The effect on point and integral average conversion of chemical reaction, coupled with radial diffusion and radial distribution of reaction times in viscous-flow tubular reactors, is reported. Solutions are given for first-order reaction over an extensive range of dimensionless rate and time variables. An expression is given for a criterion of the conditions when the contribution of diffusion is so small that it may safely be disregarded as a variable. Another criterion also is given for the situation when diffusivity is so large, in comparison with other system constants, that the simple plug flow solution may be used without incurring more than a specified error.
The hydrolysis of acetic anhydride was studied in 1/4- and 1/2-in.–diam. reactors in 10- and 15-ft. lengths. Reynolds numbers were between 40 and 400 and temperatures between 25° and 35 °C. It was found that the derived equations form a proper description of experiments in the smaller tube. Deviations from theory in the larger tube are explained in terms of free convection arising from nonisothermal conditions and from concentration gradients in the tube. Grashof criteria for initiation of convection in the system are discussed.