Bh. Chao et al., STAGNATION POINT FLOW OF A CHEMICALLY REACTIVE FLUID IN A CATALYTIC POROUS BED, International journal of heat and mass transfer, 39(14), 1996, pp. 3003-3019
The heat transfer and reaction characteristics of a chemically reactiv
e Bow near the stagnation point of a catalytic porous bed with finite
thickness are investigated theoretically. Due to the catalytic effect,
the activation energy is reduced such that chemical reaction in the b
ed becomes possible even at relatively low flow temperatures. The stea
dy state and initial transient period in the gas phase upstream and in
the catalytic porous bed are studied using both the singular perturba
tion method and the finite difference method. For the perturbation ana
lysis, a single layer model is sufficient when the bed is relatively t
hin, of the order of the characteristic thermal diffusion length scale
. For a thick bed, a multiple layer analysis is necessary. Results fro
m the steady-state analysis show that for a higher chemical reactivity
, lower flow velocity gradient, lower activation energy, and lower mas
s diffusion rate, the conversion rate from reactants to products is hi
gher so that a thinner bed can be used to reach complete reaction. Mor
eover, due to the high thermal conductivity of the solid porous materi
al, temperature profiles are modified by the heat release through chem
ical reaction only slightly for a thin bed. The flow temperature is af
fected by the reaction more significantly for a thicker bed because mo
re heat is released from the reaction, and the increased importance of
convection effect. Numerical results for the transient case exhibit t
he same characteristics as in the steady state. Copyright (C) 1996 Els
evier Science Ltd.