As coal was transported homogeneously at high pressure by adding the sodium carboxymethylcellulose (CMC), the hydrogen production from catalytic gasification of coal/CMC in supercritical water (SCW) was investigated. ...
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As coal was transported homogeneously at high pressure by adding the sodium carboxymethylcellulose (CMC), the hydrogen production from catalytic gasification of coal/CMC in supercritical water (SCW) was investigated. The experimental results showed that the molar fraction of hydrogen is higher than that in conventional gasification. H2, CO2 and CH4 are the main product gases, the higher pressure and higher CMC content is advantage of hydrogen production. Longer residence time is favorite to gasification of coal/CMC, but it is not advantage of hydrogen production from coal/CMC gasified in SCW at 20-25 MPa, 15-30 s and 650°C.
The equilibrium sand transport is simulated by Lagrange model combined with the probabilistic distributions of initial speed and angle of ejection sand grain in this paper. Five forms of the possible distributions are...
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The equilibrium sand transport is simulated by Lagrange model combined with the probabilistic distributions of initial speed and angle of ejection sand grain in this paper. Five forms of the possible distributions are summarized from the previous study results published in literature. Since the macro-quantities simulated by rational distribution should be coincident well with experimental result, the rationality of the distributions can be tested by comparing the quantities simulated from these distributions with the experimental quantities. Detailed analysis indicates that the distribution of initial speed and angle of ejected grains in equilibrium sand transport should be a monotonous decline function. According to the experimental data a segmented function comprised by an exponential distribution and a normal distribution is suggested in this paper. This distributions is confirmed by further comparison with experimental data.
Within the range of pressures from 9 to 28 MPa, mass velocities from 600 to 1200 kg/(m2s), and heat fluxes from 200 to 500 kW/m2, experiments have been performed to investigate the heat transfer to water in the inclin...
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Within the range of pressures from 9 to 28 MPa, mass velocities from 600 to 1200 kg/(m2s), and heat fluxes from 200 to 500 kW/m2, experiments have been performed to investigate the heat transfer to water in the inclined upward internally ribbed tube with the inclined angle of 19.5 degree, the maximum outer diameter of 38.1 mm, and the thickness of 7.5 mm. Based on the experiments, it was found that heat transfer enhancement of the internally ribbed tube could postpone departure from nucleate boiling at the sub-critical pressure. However, the heat transfer enhancement decreased near the critical pressure. At supercritical pressure, the temperature difference between the wall and fluid increased near the pseudo-critical temperature, but the increasing of wall temperature was less than that of departure from nucleate boiling at sub-critical pressure. When pressure was close to the critical pressure, the temperature difference between the wall and fluid greatly increased near the pseudo-critical temperature. Heat transfer to supercritical water in the inclined upward internally ribbed tube was enhanced or deteriorated near the pseudo-critical temperature with the variety of ratio between the mass velocity and the heat flux. Due to the rotational flow of the internal groove reducing the effect of nature convection, the internal wall temperature of the inclined upward internally ribbed tube uniformly distributed along the circumference. The maximum internal wall temperature difference of the inclined upward internally ribbed tube along the circumference was only 10 degree Centigrade when the fluid enthalpy exceeds 2000 kJ/kg. Considering the effect of acute variety of the fluid property on heat transfer, the correlation of heat transfer coefficient on the top of the inclined upward internally ribbed tube have been provided.
Prediction of dryout point is experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annulus with narrow gap is bilaterally heated by AC ...
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Prediction of dryout point is experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annulus with narrow gap is bilaterally heated by AC current power supply. The experimental conditions covered a range of pressure from 0.8 to 3.5 MPa, mass flux of 26.6 to 68.8 kg·m-2·s-1 and wall heat flux of 5 to 50 kW·m-2. The location of dryout is obtained by observing a sudden rise in surface temperature. Kutateladze correlation is cited and modified to predict the location of dryout and proved to be not a proper one. Considering in detail the effects of geometry of annuli, pressure, mass flux and heat flux on dryout, an empirical correction is finally developed to predict dryout point in narrow annular gap under low flow condition, which has a good agreement with experimental data.
The system of ice-making by spraying water in winter and utilizing the ice in summer is pollution-free and economizes the first investment, operating cost, and reduces the peak of electric power in summer. Through est...
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The system of ice-making by spraying water in winter and utilizing the ice in summer is pollution-free and economizes the first investment, operating cost, and reduces the peak of electric power in summer. Through establishing the energy equilibrium equation of sprayed water drop, the relation between the diameter of water droplet and the time of icing at different ambient temperature and coefficient of performance of the system of ice-making by spraying water has been obtained. The errors between the numerical solution and the experimental data lie in a range of 7% to 10%, indicating that the model is reasonable. The method of the ice making is promising in the exercisable region to substitute the mechanical refrigeration system.
By using an ensemble-averaged two-fluid model,with valid closure conditions of interfacial momentum exchange due to virtual mass force,viscous shear stress and drag force,a model for pressure wave propagation in a hor...
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By using an ensemble-averaged two-fluid model,with valid closure conditions of interfacial momentum exchange due to virtual mass force,viscous shear stress and drag force,a model for pressure wave propagation in a horizontal gas-liquid bubbly flow is *** to the small perturbation theory and solvable condition of one-order linear uniform equations,a dispersion equation of pressure wave is *** pressure wave speed calculated from the model is compared and in good agreement with existing *** to the dispersion equation,the propagation and attenuation of pressure wave are investigated *** factors affecting pressure wave,such as void fraction,pressure,wall shear stress,perturbation frequency,virtual mass force and drag force,are *** result shows that the decrease in system pressure,the increase in void fraction and the existence of wall shear stress,will cause a decrease in pressure wave speed and an increase in the attenuation coefficient in the horizontal gas-liquid bubbly *** effects of perturbation frequency,virtual mass and drag force on pressure wave in the horizontal gas-liquid bubbly flow at low perturbation frequency are different from that at high perturbation frequency.
Prediction of dryout point was experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annular with narrow gap was bilaterally heated by A...
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ISBN:
(纸本)0919784798
Prediction of dryout point was experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annular with narrow gap was bilaterally heated by AC current power supply. The experimental conditions covered a range of pressure from 0.8 to 3.5 MPa, mass flux of 60.39 to 135.6 kg/m2 and heat flux of 5 to 50 kW/m2 This paper presents a new analytical model for the prediction of dryout point for steam- water flow in narrow annular gap and bilaterally and uniformly heated tubes. The prediction of dryout point for bilaterally heated annuli was based on the droplet-diffusion model for internally heated annuli by Kirillov and Smogalev (1969, 1972). The dryout model prediction values are compared with a experimental data, showing a good agreement in accuracy for the above mentioned parametric range.
Prediction of dryout point is experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annular with narrow gap is bilaterally heated by AC ...
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Prediction of dryout point is experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annular with narrow gap is bilaterally heated by AC current power supply. The experimental conditions covered a range of pressure from 0.8 to 3.5 MPa, mass flux from 26.6 to 68.8 kg/m2 s and wall heat flux from 5.0 to 50.0 kW/m2. The location of dryout is obtained by observing a sudden rise in surface temperature, Kutateladze correlations is cited, however proved to be not a proper one for annuli gap and modified to predict the location of dryout. Considering in detail the effects of the geometry of annuli, pressure, mass flux and heat flux on dryout, an empirical correction is finally developed to predict dryout point in narrow annular gap under low flow condition which has a good agreement with experimental data.
With the theory of the Reynolds stress model applied, a mathematical model of the flow and heat transfer of the helical baffles heat exchanger is established. The commercial software FLUENT is used to simulate the inf...
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A novel segregated solution procedure for incompressible fluid flow and heat transfer problems is proposed. The new algorithm is called CLEAR (Coupled and Linked Equations Algorithm Revised). It differs from all SIMPL...
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A novel segregated solution procedure for incompressible fluid flow and heat transfer problems is proposed. The new algorithm is called CLEAR (Coupled and Linked Equations Algorithm Revised). It differs from all SIMPLE-like algorithms in that it solves the improved pressure directly, rather than by adding a correction term, and no term is dropped in the derivation of the pressure equation. Thus the effects of the neighboring velocity values are fully taken into account, and the coupling between velocity and pressure is fully guaranteed, greatly enhancing the convergence rate of the iteration process. Its robustness is improved by introducing a second relaxation factor. The mathematical formulation and the solution procedure of the CLEAR algorithm are described in detail in this article. Comprehensive discussion is conducted to describe the difference between the CLEAR algorithm and all other existing algorithms of the SIMPLE family. In Part II, six numerical application examples with available numerical solutions are provided to show the feasibility of the new algorithm. [ABSTRACT FROM AUTHOR]
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