An analytic study of heat transfer and temperature and romposition distribution was conducted for a reacting fluid in laminar flow in a tubular reactor. The reaction chosen was reversible and homogeneous of the form A Numerical solutions were obtained by machine computation for conditions of chemical equilibrium and of finite kinetics. For endothermic, dissociative reactions the radial energy transfer due to diffusion adds to the contribution due to a temporary difference. Nusselt numbers up to 10 fold greater than those for the corresponding inert system are obtained. The diffusion contribution is a maximum when the radial mass transfer is not subject to a reaction resistance; i.e. at equilibrium.
2U.revious investigations have amply demonstrated that large P increases in heat transfer coefficients, relative to inert conditions, occur for reversible and endothermic reactions of the type A F? 2U. For flow in a tube the reaction causes the temperature to decrease from the wall toward the center. This reduction in temperature causes a decrease in concentration of A, and diffusion of A , toward the wall of the tube. The energy flow due to mass transfer is toward the center because the reaction is endothermic. Hence the energy transfer associated witk mass diffusion is in the same direction as that due to the temperature gradient. This is responsible for the increase in heat transfer coefficient.The N z 0 4 @ 2N02 system has been singled out for verification of the behavior, particularly for turbulent flow('-*). The reaction rate constants for this system are so large that chemical equilibrium can be assumed. Accordingly, the composition at any point' is determined by the temperature alone; that is, the kinetics of the reaction have no influence on the temperature, composition and heat transfer coefficient.In this work the goal was to investigate the finite kinetics case and relate the results to those for chemical equilibrium.A homogeneous reacting fluid in a laminar flow, tubular reactor was chosen. With this system it is possible to write differential equations representing the combined effects of flow, heat and mass transfer, and reaction. T h e results are in the form of axial and radial profiles of temperature and composition. Such information is sufficient to determine the Nusselt number as a function of reactor length. For finite kinetics the rate is assumed to be first order in the forward direction and second order in the reverse direction. The method of solution is similar to that employed r e~e n t l y (~~'~) for heat transfer in an irreversible, first order system. T h e equations for the equilibrium case are given first since they serve as a basis for discussing the finite kineticsresults.
General Equations and AssumptionsI t is assumed that the radial diffusion rates are governed by the stoichiometry of the reaction so that On a analyse le transfert de chaleur et la distribution de temperature et composition d'un reactif fluide en Bcoulement laminaire dans un reacteur tubulaire. La reaction 6tudiBe est...
