An experimental investigation on the unsteady heat transfer process over an ice accreting airfoil surface

In the present study, an experimental investigation was performed in an Icing Research Tunnel available at Iowa State University (i.e., ISU-IRT) to quantify the unsteady heat transfer and dynamic ice accretion process over an airfoil/wing surface under different icing conditions (i.e., dry rime ice accretion vs. wet glaze ice accretion). A theoretic model was developed at first to evaluate the unsteady heat transfer process over the ice accreting airfoil/wing surface in the term of convective heat transfer coefficient. During the experiments, a high-speed infrared (IR) thermal imaging system was used to achieve temporally-resolved measurements of the surface temperature distribution over the ice accreting airfoil/wing surface. The transient behaviors of droplets impingement, surface water runback and dynamic phase changing processes over the airfoil/wing surface were characterized quantitatively based on the quantitative surface temperature measurements. Based on the time evolution of the measured surface temperature distributions over the airfoil/wing surface for the rime ice accretion case, the water collection efficiency distribution around the airfoil surface was determined quantitatively, which was then imported into the theoretic heat transfer model to estimate the convective heat transfer coefficients over the ice accreting airfoil/wing surface. The convective heat transfer coefficient was found to reach its maximum value at the airfoil stagnation point, and decrease gradually at the downstream locations. The formation of the ice roughness near the airfoil leading edge was found to be able to enhance the convective heat transfer process over the airfoil surface, which would further promote the ice formation and accretion over the roughed airfoil surface.