MIT 10 37 - Combined Internal & External Transport Resistances (3 pages)

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Combined Internal & External Transport Resistances



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Combined Internal & External Transport Resistances

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Lecture Notes


Pages:
3
School:
Massachusetts Institute of Technology
Course:
10 37 - Chemical and Biological Reaction Engineering

Unformatted text preview:

10 37 Chemical and Biological Reaction Engineering Spring 2007 Prof William H Green Lecture 22 Combined Internal External Transport Resistances Packed Bed Reactor use PFR equation dFi Ari eff dz z 0 z L Figure 1 Packed Bed Reactor ri eff ri chem ri eff ri chem if 1 if 1 1 weird BL porous catalyst particle dp Figure 2 Porous Catalyst Particle Biot Number Bi external heat transfer resistance internal heat transfer resistance Mass transfer Biot Number Cite as William Green Jr course materials for 10 37 Chemical and Biological Reaction Engineering Spring 2007 MIT OpenCourseWare http ocw mit edu Massachusetts Institute of Technology Downloaded on DD Month YYYY Bim kc d p where kc D fluid eff Dinside D diameter Bim efffluid Dinside Mears Test rA observed b R p n if kc C A bulk 0 15 where n order of rxn then C Ab C As no external diffusion limitation i e no changing concentration across the boundary layer Similarly if H rxn rA observed or theory b R p Ea h fluid RT 2 0 15 then Tb Ts text Eqn 12 63 rAno external diff limit vs rAobserved Weisz Prater if rA observed c R p 2 eff Dinside C A bulk text Eqn 12 61 1 then you can neglect internal diffusion limitations i e C As C Ab C A r 0 1000 Ea 30 RTs 0 6 100 H rxn Ea 10 1 1 1 10 1 H rxn 0 100 0 temp dep exothermic 0 1 H rxn 0 or Ea 0 Figure 3 text Figure 12 7 10 37 Chemical and Biological Reaction Engineering Spring 2007 Prof William H Green Lecture 22 Page 2 of 3 Cite as William Green Jr course materials for 10 37 Chemical and Biological Reaction Engineering Spring 2007 MIT OpenCourseWare http ocw mit edu Massachusetts Institute of Technology Downloaded on DD Month YYYY H rxn DeC As eff where De Dinside and kt heat conductivity ktTs Ci eff kc Ci b Ci s Dinside r r R ri dV kc Ci r R Ci eff Dinside kc Ci bulk r r R Ci r 0 r 0 if no significant external diffusion limit Ci r R Ci bulk rA k C A e Ea RT rAeff f k C A fit to Aeff e Ea eff RT text Table 12 1 10 37 Chemical and Biological Reaction Engineering Spring 2007 Prof William H



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