A molecular dynamics simulation study is employed to investigate the elastic and basic thermal properties of thermoset polymer based nanocomposite sample reinforced by CNT. The COMPASS force filed was used to construct the simulation box. The simulation box contains the cured epoxy resin molecules obtained from cross linking process of DGEBA and DETA which were located around the CNT (10,10). NVT and NPT ensembles were performed to equilibrate the system and convergence of temperature, energy and density have been checked. The elastic constants of molecular sample of nanocomposite were determined based on stiffness matrix and compared with the molecular results of pure resin. The results show that the Young's modulus in the transverse direction of nanocomposite model is less than that in longitudinal direction indicating the transversely isotropic behaviour at atomic scale. Glass transition temperature (Tg) and coefficient of thermal expansion (CTE) were calculated through the linear fitting of density-temperature diagram for the CNT-reinforced nanocomposite model. Atomistic simulation results showed decrease in Tg and CTE comparing to the pure epoxy. Moreover, the simulation results were compared with the measured values and good agreements are observed. پرونده مقاله

در تحقیق حاضر در مورد اثرات ارتفاع دندانه در میکروکانال دندانه‌دار دو بعدی، بر روی پارامترهای انتقال حرارت و دینامیک سیالات محاسباتی جریان آرام نانوسیال آب-اکسید آلومینیم است. بررسی‌های این تحقیق به صورت عددی با نرم افزار تجاری فلوئنت3/6 برای اعداد رینولدز10 و 100، برای چهار حالت مختلف ارتفاع دندانه انجام شده است. افزایش ارتفاع دندانه‌های داخلی یا مغشوشگرهای جریان، عملکرد انتقال حرارت جابجایی در میکروکانال را به میزان قابل توجهی افزایش می‌دهد. مشاهده می‌شود که نرخ انتقال حرارت در میکروکانال با افزایش ارتفاع دندانه و افزایش کسر حجمی نانو ذرات، بهبود می‌یابد. اما افزایش ارتفاع دندانه، باعث افزایش ضریب اصطکاک بزرگ‌تر در مقایسه با میکروکانال با ارتفاع دندانه ثابت است. در این تحقیق برای همه حالات مختلف ارتفاع دندانه، تأثیر ارتفاع دندانه بر روی پارامترهای جریان سیال بررسی شده است. نتایج در قالب پروفیل‌های سرعت و دما، عدد ناسلت و کانتورهای تابع جریان و خطوط هم دما ترسیم می-شوند...... پرونده مقاله

In this numerical study the the heat transfer and laminar nanofluid flow in the three-dimensional microchannels with triangular cross-section is simulated. For increase the heat transfer from the walls of the channel, semiattached & offset mid- truncated rib,s Placed in the canal, and the tooth geometry and the impact is studied. In this study, the water is base fluid, and the influence of the volume fraction of nanoparticles of titanium oxide on the the heat transfer and the fluid flow physics is studied. The presented results include the distribution of Nusselt number in the channel, The coefficient of friction and the thermal-fluid performance for each of the different states. The results show the existence of is the tooth on the effective flow physics. And their efficacy is highly dependent on Reynolds number. Use indentation in the microchannels, increase the heat transfer rate and the reduce the temperature gradient between the layers of the cooling fluid. Also, the presence of nanoparticles in the fluid cooling is effective and the pain increase the heat transfer by increasing the Reynolds number, the effect of nanoparticles also increase the heat transfer increases. پرونده مقاله

This work presents a model for calculating the effective ‎thermal conductivity of nanofluids. The proposed model ‎includes the effects of nanoparticles and thermal conductivity ‎base fluid.We will focus on experimental of the volume ‎concentration parameter and temperature on thermal ‎conductivity, nano-fluid combination and Multi-Walled ‎Carbon nanotubes-Oxide / Copper-paid deionized Water. This ‎water-based nanofluids, For two-step volume fractions of the ‎‎0.1, 0.2, 0.6 Percentage produced And then, Effective thermal ‎conductivity is measured precisely. In order to measure the ‎thermal conductivity of nanofluids. To measure the thermal ‎conductivity coefficient in THW method, KD2-pro and KS1 ‎probe was used, also with the fluid significantly enhancement ‎shows in thermal conductivity coefficient. Also with the fluid ‎significantly enhancement shows in thermal conductivity ‎coefficient. In lower volume fractions we observed ‎significantly increase in thermal conductivity and receive high ‎degree thermal. Due to the lack of similar studies Due to the ‎lack of similar studies to comprehensively and inefficient of ‎classical thermal conductivity, In order to estimate the thermal ‎conductivity of nanofluids An empirical model that estimates ‎the thermal conductivity of nanofluids model with deviation ‎margin is very low پرونده مقاله

In this paper, a multi-objective optimization method is implemented by using of genetic algorithm techniques in order to determine optimum configuration of solar chimney power plant. The objective function which is simultaneously considered in the analysis is output power of the plant. Output power of the system is maximized. Design parameters of the considered plant include collector radius (Rc), collector height (Hc), chimney height (Ht), chimney radius (Rt) and heat flux ( ). The multi-objective optimization results show that there are a strong positive correlation between the chimney height and the output power, as well as a negative correlation between the solar collector radius and the output power. Also, it was concluded that, output power of the plant could be considerably increased with increasing solar chimney height while increasing collector radius could slightly reduce output power This study may be useful for the preliminary estimation of power plant performance and the power-regulating strategy option for solar chimney turbines. پرونده مقاله

In this study, the electrochemical and hydrodynamic characteristics of a PEM fuel cell are investigated using an agglomerate model. Modeling is single-phase, two-dimensional, incompressible and steady-state. In this study, current density, water distribution and gas velocity inside the anode and cathode gas diffusion layers are obtained. This study using the present agglomerate model can provide a good prediction of the current density. The results show that the highest current density occurs in the areas of the interface between current collectors and gas diffusion layers. In addition, in the sharp areas, where the interface is between the current collectors and the gas diffusion layers, there is the highest flow velocity. In these areas, values of velocity gradients that can affect cell performance. Therefore, in order to achieve better performance, it is necessary to design different flow channels and gas diffusion layers and compare them with each other. The amount of water in the gas diffusion layer should be controlled so as not to reduce the chemical reaction on the cathode side. پرونده مقاله

Using the lattice Boltzmann technique, the mixed convection of nanofluid inside an inclined trapezoidal cavity in the presence of a multidirectional magnetic field is investigated. The sides of the trapezoidal hollow are adiabatic, with the upper moveable wall being cold and the lower wall being sinusoidally heated. In simulations, the temperature and flow distribution functions are utilized to determine all parameters related to the temperature and flow fields. On the hot wall, the effects of various Rayleigh numbers (Ra = 103, 104, and 105), inclined cavity angles (θ= 0°-90°), volume fractions of nanoparticles (ϕ== 0-3 percent), magnetic field intensity (Ha = 0-100), and applied magnetic field angle (= 0°-90°) were studied. According to the research, raising the Rayleigh number enhances heat transfer. Moreover, when all other parameters are held equal, raising the nanoparticle volume fraction enhances the average Nusselt number. Increasing the Hartmann number reduces the flow velocity inside the cavity, hence reducing heat transmission. Changes in the cavity's slope and the angle of the applied magnetic field have an effect on the flow and heat transfer as well. پرونده مقاله