本文選題：微濾膜 + 強(qiáng)化傳質(zhì)��； 參考：《西南石油大學(xué)》2017年碩士論文

【摘要】：膜分離技術(shù)因其過程無相變、無二次污染、分離效率高等優(yōu)點(diǎn)而受到各國的普遍重視。然而,在膜分離過程中,物料中的微粒、膠體粒子或溶質(zhì)大分子在膜上發(fā)生的吸附、孔堵、濃差極化和濾餅層的形成導(dǎo)致膜通量下降,分離效率降低,嚴(yán)重制約著膜技術(shù)的工業(yè)化進(jìn)程。湍流促進(jìn)器可以改善膜通道內(nèi)的流體動(dòng)力學(xué)條件,顯著提高壁面流速或剪切速率,有助于抑制料液中的顆粒在膜表面的沉積,減輕微濾過程的膜污染現(xiàn)象,從而有效提高微濾膜通量。本論文使用湍流促進(jìn)器強(qiáng)化錯(cuò)流微濾過程,通過CFD(Computational fluid dynamics)分析了平板膜通道內(nèi)附加不同湍流促進(jìn)器的流場,為湍流促進(jìn)器的應(yīng)用提供理論指導(dǎo)。首先,通過湍流促進(jìn)器強(qiáng)化錯(cuò)流微濾過程,以速度場、壓降以及壁面剪切應(yīng)力為指標(biāo),研究了平行排布的湍流促進(jìn)器結(jié)構(gòu)形式、排布位置對強(qiáng)化傳質(zhì)效率的影響。研究表明,基于相同的湍流促進(jìn)器形狀及膜通道結(jié)構(gòu)參數(shù),排布于流道中部("浸沒型")的湍流促進(jìn)器能獲得更高的壁面剪切應(yīng)力,其中四棱柱湍流促進(jìn)器能獲得最高的壓降和壁面剪切應(yīng)力。發(fā)現(xiàn)湍流促進(jìn)器誘發(fā)膜通道內(nèi)流體形成旋渦,引起壁面流速波動(dòng),增大壁面剪切應(yīng)力,顯著提高流體的湍動(dòng)強(qiáng)度,可以破壞邊界層的發(fā)展,抑制料液中的顆粒在膜表面沉積,從而有效提高微濾膜通量。其次,針對四棱柱湍流促進(jìn)器的結(jié)構(gòu)特點(diǎn),設(shè)計(jì)了一種新型的湍流促進(jìn)器,CFD模擬膜通道內(nèi)附加新型湍流促進(jìn)器的流場,并考察湍流促進(jìn)器結(jié)構(gòu)參數(shù),膜通道高度以及進(jìn)口速度對流場特性的影響。流場分析表明,新型的湍流促進(jìn)器能在獲得較高壁面剪切應(yīng)力的同時(shí)減小壓降,即在強(qiáng)化傳質(zhì)效果較好的同時(shí)所需的能耗更小。最后,建立了附加溫度場強(qiáng)化傳質(zhì)的湍流促進(jìn)器模型,考察了不同進(jìn)料水力攻角及進(jìn)口速度的湍流促進(jìn)器模型對微濾膜的強(qiáng)化傳質(zhì)及傳熱的影響。數(shù)值模擬結(jié)果表明:較高的進(jìn)口流速有利于增大跨膜壓差,壁面剪切應(yīng)力以及溫度極化系數(shù)τ,增大傳質(zhì)傳熱驅(qū)動(dòng)力。進(jìn)料攻角αf=45°的模型具備最優(yōu)的傳質(zhì)傳熱效果,且所需能耗最小,當(dāng)進(jìn)口速度為0.14m/s時(shí),傳質(zhì)通量達(dá)111.3Kg/m2h,是不含湍流促進(jìn)器流道的15.7倍。分析了進(jìn)料側(cè)溫度,顆粒質(zhì)量流量以及顆粒粒徑因素對膜通量的影響,對溫度場強(qiáng)化傳質(zhì)的應(yīng)用有重要的參考意義。
[Abstract]:Membrane separation technology has been paid more and more attention because of its advantages of no phase change, no secondary pollution and high separation efficiency. However, in the process of membrane separation, the adsorption of particles, colloidal particles or solute macromolecules on the membrane, pore blockage, concentration polarization and the formation of cake layer resulted in the decrease of membrane flux and separation efficiency. The industrialization process of membrane technology is seriously restricted. Turbulence promoters can improve the hydrodynamic conditions in the membrane channel, increase the wall flow rate or shear rate significantly, help to restrain the deposition of particles in the feed solution on the membrane surface, and reduce the membrane fouling phenomenon in the process of microfiltration. Thus, the flux of microfiltration membrane is increased effectively. In this paper, the cross-flow microfiltration process is enhanced by using turbulence promoters, and the flow field with different turbulence promoters in flat membrane channels is analyzed by CFD (Computational fluid dynamics), which provides theoretical guidance for the application of turbulence promoters. Firstly, the cross-flow microfiltration process was enhanced by the turbulence promoters. The effects of the parallel arrangement of the turbulence promoters on the mass transfer efficiency were studied by taking the velocity field, pressure drop and wall shear stress as the indexes. The results show that based on the same shape of turbulence promoters and structural parameters of membrane channels, turbulent promoters arranged in the middle of the channel ("immersion type") can obtain higher wall shear stress. The four-prism turbulence promoter can obtain the highest pressure drop and wall shear stress. It is found that turbulence accelerator induces vortex in membrane channel, causes wall velocity fluctuation, increases wall shear stress, increases turbulent intensity of fluid, destroys the development of boundary layer, and inhibits the deposition of particles on the membrane surface. Thus, the flux of microfiltration membrane is increased effectively. Secondly, according to the structural characteristics of the four-prism turbulence promoter, a new type of turbulence accelerator is designed to simulate the flow field in the CFD channel, and the structure parameters of the turbulence promoter are investigated. The influence of channel height and inlet velocity on the flow field characteristics. The flow field analysis shows that the new turbulence accelerator can obtain higher wall shear stress and reduce pressure drop, which means that the energy consumption is less when the mass transfer effect is better. Finally, a turbulence accelerator model with enhanced mass transfer with temperature field was established, and the effects of different hydraulic attack angles and inlet velocities on the enhanced mass transfer and heat transfer of microfiltration membrane were investigated. The numerical simulation results show that higher inlet velocity is beneficial to increase the pressure difference, wall shear stress and temperature polarization coefficient 蟿, and increase the driving force of mass transfer and heat transfer. The model with 45 擄angle of attack has the best heat transfer effect and the minimum energy consumption. When the inlet velocity is 0.14m/s, the mass transfer flux is 111.3 kg / m ~ 2 h, which is 15.7 times that of the flow channel without turbulence promoter. The effects of feed side temperature, particle mass flow rate and particle size on membrane flux were analyzed, which has important reference significance for the application of enhanced mass transfer in temperature field.
【學(xué)位授予單位】：西南石油大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O357.5

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