Transient thermal response of a highly porous ventilated brake disc

The transient thermal response of a newly developed ventilated brake disc cored with a porous medium (wire-woven bulk diamond) is compared with those of a solid brake disc and a conventionally ventilated brake disc with pin fins. The best-performing brake disc vis-a-vis the operating temperature is dependent on the duration of braking: for a short braking event, T(solid) < T(pin-finned) < T(porous); however, for extended braking T(porous) < T(pin-finned) < T(solid). These experimental results are explained in terms of the governing thermophysical parameters using a classical first-order unsteady-state differential equation. The initial rate of increase in the brake disc temperature is dominated by the thermal capacity term; hence, for a short braking event, solid discs with a large thermal capacity operate at a low temperature. However, for extended braking, ventilated discs run cooler and reach lower steady-state temperatures than solid rotors do owing to the increased convective surface area and the forced convection in the ventilated channels. With the wire-woven bulk diamond core which allows a slightly lighter disc than the conventional pin-finned disc, a substantially lower steady-state temperature can be achieved, resulting from promoted flow mixing by three-dimensional wire-woven bulk diamond ligaments which enhance convection.