共查询到19条相似文献,搜索用时 78 毫秒
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气液降膜流动中液相速度波动及其传质研究 总被引:1,自引:0,他引:1
为了研究降膜流动的动力学性质及其对气液传质过程的影响,在气液逆流的不同气液流动条件下采用激光多普勒(1aser Doppler anemometer,简称LDA)测量了降膜流动的液相速度分布和瞬时速度波动.和以往假定液膜外侧为自由表面,液膜表面处剪切力为零的Nusselt模型进行了比较,LDA测量结果表明气液逆流时降膜流动的最大液相速度出现在液膜表面之内,并且是以近界面区域的速度波动为特征的流动.在相同的降膜装置中进行了乙醇稀溶液的解吸实验,液相传质系数的实验测量值是渗透理论预测值的1~2倍.实验结果表明液相界面区域的速度波动加快了气液界面的表面更新速率,减小了传质阻力,强化了气液界面的传质过程.考虑液膜波动特征对气液接触情况的影响,从气液两相接触时间的角度出发,修正了渗透理论对液相平均传质系数的预测,预测结果和实验结果相吻合. 相似文献
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竖直管外降膜吸收传热传质过程强化的研究 总被引:9,自引:0,他引:9
对LiBr溶液在光滑管和四种换热强化管竖直管外降膜吸收过程进行了实验研究,得到了实验条件下的最佳管型,分析了非绝热吸收过程中传热传质相互作用,相互影响的关系,建立了竖直管外降膜吸收热-质传递过程的数学模型,并对该过程进行了数值计算,模型计算值与实验结果的比较证明该模型具有较好的适用性。 相似文献
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对垂直管内蒸汽和水逆向流动时的降膜蒸发、蒸汽夹带液体及传热恶化特性进行了详细的试验研究,发现降膜蒸发管工质入口端的壁温首先突然升高和出现波动.通过分析其机理和影响因素,给出了传热恶化的预测关系式. 相似文献
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热管式降膜吸收器的传热传质 总被引:7,自引:0,他引:7
对热管式降膜吸收顺溶液吸收传热传质并通过热管移出吸收热的过程进行了数值研究,根据所建立的数学模型,通过求解热管加热段外壁面溶液波动降膜的动态二维偏微分方程和热管传热方程,研究了膜雷诺数,低位余热温度,输出温度等因素对传热管质过程的影响,对进一步工作提出了新的见解。 相似文献
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A modified form of Carey'ls method for predicting the heat transfer to a turbulent falling film is presented. The new model is successfully tested against experimental data as well as other models. This method utilizes an optimization technique along with the Rombcrg integration to determine two universal constants for the modified turbulent diffusivisity model. The results show that in spite of its relative simplicity, the new model is a fairly accurate one, having an overall average error of less than 9%. 相似文献
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S. C. J. Ana B. C. Sutrodhar Rahul Basu P. Ray B. K. Dutta 《Chemical Engineering Communications》1989,79(1):27-37
An analytical solution for absorption of a gas with an accompanying first order reaction in a laminar falling film is developed. The gas flow is countercurrent to that of the liquid film. Change in the gas phase concentration because of the reaction, as it happens in practical situations, has been taken into account. Some computed results are presented to show the effects of the system parameters—namely, the reaction rate parameter, the Biot number, and the absorption factor— on the mass transfer enhancement factor and on the fractional removal of the feed gas over a given non-dimensional film length. 相似文献
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A numerical simulation and an experimental study were carried out for sensible heat transfer for a subcooled water film falling across a horizontal heated tube. A laminar model and a turbulent model were adopted to calculate the heat transfer coefficient. The whole wetting zone on the tube surface was divided into two zones: the top stagnation zone and the lateral free film flow zone. The initial boundary conditions for the free film flow zone were determined by calculating the fluid and the temperature fields in the stagnation zone. A modified wall function method was used for the turbulent model. The comparisons between the experimental data and the numerical solutions show that the experimental data agree reasonably well with the laminar model solutions. Finally, two simple correlations were proposed for predicting the convective heat transfer of a falling film for engineering applications. 相似文献
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以溶液聚合法所制得的约50μm厚的PAN薄膜为基膜成功地制备出PAN基炭薄膜。通过测量试样的重量、尺寸、分子中各基团的振动形式,膜表面结构与组分分布和序态结构的变化,对炭化行为进行了研究。测试结果表明,薄膜试样在热稳定化后和炭化后的重量损失分别为10%和39%,尺寸收缩率分别为13%和15%左右,PAN基炭股由碳、氮和氧三种基本元素所组成。随着热解温度的提高,PAN线型结构转变成具有萘啶环大共轭结构的梯形高聚物,继而生成相互交联而成的共轭碳的类石墨芳香族六角网状层面结构。 相似文献
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