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Tehran, Iran

Heidary H.,Mapna Group | Kermani M.J.,Amirkabir University of Technology
International Communications in Heat and Mass Transfer | Year: 2012

In this paper heat transfer and flow field analysis in a wavy channel linked to a porous Gas Diffusion Layer (GDL) is numerically studied. The domain is very similar to our earlier computations of proton exchange membrane fuel cells (see Khakbaz-Baboli and Kermani (2008)). The fluid temperature at the channel inlet (T in) is taken less than that of the walls (T w). The governing equations are numerically solved in the domain by the control volume approach based on the SIMPLE technique (1972). A wide spectrum of numerical studies is performed over a range of Reynolds number Re H: 100≤Re H≤1000, wave number β: 0≤β≤10, the wave amplitude α: 0≤α≤0.3 and Darcy number Da: 0.1≤Da≤0.001. Simulations show that heat transfer in channels can enhance up to 100%, depending on the duct α, β and flow Re H. Computations show excellent agreement with the literature. The present work can provide helpful guidelines to the manufactures of the compact heat exchangers. © 2011 Elsevier Ltd. Source


Heidary H.,Mapna Group | Kermani M.J.,Amirkabir University of Technology
International Journal of Thermal Sciences | Year: 2012

In this study heat transfer and fluid flow analysis in a channel with blocks attached to bottom wall and utilizing Nano-fluid is numerically studied. The fluid temperature at the channel inlet (T in) is taken less than that of the walls (T w). The governing equations are numerically solved in the domain by the control volume approach based on the SIMPLE technique. A wide spectrum of numerical simulations has been done over a range of Reynolds number, Nano-fluid volume fraction and the block number. The influence of these parameters is investigated on the local and average Nusselt numbers. From this study, it is concluded that heat transfer in channels can enhance by addition of Nano-particles, and usage of block on hot walls. Simulations show that heat transfer in channels can enhance up to 60% due to the presence of nano-particles and the blocks in channels, but there exist a saturated number of blocks, beyond which, the average Nu do not increase. The present work can provide helpful guidelines to the manufactures of the compact heat exchangers. © 2012 Elsevier Ltd. All rights reserved. Source


Heidary H.,Mapna Group | Kermani M.J.,Amirkabir University of Technology
International Journal of Hydrogen Energy | Year: 2013

In this paper, a method called "bipolar plate duct indentation" is introduced, in which some partial blocks (indents) are recommended to be placed along the fluid delivery channels being machined in bipolar plates (BPPs) of fuel cells (FCs). The indents are to enhance the over-rib convections and the kinetics of reactions in catalyst layers to improve the cell performance. As an initial step to numerically model this problem, a partially porous channel of BPP of a Direct Methanol FC (DMFC) is taken as the model geometry, and the level of heat exchange enhancement due to channel indentation is examined in this geometry. The performed parametric studies show that channel indentation enhances the heat exchange by 40%; with some minor increases in fluid delivery pumping power. From the analogy between the heat and mass transfer problems in dynamically similar problems, it is believed that the mass exchanges between the core channel and the catalyst layer in FC will enhance the same order as that in the pure heat transfer problem. The present work provides helpful guidelines to the bipolar plate manufactures of low-temperature FCs to considerably alleviate the losses on the side(s) of slow reaction electrodes. Crown Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Source


Heidary H.,Mapna Group | Kermani M.J.,Amirkabir University of Technology | Kermani M.J.,Head of Energy Conversion Research Laboratory
International Communications in Heat and Mass Transfer | Year: 2010

In this paper heat transfer and flow field in a wavy channel with nano-fluid is numerically studied. The temperature of input fluid (T c) is taken less than that of the wavy horizontal walls (T w). The governing equations are numerically solved in the domain by the control volume approach based on the SIMPLE technique. Copper-water nano-fluid is considered for simulation. A wide spectrum of numerical simulations has been done over a range of Reynolds number, Re H, 5≤Re H≤1500, nano-fluid volume fraction, Φ, 0≤φ≤20% and the wave amplitude, α, 0≤α≤0.3. The effects of these parameters are investigated on the local and average Nusselt numbers and the skin friction coefficient. Simulations show excellent agreement with the literature. From this study, it is concluded that heat transfer in channels can enhance by addition of nano-particles, and usage of wavy horizontal walls. These can enhance the heat transfer by 50%. The present work can provide helpful guidelines to the manufacturers of the compact heat exchangers. © 2010 Elsevier Ltd. Source


Baghaee H.R.,Amirkabir University of Technology | Baghaee H.R.,Mapna Group | Abedi M.,Amirkabir University of Technology
International Journal of Electrical Power and Energy Systems | Year: 2011

Contingency screening and ranking is one of the most important issues for security assessment in the field of power system operation. The objective of contingency ranking is to quickly and accurately select a short list of critical contingencies from a large list of potential contingencies and rank them according to their severity. Then suitable preventive actions can be implemented considering these contingencies that are likely to affect the power system performance. In this paper a novel approach is presented for contingency ranking based on static security assessment. This method employs weighted performance index with the application of fuzzy logic based analytical hierarchy process in order to select appropriate weighting factors to be imposed. The proposed method is applied to IEEE 30 bus system and the results are presented. © 2011 Elsevier Ltd. All rights reserved. Source

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