The Cyclonic Dryer - A Numerical And Experimental Analysis Of The Influence Of Geometry On Average Particle Residence Time

Particle residence time is an extremely important variable in a cyclonic dryer project. With the goal of obtaining a device that conduces to a long particle residence time, the influence of cyclone dimensions on particle residence time and on the type of flow is discussed here. The research was based on a device with a very high ratio of cyclone diameter to other dimensions. Simulations were developed with computational fluid dynamics techniques by the use of the commercial code CFX 4.4® of AEA Technology. Particles were treated individually. The fit of a turbulence model was also discussed. Theoretical and experimental results showed that the dimensions of the conical part of the cyclone had a very important influence on flow and consequently on particle residence time. The influence of volumetric concentration and particle diameter on particle residence time were also observed.211103112Abujelala, M.T., Lilley, D.G., Limitations and empirical extensions of the k-ε model as applied to turbulent confined swirling flows (1984) Chemical Eng. Communications, 31, pp. 223-236(2000) CFX-4.4 User Guide: Solver, , AEA Technology, United KingdomCorrêa, J.L.G., Rios, M.T.T., Silva, M.A., Nebra, S.A., Study of particle residence time in cyclones (2000) Proceedings of the 28th ENEMP, Teresópolis, RJ, pp. 165-172. , (in Portuguese)Corrêa, J.L.G., Chamma, M.O., Godoy, A.L., Silva, M.A., Nebra, S.A., Experimental study of drying and residence time of sugar cane bagasse in cyclonic devices (2001) Proceedings of 2nd Inter-American Drying Conference, Boca del Rio, Veracruz, Mexico, pp. 407-414. , ISBN 968-5401-01-2Corrêa, J.L.G., Graminho, D.R., Silva, M.A., Nebra, S.A., Simulation and experimental study of gas flow in a cyclonic chamber (2001) Proceedings of the 29th ENEMP, São João del Rei, MG, on CD-ROM, , (in Portuguese)Corrêa, J.L.G., Graminho, D.R., Silva, M.A., Nebra, S.A., Cyclone as a sugar cane bagasse dryer (2002) Proceedings of the 13th International Drying Symposium (IDS 2002), Beijing, China, C, pp. 1542-1549Corrêa, J.L.G., Silva, M.A., Nebra, S.A., Experimental and theoretical study of particle residence time in a cyclonic chamber (2002) Proceedings of the 13th International Symposium on Transport Phenomena, Elsevier, Victoria, BC, Canada, pp. 63-67. , ISBN 2-84299-391-8Corrêa, J.L.G., Peres, A.P., Graminho, D.R., Pacifico, A.L., Godoy, A.L., Silva, M.A., Nebra, S.A., Anaysis of flow in a venturi particle feeder (2002) Proceedings of the 14th Brazilian Congress of Chemical Engeneering, , (in Portuguese)Corrêa, J.L.G., Graminho, D.R., Silva, M.A., Nebra, S.A., Experimental study of sugar cane bagasse in cyclone (2003) 2nd Nordic Drying Conference, Copenhagen, DenmarkCorrêa, J.L.G., Graminho, D.R., Silva, M.A., Nebra, S.A., Cyclone as a sugar cane bagasse dryer (2003) Chinese Journal of Chemical EngineeringCorrêa, J.L.G., Discussion of cyclonic dryer project parameters (2003), Ph.D.diss., State University of Campinas, Campinas - SP(in Portuguese)Dibb, A., Silva, M.A., Cyclone as a drier - The optimum geometry (1997) Proceedings of the First Inter-American Drying Conference (IADC), Itu, SP, Brazil, B, pp. 396-403Dirgo, J., Leith, D., Performance of theoretically optimized cyclones (1985) Filtration and Separation, 22, pp. 119-125Griffiths, W.D., Boysan, F., Computational fluid dynamics (CFD) and empirical modeling of the performance of a number of cyclone samplers (1996) Journal of Aerosol Science, 27 (2), pp. 281-304Heinze, C., A new cyclone dryer for solid particles (1984) Ger Chem. Eng., 7 (4), pp. 274-279Hoekstra, A.J., Derksen, J.J., Van Den Akker, H.E.A., An experimental and numerical study of turbulent swirling flow in gas cyclones (1999) Chemical Engineering Science, 54, pp. 2055-2065Iozia, D.L., Leith, D., Effect of cyclone dimensions on gas flow pattern and collection efficiency (1989) Aerosol Science and Technology, 10, pp. 491-500Ismail, K.A., Gonçalves, M.M., Benevenuto, F.J., Instrumentação básica para engenharia (1998), Editora da Unicamp, Campinas, SP. ISBN 85-900609-1-8Jackson, R., Mechanical equipment for removing grit and dust from gases (1963), Great Britain: The British Coal Utilization Research AssociationLaunder, B.E., Reece, G.J., Rodi, W., Progress in the development of a Reynolds stress turbulence closure (1975) Journal of Fluid Mechanics, 68, pp. 537-566Lede, J., The cyclone: A multifunctional reactor for the fast pyrolysis of biomass (2000) Ins. & Eng. Chem. Research, 39, pp. 893-903Lede, J., Soulignac, H.L., Li, F., Villermaux, J., Measurement of solid particle residence time in a cyclone reactor: A comparison of four methods (1987) Chem. Eng. Proc., 22, pp. 215-222Ter Linden, A.J., Investigations into cyclone dust collector (1949) Proc. Inst. Mech. Eng. J., 160, pp. 233-251Ludera, L.M., Design methods for cyclone preheaters of rotary kilns (1989) Zement-Kalk-Gips, 1, pp. 10-12Meier, H.F., Peres, A.P., Fugihara, T.J., Martignoni, W.P., Mori, M., Comparison between turbulence models for 3-D turbulent flows in cyclones (2000) Proceedings of the XXI Cilance - Iberian Latin American Congress on Computational Methods in Engineering, Rio de Janeiro, on CD-ROMMohammadi, B., Pironneau, O., Analysis of the k-epsilon turbulence model (1994) Research in Applied Mathematics, , John Wiley and Sons, ParisMori, T., Suganuma, A., Tanaka, S., On collection efficiency of gas cyclone in coarse particle range (1968) Journal of Chemical Engineering of Japan, 1, pp. 82-86Nebra, S.A., Silva, M.A., Mujumdar, A.S., Drying in cyclones - a review (2000) Drying Technology, 18, pp. 791-832Ogawa, A., Mechanical separation process and flow patterns of cyclone dust collectors (1997) American Society of Mechanical Engineers, 50, p. 97Patankar, S.V., (1980) Numerical Heat Transfer and Fluid Flow, , Washington: Hemisphere Publishing CoXiang, S.H.R., Park, S.H., Lee, K.W., Effects of cone dimension on cyclone performance (2001) Aerosol Science, 32, pp. 549-561Santana, J.D.A.M., Arnosti Jr., S., Coury, J.R., Performance of cylindrical-conical cyclones with different geometrical configurations (2001) Brazilian Journal of Chemical Engineering, 18 (3), pp. 233-241Silva, M.A., Study of drying in cyclones (1991), Ph.D. diss., State University of Campinas, Campinas, SP(in Portuguese)Yuu, S., Jotaki, T., Tomita, Y., Yoshida, K., The reduction of pressure drop due to dust loading in a conventional cyclone (1978) Chemical Engineering Science, 33, pp. 1573-158

On the Price of Anarchy for flows over time

Dynamic network flows, or network flows over time, constitute an important model for real-world situations where steady states are unusual, such as urban traffic and the Internet. These applications immediately raise the issue of analyzing dynamic network flows from a game-theoretic perspective. In this paper we study dynamic equilibria in the deterministic fluid queuing model in single-source single-sink networks, arguably the most basic model for flows over time. In the last decade we have witnessed significant developments in the theoretical understanding of the model. However, several fundamental questions remain open. One of the most prominent ones concerns the Price of Anarchy, measured as the worst case ratio between the minimum time required to route a given amount of flow from the source to the sink, and the time a dynamic equilibrium takes to perform the same task. Our main result states that if we could reduce the inflow of the network in a dynamic equilibrium, then the Price of Anarchy is exactly e/(e − 1) ≈ 1.582. This significantly extends a result by Bhaskar, Fleischer, and Anshelevich (SODA 2011). Furthermore, our methods allow to determine that the Price of Anarchy in parallel-link networks is exactly 4/3. Finally, we argue that if a certain very natural monotonicity conjecture holds, the Price of Anarchy in the general case is exactly e/(e − 1)

Pragas da soja no Brasil e seu manejo integrado.

Pragas da soja; Pragas que atacam as folhas: Anticarsia gemmatalis (Lep.: Noctuidae); Pseudoplusia includens (Lep.: Noctuidae); Coleopteros desfolhadores; Outros organismos que atacam as folhas; Pragas que atacam vagens e graos: Percevejos sugadores de sementes; Lagartas das vagens; Brocas das vagens; Pragas que atacam plantulas, hastes e peciolos: Sternechus subsignatus (Col.: Curculionidae); Elasmopalpus lignosellus (Lep.: Pyralidae); Epinotia aporema (Lep.: Tortricidae); Outros insetos que atacam plantulas, hastes e peciolos; Pragas que atacam as raizes da soja: Coros; Percevejos-castanho-da-raiz; Outros insetos que atacam as raizes; Inimigos naturais das pragas da soja; Predadores: Hemipteros; Coleopteros; Parasitoides: Parasitoides de lagartas; Parasitoides de percevejos; Entomopatogenos: Virus; Fungos; Amostragem das pragas; Controle integrado e nivel de acao; Controle integrado das pragas que atacam as folhas: Anticarsia gemmatalis; Pseudoplusia includens e outros Plusiinae;; Coleopteros desfolhadores; Outros organismos que atacam as folhas; Controle integrado das pragas que atacam as vagens e graos: Percevejos; Lagarta-das-vagens; Broca-das-vagens; Controle integrado das pragas que atacam plantulas, hastes e peciolos: Sternechus subsignatus; Epinotia aporema; Controle integrado das pragas que atacam as raizes: Coros; Percevejo-castanho-da-raiz.bitstream/item/128003/1/ID-6173.pd

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe