中文摘要：

随着列车运行速度的提高,动能急剧增加,制动时产生的热能也大大增加,巨大的制动热负荷使制动盘产生很大的温度梯度,因此制动盘在表面对流换热系数的大小,直接影响制动盘制动过程中的散热程度.如果制动盘各表面散热不好,则容易发生制动失效和热裂纹等.本文通过萘升华传热传质比拟原理,通过实验得到制动盘表面的平均Nu与Re？之间的关联式：Nu=0.0067Re？0.814,还得到制动盘表面的Nur/Nu比值与r/R之间的关联式：Nur/Nu=0.709（r/R）？0.380,为准确分析制动盘在制动过程中的传热提供依据.

英文摘要：

As a train gains speed, its kinetic energy and the heat energy produced in its breaking process increase greatly. The huge heat load produced by braking of the brake discs strongly affects the braking efficiency. Weak convective heat transfer on the surfaces of brake discs leads to various thermal cracks and braking failure. Convective heat transfer on the surfaces of brake discs is thus an important process that affects the performance of brake discs. There have been few studies on convective heat transfer on the surface of brake discs, and the models used in the reported investigations do not reasonably match the real working conditions of the brake discs. It is well known that the models determine the fluid flow, and the fluid flow determines the convective heat transfer, It is thus difficult to apply the reported results to the real design of brake discs. Against this background, the main contributions of the present paper are the establishing of a flow model reasonably matches the actual working conditions of brake discs and the measurement of local and average convection heat transfer characteristics. To establish the model, in the experimental process the brake discs were drawn by rolling wheels that rolled on a circular orbit. To obtain the convection heat transfer characteristics, the analogy of the naphthalene sublimation technique of heat/mass transfer is adopted. The local Nusselt number on the surface of a brake disc decreases along the radius because convective heat transfer is mainly enforced by fluid flow induced by the brake disc. Because of the weaker effect of the ground surface, the average Nusselt number for the surface of a break disc is larger than that of a rotating disk in cross flow at the same Reynolds number. The average Nusselt number for the surface of a brake disc is l~ger than that for a rolling wheel at the same Reynolds number. The correlations of the local and average Nusselt numbers with the Reynolds number are established.