共查询到18条相似文献,搜索用时 160 毫秒
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降膜结晶过程的数值模拟 总被引:5,自引:0,他引:5
本文采用数值方法对在工业上有着广泛应用前景的降膜结晶分离过程进行了模拟,提出了一套描述降膜结晶过程的降膜流动、传热、传质及结晶相变相互耦合的以控制容积为基础的有限差分的湍流数值计算模型和算法。本模型的计算结果与以前简化模型的计算结果相比,更符合实验值. 相似文献
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《工程热物理学报》2010,(11)
从理论上分析了膜换湿过程中传质过程和传热过程之间的耦合关系,建立了相应的物理数学模型,发展了一种计算热质耦合的方法。分析结果表明传质过程对传热过程的影响主要体现在两方面:一是质量流携带的焓对传热过程的影响,二是吸附和脱附产生的吸附热对传热过程的影响。而传热过程对传质过程的影响主要体现在温度对膜湿阻的影响。采用数值模拟的方法对热质耦合过程进行了研究,结果表明:当热流与质量流方向相同时,热阻随湿度差的增大显著增大,而当热流与质量流方向相反时,热阻随湿度差的增大显著变小,而膜两侧湿度差对湿阻基本无影响。温度的升高会显著增大传质通量,同时降低湿阻,从而使得热流密度和热阻也受到显著的影响。 相似文献
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An experimental analysis of ammonia-water absorption process was performed for the falling film and bubble modes in a plate-type absorber. The experiments were made to examine the effects of solution flow rate and gas flow rate on the performance of the absorber. It was found that the bubble mode is superior to the falling film mode for mass transfer performance, and more heat was generated in the bubble mode. Increase of solution flow rate rarely affected the mass transfer, but improved the heat transfer. As the gas flow rate increased, fluidization occurred in the bubble mode and influenced the thermal boundary layer. However, channeling appeared in the falling film mode and decreased the heat transfer area. Increase of the gas flow rate greatly enhanced the performance of heat transfer in the bubble mode but made it worse in the falling film mode. Finally, the results were converted into dimensionless numbers to elucidate physical phenomena and we plotted Sherwood number versus Reynolds number for mass transfer performance and Nusselt number versus Reynolds number for heat transfer performance. 相似文献
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I. P. Starodubtseva A. N. Pavlenko O. A. Volodin A. S. Surtaev 《Thermophysics and Aeromechanics》2012,19(2):307-316
The dynamic process of rewetting of the overheated surface by gravitationally falling film of cryogenic liquid was firstly modeled numerically with consideration of local distribution of heat transfer coefficient in the wetting zone along the 2D front. The front shape corresponding to self-organizing regular structures observed in experiments was obtained in the numerical experiment. Evolution of the front shape was studied. It was shown that local motion velocities of different areas of the 2D wetting front differed significantly. Total time of transitional process was determined by the minimal velocity of evaporating liquid boundaries in the front zones between boiling jets. This model allows quantitative determination for the wetting front velocity, variable in time and space, and temperature fields in the heater. Reliability of calculation results was proved by direct comparison with experimental data. 相似文献
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S. P. Aktershev 《Thermophysics and Aeromechanics》2010,17(3):359-370
Heat transfer in the laminar-wavy film of liquid falling over the heated plate is studied numerically. To describe the wavy
film flow the integral model is applied. Calculation results demonstrate the effect of physical properties of liquid and wavy
flow parameters on heat transfer intensification by stationary running waves. 相似文献
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Wilko Rohlfs Georg F. Dietze Herman D. Haustein Reinhold Kneer 《The European physical journal. Special topics》2013,219(1):111-119
Three-dimensional interfacial waves developing on the free surface of falling liquid films are known to intensify heat and mass transfer. In this context, the present paper studies the effect of electrostatic as well as of thermo-capillary forces on a falling film of a dielectric liquid. Therefore, measurements of the local film thickness using a confocal chromatic imaging method were performed under isothermal and heated conditions. The experimental results show that both forces destabilize the flow. It is found, that the application of an additional electric field under heating conditions enhances the generation of rivulets, thereby reducing the overall heat transfer coefficient. 相似文献
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Investigation results on hydrodynamics, heat transfer, and crisis phenomena in laminar-wave liquid films falling down the surfaces of different geometry are presented in this study. Freon mixture R21/R114 with initial concentration of low-boiling component of 4?C16.6 % was used as the working liquid. The film Reynolds number at the inlet to the experimental section varied from 60 to 700. The heat flux density was changed within 0?C5 W/cm2. The images of wave surface of the falling liquid film and formation of dry spots were visualized and recorded by the high-speed video camera. Results of investigation of the wave structure of the film surface, measurements of heat transfer coefficients under the conditions of boiling, and critical heat fluxes in the film flow over the smooth and structured surfaces are presented. 相似文献
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水平管降膜蒸发器传热优化研究 总被引:1,自引:0,他引:1
基于分布参数方法,对大型制冷系统中的水平管外降膜蒸发进行了传热优化数值模拟计算.在计算中,分析了饱和的液态制冷剂R134a在水平的铜管束外流动蒸发的换热特性.模型考虑了不同的管子类型和2流程不同管程布置对蒸发器换热特性的影响,结果表明,蒸发器采用Turbo-EHP管的性能高于其它管;不同管程布置对蒸发器性能的影响比较大,其中,下进上出管程布置的换热性能优于其它管程布置.同时,本文考虑了传热管外"干斑"对换热的影响.本文结论对于大型制冷系统中的降膜蒸发器传热优化设计具有指导性意义. 相似文献