Correlation and Prediction of Boundary Layer Energy Transfer Rates in the Presence of Chemical Reactions and Mass Injection

Abstract

It is shown that transpiration cooling data for chemically reacting turbulent boundary layers can be successfully correlated using enthalpy driving forces, provided the energy transfer correlation is based upon the actual non-radiative energy flux q_ω ^″ at the gas/id interface, rather than the experimentally accessible flux q_ω ^″ obtained from the coolant enthalpy rise. Treated in this manner, the experimental data of Meroney and Giedt (1965, 1967) for turbulent boundary layers of H-atom rich oxyacetylene combustion product gases on a hydrogen or helium-cooled porous plate lead to a correlation identical in form to that previously obtained for non-reactive, low speed turbulent boundary layers with dissimilar gas injection at the wall. This suggests a simple and powerful scheme for predicting required transpiration cooling rates in systems for which the effects of chemical reaction (boundary layer/coolant) and variable properties are important. Similar correlation principles should carry over to laminar or turbulent boundary layers on ablating surfaces since ablation may be fruitfully regarded as a self-regulating form of transpiration cooling. The resulting heat transfer coefficient correlations can be used to systematize experimental data or complex computer calculations and could circumvent the need for lengthy computer calculations in many design applications.