Maximising heat dissipation from ventilated wheel-hub-mounted railway brake discs

Abstract

Improvement of convective heat dissipation from wheel-mounted discs presents a unique challenge due to the existence of a secondary air flow (in the circumferential direction), between the vanes and wheel web. Although this flow reduces pumping efficiency (air mass flow), it promotes air mixing between different channels and increases turbulence. Beginning with the existing design, a procedure was developed to maximise convective heat dissipation based on specific post-processing procedures and monitored parameters. These included the secondary flow (behind the vanes), air speed in the channels at specific planes and points, global air flow pattern and the distribution of the convective heat transfer coefficient. By analysing these plots and graphs it was possible to identify areas where flow and heat transfer characteristics could be improved. Ultimately, the specific power dissipation (the product of the average convective heat transfer coefficient and the disc wetted area), provided a single quantitative measure of disc design effectiveness in convective cooling. The newly developed design showed an increase in convective heat dissipation of over 10% when compared with the existing disc.