Capturing CO2 from the flue gas of a power plant based on chemical absorption method is an effective way to cut down the emission of CO2. However, the principal components in the solvent are very difficult to be measu...
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With anionic surfactant LAS assisted, series of zinc cadmium sulfide semiconductor photocatalysts were synthesized by hydrothermal method. These products were characterized by X‐ray diffraction (XRD), UV‐Vis absorpt...
With anionic surfactant LAS assisted, series of zinc cadmium sulfide semiconductor photocatalysts were synthesized by hydrothermal method. These products were characterized by X‐ray diffraction (XRD), UV‐Vis absorption spectra (UV‐Vis) and scanning electron microscopy (FESEM). The photocatalytic activities of as‐prepared samples were evaluated by photocatalytic hydrogen production from water under visible‐light irradiation. The best synthesis parameters are: Composition 0.9:0.1 (Cd:Zn molar ratio), Temperature 160 °C, Hydrothermal Time 48 Hour, LAS Concentration 1.7 mmol/L, the maximum visible‐light‐catalytic hydrogen production rate is 161.25 μmol/h (λ>430 nm) which is higher than those of by coprecipitation method. The experiment results indicate that surfactant assisted hydrothermal method is an effective way to get highly active CdZnS solid solution photocatalyst.
flow and temperature fields during the solidification of hypereutectic and hypoeutectic NH4Cl‐H2O solution in rectangular cavities were measured by a particle image velocimetry(PIV) and a weak perturbation thermocoup...
flow and temperature fields during the solidification of hypereutectic and hypoeutectic NH4Cl‐H2O solution in rectangular cavities were measured by a particle image velocimetry(PIV) and a weak perturbation thermocouple network, respectively. Double‐diffusive convections caused by the coupling effects of temperature and solute gradients were studied by the experiment. During the solidification of hypereutectic solution, the rejected water near the solidification interface will lead to dilute solute layers and double‐diffusive interfaces. As the continued rejection of water, the layer and interface will evolve into instability and a multi‐layer and multi‐interface structure will be formed. To the hypoeutectic solution, the rejection of NH4Cl near the solidification interface will form a dense solute layer. When the thickness of the dense solute layer is large enough, the coupling effects of stabilizing solute gradient and unstable temperature gradient will lead to new solute layers. The solute layers and double‐diffusive interfaces will evolve stably and have no breakup of the double‐diffusive interfaces during the solidification of hypoeutectic solution.
A model coupling two basic models, the model with interface tracking method and two‐fluid model, for simulation of incompressible gas‐liquid two‐phase flow is proposed. A united solution frame shared by the two bas...
A model coupling two basic models, the model with interface tracking method and two‐fluid model, for simulation of incompressible gas‐liquid two‐phase flow is proposed. A united solution frame shared by the two basic models is built. In the shared solution frame, the Navier—Stokes equations of the two basic models can be dealt with in a uniform form. In the proposed model, there are three phases, which are divided not only by physics but also by the length scale of interface, including the liquid phase, the large‐length‐scale‐interface gas phase and the small‐length‐scale‐interface gas phase. The special treatment named by “void fraction redistribution” is adopted for the special grids which contain all three phases. Based on the united solution frame, MCBA—SIMPLE algorithm is used to solve the equations. Two problems are calculated to show that the proposed model has the merits of the two basic models.
On the basis of a 350 MW supercritical pressure OTSC boiler, established the mathematical model for the circulation loop flow and grid pressure in a complex flow network system, and an iteration method was used to sol...
On the basis of a 350 MW supercritical pressure OTSC boiler, established the mathematical model for the circulation loop flow and grid pressure in a complex flow network system, and an iteration method was used to solve the nonlinear equations. The water wall flow distribution and temperature profile of the boiler were computed. The results show that the flow difference and heat difference are small in spiral tube water wall at BMCR, 75%BMCR load and 30%BMCR load. The metal temperatures are all in the range of allowable range, and the operation of boil is safe and reliable.
In present paper, a two‐dimensional numerical study on a standing‐wave thermoacoustic engine was performed with compressible SIMPLE algorithm based on a pressure‐correction method. First, the simulation model was d...
In present paper, a two‐dimensional numerical study on a standing‐wave thermoacoustic engine was performed with compressible SIMPLE algorithm based on a pressure‐correction method. First, the simulation model was developed, and the time‐dependent compressible thermoacoustic engine system was chosen through substantive numerical tests. Appropriate governing equations for mass, momentum and energy were introduced. Then, the computational results of the onset of the self‐excited oscillations across the entire evolution process and the acoustical characteristics of the pressure and velocity wave were presented and analyzed. In addition, the standing‐wave of the pressure and velocity along the center of the two stacks are investigated. The crucial nonlinear phenomenon that cannot be captured by the existing linear theory, like high harmonic frequencies, is also revealed in present paper. It is concluded that compressible SIMPLE algorithm could be employed in our future work to simulate and optimize thermoacoustic system. The present result is an important step toward development to predict the high‐amplitude thermoacoustic systems and optimize thermoacoustic engine performance.
The moving particle semi-implicit method (MPS) was used to simulate the typical free surface problem, 2D dam break problem, and the effect of initial particle configuration on the simulated results was analyzed. It is...
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The moving particle semi-implicit method (MPS) was used to simulate the typical free surface problem, 2D dam break problem, and the effect of initial particle configuration on the simulated results was analyzed. It is found that the reasonable results can not be achieved for too large or too small particle distance. The comparison of the results by MPS, SPH or VOF with the experimental data shows that the result by MPS is between those by VOF and by SPH. Without the consideration of viscosity, the result by MPS is closer to the experiment than that by VOF. However, the result by MPS with the consideration of viscosity may be similar to that by SPH.
The principal pressure drop in a subsea riser is generally the gravitational pressure drop component due to liquid holdup. Surfactant is a kind of Chemical compound related to flow improvement. Gas‐liquid two‐phase ...
The principal pressure drop in a subsea riser is generally the gravitational pressure drop component due to liquid holdup. Surfactant is a kind of Chemical compound related to flow improvement. Gas‐liquid two‐phase flow in subsea riser with zero and small liquid flow rates was simulated in two vertical tubes with diameters of 40 mm and 65 mm, respectively. Liquid holdup reduction of subsea riser was investigated with surfactant. The simulation was conducted at low pressure, using air as the gas phase and water as the liquid phase. Pressure drop was measured by using differential pressure transducer and holdup was obtained by trapping the liquid in the pipe section. Different trace amounts of surfactant were used in this vertical two‐phase flow system. The liquid holdups were measured at different surfactant concentrations and different gas‐liquid flow ratios. Liquid holdups with and without surfactant additives are compared and analyzed. How the foamer influences the two‐phase flow pattern was observed and the range of foamer concentration corresponding to the best holdup reduction was obtained.
The morphology of fuel nitrogen in coal and its fate during pyrolysis and the nitrogen species including N2, HCN and NH3 during coal pyrolysis and gasification have been investigated to clarify the evolution mechanism...
The morphology of fuel nitrogen in coal and its fate during pyrolysis and the nitrogen species including N2, HCN and NH3 during coal pyrolysis and gasification have been investigated to clarify the evolution mechanism of fuel nitrogen in heat treatment process. Experimental results show that the morphology of coal nitrogen in the studied Chinese raw coals generally include pyrrolic nitrogen (N‐5), pyridinic nitrogen (N‐6), quaternary nitrogen (N‐Q) and nitrogen‐oxide (N‐X). Generally, nitrogen in char is transformed to volatile and more stable components during pyrolysis. Char‐N is the major source of NOx precursors during temperature programmed pyrolysis in 600–800° C. N‐5 and N‐X in char is converted to HCN first, and HCN is then hydrogenated to NH3. N‐Q in char is the main source of nitrogen gas. The major nitrogenous gas products during rapid coal pyrolysis are N2, HCN and NH3, amongst which N2 is dominant. The yields of N2 and NOx precursors, such as HCN and NH3, increase with increased pyrolysis temperature. The major gaseous nitrogenous products during coal gasification in steam include HCN, NH3 and N2. H2O is the main source of the groups containing hydrogen, which not only participates in the reaction as a gasification agent, but also has catalysis on the reaction.
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