A two-phase flow, non-isothermal, three dimensional model was developed to study the transport phenomena in proton exchange membrane (PEM) fuel cell. Modeling results of water distribution and temperature distribution...
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A two-phase flow, non-isothermal, three dimensional model was developed to study the transport phenomena in proton exchange membrane (PEM) fuel cell. Modeling results of water distribution and temperature distribution are presented in this paper. The modeling results show that water and temperature distributions are non-uniform. Along the flow direction, water concentration in anode is decreasing while that in cathode is increasing which liquid water present in cathode;in the cross section perpendicular to the flow direction, both water concentration and liquid water saturation under the shoulder are higher than that under the channel;liquid water distribution across cathode GDL is different at different discharging voltages. Local temperature is decreasing along the flow direction, with even higher gradient when the reactant gas is insufficient;temperatures under the shoulder are lower than those under the channel;in the direction across MEA, the highest temperature is in cathode catalyst layer, and temperature gradient increases as the discharging voltage decreases;at the same discharging voltage, the thicker the PEM is, the lower the local temperatures and the temperature gradient across MEA are.
The ultra-supercritical double-reheat boiler has attracted more attention because of high parameters, low pollution and large capacity. However, there are some difficulties in the development of this technology, such ...
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The pore-grain characteristics of shale oil reservoir rocks are complex: nano-size pore throats, multi-scale of pore size and topology, and rich in organic matter. Generally, shale oil flow in nanoporous media is sign...
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The pore-grain characteristics of shale oil reservoir rocks are complex: nano-size pore throats, multi-scale of pore size and topology, and rich in organic matter. Generally, shale oil flow in nanoporous media is significantly affected by microscopic fluid slippage and adsorption on the pore surfaces, which give rise to variable slip length, viscosity ratio of adsorbed phase to bulk phase, and thickness of adsorption layer in organic & inorganic pore throats. In this study, a new pore network model is developed based on a modified shale oil flow equation to consider those combinational effects on shale oil permeability under different organic matter contents, and then is applied to provide an order analysis of those effects on the permeability of a representative shale model. Different flow patterns characterizing fluid-solid interaction are also discussed. Analysis results show that shale oil permeability is strongly influenced by the slip length. The effect of adsorption on permeability is negligible for cases considered. Shale oil flow is mainly controlled by inorganic pores when volumetric TOC is low. The influence of TOC on permeability depends on slippage and adsorption conditions in organic and inorganic matters, referred in this paper to as flow patterns. As the organic matter content increases, the connectivity of organic pores and throats improves, which further affects network permeability.
In this study, a three-dimensional (3D) thermal runaway (TR) model with conjugate heat transfer submodel is adopted. TR behaviors for a battery pack with 12 prismatic LIBs are then simulated. Three thermal safety meas...
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In this paper, the steam shape parameters and the condensation oscillation characteristics of the direct contact condensation of submerged steam jet into subcooled water were investigated through a side hole nozzle. M...
In this paper, the steam shape parameters and the condensation oscillation characteristics of the direct contact condensation of submerged steam jet into subcooled water were investigated through a side hole nozzle. Meanwhile, the dimensionless jet length and the expansion ratio versus pool water temperature and steam mass flux were obtained by measuring the photographs taken by a high speed camera. Both of them increased gradually with rise of pool water temperature and steam mass flux. A comparison of the shape parameters of three different style nozzles was also achieved. And a correlation of the dimensionless jet length was obtained, the predicted data agreed well with the experimental data, while the discrepancy was within ±5%. For the pressure oscillation versus steam mass flux, the peaks and the root mean square value of pressure oscillation were almost consistent in the range of 150-400 kgm-2s-1, while both of them increase in the range of 400-800 kgm-2s-1. The positive peak and negative peak were completely symmetrical.
Gas is a clean energy resource in comparison with oil and coal. Liquid-loading problem is frequently encountered in the process of gas production. It would directly cause the production of gas wells decreasing, even o...
Gas is a clean energy resource in comparison with oil and coal. Liquid-loading problem is frequently encountered in the process of gas production. It would directly cause the production of gas wells decreasing, even off production. A number of deliquification techniques have been suggested for solving this kind of problem, but the available techniques are not yet widely applicable. Based on the analysis, the method of deliquification with atomizing nozzle in gas wells was put forward. The test bench was designed for studying the atomization of nozzles and the liquid entrainment of gas flow. The size distribution of atomized droplets was measured by Malvern laser grain size analyzer. The Sauter mean diameters of atomized droplets were analysed under different two-phase flow conditions. The results indicate that the designed nozzles have good atomization performances and show potential application for reducing liquid loading in gas wells.
Properties of supercritical water will undergo drastic changes near the "pseudo critical" point which gives rise to a serious concern about flow instabilities under supercritical conditions. To investigate t...
Properties of supercritical water will undergo drastic changes near the "pseudo critical" point which gives rise to a serious concern about flow instabilities under supercritical conditions. To investigate the fluid flow behaviors, experiments with different system pressures (near-critical and supercritical pressure) were conducted on the Xi'an Jiao tong University's (XJTU) supercritical water test facility. Large amplitudes of mass flow flux as well as inlet pressure were found in various operation conditions. Mechanism of this unusual flow instability behavior is discussed. The oscillation behavior occurring in the present work has also been compared with that under the subcritical pressures and parameters effects are also studied.
A numerical model was developed to simulate the condensation flow of the n-octane/n-nonane in three dimension throttle. With this model the condensation properties of n-octane/n-nonane in throttle were investigated, i...
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A numerical model was developed to simulate the condensation flow of the n-octane/n-nonane in three dimension throttle. With this model the condensation properties of n-octane/n-nonane in throttle were investigated, it was found that the maximum supersaturation ratio of n-octane/n-nonane vapor in the homogeneous condensation process was very high, in comparison n-nonane was harder to condense. The influence of inlet supersaturation ratio, total pressure and total temperature on the condensation of n-nonanein in throttling flow process was analyzed. From the results, the direct influences of inlet parameters were found on the wilson point location, average droplet radius and liquid phase mass fraction.
In bubbly two‐phase flow, the gas phase and liquid phase have different flow fields. The mathematical expression for the motion of a small bubble at low Re number has been already established, the liquid velocity alo...
In bubbly two‐phase flow, the gas phase and liquid phase have different flow fields. The mathematical expression for the motion of a small bubble at low Re number has been already established, the liquid velocity along the trajectory of the bubble is calculated inversely by using the motion equation. Whole field liquid flow structure has also estimated using a spatial and/or temporal interpolation method. This paper proposes an algorithm for estimating the liquid phase flow field based on measurement data on bubble data on bubble motion. The applicability of the algorithm is examined with Taylor‐Green vortex flow as an analytical test case. Meanwhile, The result, based on the theory, has been applied to reconstruct liquid phase velocity field by using the data of bubble velocity in an aeration tank.
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