On the assumptions that the shear resistance increases linearly with increasing shear displacement between the uplift pile and surrounding soil,that the axis force is distributed as parabola along the pile length,that elastic distortion occurs when the pile is loaded,that the displacement of pile is in accord with that of the soil,and that the uplift pile failure is regarded as the soil failure,arational calculation method was proposed for calculating the deformation,ultimate displacement and shear resistance of piles.The distributions of frictional resistance and the shear displacement along the pile length were obtained with the method.The comparisons were made between the measurement results and the present results.The present theoretical results agree well with the measurement results,with the average difference being less than 12% before failure.The comparisons show that the proposed method is reasonable for uplift design and engineering construction of piles....
Mist jet impingement cooling is an enhanced heat transfer method widely used after the continuous galvanizing process.The key of a successful design and operation of the mist jet impingement cooling system lies in mastering heat transfer coefficients.The heat transfer coefficients of high temperature steel plates cooled with multiple mist impinging jets were experimentally investigated,and the effects of gas and water flow rates on heat transfer coefficients were studied.The test results illustrate that the gas flow rate has little effect on the mist heat transfer rate.It is also found that the water flow rate has a great impact on the heat transfer coefficient.When the water flow rate ranges from 0.96m3/h to 1.59 m3/h,an increase in the rate will produce a higher heat transfer coefficient with a maximum of 5650 W/( m2 · K).Compared with the conventional gas jet cooling,the heat transfer coefficient of the mist jet cooling will be much higher,which can effectively strengthen the after-pot cooling....
Two mathematical models are built to study the effects of the fluid flow on thermal distributions of the gas tungsten arc welding(GTAW) process. One model is based on the heat conductivity equation, which doesn' t take the effects of the fluid flow into account, and the other couples the laminar heat transfer and fluid flow in the weld pool, which is called laminar fluid flow model in short. The simulated results of the two models show that the pattern and velocity of the fluid flow play a critical role in determining the thermal distribution and the weld pool shape. For the laminar fluid flow model, its highest temperature is 400 K lower than that calculated with the other model and the depth of its weld pool is shallower too, which is mainly caused by the main vortex of the flow in the weld pool....
Based on the high speed video system with electrical signals collecting and wavelet analyzing, the welding processes under three different median currents with the same median time were detected. The experimental results show that, when the median current is higher, the input peak energy is lower. And the droplet transfer is almost in spray mode. The welding process is the stablest....
A three-dimensional finite element analysis of process-induced residual stress in resin transfer mold-ing (RTM) process is presented. The finite element method ( FEM ) was employed to solve the coupled equa-tions involved in the transient heat transfer and the cure kinetics of the resin, and the distributions of internal temperature and cure degree of the composite at any instant time were obtained. The self-consistent field micro-mechanics model was used to predict the cure-dependent mechanical properties of the composites. Thermal ex-pansion and cure shrinkage were included in the analysis. The thermo-elastie mechanical governing equationswere solved using the incremental stress-strain relationship based FEM and the residual stress development was predicted. The present results were validated by the comparisons with the pertinent literature. The numerical example of a half cylinder was presented. The results show that it is necessary to carry out the three-dimensional analysis due to the complex distributions of temperatures, cure degrees and process-induced stress for thick parts, which can be predicted at any point within composite structures in the present analysis....
The distribution or wavelength-dependence of the formation regions of frequently used solar lines, Hα, Hβ, CaIIH and CaII8542, in quiet Sun, faint and bright flares is explored in the unpolarized case. We stress four aspects characterising the property of line formation process: 1) width of line formation core; 2) lineformation region; 3) influence of the temperature minimum region; and 4) wavelength ranges within which one can obtain pure chromospheric and photospheric filtergrams. It is shown that the above four aspects depend strongly on the atmo spheric physical condition and the lines used. The formation regions of all the wave length points within a line may be continuously distributed over one depth domain or discretely distributed because of no contribution coming from the temperature minimum reg:on, an important domain in the solar atmosphere that determines the distribution pattern of escape photons. On the other hand, the formation region of one wavelength point may cover only one height range or spread over two domains which are separated again by the temperature minimum region. Different lines may form in different regions in the quiet Sun. However, these line formation regions be come closer ir. solar flaring regions. Finally, though the stratification of line-of-sight velocity can alter the position of the line formation core within the line band and result in the asymmetry of the line formation core about the shifted line center, it can only lead to negligible changes in the line formation region or the line formation core width. All these results can be instructive to solar filtering observations....
Theoretical and experimental studies show that during hail growth the heat and mass transfers play a determinant role in growth rates and different structures. However, many numerical model researchers made extrapolation of the key heat transfer coefficient of the thermal balance expression from measurements of evaporating water droplets obtained under small Renolds numbers (Re ≤ 200) introduced by Ranz and Marshall, leading to great difference from reality. This paper is devoted to the parameterization of measured heat transfer coefficients under Renolds numbers related to actual hail scales proposed by Zheng, which are then applied, to Hu-He 1D and 3D models for hail growth respectively, indicating that the melting rate of a hailstone is 12%-50% bigger, the evaporation rate is 10%-200% higher and the dry-wet growth rate is 10%-40% larger from the present simulations than from the prototype models....
A new test facility equipped with refrigerant and brine circulation systems, and a rotating-scraper ice-slurry generator was constructed to analyze the ice-slurry flow and heat transfer accompanied by phase change in an industrial generator. The axial and transverse brine temperature and ice fraction concentration profiles in the ice generator were measured. The heat transfer efficiency lower than the average was identified in the upper half of the ice generator and its cause was determined by conducting three-dimensional numerical simulation using a commercial CFD code, FLUENT. Approaches of improving the brine-side heat transfer rates were investigated by incorporating extra mixing blades from numerical simulation....
A brief review of Fischer-Tropsch synthesis specially in slurry reactors ispresented,
covering reaction kinetics, activity and selectivity of catalysts, productdistribution, effects of process
parameters, mass transfer and solubility of gas. Someimportant aspects of further research are
proposed for improving both theories andproduction....
Two-flux method can be used, as a simplification for the radiative heat transfer, to predict heat flux in a slab consisting of gas and particles. In the original two-flux method (Schuster, 1905 and Schwarzschild, 1906), the radiation field was assumed to be isotropic. But for gas-particles mixture in combustion environments, the scatterings of particles are usually anisotropic, and the original two-flux method gives critical errors when ignoring this anisotropy. In the present paper, a multilayer four-flux model developed by Rozé et al. (2001) is extended to calculate the radiation heat flux in a slab containing participating particles and gas mixture. The analytic resolution of the radiative transfer equation in the framework of a two-flux approach is presented. The average crossing parameter ε And the forward scattering ratio ζ are defined to describe the anisotropy of the radiative field. To validate the model, the radiation transfer in a slab has been computed. Comparisons with the exact analytical result of Modest (1993) and the original two-flux model show the exactness and the improvement. The emissivity of a slab containing flyash/CO2/H2O mixture is obtained using the new model. The result is identical with that of Goodwin (1989)....
In order to simulate field distribution rules, mathematical models for 3-D air flows and gas transfer in the goaf of the coal mining are established, based on theories of permeability and dynamic dispersion through porous media. A gas dispersion equation in a 3-D field is calculated by use of numerical method on a weighted upstream multi-element balance. Based on data of an example with a U type ventilation mode, surface charts of air pressure distribution and gas concentration are drawn by Graphtool software. Finally, a comparison between actually measured results in the model test and the numerical simulation results is made to proves the numerical implementation feasible....
Heat transfer between gas-solid multiphase flow and tubes occurs in m a ny industry processes, such as circulating fluidized bed process, pneumatic conv eying process, chemical process, drying process, etc. This paper focuses on the influence of the presence of particles on the heat transfer between a tube and g as-solid suspension. The presence of particles causes positive enhancement of h e at transfer in the case of high solid loading ratio, but heat transfer reduction has been found for in the case of very low solid loading ratio (Ms of les s than 0.05 kg/kg). A useful correlation incorporating solid loading ratio, particle s ize and flow Reynolds number was derived from experimental data. In addition, th e k-ε two-equation model and the Fluctuation-Spectrum- Random-Trajecto ry Model ( FSRT Model) are used to simulate the flow field and heat transfer of the gas-ph a se and the solid-phase, respectively. Through coupling of the two phases the mo d el can predict the local and total heat transfer characteristics of tube in gas - solid cross flow. For the total heat transfer enhancement due to particles loadi ng the model predictions agreed well with experimental data....
Chemical absorption of CO2 into aqueous slurries of Ca(OH)2 was studied in a stirred thermostatic reactor. The influence of solid loading and stirring speed on absorption rate were investigated experimentally, and the results show that the enhancement factor increases with particle content due to the increase of reactive particles in the gas-liquid interfacial region. The absorption process was controlled by the diffusion of gas molecules in slurry. The influence of stirring intensity on enhancement factor is an integration of gas-liquid and liquid-solid mass transfer variation. A novel pre-diction model of enhancement factors was proposed with the partition of interface into two various zones, .and the prediction values by the presented model are in agreement with the experimental data....
This paper is focused on the Marangoni effect in the gas-liquid mass transfer systems. A series of experiments were conducted to observe Marangoni effect by a laser Schlieren system. Experimental investigations of the occurrence of Marangoni convection were presented. The typical polygonal patterns and even the reaching of chaotic interfacial flow were observed. The visual evidences were discussed and the characteristic time and scale of Marangoni convection were obtained approximately as 0. 5 s and 1 mm according to the Schlieren images. From the perspective of hydrodynamic instability, the mechanism of the Marangoni convection was investigated. Though many external factors have influence on the interfacial instability, the local surface-tension gradient is the primary reason for the Marangoni convection. The small-scale interfacial flow increases the surface renewal rate. Consequently, due to the occurrence of the Marangoni effect, the mass transfer rate can be significantly enhanced....
Analysis and simulation of rarefied nitrogen gas flow and heat transfer were performed with the Knusden number ranging from 0.05 to 1.0, using the direct simulation of Monte Carlo (DSMC) method. The influences of the Kn number and the aspect ratio on the gas temperature and wall heat flux in the microchannels were studied parametrically. The total and local heat fluxes of the microchannel walls varying with the channel inlet velocities were also investigated in detail. It was found that the Kn number and the aspect ratio greatly influence the heat transfer performance of microchannels, and both the channel inlet and outlet have higher heat fluxes while the heat flux in the middle part of channels is very low. It is also found that the inlet free stream flow velocity has small affect on the wall total heat flux while it changes the distribution of local heat flux....
South to North Water Transfer Project in China is the largest project over centuries to solve the water shortage problem in vast areas of northern China. It comprises of three routes: the eastern, central and western route and this study mainly focused on the eastern route. As water quality is the key factor for the eastern route, this paper examined the main factors influencing water quality of the main route south of the Yellow River, by investigating the point source, non-point source (diffusive source) and internal source pollutions along the main eastern route and in its drainage basins, and assessing the current water quality in the waterways. According to the complicated and combined systems of rivers and lakes in this route, one-dimensional water quantity and quality model for rivers and two-dimensional model for lakes were developed to simulate the hydrodynamic and pollutant transport processes. The numerical method and model algorithm were described. The values of model parameters were estimated by using field-monitoring data along the main route and the inverse modeling technique. Established models were employed to predict the degradations of CODMn and NH4+-N in the main stream, under the conditions of current pollution loads and different hydrologic conditions. Schemes were present for controlling total quantities of pollutants from point source and non-point source along the main route to secure water quality for the eastern route....
For the low price of coal and ineffective environmental management in mining area,China is in the dilemma of the increasing coal demand and the serious environmental issues in mining area.The more coal that is exported from a region,the more heavily it suffers from the environmental impacts of coal export.In this paper,the temporal and spatial process of exporting coal from Shanxi to other provinces of China is traced between 1975 and 2005.The coal net export of Shanxi increased to 370.69 million tonnes in 2005,representing an average annual growth rate of 7.5％ from 1975 to 2005.With the increase of the amount of coal export from Shanxi,the Environmental Loads Transfer (ELT) that import provinces input to mining areas of Shanxi are rising.Effective means of internalizing the environmental externality of ELT lie in:1) setting up a coal sustainable development fund to restore environment of coal mining area; 2) enforcing environment tax,financial transfer payment and transferring advantage technology of pollution reduction to coal export area; and 3) reducing coal regional flow by reducing coal demand from power generation and heating and other industries....
利用高速摄像仪实验研究了微通道内二乙醇胺（DEA）/乙醇溶液吸收 CO2的传质过程〖。采用图像法得到微通道内气泡的体积变化，根据微通道进出口压力，计算得到了气液两相从开始接触到平衡时的平均传质系数 k。分别考察了气液相流量和 DEA 浓度对传质系数的影响。结果表明：传质系数随着液相流量和溶液中 DEA 浓度增大而增大。对于给定的液相流量和 DEA 浓度，k 随着气相流量增大而增大并逐渐趋于一个恒定值。提出了一个传质系数预测式，预测值和实验结果吻合良好。...
