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Taleb Zarei Masoud Farsiani Jamshid Khorshidi 《Korean Journal of Chemical Engineering》2017,34(1):150-159
In order to better understand the hydrodynamics of valve trays, air-water operation in an industrial scale tower with 1.2 m of diameter, consisting of two 14% valve trays, was studied. Experimental results of clear liquid height, froth height, average liquid holdup, dry pressure drop, total pressure drop, weeping and entrainment were investigated, and empirical correlations were presented. Then, a three-dimensional computational fluid dynamics (CFD) simulation in an Eulerian framework for valve tray with ANSYS CFX software was done. The drag coefficient, which was used in the CFD simulations, was calculated from the data obtained in the experiments. The simulation results were found to be in good agreement with experimental data at this industrial scale. The objective of the work was to study the extent to which experimental and CFD simulations must be used together as a prediction and design tool for industrial trays. 相似文献
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Computational fluid dynamics (CFD) has recentlyemerged as an effective tool for the investigation of the hydraulic parameters and efficiency of tray towers. The computation domain was established for two types of oriented valves within a tray and meshed into two parts with different grid types and sizes. The volume fraction correlation concerning inter-phase momentum transfer source was fitted based on experimental data, and built in UDF for simulation. The flow pattern of oriented valve tray under different operating conditionswas simulated under Eulerian-Eulerian framework with realizable k-ε model. The predicted liquid height from CFD simulation was in good agreement with the results of pressure drop and volume fraction correlations. Meanwhile, the velocity distribution and volume fraction of the two phases were demonstrated and analyzed, which are useful in design and analysis of the column trays. 相似文献
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Jun Wang Xin Zhou Ben Gao Chunxiang Huang Jiarui Sun Xueni Sun Hui Shao Jiangquan Ma Yixin Leng 《American Institute of Chemical Engineers》2019,65(11):e16722
Weeping is an important hydraulic parameter that needs to be considered for valve trays and for calculations in the distillation field. Therefore, the accurate prediction of weep rate is crucial for the optimal design of valve trays. First, the effects of gas and liquid loads and weir height on weep rate, tray pressure drop, and actual bubbling area were studied in a 1.5 m × 0.61 m cold simulator. Second, the weep modes on the valve tray were analyzed in detail. A theoretical model was then derived to calculate weeping. The model showed a clear relationship between the weep rate and the fractional bubbling area. The experimental data showed that the weir height substantially affected the orifice coefficient of the liquid passing through the valve. Finally, the relation between weir height and orifice coefficient was obtained by fitting the experimental data. The agreements were good, and the maximum deviations were approximately 25%. 相似文献
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木文以空气-水系统在1200×400mm矩形装置内对网孔塔板的流体力学进行了试验研究。试验所采用的塔板参数和操作条件为:塔板开口宽度为3、3.5、4、4.5及4.7mm;塔板开孔率为9.9、12.3、13.2、14.9及15.4%; 挡沫板宽度为150、200、250、300mm;板间距为400、500、600、700及800mm;液流强度为20、30、45、60m~3/m·h;气体空塔速度为0.60—2.8m/s。测定了各有关参数对塔板压降、雾沫夹带和泄漏的影响,并对试验数据进行了关联,得出了计算塔板压降、雾沫夹带、泄漏、上限气速、下限气速及操作弹性等的关系式,以便用于网孔塔板的设计。 相似文献
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The hydrodynamic parameters of a Nye tray were investigated by performing experiments in a tower with a diameter of 1.22 m. Air was used as the gas phase and water was used as the liquid phase. A number of parameters such as the dry pressure drop, the total pressure drop, the clear liquid height, the froth height, and the entrainment were measured. A tray stability factor was obtained using the amount of weeping, the clear liquid height, the dry pressure drop, and the Froude number. All experiments were repeated for the matching sieve tray under the same conditions. Ultimately, advantages and disadvantages were compared, and the results demonstrated that the Nye tray has a couple of advantages over the sieve tray, except that the sieve tray is slightly more stable. 相似文献
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The capacity of a column is limited by the distribution of gas and liquid, especially in case of large‐diameter cross‐flow trays. In order to solve the bottleneck, a new counter‐flow tray named total spray tray (TST) was put forward. Taking air/water as medium, the hydrodynamic behavior, including the pressure drop, weeping, entrainment, and clear liquid height, was investigated, in comparison with the CTST, which had a higher capacity. Based on experimental data, the correlations of the TST pressure drop were established by regression analysis method. The experimental results show that the TST has a lower wet pressure drop and less weeping. More interestingly, its clear liquid height can be self‐adjusting with the variation of the gas kinetic energy factor, which is beneficial to improving the capacity. 相似文献
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Screen trays are proprietary devices similar to sieve trays which are used in distillation and absorption applications. The pressure drop, liquid holdup and entrainment are measured for screen trays in an air/water column and compared to results obtained with sieve trays. The effciencies of both types of trays were compared in a distillation column using systems of various physical properties (methanol/water, acetic acid/water and cyclohexane/n-heptane mixtures). It was found that the screen tray has a lower dry pressure drop, higher liquid holdup, lower entrainment and weeping, and higher jet flooding capacity than the sieve tray. However, the effciencies of both trays are similar for the systems studied. A model was developed for predicting total pressure drop for screen trays using an air/water column. The model was tested using results for methanol/water, cyclohexane/n-heptane and acetic acid/water systems at total reflux. The deviations are within +/- 20% for 90% of the data points. The effect of a bed of mesh packing on the screen tray was also studied. It was found that the packing led to a higher tray effciency, but resulted in a higher tray pressure drop. 相似文献
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Screen trays are proprietary devices similar to sieve trays which are used in distillation and absorption applications. The pressure drop, liquid holdup and entrainment are measured for screen trays in an air/water column and compared to results obtained with sieve trays. The effciencies of both types of trays were compared in a distillation column using systems of various physical properties (methanol/water, acetic acid/water and cyclohexane/n-heptane mixtures). It was found that the screen tray has a lower dry pressure drop, higher liquid holdup, lower entrainment and weeping, and higher jet flooding capacity than the sieve tray. However, the effciencies of both trays are similar for the systems studied. A model was developed for predicting total pressure drop for screen trays using an air/water column. The model was tested using results for methanol/water, cyclohexane/n-heptane and acetic acid/water systems at total reflux. The deviations are within +/- 20% for 90% of the data points. The effect of a bed of mesh packing on the screen tray was also studied. It was found that the packing led to a higher tray effciency, but resulted in a higher tray pressure drop. 相似文献
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Jun Wang XiuYing Yao Tao Chen ChuanXiang Huang XueNi Sun Hui Shao YiXin Leng Chong Peng Jing Zhong JunCheng Jiang 《American Institute of Chemical Engineers》2022,68(9):e17720
Weeping is an important hydraulic parameter for the design and optimization of perforated plates because it determines the lower limit of the tray operation (vapor load). Therefore, an accurate prediction of the weep rate is very important. First, according to our theoretical analysis of the weeping phenomena of large-scale perforated trays, we proposed three weep modes on a perforated tray: (1) random weeping in the bubbling zone, (2) dumping in the nonbubbling zone, and (3) liquid fluctuation-induced weeping. Second, a weep rate model was developed, and the literature data were correlated to determine model parameters. Results showed the fractional hole area substantially affects the model parameters. We also examined the effects of the tray structure, flow parameter, and fluid physical properties on the weep rate. Finally, the developed model was used to predict the weep rate of different scale trays reported in references, and the prediction results showed good agreements. 相似文献
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The weeping phenomenon was investigated using some experimental tests and a numerical model. The tests were performed within a 1.22‐m‐diameter pilot‐scale column including two chimney trays and two Nye test trays with an air‐water system. The rates of weeping were measured in the Nye trays with two heights of the weir and a hole area of 5 %. Moreover, the weeping rates in the outlet and inlet halves of the Nye tray and the total weeping rate were calculated. In the next step, an Eulerian‐Eulerian computational fluid dynamics (CFD) technique was used. The results show good agreement between the attained CFD findings and the experimental data. 相似文献
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Hongkang Zhao Qunsheng Li Gangqiang Yu Chengna Dai Zhigang Lei 《American Institute of Chemical Engineers》2019,65(5):e16563
An evolution of the traditional sieve tray, the flow-guiding sieve tray (FGST), has been utilized in many separation processes, especially for handling viscous systems. The objectives of this work are to optimize the design process of FGSTs and realize the full potential of their separation performance. A computation fluid dynamic (CFD) model that incorporated the modified interphase momentum transfer term was developed. Simulated measures of hydrodynamic performance, such as pressure drop, weeping, entrainment, and clear liquid height agree well with the experimental data, thus verifying the accuracy and reliability of the CFD model established in this work. Furthermore, based on the obtained hydrodynamic parameters, a quantitative model for designing flow-guiding holes was established and validated by modifying an experimental FGST (diameter 476 mm) and reconstructing an industrial sieve-tray tower (diameter 1,200 mm). The hydrodynamic parameters and quantitative model are of vital importance for better design and further modification of FGST. 相似文献
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Taleb Zarei Ehsan Abedini Rahbar Rahimi Jamshid Khorshidi 《Korean Journal of Chemical Engineering》2017,34(4):969-976
This paper addresses an investigation on the hydrodynamic behavior of a new type of cap trays called conical cap tray (ConCap tray). A 3-D computational fluid dynamics model was developed to predict the hydrodynamics of the ConCap tray which is operated in the spray regime. The model considers two phase flow of gas and liquid in a VOF-like code framework. The homogeneous multiple size group model (MUSIG model) and shear stress transport (SST) turbulence model were implemented. Detailed insights into the hydrodynamic behavior of the inside of the cones were obtained. The relation between velocity, pressure and cross section area of the flow inside the cone also was formulated. The computational fluid dynamic (CFD) results show that the pressure variation in the cones forces the liquid on the tray to be highly turbulent, which leads to deform the interface to break up. Effect of different riser heights was also studied by CFD simulations. The results show that the riser height has a significant role in the hydrodynamics of the tray, especially in uniform gas distribution in the tray and reducing weeping rates. 相似文献
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Understanding 3 pass trays is the key to design of 6 pass trays, such as those in the large towers expected in carbon-capture services. This paper presents a hydraulic distribution model for 3 pass trays with no liquid or vapor equalization. The model is verified by comparison with FRI's test data and with one operating tower. Our paper predicts good distribution for the 3 pass trays tested at FRI, and shows that the poor efficiencies in some of the tests were due to losing the downcomer seals and not tray maldistribution. The model predicts good distribution at maximum rates in the operating tower, but finds that at lower rates, where valves open and close, there is an extreme sensitivity of vapor distribution to small pressure drop variations. This sensitivity precludes reliable modeling of distribution in this region and may define an unstable region in the operation of 3 pass trays. 相似文献
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The novel SiC foam valve tray was made of thin slices of SiC foam material with a high specific surface area. Hydrodynamic performances of the novel SiC foam valve tray were studied with air-water system at atmospheric pressure. These performance parameters included pressure drop, entrainment, weeping and clear liquid height. The mass transfer efficiency of the SiC foam valve tray was measured in laboratory plate column. Compared with the F1 float valve tray, the dry pressure drop was decreased about 25%, the entrainment rate was about 70% lower at high gas load, the weeping was much better, and the mass transfer efficiency was far higher. Thus, the overall performance of the novel SiC foam valve tray was better than that of F1 float valve tray. 相似文献