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71.
Improvement in the cooling system performance by making the temperature distribution uniform is an essential part in design of polymer electrolyte membrane fuel cells. In this paper, we proposed to use water-CuO nanofluid as the coolant fluid and to fill the flow field in the cooling plates of the fuel cell stack by metal foam. We numerically investigated the effect of using nanofluid at different porosities, pore sizes, and thicknesses of metal foam, on the thermal performance of polymer electrolyte membrane fuel cell. The accuracy of present computations is increased by applying a three-dimensional modeling based on finite-volume method, a variable thermal heat flux as the thermal boundary condition, and a two-phase approach to obtain the distribution of nanoparticles volume fraction. The obtained results indicated that at low Reynolds numbers, the role of nanoparticles in improvement of temperature uniformity is more dominant. Moreover, metal foam can reduce the maximum temperature for about 16.5 K and make the temperature distribution uniform in the cooling channel, whereas increase in the pressure drop is not considerable. 相似文献
72.
Fluid flow manifold plays a significant role in the performance of a fuel cell stack because it affects the pressure drop, reactants distribution uniformity and flow losses, significantly. In this study, the flow distribution and the pressure drop in the gas channels including the inlet and outlet manifolds, with U- and Z-type arrangements, of a 10-cell PEM fuel cell stack are analyzed at anode and cathode sides and the effects of inlet reactant stoichiometry and manifold hydraulic diameter on the pressure drop are investigated. Furthermore, the effect of relative humidity of oxidants on the pressure drop of cathode are investigated. The results indicate that increase of the manifold hydraulic diameter leads to decrease of the pressure drop and a more uniform flow distribution at the cathode side when air is used as oxidant while utilization of humidified oxidant results in increase of pressure drop. It is demonstrated that for the inlet stoichiometry of 2 and U type manifold arrangement when the relative humidity increases from 25% to 75%, the pressure drop increases by 60.12% and 116.14% for oxygen and air, respectively. It is concluded that there is not a significant difference in pressure drop of U- and Z-type arrangements when oxygen is used as oxidant. When air is used as oxidant, the effect of manifold type arrangement is more significant than other cases, and increase of the stoichiometry ratio from 1.25 to 2.5 leads to increase of pressure drop by 527.3%. 相似文献
73.
Meera Mahadevan Sangyool Lee Serguei V. Dessiatoun Michael Ohadi Ebrahim Al Hajri Kyu Yong Choi 《化学工程与技术》2016,39(2):293-300
The feasibility of using a microtubular reactor for heterogeneous polymerization of ethylene was investigated experimentally. Chemically inert polymer tubing of 800–2300 μm in inner diameter was fabricated and used as a polymerization reactor. Nonporous silica nanoparticles with a diameter of 400 nm were synthesized and used as support for the high‐activity rac‐ethylene(indenyl)2ZrCl2 catalyst with methylaluminoxane as cocatalyst and toluene as diluent. Large‐diameter microtubular reactors were also successfully used to conduct heterogeneous polymerization of ethylene in continuous reaction operations. High initial catalyst activity was obtained and the overall polymerization activity per volume or reactor length was quite high. No particle fragmentation occurred and the polymer particles were covered with small subgrains or nanofibrils with a diameter of 30 nm. 相似文献
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76.
Asghari Kaljahi Ebrahim Amini Birami Farideh 《Bulletin of Engineering Geology and the Environment》2015,74(3):959-969
Bulletin of Engineering Geology and the Environment - Kandovan is one of the geo-tourism attractions in the East Azarbaijan Province of Iran, where rural houses were carved within the cone-shaped... 相似文献
77.
Kaveh Mohammad Amiri Chayjan Reza Taghinezhad Ebrahim Abbaspour Gilandeh Yousef Younesi Abdollah Rasooli Sharabiani Vali 《Engineering with Computers》2019,35(3):1045-1058
Engineering with Computers - In this paper, multi-stage continuous belt (MSCB) dryer was used for carrot slices drying. Experiments were performed at three air speeds (1, 1.5, and 2 m/s)... 相似文献
78.
Abbas Roozbahani Ebrahim Ebrahimi Mohammad Ebrahim Banihabib 《Water Resources Management》2018,32(15):4985-5005
Groundwater resources are steadily subjected to increasing water demands. The aquifers are considered as the most accessible source of fresh water. In recent years, they have been faced with severe water withdrawal in arid and semi-arid countries like Iran and thus some aquifers was considered as forbidden aquifers that it means the water withdrawal from these aquifers is unauthorized. Given a critical situation, groundwater resources management in the form of tools such as monitoring the level of the aquifers and developing the restoring scenarios is essential. Therefore, for this purpose, a framework has been developed based on prediction of groundwater level using Bayesian Networks (BNs) model. Furthermore, Multi Criteria Decision Making methods (MCDM) techniques proposed and employed for ranking of proposed groundwater management scenarios. This framework was evaluated for restoring the Birjand aquifer in Iran in different hydrological conditions. A probabilistic Dynamic BN was proposed for groundwater level prediction under uncertainties. After analyzing the obtained results, the applicable short term scenarios for groundwater management as well as appropriate economic, social and technical criteria were defined for decision making procedure. Then, using elicitation of decision makers’ opinions on the relative importance and performance of criteria, SAW, TOPSIS and PROMETHEE-II techniques were applied to rank the scenarios and the obtained results were aggregated by Borda method for final ranking of the scenarios. Lastly, the final results demonstrates the capability of the proposed framework for groundwater resources planning and management which can be employed for reducing the risk of aquifer level declining. 相似文献
79.
Nasrollah Najibi Ilkhechi Amin Ranjbar Aghjehkohal Ebrahim Feyzi TanourAghaj Mahdi Mozammel 《Journal of Materials Science: Materials in Electronics》2017,28(6):4598-4605
In this study, preparation of Si and Cd co doped (5 mol% Si and 5–20 mol% Cd) TiO2 dip-coated thin films on glass substrates via sol–gel process have been investigated. The samples were characterized by X-ray diffraction (XRD) and Scanning electron microscopy analysis after heat treatments. XRD results suggested that adding dopants has a great effect on crystallinity and particle size of TiO2. Titania rutile phase formation was inhibited by Si4+ and promoted by Cd2+ doping. But the effect of Cd doped appeared at high concentration. Accordingly, the thin films showed various water contact angles. The water contact angles changed from 69.0° to 9.6° by changing the content of Cd doped. 相似文献
80.
Zeyad Ghaleb Al-Mekhlafi Ebrahim Mohammed Senan Taha H. Rassem Badiea Abdulkarem Mohammed Nasrin M. Makbol Adwan Alownie Alanazi Tariq S. Almurayziq Fuad A. Ghaleb 《计算机、材料和连续体(英文)》2022,72(1):775-796
Stroke and cerebral haemorrhage are the second leading causes of death in the world after ischaemic heart disease. In this work, a dataset containing medical, physiological and environmental tests for stroke was used to evaluate the efficacy of machine learning, deep learning and a hybrid technique between deep learning and machine learning on the Magnetic Resonance Imaging (MRI) dataset for cerebral haemorrhage. In the first dataset (medical records), two features, namely, diabetes and obesity, were created on the basis of the values of the corresponding features. The t-Distributed Stochastic Neighbour Embedding algorithm was applied to represent the high-dimensional dataset in a low-dimensional data space. Meanwhile,the Recursive Feature Elimination algorithm (RFE) was applied to rank the features according to priority and their correlation to the target feature and to remove the unimportant features. The features are fed into the various classification algorithms, namely, Support Vector Machine (SVM), K Nearest Neighbours (KNN), Decision Tree, Random Forest, and Multilayer Perceptron. All algorithms achieved superior results. The Random Forest algorithm achieved the best performance amongst the algorithms; it reached an overall accuracy of 99%. This algorithm classified stroke cases with Precision, Recall and F1 score of 98%, 100% and 99%, respectively. In the second dataset, the MRI image dataset was evaluated by using the AlexNet model and AlexNet + SVM hybrid technique. The hybrid model AlexNet + SVM performed is better than the AlexNet model; it reached accuracy, sensitivity, specificity and Area Under the Curve (AUC) of 99.9%, 100%, 99.80% and 99.86%, respectively. 相似文献