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1.
The relation between the critical radius and the particle size distribution for generalized Ostwald type ripening processes whereby the mass transfer coefficient is modelled by a power law was derived. The critical radius is determined by the growth rate, the mass transfer coefficient and the mass balance, and is independent of whether the limiting stationary growth regime has been obtained. 相似文献
2.
在提拉法晶体生长中,坩埚内的熔体受到多种驱动力的作用,主要包括:由熔体内部温差驱动的浮力、自由表面温度梯度导致的热毛细力、坩埚和晶体旋转产生的离心力和科里奥力,因而坩埚内的熔体流动表现出复杂的非线性流动状态.通过数值计算,模拟熔体内的对流流动、温度分布及晶体生长界面的形态,研究了晶体生长过程中,热质传输从对称到非对称的演化以及对流对固液面表面造成的影响. 相似文献
3.
建立水蒸气蒸馏分离植物挥发油传质过程数学模型．对常规蒸馏器进行改进，加入搅拌装置强化了传质．通过３种植物蒸馏的实验数据，求取了总传质系数值并验证了数学模型，并讨论了搅拌转速对传质系数的影响． 相似文献
4.
通过对现有化工原理吸收实验装置的分析,设计出了一种多功能化工原理吸收实验装置,并将实验室的现有吸收实验装置进行了改造。与传统装置相比,新开发的实验装置具有以下功能:可以测定多种散装填料的吸收传质系数;不同类型填料的吸收传质系数;单一的规整填料的吸收传质系数以及规整填料和散装填料的混合吸收传质系数。通过填料吸收塔实验装置的改进,使学生对填料吸收实验的印象更加深刻,实验教学内容更加丰富,增强学生的创新意识,锻炼了学生的实践能力。 相似文献
5.
Danckwert's method was used to determine the specific interfacial area, a, and the individual mass transfer coefficient, kL, during absorption of CO2 in a bubble column with an anionic surfactant in the carbonate-bicarbonate buffer solution and NaAsO2 as catalyst, the presence of which decreases the specific interfacial area and the individual mass transfer coefficient. The specific interfacial area and the individual mass transfer coefficient increase with increasing superficial gas velocity. The specific interfacial area decreases whereas the individual mass transfer coefficient increases with increasing temperature. The results of experiments were used to determine the dependence of a, kL, and kLa on the surface tension, the temperature of the absorption phase, and the superficial velocity of the gas. The calculated results from the correlation were found to be within 10% deviation from the actual experimental results. 相似文献
6.
Marangoni effectis of interestto the chemical en-gineers from both scientific and practical points ofview[1—6]. The Marangoni convection contributes tothe renewal of the interfacial surface and is capable ofincreasing the mass transfer rate, resulting in intensi-fication of separation processes such as distillation,extraction, absorption, and desorption. The theoretical studies of Marangoni instability inthe past were focused on determining the critical tran-sition point. The critical condit… 相似文献
7.
This study deals with the effect of hydrotropes on the solubility and mass transfer coefficient of salicylic acid. The solubility and mass transfer studies were performed using the hydrotropes, i.e., sodium acetate, sodium salicylate, citric acid, and urea at concentrations of 0-3.0 mol/L and system temperatures of 303-333 K. It was found that the solubility and mass transfer coefficient of salicylic acid increases with increase in hydrotrope concentration and also with system temperature. All hydrotropes used in this work showed an enhancement in solubility and mass transfer coefficient to different degrees. The maximum enhancement factor values were determined for all hydrotropes used in this study. The highest value was 28.08 for solubility studies and 10.42 for mass transfer studies. The performance of hydrotropes was measured in terms of the Setschenow constant （Ks）. The highest value observed was 0.696. 相似文献
8.
The space effects of deep pit slope are analyzed by an elastic mechanics principle. The interaction among the critical slide angle, the friction coefficient, the cohesion, and the horizontal radius of the deep pits is derived in this paper. It indicates that the deeper the pit is excavated, the greater the critical slide angle is. Both the theory for reducing stripping waste rock in deep pit and the approach to determining the configuration of the stable slope are developed from the interaction. The theory in this paper comprises the preceding principles of stability analysis of slopes and is suitable for analyzing that of deep pit. 相似文献
9.
围绕超临界流体萃取过程中的传质、传质系数的计算,超临界流体萃取速率、传质阻力,超临界流体通过固定床的压降以及超临界流体萃取过程中的影响因素等动力学问题进行了探讨和阐述,对于超临界流体萃取技术的应用与过程操作具有参考价值。 相似文献
10.
基于FLUENT软件对制冷剂R134a在水平螺旋槽管管外沸腾换热进行了三维数值模拟,得到了其饱和泡状沸腾过程中体积含汽率的分布规律和换热系数,并和光管进行了比较。结果表明螺旋槽管外侧能够很好地强化沸腾传热。此外,还通过改变边界条件分析了质量流量、热流密度的变化对螺旋管管外沸腾换热系数的影响。 相似文献
11.
Numerical study of heat transfer characteristics of downward supercritical kerosene flow inside circular tubes 总被引：3，自引：0，他引：3
The heat transfer characteristics of China RP-3 aviation kerosene flowing in a vertical downward tube with an inner diameter of 4 mm under supercritical pressures are numerically studied. A ten-species surrogate model is used to calculate the thermophysical properties of kerosene and the re-normalization group (RNG) k-ε turbulent model with the enhanced wall treatment is adopted to consider the turbulent effect. The effects of mass flow rate, wall heat flux, inlet temperature, and pressure on heat transfer are investigated. The numerical results show that three types of heat transfer deterioration exist for the aviation kerosene flow. The first type of deterioration occurred at the tube inlet region and is caused by the development of the thermal boundary layer, while the other two types are observed when the inner wall temperature or the bulk fuel temperature approaches the pseudo-critical temperature. The heat transfer coefficient increases with the increasing mass flow rate and the decreasing wall heat flux, while the inlet bulk fluid temperature only influences the starting point of the heat transfer coefficient curve plotted against the bulk fluid temperature. The increase of inlet pressure can effectively eliminate the deterioration due to the small variations of properties near the pseudo-critical point at relatively high pressure. The numerical heat transfer coefficients fit well with the empirical correlations, especially at higher pressures (about 5 MPa). 相似文献
12.
A mathematical model of the dynamic behavior of countercurrent chromatography was proposed, and the model parameters, including the partition coefficient, the axial dispersion coefficient, the intraparticle diffusion coefficient and the external mass ransfer coefficient were calculated by the method of chromatogram moment analysis. Comparison of the experimental chromatograms of caffeine and theophylline determined in this work with the simulated curves computed by the proposed model showed fairly good agreement. Further, the difference between the average identified the partition coefficients by chromatogram moment analysis and the experimental values was small also, and the relationship between the external mass transfer rate and the linear velocity was similar to that obtained with solid-liquid chromatography. 相似文献
13.
对Ag纳米线的熔化和过热作了研究，提出了一种经典热力学模型对Ag纳米线的过热机制作了阐述；当考虑到低能Ag／Ni界面的作用时，推导了过热的定量表达式，说明了过热与纳米线的半径和界面能有密切关系． 相似文献
14.
利用相分离法制备了亲水性聚偏氟乙烯（PVDF）-氯化锂共混膜,通过接触角测量和水蒸气吸附实验评价了膜的亲水性,并通过水蒸气渗透实验测试了总传质系数和水蒸气渗透速率.实验结果表明：随着铸膜液中氯化锂含量的增加,PVDF膜的接触角明显降低,同时,PVDF膜对水蒸气的吸附能力随之增加.当氯化锂质量分数低于2.5%时,水蒸气在膜中的总传质系数略有增加,当氯化锂质量分数高于2.5%时,总传质系数明显增加,而水蒸气在膜中渗透速率随氯化锂含量的增加而增加.因此,氯化锂的加入可以显著提高PVDF膜的亲水性,进而增强水蒸气的渗透性能. 相似文献
15.
The transmission performance of cycloid ball planetary transmission (CBPT) is affected by cycloid tooth undercutting directly, and the design of CBPT can be optimized by the non-undercutting condition. Firstly, the theoretical equation of cycloid tooth is given, and the curvature radius of cycloid tooth profile is derived. Secondly, according to the relationship between the curvature radius and the distribution circle of balls, the non-undercutting condition of cycloid tooth profile is established, and the non-undercutting critical condition is deduced. Finally, the validity of the non-undercutting critical condition is verified by simulation. The result shows that the non-undercutting critical condition can be used to optimize the design of CBPT 相似文献
16.
刘丽芳 《清华大学教育研究》2010,31(3)
采用中国社会科学院经济研究所"中国城乡居民收入分配"课题组2002年住户调查数据,运用分位数回归系数的变异系数作为风险值,本文计算出中国教育个人投资风险值,并与其他国家进行比较.结果表明,中国个人教育投资风险为0.18,相对于其他国家较高.笔者提出两点建议,一是结合个人教育投资风险现状,引导高等教育理性需求;二是制定以风险转移和分担为核心的成本分担机制和学生贷款政策. 相似文献
17.
为了探索油气在冷凝回收过程中的冷凝规律,采用气液两相流模型描述了油气在竖直管内湍流流动时的冷凝过程.采用有效传质系数描述了油气组分的质量传递.模拟了油气在管内冷凝时的温度、管内压力、液膜厚度和Nusselt数的变化,得到了入口油气和管壁的温差、雷诺数对冷凝率和Nusselt数的影响.结果显示：增大入口雷诺数能显著增强传热和冷凝,但是增大入口油气和管壁的温差对冷凝率的影响较小;另外,还发现传质阻力对油气冷凝率有较大影响.此模型的计算结果与先前的实验数据能够很好地符合. 相似文献
18.
马海珠 《浙江教育学院学报》2005,(5):46-52
利用旋转异构态模型和伪立体化学平衡统计方法,得到考虑侧基的均方回转半径及温度系数的改进公式,研究典型的大侧基聚衣康酸酯链的构象和构型性质.并通过数值计算,研究无规聚衣康酸酯链均方回转半径特征比、温度系数与构象能的关系,研究链规整程度对均方回转半径特征比的影响. 相似文献
19.
对顶喷流化床中的颗粒干燥过程进行模拟.引进润湿率参数表示喷雾液滴对流化颗粒的有限润湿,并利用聚丙烯和水物系的实验数据回归得到了该物系的润湿率表达式.通过得到的润湿率对顶喷流态化过程进行模拟,模拟结果与实验结果基本一致,润湿率及过程模型得到了验证. 相似文献
20.
Xia Fengshun Li Wenpeng Guo Junheng Han You Zhang Minqing Wang Baoguo Li Wei Zhang Jinli 《天津大学学报(英文版)》2021,27(5):409-421
A pore-array intensified tube-in-tube microchannel (PA-TMC), which is characterized by high throughput and low pressure drop, was developed as a gas–liquid contactor. The sulfite oxidation method was used to determine the oxygen efficiency (φ) and volumetric mass transfer coefficient (kLa) of PA-TMC, and the mass transfer amount per unit energy (ε) was calculated by using the pressure drop. The effects of structural and operating parameters were investigated systematically, and the two-phase flow behavior was monitored by using a charge-coupled device imaging system. The results indicated that the gas absorption efficiency and mass transfer performance of the PA-TMC were improved with increasing pore number, flow rate, and number of helical coil turns and decreasing pore size, row number, annular size, annular length, and surface tension. The φ, ε and kLa of PA-TMC could reach 31.3%, 1.73 × 10−4 mol/J, and 7.0 s−1, respectively. The Sherwood number was correlated with the investigated parameters to guide the design of PA-TMC in gas absorption and mass transfer processes.
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