Heat and mass fluxes in presence of superficial reaction in a not completely developed laminar flow

A mathematical model has been developed in order to study the effect of superficial reaction, the catalytic propane combustion, and its coupling with the fluid flow on mass and energy fluxes between gas and solid phase in a monolithic reactor. Simulations have been performed at different values of the gas inlet temperature and propane mass fraction. The effect of heat produced at the wall by the chemical reaction on fluid flow is studied separately from the entrance effect. A new interpretation of the real driving force is proposed, which is able to correctly predict, in a very simple manner, the values of fluxes independently of the presence of Graetz entrance effects. Also the dependency of the Nu and Sh numbers with the gas inlet temperature and propane mass fraction is correctly included. This result leads to a different definition of the Nu and Sh numbers and, for the cases investigated numerical correlations are also given.