Energy balance of the airflow boundary layer in the brake disc ventilation

Abstract

Abstract Airflow through the brake disc ventilation causes the formation of a boundary layer at the walls. It affects both the dynamic processes related to air exchange in the space between the walls and thermal processes associated with air insulation of the heated surfaces of the ventilation ducts. The present paper aims to develop a model for calculating plane airflow in a ventilation duct in polar coordinates. Using the Navier-Stokes equations and the equations of the energy balance of the airflow boundary layer, we succeeded in determining the elements that affect the intensity of changes in the air masses in the boundary layer and the elements that are responsible for the thermal conductivity of the thermal boundary layer of the airflow. Besides, we obtained an energy balance equation, which takes into account the enthalpy and thermodynamic parameters of the thermal boundary layer, as well as found the possibilities of influencing the heat exchange processes by minimizing factors of the heat-insulating boundary layer. Finally, we specified the dependence of the boundary layer temperature on the temperature of the walls of the brake disc ventilation. The obtained dependences lay the ground for formulating variants of the influence on the heat-insulating boundary layer of the airflow, namely, the design of a forced air supply system at different angles of attack into the ventilation cavity of the brake disc or the manufacture of ventilation ducts with complex geometry.