers (monolayer, bilayer and trilayer) for three different gate insulators (ZrO2, PVA and CYEPL) were studied its current–voltage (I-V) characteristics by using the gradual-channel approximation model. The device exhibits a typical output curve of a field-effect transistor (FET). Source-drain voltage (Vds) was also investigated to study the effects of gate dielectric on electrical performance for OFET. The effect of capacitancesemiconductor in performance OFETs was considered. The values of current and transconductance which calculated using MATLAB simulation. It exhibited a value of current increase with increasing source-drain voltage.
The absorption spectrum for three types of metal ions in different concentrations has been studying experimentally and theoretically. The examination model is by Gaius model in order to find the best fitting curve and the equation controlled with this behavior. The three metal ions are (Copper chloride Cu+2, Iron chloride Fe+3, and Cobalt chloride Co+2) with different concentrations (10-4, 10-5, 10-6, 10-7) gm/m3. The spectroscopic study included UV-visible and fluorescence spectrum for all different concentrations sample. The results refer to several peaks that appear from the absorption spectrum in the high concentration of all metal ions solution.
... Show MoreThree-dimensional cavity was investigated numerical in the current study filled with porous medium from a saturated fluid. The problem configuration consists of two insulated bottom and right wall and left vertical wall maintained at constant temperatures at variable locations, using two discretized heaters. The porous cavity fluid motion was represented by the momentum equation generalized model. The present investigation thermophysical parameters included the local thermal equilibrium condition. The isotherms and streamlines was used to examine energy transport and momentum. The meaning of changing parameters on the established average Nusselt number, temperature and velocity distribution are highlighted and discussed.
The corrosion inhibition of low carbon steel in1N HCl solution in the presence of peach juice at temperature (30,40,50,and 60)°C at concentration ( 5, 10, 20, 30, 40and 50 cm3/L)were studied using weight loss and polarization techniques. Results show that the inhibition efficiency was increased with the increase of inhibitor concentration and increased with the increase of temperature up to 50ºC ,above 50ºC (i.e. at 60 ºC) the values of efficiency decreases. Activation parameters of the corrosion process such as activation energies, Ea, activation enthalpies, ΔH, and activation entropies, ΔS, were calculated. The adsorption of inhibitor follows Langmuir isotherm. Maximum inhibition efficiency obtained was a bout 91% at 50ºC in the
... Show MoreThe ulma is one of the most spread social phenomenon.It occupies people in their different tendencies,the ulma imposes itself strongly in their social ,economic and politic sidies.
The problem of freedom quarrel is the older problem in creation .The groups as well as the individuals look for their liberty and it is restricted, they isolate themselves from others for a achieving it. Isolation phenomenon is one of common humanity phenomenon among individuals for looking of individuals psychological and social compatibility with other and society so they feel anxiety and tension and restriction of will and freedom. IT is known that college student from the major never in development and ren
... Show MorePraise be to God, Lord of the worlds, and prayers and peace be upon our master Muhammad and his family and companions until the Day of Judgment.
The words of God Almighty are for the sake of the greatest and greatest speech, and the scholars, may God have mercy on them, raced.
To dive into knowing the word of God and what he intended, so they wrote in it the literature and collected works in it, and explained it to those after them.
And when the noble companions, were extremely eloquent and eloquent, because the Holy Qur’an was revealed in the language of the Quraysh, and all the Arabs knew their language, they understood the Holy Qur’an and applied it p
In this study, pebble bed as an absorber and storage material was placed in a south facing, flat plate air-type solar collector at fixed tilt angle of (45°). The effect of this material and differ- ent parameters on collector efficiency has been investigated experimentally and
theoretically. Two operation modes were employed to study the performance of the solar air heater. An inte- grated mode of continuous operation of the system during the period of (11:00 am – 3:00 pm) and non-integrated mode in which the system stored the solar energy through the day then used the stored energy during the period of (3:00 pm – 8:00 pm). The results of parametric study in case of continuous operating showed that the maximum average temperatur