Heat transfer in a chemically reacting system (nitrogen tetroxide‐dioxide)

The effect of chemical reaction on heat transfer was investigated analytically for the dissociating system N2O4 {article}{empty}{document}{document} 2NO2 in turbulent pipe flow. The Reynolds, Colburn, and Deissler analogies were adapted to reacting systems to determine local values of h′/h, the ratio of the heat transfer coefficient for a reacting system to that for the same system under frozen nonreacting conditions. The coefficient h′ was determined by using effective thermal conductivities and heat capacities composed of a frozen and a reacting contribution. The equations for the effective properties, derived in this paper from heat transfer considerations, are in agreement with those developed from thermodynamics and statistical mechanics. The effective properties vary significantly with temperature. Hence, the adaptation of Deissler's analogy, which was originally developed to consider the radial variation of physical properties across the pipe radius for an inert system, would be expected to give the most reliable results in this reacting system. In the range of variables studied it is found that the heat transfer coefficient for a reacting system may be as much as eighteen times the coefficient for a similar, frozen system. The results from the approximate Reynolds and Colburn analogies, which are evaluated by the use of mean physical properties, yield maximum values of h′/h of about 9. The study covers a Reynolds number range of 10,000 to 200,000 and tube wall temperatures of 300° to 370°K.