Heat and mass transfer coefficients in catalytic monoliths

被引:120
作者
Gupta, N [1 ]
Balakotaiah, V [1 ]
机构
[1] Univ Houston, Dept Chem Engn, Houston, TX 77204 USA
关键词
heat transfer; mass transfer; surface reaction; monolith; Graetz problem;
D O I
10.1016/S0009-2509(01)00134-8
中图分类号
TQ [化学工业];
学科分类号
0817 ;
摘要
We analyze the classical Graetz problem in a tube with an exothermic surface reaction and show that the heat(mass) transfer coefficient is not a continuous function of the axial position and jumps from one asymptote to another at ignition/extinction points. We show that the steady-state heat(mass) transfer coefficient is not a unique function of position in parameter regions in which the Graetz problem with surface reaction has multiple solutions. We also analyze the more general two-dimensional model (with axial conduction/diffusion included and Danckwerts boundary conditions) and show that for fixed values of the reaction parameters, the heat(mass) transfer coefficient has three asymptotes. Unlike the Graetz problem, in this case the heat(mass) transfer coefficient is always finite and bounded at the inlet and is given by a new asymptote. We present analytical expressions for all three asymptotes for the case of fiat and parabolic velocity profiles. It is also shown that in catalytic monoliths, ignition/extinction may often occur in the entry region and hence the local transfer coefficients and not the average values proposed in the literature determine the ignition/extinction behavior. Finally, we use the new results to develop and analyze an accurate one-dimensional two-phase model of a catalytic monolith with position dependent heat and mass transfer coefficients and determine analytically the dependence of the ignition/extinction locus on various design and operating parameters. (C) 2001 Elsevier Science Ltd. All rights reserved.
引用
收藏
页码:4771 / 4786
页数:16
相关论文
共 26 条
[1]  
[Anonymous], 1937, CHEM ING
[2]   MASS-TRANSFER WITH A CHEMICAL-REACTION OF THE 1ST ORDER - ANALYTICAL SOLUTIONS [J].
APELBLAT, A .
CHEMICAL ENGINEERING JOURNAL AND THE BIOCHEMICAL ENGINEERING JOURNAL, 1980, 19 (01) :19-37
[3]  
ARFKEN G, 1985, MATH METHODS PHYSICI
[4]  
Balakotaiah, 1996, CHEM ENG EDUC, V30, P234
[5]   A simplified model for analyzing catalytic reactions in short monoliths [J].
Balakotaiah, V ;
Gupta, N ;
West, DH .
CHEMICAL ENGINEERING SCIENCE, 2000, 55 (22) :5367-5383
[6]   A SERIES SOLUTION FOR MASS-TRANSFER IN LAMINAR-FLOW WITH SURFACE-REACTION [J].
BASIC, A ;
DUDUKOVIC, MP .
AICHE JOURNAL, 1991, 37 (09) :1341-1353
[7]   STOFFTRANSPORT BEI WANDREAKTION IM EINLAUFGEBIET EINES STROMUNGSROHRES [J].
BRAUER, HW ;
FETTING, F .
CHEMIE INGENIEUR TECHNIK, 1966, 38 (01) :30-&
[8]  
Carslaw H. S., 1959, CONDUCTION HEAT SOLI
[9]  
Danckwerts P.V., 1970, GAS LIQUID REACTIONS
[10]   A COMPARISON OF LUMPED AND DISTRIBUTED MODELS OF MONOLITH CATALYTIC COMBUSTORS [J].
GROPPI, G ;
BELLOLI, A ;
TRONCONI, E ;
FORZATTI, P .
CHEMICAL ENGINEERING SCIENCE, 1995, 50 (17) :2705-2715