Gas Flow Research Papers - Academia.edu (original) (raw)

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We have developed a modified physical vapor transport (M-PVT) growth technique for the preparation of SiC single crystals which makes use of an additional gas pipe in order to control the gas phase composition of the conventional physical... more

We have developed a modified physical vapor transport (M-PVT) growth technique for the preparation of SiC single crystals which makes use of an additional gas pipe in order to control the gas phase composition of the conventional physical vapor transport (PVT) configuration. We discuss ...

Transparent conducting ZnO:F was deposited as thin films on soda lime glass substrates by atmospheric pressure chemical vapor deposition (CVD) deposition at substrate temperatures of 480–500 °C. The precursors diethylzinc,... more

Transparent conducting ZnO:F was deposited as thin films on soda lime glass substrates by atmospheric pressure chemical vapor deposition (CVD) deposition at substrate temperatures of 480–500 °C. The precursors diethylzinc, tetramethylethylenediamine and benzoyl fluoride were dissolved in xylene. The solution was nebulized ultrasonically and then flash vaporized by a carrier gas of nitrogen preheated to 150 °C. Ethanol was vaporized separately, and these vapors were then mixed to form a homogeneous vapor mixture. Good reproducibility was achieved using this new CVD method. Uniform thicknesses were obtained by moving the heated glass substrates through the deposition zone. The best electrical and optical properties were obtained when the precursor solution was aged for more than a week before use. The films were polycrystalline and highly oriented with the c-axis perpendicular to the substrate. The electrical resistivity of the films was as low as 5 × 10−4 Ωcm. The mobility was about ...

In this work an experimental study is carried out to determine the thermo-hydraulic performance of an intercooler (IC) with flat tubes provided with triangular plain internal fins and louvered external fins when it is used on a car... more

In this work an experimental study is carried out to determine the thermo-hydraulic performance of an intercooler (IC) with flat tubes provided with triangular plain internal fins and louvered external fins when it is used on a car equipped with a low pressure EGR. The main unknowns to be answered are the thermo-hydraulic characteristics of the IC working under humid conditions induced by EGR, the conditions under which the water content in the mixture of air and exhaust gases begins to condense and the conditions under which the condensed water will be retained inside the IC. The exhaust gases are here replaced by a mixture of dry air and water vapour which are mixed upstream of the IC. The IC is submitted at the following testing conditions: on the ambient air side, the air temperature is fixed at around 20°C and the air velocity is settled at 1, 2 and 4ms−1; on the exhaust gases side, the supply temperature was varied between 90 and 150°C, with dry gas flow rates of 20, 50 and 100gs−1, and water contents varying between almost 0 and 0.09kgwkgg−1. At these conditions the IC transfers between 1 and 13kW with overall heat transfer conductance varying between 0.05 and 0.38kWK−1 and effectivenesses between 0.3 and 0.97. A water accumulation inside the IC was detected for the tests carried out at low dry gas flow rate of 20gs−1 and for all the water content explored here (higher than 0.02kgwkgg−1).

The cyclone-type separator with swirling baffle and bottom take off of clean gas is a patented technique for separating solid particles from gases. Main relative dimensions of the separator are the same as given by Stairmand [C.J.... more

The cyclone-type separator with swirling baffle and bottom take off of clean gas is a patented technique for separating solid particles from gases. Main relative dimensions of the separator are the same as given by Stairmand [C.J. Stairmand, The design and performance of cyclone separators, Trans. Inst. Chem. Eng. 29 (1951), 356–383] for the high efficiency cyclone. The principal part of the construction is the cylinder-shape swirling baffle with the flow gaps cut on its surface. The article presents the theoretical model of the new construction of cyclone-type separator with swirling baffle and bottom take off of clean gas. Calculational model to predict the collection efficiency was based on Leith and Licht cyclone calculational method [D. Leith, W. Licht, The collection efficiency of cyclone-type particle collectors — a new theoretical approach, AIChE Symp. Ser. 68 (126) (1972), 196–206]. The main assumption of the developed model is that the tangential velocity distribution is o...

A 3D numerical study was carried out to analyze flow, heat and mass transfer first in a single half-cell cathode channel of proton exchange membrane (PEM) fuel cell. From practical point of view, it is necessary to put the appropriate... more

A 3D numerical study was carried out to analyze flow, heat and mass transfer first in a single half-cell cathode channel of proton exchange membrane (PEM) fuel cell. From practical point of view, it is necessary to put the appropriate number of cells in a stack. Hence, the above study on a single half-cell is extended to a stack of channels. Due to stacking, the assumption of uniform flow distribution would no longer hold true. Therefore, the channel flow-maldistribution is considered. The water formed at the active surface due to the electrochemical reaction diffuses through the porous layer and eventually enters the gas flow duct. The higher gas velocities in the duct result in faster water vapour removal which leads to a lower value of water vapour into the duct and hence a lower Nusselt number.

The plasma spray process is widely used to produce thick coatings by the successive pilling of particles deposited in a molten or semi-molten state on a prepared substrate. However, this process includes time-dependent phenomena that... more

The plasma spray process is widely used to produce thick coatings by the successive pilling of particles deposited in a molten or semi-molten state on a prepared substrate. However, this process includes time-dependent phenomena that affect the reliability of the process and reproducibility of coating. These phenomena are principally linked to the continuous movement of the electric arc root on the anode wall in the plasma gun. Such a movement leads to arc length variations resulting in fluctuations in arc voltage, enthalpy input to the flow and instabilities in the plasma jet. This paper presents an attempt to develop a time-dependent and 3-D model of the plasma spray process that can provide a useful insight in the time-evolution of the performance of the process. The effect of the transient behaviour of the arc on the gas flow is modelled with a time dependant heat source located inside the nozzle and evolving with the arc voltage. The first stage of the study consisted in the validation of the flow model thanks to the comparison of steady-state computed results with experimental data. The second dealt the time-dependant simulation of the flow.

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