The convective heat transfer characteristics on outside surface of vehicle brake disc

The brake disc of a high-speed train can produce huge heat in the process of steep brake or parking brake. Thus the heat transfer characteristics of the high-speed train brake discs are the basic information needed to design them. The main works of the present paper are to establish a flow model that is similar to the actual brake disc working conditions, and to obtain the local and average convective heat transfer characteristics of the outside surface of vehicle break disc experimentally. The naphthalene sublimation technique of heat/mass transfer analogy method is used. The significant result is that the diameter ratio of the brake disc to the wheel determines the convective heat transfer characteristics on the vehicle's brake disc outside surface. Due to the influence of the ground, the average Nusselt number on the surface of a break disc is larger than that of a rotating disc in crossflow at the same Reynolds number. The local Nusselt number on the surface of a break disc decreases along the radius direction. The correlations of the local and average Nusselt numbers, Reynolds number, and the diameter ratio of brake disc to wheel are established. The average Nusselt number is larger than that on the surface of a rolling wheel at the same Reynolds number.