Numerical Simulation of Coupled Heat and Mass Transfer for Airfoil Ice Protection Systems

The design of ice thermal protection systems is multidisciplinary and highly integrated with that of other aircraft systems and aircraft aerodynamics, thus requiring knowledge of atmospheric conditions, numerical simulation methods, and testing procedures for aircraft to be certified under national airworthiness regulations. Using simulations in the certification process may reduce the required icing tunnel and flight tests, provided that the system’s thermal behavior is accurate. Simulations can anticipate system thermal performance by predicting surface temperatures, runback water flow, and runback freezing rates. The results demonstrate compliance with regulations and are validated by tests in the certification phase of the aircraft. A thermal analysis code applies the first law of thermodynamics and the water continuity equations to the airfoil exposed to icing conditions in a steady-state regime. In addition to the effects of phase change by evaporation, freezing, and melting, the code considers the impact of the streamwise temperature gradient, water hydrodynamics, and laminar-turbulent transition. Correlations predict both the onset and length of the laminar-turbulent transition. The runback water flow is assumed to follow two regimes: film and rivulets. Within the impingement limits, runback water runs as a film and flows downstream as rivulets. The present chapter also uses two other procedures: (1) the superposition method and (2) a 2D boundary layer differential code by Reynolds Averaged Navier Stokes. Results from non-isothermal and isothermal superposition and differential boundary layers were compared with experimental data from the NASA icing tunnel, which were used to validate the proposed code.