Complex heat exchange in brake friction pairs

In the article, the following issues are considered: general principles of complex heat transfer in friction pairs of brake devices; radiant heat exchange from the rough surfaces of the metal friction elements of the brakes; the combined action of the fields of thermal conductivity and radiation in the metal friction elements of the brakes. The role of the thermal and dynamic boundary layers resulting from air-washing of metal brakes with open friction pairs and their effect on cooling is discussed. A new relationship between the Biot and Nusselt criteria is shown, which is presented in the form of thermal resistances of the surface and near-surface layers of the brake pulley rim. A comparison of the combined action of the fields of thermal conductivity and radiation in the metal friction elements of the brakes showed that the radiation efficiency is 1.5–1.7 W·m–2 times higher than the thermal conductivity. Radiation efficiency is the ratio of the power of the heat flux to the unit area through which the heat flux passes.