Nanosize WS2 sensitized mesoporous TiO2 was prepared to extend the adsorption of the wide band gap TiO2 into visible light region. Compared with nonporous particle TiO2 substrate, it was found that the existence of me...
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ISBN:
(纸本)9781622765409
Nanosize WS2 sensitized mesoporous TiO2 was prepared to extend the adsorption of the wide band gap TiO2 into visible light region. Compared with nonporous particle TiO2 substrate, it was found that the existence of mesopore is important for larger amount of WS 2 loading and inhibition of the light-induced detachment of WS 2 particles from the TiO2 substrate during photocatalytic reaction, which leads to higher photocatalytic activity and stability. We also found that the rate-determining step for photocatalytic hydrogen production is the transfer of electrons from TiO2 substrate to H+ in solution, when the recombination between electrons and holes within TiO 2 could be neglected. In this case, deposition of Pt at the surface of semiconductor is indispensable for efficient hydrogen production.
Reactive distillation processes for synthesis of ethylene glycol (EG) and ethyl tert-butyl ether (ETBE) were modeled with the simulation package ASPEN PLUS. The input multiplicity and output multiplicity were disc...
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Reactive distillation processes for synthesis of ethylene glycol (EG) and ethyl tert-butyl ether (ETBE) were modeled with the simulation package ASPEN PLUS. The input multiplicity and output multiplicity were discussed with the method of sensitivity analysis for both cases. In EG production process, steady state multiplicities were studied in terms of effective liquid holdup volume and boil-up ratio. In ETBE synthesis process, the user kinetic subroutine was supplied into ASPEN PLUS firstly, and then the composition, temperature and reaction-rate profiles within the reactive distillation column were presented in detail. A set of stable solution branches based on distinct initial guesses for a range of boil-up ratio were found in EG synthesis. Input multiplicities were observed for a range of reboiler duty at several values of reflux ratio for ETBE synthesis process. These results can be used to avoid excessive energy consumption and achieve optimum design of reactive distillation column.
The upward multiphase cross flow and heat transfer in the vertical tube may occur in oil production and chemical facilities. In this study, the local flow patterns of an upward gas-water two phase cross flow in a vert...
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The upward multiphase cross flow and heat transfer in the vertical tube may occur in oil production and chemical facilities. In this study, the local flow patterns of an upward gas-water two phase cross flow in a vertical tube with a horizontal rod have been investigated with an optical probe and the digital high speed video system. The local flow patterns are defined as the bubble, slug, churn and annular flow patterns. Optical probe signals are ana- lyzed in terms of probability density function, and it is proved that the local flow patterns can be recognized by this method. The transition mechanisms between the different flow patterns have been analyzed and the corresponding transitional models are proposed. Finally, local flow pattern maps of the upward gas-water two-phase flow in the vertical tube with a horizontal rod are constructed.
Because of the practical importance of two-phase instabilities, substantial efforts have been made to date to understand the physical phenomena governing such instabilities and to develop computational tools to model ...
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Because of the practical importance of two-phase instabilities, substantial efforts have been made to date to understand the physical phenomena governing such instabilities and to develop computational tools to model the dynamics. The purpose of this study is to present a numerical model for the analysis of flow-induced instabilities in forced-convection steam generator. The model is based on the assumption of homogeneous two-phase flow and thermodynamic equilibrium of the phases. The thermal capacity of the heater wall has been included in the analysis. The model is used to analyze the flow instabilities in the steam generator and to study the effects of system pressure, mass flux, inlet temperature and inlet/outlet restriction, gap size, the ratio of do /di, and the ratio of qi/qo on the system behavior.
Prediction of critical heat flux (CHF) in annular flow is important for the safety of once- through steam generator and the reactor core under accident conditions. The dryout in annular flow occurs at the point where ...
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Prediction of critical heat flux (CHF) in annular flow is important for the safety of once- through steam generator and the reactor core under accident conditions. The dryout in annular flow occurs at the point where the film is depleted due to entrainment, deposition, and evaporation. The film thickness, film mass flow rate along axial distribution, and CHF are calculated in vertical upward round tube on the basis of a separated flow model of annular flow. The theoretical CHF values are higher than those derived from experimental data, with error being within 30%.
This article presents a theoretical investigation on the steady-state natural circulation characteristics of a new type of pressurized water reactor. Through numerically solving the one-dimensional steady-state single...
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This article presents a theoretical investigation on the steady-state natural circulation characteristics of a new type of pressurized water reactor. Through numerically solving the one-dimensional steady-state single-phase conservative equations for the primary circuit and the steady-state two-phase drift-flux conservative equations for the secondary side of the steam generator, the natural circulation characteristics were studied. On the basis of the preliminary calculation analysis, it was found that natural circulation mass flow rate was proportional to the exponential function of the power and that the value of the exponent is related to the operating conditions of the secondary side of the steam generator. The higher the outlet pressure of the secondary side of the steam generator, the higher the primary natural circulation mass flow rate. The larger height difference between the core center and the steam generator center is favorable for the heat removal capacity of the natural circulation.
With the novel and simple current distribution measurement gasket developed by MPFL, the performance of a single PEM fuel cell with serpentine flow field was investigated without modifying any of its components. Inhom...
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ISBN:
(纸本)9781622765409
With the novel and simple current distribution measurement gasket developed by MPFL, the performance of a single PEM fuel cell with serpentine flow field was investigated without modifying any of its components. Inhomogeneous current distributions were demonstrated clearly by the measurement results. Current distribution at different cell operating parameters, including reactant gas flow rate, reactant gas humidification temperature and cell operating temperature, were measured and the effects of such parameters were analyzed. Reactant gas flow rate exert effects on current distribution by influencing the reactant concentration distribution, while the critical effects of gas humidification and cell temperature is caused by their significant influence on water balance and water distribution in PEM fuel cell. To fully understand the combined effects of such factors, simultaneous measurement of current distribution, reactant distribution, temperature distribution and humidification distribution is necessary and will be helpful.
Based on mechanistic analysis of gas-liquid slug flow in vertical wellbore, a convenient model for pressure gradient calculation was developed by equivalent unit cell approach. The method of predicting liquid holdup i...
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Based on mechanistic analysis of gas-liquid slug flow in vertical wellbore, a convenient model for pressure gradient calculation was developed by equivalent unit cell approach. The method of predicting liquid holdup in liquid slug was determined according to experimental data, and correlation experimental data from literatures were used to evaluate the model. The analysis results show that this model is relative to few parameters and easy to calculate, and the test data from different sources can be predicted with fairly well precision. In addition, much difference results can be achieved by variant correlations for liquid holdup in liquid slug, but the prediction of pressure gradient is not sensitive to the liquid holdup under the experimental conditions.
In Part I [Wei et al., 2004, 2004 ASME Int. Mech. Eng. Conference], we presented the experimental results for swirling flows of water and cetyltrimethyl ammonium chloride (CTAC) surfactant solution in a cylindrical ve...
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The swirling flows of water and CTAC (cetyltrimethyl ammonium chloride) surfactant solutions (50-1000 ppm) in an open cylindrical container with a rotating disc at the bottom were experimentally investigated by use of...
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