Peanut shell,mixed with sodium carboxymethylcellulose,was gasified at a temperature of 450℃ and a pressure range from 24 to 27 MPa with the presence of different catalysts,including K2CO3,ZnCl2 and *** experimental r...
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Peanut shell,mixed with sodium carboxymethylcellulose,was gasified at a temperature of 450℃ and a pressure range from 24 to 27 MPa with the presence of different catalysts,including K2CO3,ZnCl2 and *** experimental results show that different catalysts have greatly different effects on the *** efficiency (GE),hydrogen gasification efficiency (GHE),carbon gasification efficiency (GCE),yield of hydrogen production (YH2) and potential yield of hydrogen production (YPH2) are applied to describe the catalytic *** the result of gaseous components,ZnCl2 has the highest hydrogen selectivity,K2CO3 is lower,and Raney-Ni is the lowest,but Raney-Ni is the most favorable to gasify biomass among the three catalysts,and its GE,GHE,GcE reach 126.84%,185.71%,94.24%,*** expected,hydrogen selectivity increased and CH4 reduced rapidly when the mixture of ZnCl2 and Raney-Ni is used under the same *** optimization mixture appeared when 0.2 g of ZnCl2 was added to 1 g of Raney-Ni,43.56 g·kg-1 of hydrogen production was *** addition,the catalytic mechanisms of different catalysts were analyzed,and the possible reaction pathway was brought forward,which helped to explain the experiment phenomena and results correctly.
The molten salt reactor (MSR), which is one of the generation IV reactors, can meet the demand of transmutation and breeding. The thermodynamic properties of the molten salt system like LiF-NaF-BeF2 influence the desi...
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The molten salt reactor (MSR), which is one of the generation IV reactors, can meet the demand of transmutation and breeding. The thermodynamic properties of the molten salt system like LiF-NaF-BeF2 influence the design and construction of the fuel salt and coolant in the MSR for the new generation. In this paper, the equation of state of the ternary system 15%LiF-58%NaF-27%BeF2, over the temperature range from 873.15 to 1 073.15 K at one atmosphere pressure, is described using a modified Peng-Robinson (PR) equation. The densities of the ternary system and its components are estimated by this equation directly, and compared with the experimental data. Based on the equation of state, the other thermodynamic properties such as the enthalpy, entropyand heat capacity at constant pressure are estimated by the residual function method and the fugacity coefficient method respectively. The densities calculated by PR equation are highly in agr eement with the experimental data, and the enthalpy, entropy and heat capacity evaluated by the two different methods are consistent with each other. It can be concluded that the modified PR equation can be applied to evaluate the density of the molten salt system, and it is recommended that it be used as the basis to estimate the enthalpy, entropy and heat capacity of the molten salt system.
Within the pressure range of 9-28 MPa,mass 200-500 kW/m2,experiments were performed to investigate the heat transfer to water in the inclined upward internally ribbed tube with an inclined angle of 19.5 degrees,a maxi...
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Within the pressure range of 9-28 MPa,mass 200-500 kW/m2,experiments were performed to investigate the heat transfer to water in the inclined upward internally ribbed tube with an inclined angle of 19.5 degrees,a maximum outer diameter of 38.1 mm,and a thickness of 7.5 *** 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 ***,the heat transfer enhancement decreased near the critical *** supercritical pressure,the temperature difference between the wall and the fluid increased near the pseudo-critical temperature,but the increase of wall temperature was less than that of departure from nucleate boiling at sub-critical *** pressure is closer to the critical pressure,the temperature difference between the wall and the fluid increased greatly near the pseudo-critical *** 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 *** the rotational flow of the internal groove reduced the effect of natural convection,the internal wall temperature of internally ribbed tube uniformly distributed along the *** maximum internal wall temperature difference of the tube along the circumference was only 10 degrees when the fluid enthalpy exceeded 2 000 J/*** the effect of acute variety of the fluid property on heat transfer,the correlation of heat transfer coefficient on the top of the internally ribbed tube was orovided.
Wavelike slug-flow is a representative flow type in horizontal pneumatic *** theory was introduced to establish a 3D kinetic numerical model for wavelike slug gas-solid flow in this *** motion of particulate slugs in ...
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Wavelike slug-flow is a representative flow type in horizontal pneumatic *** theory was introduced to establish a 3D kinetic numerical model for wavelike slug gas-solid flow in this *** motion of particulate slugs in horizontal pipes was numerically *** formation and motion process of slugs and settled layer were *** characteristics of the flow,such as pressure drop,air velocity distribution,slug length and settled layer thickness,and the detailed changing characteristics of slug length and settled layer thickness with air velocity were *** results indicate that kinetic theory can represent the physical characteristics of the non-suspension dense phase flow of wavelike slug pneumatic *** experiment in this paper introduced a new idea for the numerical calculation of slug-flow pneumatic conveying.
The experimental results of the deformation and breakup of a single drop immersed in a Newtonian liq-uid and subjected to a constant shear rate which generated by counter rotating Couette apparatus were presented in t...
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The experimental results of the deformation and breakup of a single drop immersed in a Newtonian liq-uid and subjected to a constant shear rate which generated by counter rotating Couette apparatus were presented in this paper. From experimental observations, the breakup occurred by three mechanisms, namely, necking, end pinching, and capillary instability. Quantitative results for the deformation and breakup of drop are presented. The maximum diameter and Sauter mean diameter of daughter drops and capillary thread radius are linearly related to the inverse shear rate and independent of the initial drop size, the dimensionless wavelength which is the wave-length divided by the thread width at breakup is independent of the shear rate and initial drop size, and the deforma-tion of threads follows a pseudo-affine deformation for Cai/Cac larger than 2.
Three-dimensional numerical simulation results are presented for a fin-and-tube heat transfer surface with vortex *** effects of the Reynolds number (from 800 to 2 000) and the attack angle (30° and 45°) of ...
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Three-dimensional numerical simulation results are presented for a fin-and-tube heat transfer surface with vortex *** effects of the Reynolds number (from 800 to 2 000) and the attack angle (30° and 45°) of a delta winglet vortex generator are *** numerical results are analyzed on the basis of the field synergy principle to explain the inherent mechanism of heat transfer enhancement by longitudinal *** secondary flow generated by the vortex generators causes the reduction of the intersection angle between the velocity and fluid temperature *** addition,the computational evaluations indicate that the heat transfer enhancement of delta winglet pairs for an aligned tube bank fin-and-tube surface is more significant than that for a staggered tube bank fin-and-tube *** heat transfer enhancement of the delta winglet pairs with an attack angle of 45° is larger than that with an angle of 30°.The delta winglet pair with an attack angle of 45° leads to an increase in pressure drop,while the delta winglet pair with the 30°angle results in a slight *** heat transfer enhancement under identical pumping power condition for the attack angle of 30° is larger than that for the attack angle of 45°either for staggered or for aligned tube bank arrangement.
Based on the fundamental conservation principles-the mass,momentum,and energy conservation equtions of liquid films and the momentum conservation equation of vapor core,a theoretical three-fluid model has been develop...
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Based on the fundamental conservation principles-the mass,momentum,and energy conservation equtions of liquid films and the momentum conservation equation of vapor core,a theoretical three-fluid model has been developed to predict the dryout point of upward annular flow in vertical narrow annuli with bilateral *** range of the parameters are:pressure from 0.5 to 5.0 MPa;mass flow Through numerically solving the model,the relationships among the parameters of the critical quality (Xc),critical heat flux (QCHF),mass flow rate,system pressure,and the ratio of heat flux on the inner wall of the outer tube to that on the outer wall of the inner tube (qo/qi) are obtained and *** predicted results accurately match with the experimental *** a fixed qo,Xc will increase with the decreases in the gap size and the tube curvature when the dryout point occurs on the outer wall of the inner ***,for a fixed qi,when the dryout point occurs on the inner wall of the outer tube,the parametric trend is *** the dryout point on the inner and outer walls occurs simultaneously,Xc reaches a peak value,and the ratio of qo/qi at this position changes with the gap size and the tube curvature.
Hydrogen is a clean energy *** abundant coal sources and green biomass energy into hydrogen effectively and without any pollution promotes environmental *** co-gasification performance of coal and a model compound of ...
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Hydrogen is a clean energy *** abundant coal sources and green biomass energy into hydrogen effectively and without any pollution promotes environmental *** co-gasification performance of coal and a model compound of biomass,carboxymethylcellulose (CMC)in supercritical water (SCW),were investigated *** influences of temperature,pressure and concentration on hydrogen production from co-gasification of coal and CMC in SCW under the given conditions (20-25 MPa,650℃,15-30 s) are discussed in *** experimental results show that H2,CO2 and CH4 are the main gas products,and the molar fraction of hydrogen reaches in excess of 60%.The higher pressure and higher CMC content facilitate hydrogen production;production is decreased remarkably given a longer residence time.
An experimental study on the natural convection heat transfer on a horizontal downward facing heated surface in a water gap was carried out under atmospheric pressure conditions. A total of 700 experimental data point...
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An experimental study on the natural convection heat transfer on a horizontal downward facing heated surface in a water gap was carried out under atmospheric pressure conditions. A total of 700 experimental data points were correlated using Rayleigh versus Nusselt number in various forms, based on different independent variables. The effects of different characteristic lengths and film temperatures were discussed. The results show that the buoyancy force acts as a resistance force for natural convecti on beat transfer ona downward facing horizontal heated surface in a confined space. For the estimation of the natural convection heat transfer under the present conditions, empirical correlations in which Nusselt number is expressed as a function of the Rayleigh number, or both Rayleigh and Prandtl numbers, may be used. When it is accurately predicted, the Nusselt number is expressed as a function of the Rayleigh and Prandtl numbers, as well as the gap width-to-heated surface diameter ratio; and uses the temperature difference between the heated surface and the ambient fluid in the definition of Rayleigh number. The characteristic length is the gap size and the film temperature is the average fluid temperature.
Gasification of high moisture content biomass in supercritical water has been identified as a promising alternative system for producing renewable hydrogen. Supercritical water partial oxidation is the process by whic...
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ISBN:
(纸本)1563479028
Gasification of high moisture content biomass in supercritical water has been identified as a promising alternative system for producing renewable hydrogen. Supercritical water partial oxidation is the process by which an oxidant appears during the reaction. The key advantage of this process is the rapid heating of the gasification medium, resulting in less char formation and improved hydrogen yield. Many researchers have studied the supercritical water gasification of model compounds. However, real biomass which is of importance for large production of hydrogen has yet to be thoroughly examined. In this paper, gasification of high moisture content municipal sludge was studied in a continuous reactor employing hydrogen peroxide as an oxygen source. The reaction was tested across temperatures and pressures in the range of 673 to 873 K and 24 to 30 MPa, and across various residence times ranging from 3 to 15 minutes. We found that sludge at low concentrations can be completely gasified with no observable char or tar formation. The improvement of gasification efficiency by partial oxidation was accompanied with a high yield of hydrogen and carbon monoxide. Through this, we evaluated the energy efficiency of sludge gasification. Our thermodynamic calculations show that the energy efficiency reaches 50% when considering hydrogen, carbon monoxide, and methane as the valuable gases in the ideal case. Taking into account the energy recovery from the hot water at 30 MPa and 873 K and assuming the ideal scenario of no external heat loss, the overall energy yield potentially reaches 85%. Our results show that the key mechanism of the gasification process is energy recovery, as the chemical reaction is endothermic and requires high temperatures.
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