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In this article, the free and forced convectional heat transfer in a rectangular porous fin with considering pressure loss across the fin length is investigated analytically. A well-known Differential transformation method is employed to obtain the solution of energy balance equation. Convergence of obtained solution is examined by previous works and they are found to be in a good agreement. In order to simulate heat transfer through porous media, Darcy model is applied. Also convective heat transfer coefficient is assumed to be constant. Dimensionless temperature distribution is defined as a function of convection and porosity parameters. Also the effects of pressure loss across the fin length on the temperature distribution, rate of heat transfer, fin efficiency and effectiveness of fin are studied. A comparative study is also made between the porous and solid fins for an equal mass of fins. It is highlighted that the porous fin transfer always more heat at specific condition compared to the solid fin. Results show that all of thermal parameters are influenced by pressure loss parameter. So in order to reach to high fin efficiency, pressure loss across the fin length should be controlled.

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In this work growth and characterization of potassium chloride with nanodiamond is studied. Crystals were grown in Czochralski crystal growth method. KCl crystals are doped with 0.5, 1 and 1.5 percent nanodiamond (ND) impurities. Breaking cross sections of the pure and doped crystals were characterized by (scanning electron microscopy) SEM. As a result, increasing the doping percentage of the ND in the KCl crystal, leads to arising the surface roughness and nicks curvature on the fracture cross section of the crystal. It means that ND doping inside KCl crystal caused to increase mechanical hardness of the crystal and increasing the doping percentage results more mechanical resisting crystal. On the other hand, Vickers microhardness scale is used in this study. Hardness is too complex to be described by first principles. Based on the dielectric chemical bond theory, a semiempirical theoretical formulation of the hardness of pure and doped crystals is introduced. Analyzing of the results shows increasing of the nanodiamond doping leads to increasing of mechanical resistance of the samples.

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Jet injected transversely into a crossflow is used to the propulsion system such as, turbo jet engines, ram jet and scram jet engines and cooling of combustion chamber. Earliest research of a jet in a crossflow has been motivated by applications related to environmental problems such as plume dispersal from exhaust but gradually its application increased. In comparison to co-axial injection, transversely injection have a better efficiency. Difference in direction of injection helped to forming the smaller particles indeed, increases the combustion chamber performance. In this paper, effective factors on liquid jet trajectory and breakup are studied. Effect of nozzle geometry, Weber number and moment ratio of liquid jet to the air crossflow are investigated and equation of trajectory for elliptical and circular nozzle is obtained. In addition, length and height of breakup point are obtained and Show that the elliptical and circular liquid jet trajectory have different together. Also the breakup height equation has investigated and comparison to other study. These results are very important for designing of combustion chamber. The results compared to other researchers, the results shows, answers have a good compatibility and accuracy, and they are reliable and trustworthy.

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In this study, the analysis of heat transfer in porous fin considering thermal radiation and natural convection is investigated. In order to model radiation, discrete ordinates method is used. Also, Darcy–Brinkman–Forchheimer model is applied for simulating porous media. A Least square method and numerical simulation (computational fluid dynamics) are applied to obtain the solution of governing equations. In addition, accuracy of LSM results is compared with the numerical simulation results. Moreover, the effects of homogeneous and non-homogeneous porosity along the porous media, Rayleigh number, Darcy number, porosity, surface emissivity, on temperature distribution along the length of porous fin and Nusselt number are investigated. Results show that the numerical simulation and LSM results are in good agreement with each other (With average error of 3.39%). Also neglecting thermal radiation effect in heat transfer analysis of porous fin leads to 10- 20% error in the Nusselt number value. Moreover, by applying nonlinear variable porosity along the porous media, the Nusselt number will increase up to 23% with respect to the homogeneous porosity. So in order to enhance heat transfer rate, porosity profile should be applied appropriately along the porous media.

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The statics of droplet hanging from the parallel fibers and the dynamics of droplet impact on the parallel fibers are investigated using high-speed imaging and volume of fluid numerical simulation. Experimental results show for the parallel fibers, the maximum volume of the droplet, which is able to hang statically from the fibers is measured to vary between 1.85 to 1.9 times of the one measured for a single fiber. The dynamics of droplet impact have been studied by varying the radius of the impacting droplet, the fibers radius, and the distance between the fibers. The threshold velocity of droplets by fibers has been obtained both experimentally and numerically with the fluid volume method. The results show that by increasing the impacting droplet radius and decreasing the fibers radius, the threshold velocity of droplet capture decreases. The maximum threshold velocity of droplet capture with parallel fibers varies in the range of 1.5 to 1.8 times of the threshold velocity of capture with a single fiber. The maximum threshold capture velocity of droplets occurs where the distance between fibers is in the range of 0.35 to 0.5 times of impacting droplet diameter. The threshold capture velocity on parallel fibers is also obtained analytically, using the energy balance method. The results of the analytical solution are in a fair agreement with experimental data and numerical simulation results.