膜管内低压气体输运模拟及低温等离子体改性研究

发布时间：2018-03-08 20:53

本文选题：流动模拟　切入点：低温等离子体　出处：《北京理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：膜分离作为一种新型的分离技术,具有能耗低、分离效率高等优点。不同膜材料的亲疏水性能不同,为了减轻使用过程中的膜污染和应对不同分离体系所需膜的亲疏水性能要求,提高分离效率,故需对膜进行一定的修饰改性。其中,等离子体改性技术应用甚为广泛。本文主要针对低温等离子体亲水改性中空纤维膜内表面的问题,使用FLUENT软件对细管内空气的流动状态进行模拟,在此基础上,利用远程动态低温等离子体对细管管道内表面进行活化改性实验研究。首先,利用FLUENT流体流动模拟软件对空气介质(密度取理想密度)在不同管径内的流动进行模拟,分别对流动的压力场、密度场和速度场进行了研究;同时,将计算机模拟输出的出口质量流量与泊肃叶公式计算得到的质量流量进行了对比。验证了低压下空气流动基本符合连续流体流动规律,并对比模拟与计算结果得到在一定的低压下,长度为500 mm内径大于10 mm时使用FLUENT模拟是可行的。当内径为5-8 mm时,模拟误差约为10%,但结果仍然可以为细径管内低温等离子体的输运规律提供一定的指导作用。然后,采用本研究组的远程动态低温等离子体发生装置,对不同内径的替代膜—硅橡胶管内表面进行活化,在空气中暴露后进行体现亲水性变化的水接触角测试,并对改性前后的膜管内表面进行了傅里叶红外光谱(FTIR)、X-射线光电子能谱(XPS)、扫描电镜(SEM)等性能的表征。此外,分别研究了等离子体操作条件和组件结构对活化改性效果的影响,并对改性后管壁面亲水稳定性进行了考察。结果表明,有效改性距离与功率呈正相关,但功率越大表面刻蚀越严重;在压力20±5 pa下,流量控制在1 sccm的有效改性距离达到最长;在一定的操作条件下,管内径越大其有效改性距离越长,当内径大于等于5 mm时有效距离达到10 cm以上,硅橡胶管只经活化处理而不进行后续接枝,其疏水性恢复时间接近20天;在所研究的范围内,有效改性距离比辉光距离长7 cm至10.5 cm。综上所述,如果对膜管组件采取两端处理,组件的有效改性距离可达到20cm-30 cm,有望满足实际应用组件改性的要求。本文的研究结果对实际中空纤维膜内表面改性研究有一定的指导意义。
[Abstract]:As a new separation technology, membrane separation has the advantages of low energy consumption and high separation efficiency. In order to reduce the membrane fouling during use, to meet the hydrophobic performance requirements of different separation systems and to improve the separation efficiency, it is necessary to modify the membrane to a certain extent. Plasma modification technology is widely used. In this paper, the flow state of air in a thin tube is simulated by FLUENT software, aiming at the problem of low temperature plasma hydrophilic modification of the inner surface of hollow fiber membrane. An experimental study on the activation modification of the inner surface of a tube by remote dynamic low-temperature plasma was carried out. Firstly, the flow of air medium (density with ideal density) in different pipe diameters was simulated by FLUENT fluid flow simulation software. The pressure field, density field and velocity field of the flow are studied respectively. The mass flow at the outlet of the simulated output is compared with the mass flow calculated by the Poisson's formula. It is verified that the air flow under low pressure basically accords with the law of continuous fluid flow. The results of simulation and calculation show that it is feasible to use FLUENT simulation when the length is 500mm or more than 10mm at a certain low pressure, when the inner diameter is 5-8 mm. The simulation error is about 10, but the results can still provide some guidance for the transport law of low temperature plasma in fine diameter tube. Then, the remote dynamic low temperature plasma generator of this research group is used. The inner surface of silicone rubber tube with different internal diameters was activated, and the hydrophilic contact angle was measured after exposure to air. The properties of the inner surface of the membrane tube before and after modification were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), etc. In addition, the effects of plasma operating conditions and component structure on the activation modification effect were studied, respectively. The hydrophilic stability of the modified tube wall was investigated. The results showed that the effective modification distance was positively correlated with the power, but the more power the surface etching was, the more serious the surface etching was, the longest effective modification distance was obtained when the flow rate was controlled at 1 sccm under the pressure of 20 卤5pa. Under certain operating conditions, the larger the inner diameter of the tube is, the longer the effective modification distance is. When the inner diameter is greater than or equal to 5 mm, the effective distance is more than 10 cm, and the silicone rubber pipe is only activated without subsequent grafting. The hydrophobicity recovery time is close to 20 days; in the range studied, the effective modification distance is 7 cm to 10.5 cm longer than the glow distance. The effective modification distance of the module can reach 20cm-30 cm, which is expected to meet the requirements of practical application. The results of this paper have a certain guiding significance for the study of internal surface modification of hollow fiber membrane.
【学位授予单位】：北京理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ028.8

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