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11.
Merits of the Fernandes model(Fernandes et al.1983)for two-phase slug flow in verticaltubes are reviewed in this paper.While predicting many macroscopic parameters of slug flow in verti-cal tubes,it fails to present correctly the trend that the average voidage in liquid slugs increases asthe rising velocity of Taylor bubbles is increased.It is also desirable to extend its application toelectrolyte systems, and to churn flow conditions.Based on the diagnostic analysis,the model equa-tion for gas entrainment by falling liquid film is reformulated and the influence of surface tension isalso accounted for.Development of the falling liquid film is recognized in the revised model in or-der to suit the case of short Taylor bubbles as well.The modified model predicts the variation of av-erage voidage in liquid slugs in good agreement with available experimental data. 相似文献
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A theoretical investigation has been conducted for the prediction of the critical height at the onset of gas entrainment during single discharge from a stratified, two‐phase region, through a branch installed on an inclined flat wall. The predicted critical height at the onset of gas entrainment was proven to be a function of Froude number (Fr) and density ratio of the interface fluids. Three different experimental data sets at wall inclination angles of zero, 45 and 90 degrees (i.e. side, inclined and bottom branches) were used for comparisons. A good concurrence was illustrated between the experimental and theoretical values. 相似文献
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根据填料塔内气液传质的特点,将填料由固定改为跳动形式,采用新型的气液分布器、雾沫分离器,增加防壁流环等,提高传质效率,降低阻力. 相似文献
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分别以水、氨、R290、R22、R134a为工质,计算分析了在不同膨胀比压缩比条件下圆柱形及圆锥形混合室两种结构喷射器的喷射系数,并定义了等喷射系数压缩比、等喷射系数参数线和参数区。膨胀比恒定,压缩比小于等喷射系数压缩比时,圆柱形混合室的喷射系数较圆锥形的大;压缩比大于等喷射系数压缩比时,圆锥形混合室喷射系数较圆柱形的大。由等喷射系数参数线知,随膨胀比增大,等喷射系数压缩比减小。在等喷射系数参数区内,两种结构喷射器效率相当;在等喷射系数参数区左边,宜使用圆柱形混合室;在等喷射系数参数区右边,宜使用圆锥形混合室。绝热指数对等喷射系数参数区的分布具有决定作用。 相似文献
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A roll-coating experimental system is used to study the effect of pre-wetting on dynamic contact angles, the interfacial displacement depth, and the associated phenomenon of air entrainment. The system consists of a roll, which is horizontally rotating in a liquid pool. The dynamic contact angle is recorded by a macrophotography system. The test liquids are glycerol solutions with viscosities in the range 104 < μ < 748 mPa · s. The value of (μV/ρg)0.5 is taken as the characteristic length to be used in the dimensionless relationships which correlate experimental measurements. The effect of base layer entry angle into the liquid pool on the dynamic contact angles and other flow parameters is studied. Comparison is made with measurements in dry tape-coating and other pre-wet roll–coating systems. 相似文献
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Subhasish Mitra Elham Doroodchi Geoffrey M. Evans Vishnu Pareek Jyeshtharaj B. Joshi 《American Institute of Chemical Engineers》2016,62(1):295-314
Hydrodynamics of collision interactions between a particle and gas‐liquid interface such as droplet/film is of keen interest in many engineering applications. The collision interaction between a suspended liquid (water) film of thickness 3.41 ± 0.04 mm and an impacting hydrophilic particle (glass ballotini) of different diameters (1.1–3.0 mm) in low particle impact Weber number ( ) range (1.4–33) is reported. Two distinct outcomes were observed—particle retention in the film at lower Weber number and complete penetration of the film toward higher Weber number cases. A collision parameter was defined based on energy balance approach to demarcate these two interaction regimes which agreed reasonably well with the experimental outcomes. It was shown that the liquid ligament forming in the complete penetration cases breaks up purely by “dripping/end pinch‐off” mechanism and not due to capillary wave instability. An analytical model based on energy balance approach was proposed to determine the liquid mass entrainment associated with the ligament which compared well with the experimental measurements. A good correlation between the %film mass entrained and the particle Bond number ( ) was obtained which indicated a dependency of Bo1.72. Computationally, a three‐dimensional CFD model was developed to simulate these interactions using different contact angle boundary conditions which in general showed reasonable agreement with experiment but also indicated deficiency of a constant contact angle value to depict the interaction physics in entirety. The computed force profiles from computational fluid dynamics (CFD) model suggest dominance of the pressure force over the viscous force almost by an order of magnitude in all the Weber number cases studied. © 2015 American Institute of Chemical Engineers AIChE J, 62: 295–314, 2016 相似文献