降膜微通道内液相成膜特性及气-液传热过程数值模拟
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摘要
采用流体体积函数(VOF)模型对浓硫酸(w=98%)在降膜微通道内的降膜流动及气-液两相传热行为进行了二维数值模拟。重点分析了液相入口流速对液膜厚度、液膜内速度分布的影响,结果表明液膜厚度与入口流速成正比,液膜内速度呈抛物线型分布。模拟研究了气-液两相入口流速、温度等因素对相间传热系数的作用规律,结果表明传热系数随气、液入口流速的增加而增加,随气相入口温度的增加而降低。与传统设备相比,降膜微通道内模拟所得的液膜努塞尔(Nu)数提高约8.77倍。
Falling film micro-reactor(FFMR) has incomparable advantage in highly exothermic and fast reactions when compared with conventional reactors due to its characteristics of high specific surface area, easy separation of products and low scale-up effect. The superior chemical reaction performance exhibited by the FFMR strongly depends on the hydrodynamic behaviors of the liquid film and the heat transfer characteristics of gas-liquid interphase in the falling film microchannel. A transient computational fluid dynamics(CFD) model with the volume of fluid(VOF)method was employed to simulate the hydrodynamic behaviors of concentrated sulfuric acid w=98 % in a home-made falling film microchannel reactor. The gas-liquid heat transfer behaviors of H2 SO4-air in the FFMR was also simulated.Surface tension plays a significant role on film-forming process within the Re and Ca range of 0.001 33―0.066 7 and7.00×10-5― 3.50×10-3, respectively. The influences of liquid inlet velocity on the liquid film thickness and velocity distribution of the film were studied systematically. The results show that the liquid film thickness is proportional to the liquid inlet velocity and the velocity profiles across the film are parabolic curves. The simulated results match the Nusselt predicated results well within a deviation of 0.5%. The effects of gas inlet velocity, gas temperature and liquid inlet velocity on heat transfer coefficient were analyzed. Simulation results show that the increase of both gas inlet velocity and liquid inlet velocity exerts a positive effect on heat transfer coefficient, but the influence of gas temperature on heat transfer coefficient is negative for the increasing viscosity of gas with increasing temperature in FFMR, the heat transfer resistance strongly depends on the heat transfer resistance of gas side. The Nusselt number in FFMR is almost 8.77 times of that in the traditional reactors, which indicates that gas-liquid heat transfer can be intensified effectively by the FFMR. The results are scientific significance to discover the falling film behaviors and gas-liquid heat transfer in FFMR, and provide a theoretical basis for exploring and designing of new reactors.
Falling film micro-reactor(FFMR) has incomparable advantage in highly exothermic and fast reactions when compared with conventional reactors due to its characteristics of high specific surface area, easy separation of products and low scale-up effect. The superior chemical reaction performance exhibited by the FFMR strongly depends on the hydrodynamic behaviors of the liquid film and the heat transfer characteristics of gas-liquid interphase in the falling film microchannel. A transient computational fluid dynamics(CFD) model with the volume of fluid(VOF)method was employed to simulate the hydrodynamic behaviors of concentrated sulfuric acid w=98 % in a home-made falling film microchannel reactor. The gas-liquid heat transfer behaviors of H2 SO4-air in the FFMR was also simulated.Surface tension plays a significant role on film-forming process within the Re and Ca range of 0.001 33―0.066 7 and7.00×10-5― 3.50×10-3, respectively. The influences of liquid inlet velocity on the liquid film thickness and velocity distribution of the film were studied systematically. The results show that the liquid film thickness is proportional to the liquid inlet velocity and the velocity profiles across the film are parabolic curves. The simulated results match the Nusselt predicated results well within a deviation of 0.5%. The effects of gas inlet velocity, gas temperature and liquid inlet velocity on heat transfer coefficient were analyzed. Simulation results show that the increase of both gas inlet velocity and liquid inlet velocity exerts a positive effect on heat transfer coefficient, but the influence of gas temperature on heat transfer coefficient is negative for the increasing viscosity of gas with increasing temperature in FFMR, the heat transfer resistance strongly depends on the heat transfer resistance of gas side. The Nusselt number in FFMR is almost 8.77 times of that in the traditional reactors, which indicates that gas-liquid heat transfer can be intensified effectively by the FFMR. The results are scientific significance to discover the falling film behaviors and gas-liquid heat transfer in FFMR, and provide a theoretical basis for exploring and designing of new reactors.
引文
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[24]高国华,陈建民,李鑫钢,等.规整填料波纹结构上的二维两相流模拟方法[J].化工进展,2010,29(9):1597-1602,1608.
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[31]胡静,张涛,张帅,等.[BMim][HSO4]/H2SO4二元体系的黏度及其表面张力[J].石油化工,2017,46(9):1161-1167.
[32]杨世铭,陶文铨.传热学[M].第4版.北京:高等教育出版社,2006.
[33]WEN X,LIANG C,ZHANG X.Experimental study on heat transfer coefficient between air and liquid in the cross-flow heat-source tower[J].Building and Environment,2012,57:205-213.
[34]CHILTON T H,COLBURN A P.Mass transfer(absorption)coefficients prediction from data on heat transfer and fluid friction[J].Industrial&Engineering Chemistry,1934,26(11):1183-1187.
[35]Cussler E L.Diffusion:Mass Transfer in Fluid Systems[M].3rd edition.Cambridge:Cambridge University Press,2009.
[2]ROBERGE D M,DUCRY L,BIELER N,et al.Microreactor technology:A revolution for the fine chemical and pharmaceutical industries?[J].Chemical Engineering&Technology,2005,28(3):318-323.
[3]HESSEL V,L?WE H.Microchemical engineering:Components,plant concepts user acceptance:PartⅠ[J].Chemical Engineering&Technology,2003,26(1):13-24.
[4]刘兆利,张鹏飞.微反应器在化学化工领域中的应用[J].化工进展,2016,35(1):10-17.
[5]YEONG K K,GAVRIILIDIS A,ZAPF R,et al.Catalyst preparation and deactivation issues for nitrobenzene hydrogenation in a microstructured falling film reactor[J].Catalysis Today,2003,81(4):641-651.
[6]ZANFIR M,GAVRIILIDIS A,WILLE C,et al.Carbon dioxide absorption in a falling film microstructured reactor:Experiments and modeling[J].Industrial&Engineering Chemistry Research,2005,44(6):1742-1751.
[7]REHM T H,BERGUERAND C,EK S,et al.Continuously operated falling film microreactor for selective hydrogenation of carbon-carbon triple bonds[J].Chemical Engineering Journal,2016,293:345-354.
[8]JAèHNISCHA K,BAERNSA M,HESSELB V,et al.Direct fluorination of toluene using elemental fluorine in gas/liquid microreactors[J].Journal of Fluorine Chemistry,2000,105(1):117-128.
[9]MULLER A,COMINOS V,HESSEL V,et al.Fluidic bus system for chemical process engineering in the laboratory and for small-scale production[J].Chemical Engineering Journal,2005,107(1/3):205-214.
[10]STEINFELDT N,ABDALLAH R,DINGERDISSEN U,et al.Ozonolysis of acetic acid 1-vinyl-hexyl ester in a falling film microreactor[J].Organic Process Research&Development,2007,11(6):1025-1031.
[11]TANG S,SCURTO A M,SUBRAMANIAM B.Improved1-butene/isobutane alkylation with acidic ionic liquids and tunable acid/ionic liquid mixtures[J].Journal of Catalysis,2009,268(2):243-250.
[12]任先艳,刘才林,杨军校,等.羧酸酯化技术进展[J].材料导报,2008,22(S3):292-295.
[13]ZHOU F,ZHANG B,YAO C,et al.Cyclization of pseudoionone catalyzed by sulfuric acid in a microreactor[J].Chemical Engineering&Technology,2016,39(5):849-856.
[14]GAN P,TANG S.Research progress in ionic liquids catalyzed isobutane/butene alkylation[J].Chinese Journal of Chemical Engineering,2016,24(11):1497-1504.
[15]ZHANG Y,ZHANG T,GAN P,et al.Solubility of isobutane in ionic liquids[BMIm][PF6],[BMIm][BF4],and[BMIm][Tf2N][J].Journal of Chemical&Engineering Data,2015,60(6):1706-1714.
[16]JIN K,ZHANG T,JI J,et al.Functionalization of MCM-22by dual acidic ionic liquid and its paraffin absorption modulation properties[J].Industrial&Engineering Chemistry Research,2015,54(1):164-170.
[17]LI H,ZHANG T,YUAN S,et al.MCM-36 zeolites tailored with acidic ionic liquid to regulate adsorption properties of isobutane and 1-butene[J].Chinese Journal of Chemical Engineering,2016,24(12):1703-1711.
[18]李红霞,张涛,唐盛伟.负载离子液体调节MCM-36上异丁烷和1-丁烯的相对吸附量[J].华东理工大学学报(自然科学版),2016,42(6):743-751.
[19]LI Y,ZHANG T,TANG S.Adsorption/desorption of 2,2,4-trimethylpentane on MCM-36 zeolite functionalized by acidic ionic liquid[J].Adsorption,2018,24(2):179-190.
[20]唐盛伟,王丹,张涛,等.一种用于C4烷基化反应的毫米级小通道反应器:CN201810173559.2[P].2018-03-02.
[21]CHASANIS P,LAUTENSCHLEGER A,KENIG E Y.Numerical investigation of carbon dioxide absorption in a falling-film micro-contactor[J].Chemical Engineering Science,2010,65(3):1125-1133.
[22]ISHIKAWA H,OOKAWARA S,YOSHIKAWA S.A study of wavy falling film flow on micro-baffled plate[J].Chemical Engineering Science,2016,149:104-116.
[23]唐盛伟,杨永昌,张涛,等.一种利用体视显微镜测量降膜微通道内液膜厚度及流体力学行为的装置及方法:CN201810061458.6[P].2018-01-23.
[24]高国华,陈建民,李鑫钢,等.规整填料波纹结构上的二维两相流模拟方法[J].化工进展,2010,29(9):1597-1602,1608.
[25]TOURVIEILLE J N,BORNETTE F,PHILIPPE R,et al.Mass transfer characterisation of a microstructured falling film at pilot scale[J].Chemical Engineering Journal,2013,227:182-190.
[26]BRACKBILL JU,KOTHE DB,ZEMACH C.A continuum method for modeling surface tension[J].Journal of Computational Physics,1992,100(2):335-354.
[27]袁猛,胡剑光,陈剑佩,等.微结构壁面降膜波动的统计特性[J].华东理工大学学报(自然科学版),2012,38(3):293-300.
[28]ZHOU D W,GAMBARYAN-ROISMAN T,STEPHAN P.Measurement of water falling film thickness to flat plate using confocal chromatic sensoring technique[J].Experimental Thermal and Fluid Science,2009,33(2):273-283.
[29]K APITZA P L.Collected Papers of P.L.Kapitza[M].Oxford:Pergamon Press,1964.
[30]张帅,张涛,唐盛伟.[BMim][HSO4]-H2SO4二组分物系密度的测定及相关热力学性质的研究[J].石油化工,2016,45(8):957-965.
[31]胡静,张涛,张帅,等.[BMim][HSO4]/H2SO4二元体系的黏度及其表面张力[J].石油化工,2017,46(9):1161-1167.
[32]杨世铭,陶文铨.传热学[M].第4版.北京:高等教育出版社,2006.
[33]WEN X,LIANG C,ZHANG X.Experimental study on heat transfer coefficient between air and liquid in the cross-flow heat-source tower[J].Building and Environment,2012,57:205-213.
[34]CHILTON T H,COLBURN A P.Mass transfer(absorption)coefficients prediction from data on heat transfer and fluid friction[J].Industrial&Engineering Chemistry,1934,26(11):1183-1187.
[35]Cussler E L.Diffusion:Mass Transfer in Fluid Systems[M].3rd edition.Cambridge:Cambridge University Press,2009.