Experimental heat transfer and flow analysis of a vented brake rotor

Abstract

Brake rotors generate an opposing torque to a shaft, converting kinetic energy to heat thus necessitating heat transfer considerations. To better understand convection through the fins of a brake rotor, experimental and analytical methods were employed. The experimental approach involved two aspects, assessment of both heat transfer and fluid motion. A transient experiment was conducted to quantify the internal (fin) convection and external (rotor surface) convection terms for three nominal speeds. For the given experiment, conduction and radiation were determined to be negligible. Rotor rotational speeds of 342, 684, and 1025 [rpm] yielded fin convection heat transfer coefficients of 27.0, 52.7, 78.3 [W m −2 K −1], respectively, indicating a linear relationship. At the slowest speed, the internal convection represented 45.5% of the total heat transfer, increasing to 55.4% at 1025 [rpm]. Analytical solutions were evaluated where possible for the convective terms and found to be comparable to the experimental results. The flow aspect of the experiment involved the determination of the velocity field through the internal passages formed by the radial fins. Utilizing PIV (particle image velocimetry), the phase-averaged velocity field was determined. A number of detrimental flow patterns were observed, notably entrance effects and the presence of recirculation on the suction side of the fins.