Notebook blower inlet flow and acoustics: Experiments and simulations

This paper discusses methods of evaluating performance for small centrifugal blowers used for electronics cooling in notebooks and other mobile computing platforms. Results from experimental measurements of pressure, flow, and acoustics are presented along with three dimensional computational fluid dynamics modeling results for pressure and flow, which provide added insight into the blower aerodynamics. The results show that the installation condition for the blower affects not only the pressure and flow characteristics of the blower, but also its acoustic performance. Parametric studies of inlet geometries are also presented—studying the flow and acoustic impact of both inlet clearance gaps and inlet grille morphology. These studies show that there is an optimum inlet clearance of 2–3 mm for these blowers, and that the blower acoustics are sensitive to grille morphology, particularly at low clearances. Narrow slotted grilles with a circular pattern are shown to reduce blower acoustic noise by as much as 7 dB compared to the more common straight slotted or ‘jail bar’ configuration. The results presented confirm the importance of evaluating blowers under installed conditions, due to the strong sensitivity of performance to the inlet geometry conditions.