Experimental investigation of the aero-thermal characteristics at the exit of an automotive vented brake disc

The paper reports on an experimental investigation of the aero-thermal flow field configuration at the exit of a vented automotive brake disc. The main goal is to obtain a deeper insight of the aero-thermal phenomena upon which brake efficiency strongly depends; a second goal is to generate a complete data set for CFD code validation. A multiple pin disc geometry was tested at two disc rotational speeds and at four moderate braking conditions. The experiments were mainly focused on a coupled thermal and fluid dynamics survey. Local mean temperature and velocity measurements at disc exit were carried out in the relative frame; global parameters, as the vented mass flow rate, the heat power released to the vented air and the internal convective heat transfer coefficient were then evaluated. It was found that the flow structure does not really change, varying the rotational speed and the braking conditions. The heat power increases with increasing the disc temperature, but it does not scale with rotational speed. The convective heat transfer coefficient showed quite large values, reducing for higher disc temperatures. The convective heat transfer coefficient variation for different Reynolds number was found to be consistent with empirical correlations generally used for heat exchangers.