The reduction furnace is the main reactor for manufacturing polysilicon. This present work has numerically investigated the effect of mass transfer on the CVD process. The results indicate that the thermal diffusion ratio of the species is two orders of magnitude lower than the Sherwood number, so that the thermal diffusion can be ignored. Moreover, the ratio of DaHCl/DaTCS indicates that the mass transfer of HCl is the control mass transfer step. Depending on the rod surface temperature, the CVD process can be controlled by HCl mass transfer or CVD reaction. Based on the relationship between mass transfer and reaction, three strategies to achieve uniform and high deposition rate have been proposed, including reducing inlet velocity, decreasing surface temperature of the rod near the jets developing stage and optimizing rod away from the jets developing stage.

A confined jet in a cavity exhibits complex vortex dynamics and transport behavior governed by geometric confinement and jet inertia. In this study, a single upward jet in a cylindrical cavity is investigated using flow visualization, large-eddy simulation (LES), and unsteady Reynolds-averaged Navier-Stokes (URANS) simulations over a wide range of jet Reynolds numbers and cavity aspect ratios. Three distinct flow regimes are identified and mapped in H/D similar to Re-jet space: (i) head-impact laminar flow, largely insensitive to H/D; (ii) sidewall-oscillatory turbulent flow for H/D > 3.0; and (iii) head-impact turbulent flow for 0.6-0.8 <= H/D < 3.0. Oscillatory behavior originates from asymmetric evolution of large-scale vortex structures, with a hierarchical distribution of turbulent intensity from the jet core to reverse and secondary flows. A cavity-based Reynolds number is introduced to characterize global transport, and the resulting parameter Re-body/Re-jet provides a unified description of momentum redistribution across scales. For H/D > 2.2, the volumetric flow rate distributions collapse onto a unimodal profile with a peak value of approximately 0.8. For 0.6-0.8 < H/D < 2.2, the distribution transitions to an M-shaped profile, reflecting the competing contributions of primary and secondary flows. Below this range, the profile reverts to unimodal with a higher peak (>1.2), corresponding to the suppressed secondary flow and dominant cavity-scale circulation. These results provide a unified scaling framework linking flow regimes, vortex dynamics, and cavity-scale transport in confined jet-cavity systems.

Gas absorption is widely used in chemical, environmental, and energy industries for CO2 capture, gas purification, yet its industrial performance is often constrained by high pressure drop, limited flooding capacity, and insufficient mass-transfer efficiency in packed absorbers, particularly when handling high-viscosity liquids. In this study, a vertical packing configuration guided by the twin-liquid film concept is proposed to intensify hydrodynamics and mass transfer while accommodating emerging high-performance absorbents. The structure-performance relationships among packing geometry, twin-liquid film flow patterns, and packing performance are systematically investigated. Results demonstrate that vertical packings exhibit substantially reduced pressure drop under high liquid loads while simultaneously enhancing gas-liquid mass transfer through stabilized twin-liquid films, achieving a favorable balance between hydraulic resistance and transfer efficiency compared with conventional corrugated structured packings. Flooding behavior is shown to be strongly governed by packing geometry even at identical specific surface area and porosity, with vertical configurations providing markedly higher throughput capacity. For windowed packings, optimized window size and wall-to-window area ratio effectively delay flooding by mitigating droplet entrainment and maintaining liquid-film stability. Under high-viscosity conditions, windowed structures outperform non-windowed counterparts due to enhanced twin-film robustness, although interfacial effects become dominant when channel dimensions approach the capillary length. Furthermore, a unified flooding model incorporating fluid properties, operating conditions, and geometric parameters is developed, significantly improving flooding prediction accuracy for windowed vertical packings. Overall, within the scope of the present model systems, the proposed vertical packing provides a promising basis for developing low-resistance, high-throughput gas-liquid absorption equipment.

The flow patterns of twin-liquid film, which combine wall-bounded film supported by a solid wall and confined-free film through the opening window, have been investigated by high-speed cameras. The effects of window length, fluid viscosity, and surface tension on flow patterns have been investigated with the variation of liquid Reynolds number (ReL) and gas velocity (U). The experiments revealed a spectrum of confined-free film flow patterns, including droplets, columns, films, and bubbles. It has been established that gas shear stress exerts negligible influence on twin-liquid films at gas velocities below 3 m/s. With increasing gas velocity, the confined-free film exhibits periodic oscillation due to the gas shear and results in a periodic flow rate distribution on the wall beneath the window, which induces the periodic large waves of the wall-bounded film and bubbles formation downstream of the window. Ligament breakup at lower ReL and bag breakup at higher ReL (with a gas velocity exceeding 7 m/s) are identified as two primary breakup modes of the twin-liquid film. Based on the diverse film flow patterns, two correlations correlating the flow pattern transitions of the twin-liquid film with gas velocity, liquid properties, operating conditions, and window geometry have been established.

High-viscosity substances and systems are widespread in modern chemical engineering. The twin-liquid film, which combines a wall-bounded film supported by a solid wall and a confined-free film through the opening window, provides an effective way to enhance the interfacial heat and mass transfer of high-viscosity non-Newtonian fluid as well as Newtonian fluid. The average thickness, velocity, and pressure differences of the twin-liquid film are correlated with the effective viscosity (mu eff) and effective Reynolds number(Re eff) unified regardless of fluid rheology. The local differences in the film thickness and velocity between the Newtonian and non-Newtonian twin-liquid films increase with window length, plate thickness, and mu eff. When the diffusion coefficient is inversely proportional to viscosity, the stretching and contraction of the confined-free film with shear-thinning fluid not only boost convective mass transfer but also amplify diffusion, synergistically increasing the mass transfer rate by 5.5 times compared to the solid plate. Twin-liquid films provide a cost-effective approach to enhancing heat and mass transfer efficiency in high-viscosity non-Newtonian systems, such as ionic liquids and nanofluids.

This study examines the differences in performance between orbitally shaken bioreactors (OSBs) and stirred tank bioreactors (STBs) in Chinese Hamster Ovary (CHO) cell perfusion culture in response to the growing market demand for monoclonal antibodies (mAbs). Although OSBs demonstrated higher cell densities, a notable reduction in specific antibody production rates was observed during the mid-to-late phases of the culture compared with STBs. To elucidate the underlying mechanisms, the rheological behaviour of high-density cell suspensions in both reactor types was initially characterised, confirming their adherence to the Sisko fluid model. Computational Fluid Dynamics (CFD) analysis revealed the influence of these rheological properties on the shear stress distribution and mass transfer. This analysis identified the key limiting factors for achieving higher cell densities: mass transfer efficiency in OSBs and shear stress in STBs. Using an Euler–Lagrangian cell-tracking methodology to analyse cellular “lifelines”, it was determined that OSBs exhibited approximately twice the number and frequency of shear stress peak occurrences compared to STBs. This persistent mechanical stimulation likely contributes to the reduced specific antibody production rates observed. This comprehensive investigation not only clarifies the comparative advantages and limitations of different bioreactor types in perfusion culture but also provides a robust theoretical basis and technical guidance for informed reactor selection, optimisation, and scale-up in industrial production environments.

Fine metal mask (FMM), serving as the patterning mask during the red-green-blue organic material deposition process, is essential for achieving ultra-high-definition and higher resolution OLED panel fabrication. The essence of the FMM fabrication process is the reactive flow. To match the mask shape with the desired final etched cavity opening, especially to improve etching differences at corners, this study has numerically investigated the FMM etching process based on the finite element method. The reliability of the model has been validated by comparing the simulation results with experimental data. The concentration and velocity distributions of the FeCl3 solution within the etching cavity have been analyzed, and the morphological changes of the etching cavity are investigated. The reason for the etching discrepancies between the R angle and the straight side has been elucidated. It reveals that the etching profile of the R angle is closely related to the mask structural parameters. Furthermore, the optimal R angle mask shape is determined using range analysis. The results contribute to the improvement of the etching accuracy at the R angle.

The twin-liquid film, which combines wall-bounded film supported by a solid wall and confined-free film through the opening window, has been investigated on a plate with multi-windows. The interaction of wall-bounded film and confined free film has been discussed and the optimal window configurations are obtained with consideration of mass transfer enhancement as well as film stability. The mass transfer rate of the opening window plate is increased by 1.9-2.6 times compared with the solid plate. The acceleration and thinning of the confined-free film are the primary causes of its mass transfer enhancement, with additional contributions from the thinning of the wall-bounded film. To achieve the highest mass transfer efficiency as viscosity increases and diffusion coefficient decreases, it is crucial to maximize the window size without compromising film formation. Twin-liquid films show promising applications in the reactors involving highly viscous fluids such as carbon capture and devolatilization.

To obtain dense polysilicon, the deposition rate of polysilicon needs to match the surface migration rate of silicon atoms. For this purpose, a numerical model has been established to simulate the deposition rate and the surface temperature of the polysilicon rods in a 45-pair rods reduction furnace. Meanwhile, the distributions of dense and non-dense polysilicon on the rod surface have been obtained based on the production data from the same reduction furnace. Further, by combining the numerical results and production data, a ratio Phi of deposition rate to temperature has been proposed. The results reveal that Phi of 8.0 x 10-7 kg & sdot;m-2 & sdot;s-1 & sdot;K-1 can be considered as a threshold to ensure the generation of dense polysilicon. Moreover, using the established numerical model, the operation conditions have been optimized. On the basis of existing operation conditions, reducing the surface temperature of the rods by 10 % and the trichlorosilane (TCS) feed rate by 10 % is beneficial for the generation of dense polysilicon. The results show that the proportion of non-dense polysilicon can be decreased to 2.3 % with a 4.3 % reduction in the deposition rate under the optimized operation conditions.

With the rapidly growing demand for monoclonal antibodies (mAbs) worldwide, optimizing the high-density and ultra-high-density cultivation processes of Chinese hamster ovary (CHO) cells has become crucial for enhancing production efficiency. Shear stress and mass transfer have always been the vital operating parameters for the bioreactor in creating a suitable microenvironment for cell growth and antibody production. However, researchers have not actively focused on the rheology of CHO cell suspensions and its impact on these parameters in bioreactors. The factors influencing the rheology of suspensions were first investigated in this study. The findings demonstrated that the shear-thinning behavior of the suspension was primarily affected by the cell volume fraction (Φ). As Φ increases, the shear-thinning behavior gradually weakened, and the viscosity increased. The Sisko model was used to characterize rheology, while computational fluid dynamics simulations evaluated its impact on bioreactor performance. The simulation results revealed that the rheology of the suspensions caused a multiple increase in shear stress and a 10%-40% decrease in the volumetric mass transfer coefficient (kLa) in the bioreactor. Therefore, the effects of rheology cannot be ignored while designing operating parameters. This study established empirical correlations among Pg/V, Vg, Φ, and kLa, thus delivering guidance for selecting appropriate operating parameters in high-density and ultra-high-density cell cultivation processes. The findings provide a scientific foundation for optimizing CHO cell cultivation processes and quantifying suitable microenvironment parameters for cell growth and production. They also offer novel ideas and strategies for scaling up and optimizing the structural parameters of bioreactors.

Gas-liquid flow and pressure drop in a packed column are closely related with the geometric characteristics of the packings. Motivated by the understanding of shape evolution of random packings, particularly the increasing perforation of the packings' wall, i.e., higher opening hole ratio, the influences of the packing shape, including its individual shape and its stacking configurations, on the performance of the packed column have been investigated by experiments and numerical simulation. The experiments were conducted on three representative packings under three stacking configurations to examine their orientation effects. The results show that the influence of stacking configurations on pressure drop has been reduced with the shape evolution of the random packings from the Raschig Ring and Pall Ring to the Raschig Super-Ring. An angular factor was introduced to quantify the orientation-dependent resistance and incorporated into a modified dry pressure drop model based on Makowiak's work, which demonstrated improved accuracy. For the randomly stacked configuration, CFD-DEM simulation results show that a higher opening hole ratio could reduce gas maldistribution and increase the proportion of an effective interfacial area. These findings offer insights into the coupling mechanism between individual packing geometry, stacking characteristics, and bed performance and is beneficial to the rational design of high-performance random packings for large-scale separation processes.

The uniform growth of polysilicon rods is essential for CVD process in the reduction furnace. Considering the complex interaction of CVD reaction and transport phenomena, the reaction engineering analysis of CVD reaction has been investigated and the requirements for the design and operation of CVD reactor are proposed concerning temperature and species concentrations. Based on the numerical simulation of CVD process in a reduction furnace with 12 pairs of rods, the non-uniform deposition is mainly attributed to the mismatching between the TCS transportation and consumption. Moreover, two measures have been attempted. One is to enhance axial mixing by increasing inlet velocity and the other is to reduce TCS consumption by reducing inlet TCS mole fraction and heat flux at the rod surface. Both measures have been confirmed beneficial for the uniform growth of the polysilicon rods.

The temperature homogeneity at polysilicon rods significantly affects the uniformity growth of the polysilicon rod and the product quality in reduction furnace. The heat transfer phenomena on the rod surface includes electric heating, radiation heat transfer, convection heat transfer, heat conduction and reaction heat. In this paper, a representative configuration (RC) of heat transfer model was selected from a "honeycomb" industrial furnace. The flow patterns with different outlets have been numerically investigated and the dependency of surface temperature distribution on the inlet velocity as well as the geometric parameters has been investigated. Gr/Re2d = 100 is set as the transition point determining the natural convection and mixed convection heat transfer. The results indicated that the axial temperature difference at the rod surface has close relationship with the complicated convection heat transfer. With rods growth, the main difference of local heat loss is caused by radiation rather than convection heat transfer.

As emerging green solvents, ionic liquids (ILs) have promising applications in many fields. However, its long reaction time and high price restrict its industrial application. The main reason for this is due to the generation of droplets during the synthesis reaction. Aiming at the process intensification of the 1-methylimidazole (MIM)-based ILs, this paper has studied the evolution behavior of the droplets during its synthesis according to droplet breakage theory. The results show that the droplet size distribution (DSD) and its number density are closely related to the reaction progress. By comparing the Kolmogoroff microscale and droplet size, the synthesis process can be divided into Reaction stage I, when the conversion of MIM is below 60%, and Reaction stage II, when the conversion of MIM is beyond 60%. High stirring speed and temperature increase have been put forward for each stage. The reaction time can be effectively reduced by 43.93%, which is instructive in improving the production efficiency of [BMIM]Br.

As the leading polyester product chain, para-xylene (PX) is the most important xylene isomer. In industry, high purity paraxylene is mainly produced by adsorption separation technology. In this study, the PX adsorption process has been investigated by a 3D particle-resolved CFD model. For spherical particle packed beds, the channeling effect, flow stagnation and backflow regions are the main factors leading to non-ideal flow. According to the residence time distribution (RTD) and adsorbent efficiency, the more uniform the flow in the packed bed, the higher the adsorption separation efficiency. Therefore, low feed flow rate and large bed-to-particle diameter ratio (N) are beneficial to the adsorption process. In addition, the effect of particle geometries (trilobe, five-lobe, Raschig ring, four-spoke ring, and six-hole cylindrical) on the flow and adsorption characteristics of the packed bed has been investigated in terms of pressure drop, adsorbed amount and adsorbent efficiency. Internal void particles perpendicular to the flow direction are unfavorable for the adsorption process. The four-spoke ring adsorbent with more surface areas has the largest bed adsorbed amount and exhibits the best adsorption performance. The trilobe adsorbent has the largest adsorbed amount per unit bed pressure drop and is the optimally shaped adsorbent for industrial PX adsorption separation.

During the ex vivo expansion of umbilical cord-derived mesenchymal stem cells (hUCMSCs) in a stirred tank bioreactor, the formation of cell–microcarrier aggregates significantly affects cell proliferation and physiological activity, making it difficult to meet the quantity and quality requirements for in vitro research and clinical applications. In this study, computational fluid dynamic (CFD) simulations were used to investigate the effect of an impeller structure in a commercial spinner flask on flow field structure, aggregate formation, and cellular physiological activity. By designing a modified impeller, the aggregate size was reduced, which promoted cell proliferation and stemness maintenance. This study showed that increasing the stirring speed reduced the size of hUCMSC-microcarrier aggregates with the original impeller. However, it also inhibited cell proliferation, decreased activity, and led to spontaneous differentiation. Compared to low stirring speeds, high stirring speeds did not alter the radial flow characteristics and vortex distribution of the flow field, but did generate higher shear rates. The new impeller’s design changed the flow field from radial to axial. The use of the novel impeller with an increased axial pumping rate (Q z ) at a similar shear rate compared to the original impeller resulted in a 43.7% reduction in aggregate size, a 37.4% increase in cell density, and a better preservation of the expression of stemness markers (SOX2, OCT4 and NANOG). Increasing the Q z was a key factor in promoting aggregate suspension and size reduction. The results of this study have significant implications for the design of reactors, the optimisation of operating parameters, and the regulation of cellular physiological activity during MSC expansion. Graphical Abstract

The flow distribution is of significance to the fuel cell performance and durability, which has been studied from a theoretical and practical level in this work. The transverse-flow-control-based mechanism behind flow distribution processes is revealed. The core lies in the reasonable generation and distribution of transverse flow, which are the prerequisite and co-requisite for flow homogeneity. For the dual purpose, a novel design of combined-mesh-type distribution zone is proposed incorporating central horizontal meshes and lateral vertical meshes. The design philosophy and methodology are clarified. Under these guidelines, the novel distributor design is applied to different flow field plate geometries including the shorter distribution zone, higher expansion ratio, and scaled-up fuel cell. Through organized and detailed simulations, two key geometrical parameters (porosities of central and lateral meshes) are quantified and the superior effect on flow distribution is validated.

以聚醚砜(PESU)为膜材料,聚乙烯吡咯烷酮为致孔剂,水为非溶剂,N,N-二甲基乙酰胺为溶剂,采用非溶剂致相分离的干喷湿纺法制备PESU中空纤维膜丝,探究了气隙湿度、PESU含量、牵伸倍数、喷板温度、凝固浴温度等因素对膜丝微结构的影响.使用扫描电子显微镜观察了膜丝截面形貌结构并对膜丝组件的牛血清蛋白(BSA)截留性能进行了表征.结果表明,在PESU质量分数为15%～18%、气隙湿度为60%、喷板温度为30℃、凝固浴温度为70℃及牵伸倍数为2.5～3倍的条件下可制得内皮层较薄、支撑层呈海绵孔结构的中空纤维膜;气隙湿度由50%增加至60%时,膜丝内皮层厚度占比由10.02%减小至4.07%;膜丝内皮层厚度占比随PESU含量的增大及喷板温度的提高而增加,随牵伸倍数的增大、气隙湿度的提升及凝固浴温度的升高而下降;所制得的带内皮层的截面海绵状结构中空纤维膜对BSA截留率皆在98%以上.

Polyether sulfone hollow fiber membrane was prepared via nonsolvent-induced phase separation process using dimethylacetamide (DMAc) as a solvent, Polyvinylpyrrolidone (PVP-K30) and water as additives. The mechanism of air gap environment in the membrane structure formation was studied. The scanning electron microscope microstructure morphology revealed that the air gap environment induced the microstructure formation of membranes. The low humidity air gap environment was not conducive to the surface pore formation and hard to obtain surface pores until lowering the dope solution temperature. The high humidity can easily induce the formation of large out surface pore structure along with the decreases of the surface pore uniformity. As air gap humidity and distance increased, the membrane cross section structure near the outer surface tends to be looser and that near the inner surface became denser, while the proportion of finger-like pores in the cross section initially increased and stabilized. At 100 RH, the average outer surface pore size increased from 0.192 mu m at an air gap distance of 20 cm to 0.351 mu m at 50 cm, the corresponding pore density decreased from 2.66 to 1.13 pores/mu m(2), and the percentage of the inner skin layer thickness increased from 3.26% to 7.69%.