本文選題：攪拌　切入點：數(shù)值模擬　出處：《北京化工大學(xué)》2015年碩士論文

【摘要】：氣液反應(yīng)器在化工領(lǐng)域是一種常用的反應(yīng)器,攪拌槽是氣液反應(yīng)器中的一種。攪拌的方式中最傳統(tǒng)的方式是機械攪拌。機械攪拌的原理概括起來就是槽內(nèi)液體通過攪拌軸及攪拌槳的帶動,在攪拌槽內(nèi)做旋轉(zhuǎn)運動。對于氣液兩相的混合,評價氣液兩相的好壞也是由多方面因素構(gòu)成的。從宏觀上看,包括攪拌功率、平均氣含率、氣液兩相的流型,從介觀上看,包括局部氣含率、氣泡尺寸分布等因素。若攪拌槽內(nèi)有反應(yīng)或傳熱等更復(fù)雜的現(xiàn)象,還需要考慮氣液相界面積、氣液相比熱等參數(shù)的影響。在本論文中,主要考慮了轉(zhuǎn)速、通氣量、攪拌槳型、攪拌槳層間距、氣體分布器直徑對氣液分散效果的影響。本論文借助CFD數(shù)值模擬,對氣液兩相在攪拌槽內(nèi)的情況進(jìn)行了研究,并通過模擬得到的數(shù)據(jù)與實驗數(shù)據(jù)進(jìn)行對比。論文選取的主要流體是粘度0.12 Pa-s的甘油水溶液,其他粘度的溶液還包括水、0.01Pa·s和0.05 Pa·s的甘油水溶液。具體得到結(jié)果如下：對于槳型的選擇,論文選取了兩種攪拌槳型,分別是InterMigDU和InterMigUD,在相同的通氣量和攪拌轉(zhuǎn)速下,InterMigUD會有更好的效果,InterMigUD消耗的功率小且有較大的平均氣含率。從氣泡分布方面來看,InterMigUD氣泡分布的不均勻度大于InterMigDU,但是InterMiguD有更大的傳質(zhì)系數(shù)。對于層間距的討論選取了三種層間距,分別是0.36D,0.5D和0.69D。由于整體的液位是1.49T,因此對于層間距的選擇,本文建議△/D不宜過大。層間距為0.36D時,整體氣含率居中,但是有較高的容積傳質(zhì)系數(shù),氣泡尺寸的均勻性也是三者中最好的。層間距為0.5D時,整體氣含率最大,容積傳質(zhì)系數(shù)和均勻度略小于0.36D時的層間距。對于不同直徑的氣體分布器來講,文中選取了五種不同直徑的氣體分布器,分別是0.3T、0.4T、0.55T、0.65T、0.75T,結(jié)果發(fā)現(xiàn),隨著氣體分布器直徑的增大,氣液混合效果越來越好,整體氣含率增加,均勻度趨于良好,容積傳質(zhì)系數(shù)逐漸增大。因此,對于氣液攪拌,適當(dāng)?shù)脑龃髿怏w分布器直徑是有益處的。文中選取了水和三種甘油水溶液,以水作為基礎(chǔ)比對,發(fā)現(xiàn)隨著粘度的增加,功率消耗增加,整體氣含率也呈遞增趨勢,平均氣泡尺寸變大,容積傳質(zhì)系數(shù)呈遞減趨勢,由于所模擬的范圍均處于過度流及湍流下,因此液相的流型并沒有太大的差異。以上結(jié)果的部分?jǐn)?shù)值與實驗數(shù)據(jù)進(jìn)行了對比,二者吻合良好,因此文中的其他模擬條件均采用了相同的模擬方法進(jìn)行計算,并認(rèn)為此種模擬方法可以推廣到類似的中粘體系中,為工業(yè)生產(chǎn)提供參考。
[Abstract]:The gas-liquid reactor is a kind of commonly used reactor in the chemical industry. The mixing tank is one of the gas-liquid reactors. The most traditional way of stirring is mechanical agitation. The principle of mechanical stirring is that the liquid in the tank is driven by the mixing shaft and the impeller. For the mixing of gas-liquid two-phase, the evaluation of gas-liquid two-phase is also made up of many factors. From the macroscopic view, including mixing power, average gas holdup, gas-liquid two-phase flow pattern, from the mesoscopic point of view, These factors include local gas holdup and bubble size distribution. If there are more complicated phenomena such as reaction or heat transfer in the stirred tank, the influence of the boundary area of gas and liquid, the ratio of gas to liquid heat should be taken into account. In this paper, the rotational speed is mainly considered. The effects of aeration volume, impeller type, pitch between impeller layers and diameter of gas distributor on the gas-liquid dispersion effect are studied in this paper by means of CFD numerical simulation. The main fluid selected in this paper is glycerol aqueous solution with viscosity of 0. 12 Pa-s. Other viscosity solutions include glycerol aqueous solution of 0.01 Pa s and 0.05 Pa s. The results are as follows: for the selection of propeller type, two kinds of agitator type are selected in this paper. InterMigDU and InterMigUD have better effect under the same aeration rate and stirring speed, the power consumed by InterMigUD is smaller and the average gas holdup is larger than that of InterMigUD. In terms of bubble distribution, the inhomogeneity of intermigUD bubble distribution is greater than that of InterMigDUD, but InterMiguD is more effective than InterMigUD. There is a larger mass transfer coefficient. For the discussion of interlayer spacing, three kinds of interlayer spacing are selected. Because the whole liquid level is 1.49T, it is suggested that the selection of interlayer spacing should not be too large. When the interlayer spacing is 0.36D, the overall gas holdup is in the middle, but the volumetric mass transfer coefficient is higher. The uniformity of bubble size is also the best of the three. When the interlayer spacing is 0.5D, the overall gas holdup is the largest, and the volumetric mass transfer coefficient and uniformity are slightly less than 0.36D. for gas distributors with different diameters, Five kinds of gas distributors with different diameters are selected in this paper. The results show that the gas-liquid mixing effect increases with the increase of the diameter of the gas distributor, the gas holdup increases and the uniformity tends to be good. The volumetric mass transfer coefficient increases gradually. Therefore, for gas-liquid stirring, it is beneficial to increase the diameter of the gas distributor properly. In this paper, water and three kinds of glycerol aqueous solutions are selected and compared on the basis of water, it is found that with the increase of viscosity, With the increase of power consumption, the overall gas holdup tends to increase, the average bubble size increases and the volumetric mass transfer coefficient decreases. Therefore, there is not much difference in the flow pattern of liquid phase. Some of the above results are compared with the experimental data, which are in good agreement with each other, so the other simulation conditions in this paper are calculated by the same simulation method. It is considered that this simulation method can be extended to similar meso-viscous systems and provide a reference for industrial production.
【學(xué)位授予單位】：北京化工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TQ027.2

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本文編號：1669781