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孔盘式液体分布器内液体流动对布液孔出流均匀性的影响 总被引:1,自引:0,他引:1
借助包括双欧拉均相多相流模型、VOF界面追踪方法和SST k-ω湍流模型的CFD模型,对孔盘式液体分布器内的流场对布液孔出流均匀性的影响进行研究。首先以单孔流动时的液体流量为标准值,通过与标准值的偏差来评估布液孔的出流不均。根据偏差的大小,可以衡量分布器内流动对布液孔出流的影响。然后结合孔前流动区概念对模拟结果进行分析,发现布液孔出流不均是由分布器内液体流动不均造成的。最后,提出了通过改变进料管位置来优化盘式液体分布器结构。计算结果表明,改变进料管的位置可以避免大规模不良分布,进而提高液体分布器的性能。 相似文献
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《化学工程》2021,49(4)
山茶油是一种具有高附加值、丰富保健功能的天然产品。由于目前山茶油的深加工技术尚不完善,采用的化学精炼工艺脱除山茶油中游离脂肪酸时存在皂脚等物质残留问题,难以达到国家标准(GB/T11765—2018)的要求。刮膜式分子蒸馏技术独特的动态膜温和蒸发过程,在精细化工分离与提纯中占据着绝对的优势。为了获得最佳的山茶油分离参数与分离机理,文中采用CFD方法对刮膜式分子蒸馏技术精制山茶油的过程进行数值模拟,结果表明:蒸发器内液膜分布和传热系数变化受转子转速和进料速度影响较大;当蒸发温度为190℃、刮膜器转速为300 r/min、进料速度为900 g/h时系统的综合指标为最佳,该模拟结果对分子蒸馏精制山茶油的工艺优化及工艺参数控制具有较好的参考价值。 相似文献
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薄膜蒸发器内流体流动特性的数值模拟 总被引:6,自引:0,他引:6
建立了薄膜蒸发器的计算模型,采用大型计算流体力学(CFD)分析软件CFX4.4模拟了薄膜蒸发器内水及粘性料液的流动过程,得到了各种速度分布. 结果表明,刮板转速、进料量对流体流动状态影响显著. 提高刮板转速,可明显促进液膜和圈形波内流体的物质交换. 在任一转速下,各料液均存在同一最佳进料量,此时其圈形波截面内平均速度达到最大值. 对纯物质水,最佳进料量对应的流动边界层厚度与膜厚之比最小. 粘性料液和水的轴向速度分布存在差异,且在液膜厚度内未形成明显的流动边界层. 相似文献
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使用CFD软件建立了刮膜式分子蒸馏器的三维模型,以EHP-EHS混合物为研究对象,并通过编写用户自定义函数(UDF),研究刮膜式分子蒸馏过程传质存在时的传热特性,得到充分发展的温度场及流场,分析了蒸发壁面温度的分布及转子转速对其影响和局部Nu数的分布。结果表明:液膜表面的升温过程是周期地和波动地达到动态稳定温度的;转子转速越大,周期越小,温度波动次数越多,温度稳定性越好;局部Nu数在刮膜器刮擦的位置突增,刮膜器的刮擦作用是影响平均Nu数增大的主要因素。经过壁面优化,液体湍流程度增大,传热效果得到不同程度的增强,凸起矩形排列、三角形排列、螺旋形排列时平均Nu数分别是光滑蒸发面的1.32倍、1.23倍、1.04倍,为进一步优化刮膜式分子蒸馏器提供参考。 相似文献
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《高校化学工程学报》2017,(5)
采用欧拉模型与多孔介质模型对柱式膜组件的曝气过程中气液两相流进行了计算模拟,研究了曝气量、曝气孔数目以及相对位置对膜组件的气液两相分布、流体湍流黏度、液体速度场的影响,模拟数据与实验数据吻合良好。研究结果表明:随着曝气孔数目增加与相对位置均匀排布使得膜组件内气液两相分布更加均匀;湍流黏度随着曝气量增大而增大,当曝气量达到5 m~3×h~(-1)时,湍流黏度不再增加;随着曝气孔数目增加与相对位置的均匀排布使得液体形成较多涡流流动与循环流动。增加曝气孔数目与优化曝气孔相对位置能够有效提高组件内部流场的均匀分布,有利于膜丝的清洗。 相似文献
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详细介绍并分析了干膜用聚酯薄膜疵点的分类和产生原因。大疵点形成的原因为煳料造成的内部杂质和外来杂质造成的表面杂质,小疵点形成的原因为添加剂粒子团聚造成的内部原因和辊筒烙印造成的表面原因。 相似文献
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PET薄膜为干膜光阻层的载体,起保护作用,主要是隔绝氧气、分层和避免机械划伤,在曝光之后显影之前除去。其厚度呈现逐渐变薄的趋势,主要为15~19μm。 相似文献
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Bong Seock Kim Ji Hyun Park Nayeong Hong Joonwon Bae Cheol-Soo Yang Kyusoon Shin 《Journal of Industrial and Engineering Chemistry》2013,19(5):1631-1637
Here we present ultrathin carbon films derived from polyacrylonitrile precursor film. Subsequent carbonization was investigated to examine the optical and electrical properties of resulting carbon films. The precursor PAN solution was carefully prepared and heated in order to have thin and uniform PAN film, and X-ray reflectivity of the precursor film and the carbon film shows uniformity. X-ray diffraction pattern of the carbon film indicated that the obtained carbon films possess low crystallinity. It was also found that the thickness for ultrathin carbon film from PAN layer showed counterbalanced optical and electrical performance in the range of experiment. 相似文献
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Systematic methodologies are developed for modeling and control of film porosity in thin film deposition. The deposition process is modeled via kinetic Monte Carlo (kMC) simulation on a triangular lattice. The microscopic events involve atom adsorption and migration and allow for vacancies and overhangs to develop. Appropriate definitions of film site occupancy ratio (SOR), i.e., fraction of film sites occupied by particles over total number of film sites, and its fluctuations are introduced to describe film porosity. Deterministic and stochastic ordinary differential equation (ODE) models are also derived to describe the time evolution of film SOR and its fluctuation. The coefficients of the ODE models are estimated on the basis of data obtained from the kMC simulator of the deposition process using least-square methods and their dependence on substrate temperature is determined. The developed ODE models are used as the basis for the design of model predictive control (MPC) algorithms that include penalty on the film SOR and its variance to regulate the expected value of film SOR at a desired level and reduce run-to-run fluctuations. Simulation results demonstrate the applicability and effectiveness of the proposed film porosity modeling and control methods in the context of the deposition process under consideration. 相似文献
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A starch‐based biodegradable (BD) low density polyethylene (LDPE) film can be directly printable without any corona treatment, unlike virgin LDPE film. Such a film shows poor adhesion and nail scratch resistance of the ink on the printed area of the film. In order to increase the adhesion and nail scratch resistance of the ink on the printed BD film, grafting of acrylonitrile onto the BD film is carried out. The polyacrylonitrile grafted BD film shows better adhesion, nail scratch resistance, and printability. The printability of the polyacrylonitrile grafted BD film is comparable to the conventional corona treated LDPE film. The extent of printability is a function of the surface smoothness, as well as the optimum percentage of grafting on the biodegradable film. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1273–1277, 2001 相似文献
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A new dielectric elastomer (DE) film, which was able to show anisotropic large plane deformation actuated by an external electric field, was designed and synthesized. Specifically, an asymmetric di-vinyl monomer cyclohex-3-enylmethyl acrylate (CEA) was incorporated into the middle block of poly(styrene-b-butyl acrylate-b-styrene) as potential crosslinking points. By widely used UV curing technique through a mask, the DE films could be locally hardened any area one selected. This could break the symmetry of the actuation deformation on the DE film plane, maximizing the deformation in a given direction while the actuation area strain remained unchanged. The actuation strainy/strainx reached 2.3, strain in x direction was 10.3% while in y direction was 23%, when the DE film of S(BA-ran-CEA)S with 2.5 mol % CEA incorporated was locally hardened in the form of soft and hard belt of 1 mm width alternatively along y direction. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48795. 相似文献
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为了提高壳聚糖/玉米醇溶蛋白膜的机械性能,将壳聚糖液与玉米醇溶蛋白液共混,向其中加入0%、15%、30%、45%(w/w)的油酸改性,研究膜液的粒径、zeta电位、静态和动态流变特性;然后,分析油酸添加量对膜阻隔性能,机械性能和相容性的影响。结果表明:添加油酸后,膜液体系粒径增大、分散均匀,添加30%油酸的膜液分散性更好,PDI为0.34,粒径为1307.5nm。随着油酸含量增大,膜液粘度减小,流动指数增大,弹性模量和粘性模量增加。OA-30膜机械性能较好,抗拉强度达到36.37MPa,断裂延伸率达到22.32%。膜的阻隔性增强,水蒸气、氧气透过率分别降低了44.21%和66.52%。复合膜中壳聚糖与玉米醇溶蛋白分子相容性好,表面光滑平整。综上所述,油酸改性改善了壳聚糖/玉米醇溶蛋白复合膜性能。 相似文献
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A novel high‐performance resin film, coded 4508B, suitable for the resin film infusion (RFI) process, was developed. It was prepared from 4,4′‐bismaleimidodiphenylmethane (BDM), o,o′‐diallylbisphenol A (BA), polyethersulfone (PES), and polyimide (PI). The resin and its composite, reinforced by glass fiber cloth, were prepared and characterized in detail. The results showed that the resin film was stable at room temperature, its infusion temperature was 120°C, and the pot life was more than 60 min. In addition, the cured resin and the composite prepared by the RFI process had good thermal and mechanical properties and hot‐wet resistance. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2918–2922, 2001 相似文献