Heat transfer in nonequilibrium dissociated hypersonic flow with surface catalysis and second-order effects.

An experimental investigation of heat transfer to hemispheres with both catalytic and noncatalytic surfaces in nonequilibrium dissociated hypersonic nitrogen flow has been conducted. The wind-tunnel flow conditions provided low Reynolds numbers, allowing the assumption of completely frozen shock and boundary layers while introducing the influences of second-order boundary-layer effects such as vorticity interaction. The results for copper surfaces, when correlated using the stagnation-point heat-transfer equation of Rosner together with Lees' heat-transfer distribution, are in good agreement with the second-order theory of Cheng under the assumption of complete surface recombination of atoms. Reductions in heat-transfer rate up to 40% were obtained with the use of noncatalytic coatings applied to the probes. Typically, values of the recombination coefficient range between 0.01 and 0.1 for the noncatalytic surfaces, compared with 1.0 for the catalytic surfaces.