Hamidreza Sadeghifar

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Keywords: Nusselt number Heat transfer coefficient Laminar Parallel cylinders Rectangular array Unequal cylinder temperatures a b s t r a c t Axial flows over cylinders are frequently encountered in practice, e.g. in tubular heat exchangers and reactors. Using the Integral method, closed-form relationships are developed for heat transfer coefficients or(More)
h i g h l i g h t s g r a p h i c a l a b s t r a c t An analytic robust model is developed for estimating GDL thermal conductivity. The model considers PTFE addition to the GDL. Thermal conductivity of MPL is accurately measured in a compression range of 2e14 bar. Effect of thermal conductivity on PTFE, MPL, and compression is considered. Thermal contact(More)
h i g h l i g h t s g r a p h i c a l a b s t r a c t < A statistical model is developed for estimating GDL thermal conductivity. < The model considers the statistical distribution of GDL geometrical parameters. < Angle and aspect ratio distributions are measured for some GDLs. < The dependency of thermal conductivity on geometrical parameters is(More)
h i g h l i g h t s g r a p h i c a l a b s t r a c t Optical images show that GDL fibers are wavy and not straight. Thermal contact resistance (TCR) decreases with fiber wavelength. TCR increases with curvature, diameter and amplitude of fiber and GDL porosity. TCR does not change with fiber length. TCR variations with geometric parameters are higher at(More)
little attention has been paid to the geometrical parameters of Gas Diffusion Layers (GDLs), as many researchers have reported the GDL transport properties, like thermal conductivity, as a function of only one parameter; porosity. In this paper, a statistical unit cell approach is presented for estimation of the thermal conductivity on the basis of measured(More)
h i g h l i g h t s g r a p h i c a l a b s t r a c t Thermal conductivity of graphite bi-polar plates (BPP) decreases with temperature. Thermal Contact resistance (TCR) between BPP and GDLs decreases with compression. GDL-BPP TCR increases with MPL and PTFE, regardless of the PTFE loading. High PTFE loading, MPL, and BPP out-of-flatness increase the TCR(More)
Porosity Micro porous layer (MPL) Gas diffusion layer (GDL) Fuel cells a b s t r a c t The present study reveals that the conventional notion that thermal contact resistance increases with porosity does not necessary hold. It is proved through a mechanistic robust model that, under specific circumstances, the porosities of two contacting bodies attain a(More)
To solve nonlinear equations by an optimization method, scaling is very important. Two types of poor scaling where: (a) the variables differ greatly in magnitude ; (b) the merit function of system is highly sensitive to small changes in certain variables and relatively insensitive to changes in other variables. If poor scaling is ignored, the algorithm may(More)
Through-plane thermal conductivity of 14 SIGRACET gas diffusion layers (GDLs), including series 24 & 34, as well as 25 & 35, are measured under different compressive pressures, ranging from 2 to 14 bar, at the temperature of around 60 ͦ C. The effect of compression, PTFE loadings, and micro porous layer (MPL) on thermal conductivity of the GDLs and their(More)
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