Energy Dissipation and Shear Rate with Geometry of Baffled Surface Aerator
DOI:
https://doi.org/10.3329/cerb.v14i2.4910Keywords:
energy dissipation, mixing, shear rate, surface aeratorAbstract
The geometric parameters of surface aeration systems govern the process phenomena. The dissipation rate of turbulent kinetic energy (ε) and shear rate (γ) are the key process parameters for mixing in surface aerators. Present work by doing numerical computation by visimix® analyzes the effect of geometric parameters (impeller diameter, cross-sectional area of the tank, liquid height, width of the baffle, rotor blade length and immersion height) on ε and γ. Analysis has been done by making the geometric parameters non-dimensionalized through rotor diameter. With an increase in liquid height and baffled width, there is an increase in the case of energy dissipation and shear rate values. In the case of tank area and blade length, it is vice versa. Energy dissipation and shear rate are not affected by the variation in immersion height of the impeller.
Keywords: energy dissipation; mixing; shear rate; surface aerator
DOI = 10.3329/cerb.v14i2.4910
Chemical Engineering Research Bulletin 14 (2010) 92-96
Downloads
221
919
References
Fair G, Gayer J and Okum D, Elements of water supply and waste water disposal, John Wiley and Sons, 1967
McWhirter JR, Chern JM and Hutter JC, Oxygen Mass Transfer Fundamentals of Surface Aerators, Industrial & Engineering Chemistry Research, 1995. 34(8):pp. 26442654. doi:10.1021/ie00047a013
Rao AR and Kumar B, Scale-up criteria of square tank surface aerator, Biotechnology and Bioengineering, 2007. 96(3):pp. 464470. doi:10.1002/bit.21149
Rao A and Kumar B, Scaling Up of the Geometrically Similar Unbaffled Circular Tank Surface Aerators, Chemical Engineering & Technology, 2008. 31(2):pp. 287293. doi:10.1002/ceat.200700300
Hu WS, Meier J and Wang DIC, Use of surface aerator improve oxygen transfer in cell culture, Biotechnology and Bioengineering, 1986. 28(1):pp. 122125. doi:10.1002/bit.26028012
Ognean T, Dimensionless criteria for estimating oxygen transfer in aeration systems, Biotechnology and Bioengineering, 1993. 41(11):pp. 10141020. doi:10.1002/bit.260411103
Bliem R, Konopitzky K and Katinger H, Bioreactor Systems and Effects, Ch. Industrial animal cell reactor systems: Aspects of selection and evaluation, Advances in Biochemical Engineering/Biotechnology, Springer, 1991. pp. 126, doi:10.1007/Bfb0000746. doi:10.1007/Bfb0000746
Kawase Y andMoo-YoungM, Volumetric mass transfer coefficients in aerated stirred tank reactors with Newtonian and non-Newtonian media, Chemical Engineering Research and Design, 1988. 66:pp. 284288
Gilbertson JA, Sen A, Behie LA and Kallos MS, Scaled-up production of mammalian neural precursor cell aggregates in computercontrolled suspension bioreactors, Biotechnology and Bioengineering, 2006. 94(4):pp. 783792. doi:10.1002/bit.20900
Yianneskis M, Popiolek Z and Whitelaw JH, An experimental study of the steady and unsteady flow characteristics of stirred reactors, Journal of Fluid Mechanics, 1987. 175:pp. 537555. doi:10.1017/S002211208700051X
Schäfer M, Höfken M and Durst F, Detailed LDV Measurements for Visualization of the Flow Field Within a Stirred-Tank Reactor Equipped with a Rushton Turbine, Chemical
Engineering Research and Design, 1997. 75(8):pp. 729736. doi:10.1205/026387697524399
Yianneskis M and Whitelaw J, On the structure of the trailing vortices around Rushton turbine blades, Chemical Engineering Research and Design, 1993. 71(a):pp. 543550
Kumar B and Rao AR, Oxygen transfer and energy dissipation rate in surface aerator, Bioresource Technology, 2009. 100(11):pp. 28862888. doi:10.1016/j.biortech.2008.12.031
Gjaltema A, Tijhuis L, van Loosdrecht MCM and Heijnen JJ, Detachment of biomass from suspended nongrowing spherical biofilms in airlift reactors, Biotechnology and Bioengineering, 1995. 46(3):pp. 258269. doi:10.1002/bit.260460309
Gjaltema A, van der Marel N, van Loosdrecht MCM and Heijnen JJ, Adhesion and biofilm development on suspended carriers in airlift reactors: Hydrodynamic conditions versus surface characteristics, Biotechnology and Bioengineering, 1997. 55(6):pp. 880889
Leenen EJTM, Dos Santos VAP, Grolle KCF, Tramper J and Wijffels R, Characteristics of and selection criteria for support materials for cell immobilization in wastewater treatment, Water Research, 1996. 30(12):pp. 29852996. doi:10.1016/S0043-1354(96)00209-6
dos Santos VAPM, Leenen EJTM, Rippoll MM, van der Sluis C, van Vliet T, Tramper J and Wijffels RH, Relevance of rheological properties of gel beads for their mechanical stability in bioreactors, Biotechnology and Bioengineering, 1997. 56(5):pp. 517529
A Review of the Main Mathematical Models Used in the VisiMix Software, VisiMix Ltd.: http://www.visimix.com
Pope S, Turbulent Flows, Cambridge University Press, Cambridge, 2000
Saarenrinne P and Piirto M, Turbulent kinetic energy dissipation rate estimation from PIV velocity vector fields, Experiments in Fluids, 2000. 29(0):pp. S300S307. doi:10.1007/s003480070032
Cutter LA, Flow and turbulence in a stirred tank, AIChE Journal, 1966. 12(1):pp. 3545. doi:10.1002/aic.690120110
Wu H and Patterson G, Laser-Doppler measurements of turbulent-flow parameters in a stirred mixer, Chemical Engineering Science, 1989. 44(10):pp. 22072221. doi:10.1016/0009-2509(89)85155-3
Zhou G and Kresta S, Distribution of energy between convective and turbulent flow for three frequently used impellers, Chemical Engineering Research and Design, 1996. 74(a):pp. 379389
Okamoto Y, Nishikawa M and Hashimoto K, Energy dissipation rate distribution in mixing vessels and its effects on liquid-liquid dispersion and solid-liquid mass transfer, International Chemical Engineering, 1981. 21(1):p. 88-94
Costes J and Couderc J, Study by laser Doppler anemometry of the turbulent flow induced by a Rushton turbine in a stirred tank: Influence of the size of the unitsI. Mean flow and turbulence, Chemical Engineering Science, 1988. 43(10):pp. 27512764. doi:10.1016/0009-2509(88)80018-6
Zhou G and Kresta SM, Impact of tank geometry on the maximum turbulence energy dissipation rate for impellers, AIChE Journal, 1996. 42(9):pp. 24762490. doi:10.1002/aic.690420908
Liu K and Neeld K, Simulation of mixing and heat transfer in stirred tanks with VisiMix Solutia Inc., in Topical Conference on Process Development from Research to Manufacturing: Industrial Mixing and Scale-up, AICHE Annual Meeting, Dallas, TX, 1999
Genck W, Optimizing crystallizer scale up, Chemical Engineering Progress, 2003. 99:pp. 3644
Nagata S, Mixing Principles and applications, John Wiley & Sons, 1975
Sánchez Pérez J, Rodríguez Porcel E, Casas López J, Fernández Sevilla J and Chisti Y, Shear rate in stirred tank and bubble column bioreactors, Chemical Engineering Journal, 2006. 124(1-3):pp. 15. doi:10.1016/j.cej.2006.07.002
Metzner AB and Otto RE, Agitation of non-Newtonian fluids, AIChE Journal, 1957. 3(1):pp. 310
Kresta SM and Wood PE, The flow field produced by a pitched blade turbine: Characterization of the turbulence and estimation of the dissipation rate, Chemical Engineering Science, 1993. 48(10):pp. 17611774. doi:10.1016/0009-2509(93)80346-R
Ciofalo M, Brucato A, Grisafi F and Torraca N, Turbulent flow in closed and free-surface unbaffled tanks stirred by radial impellers, Chemical Engineering Science, 1996. 51(14):pp. 35573573. doi:10.1016/0009-2509(96)00004-8
Lu WM, Wu HZ and Ju MY, Effects of baffle design on the liquid mixing in an aerated stirred tank with standard Rushton turbine impellers, Chemical Engineering Science, 1997. 52(21-22):pp. 38433851. doi:10.1016/S0009-2509(97)88929-4
