Cooling of electronic components by steady/unsteady air flow

The presented study focuses on the heat transfer and power consumption characteristics of an off-the-shelf heat sink and axial fan CPU cooling system and the detailed analysis of the airflow, aiming to optimize the cooling method and save energy. Thermal/power characteristics are experimentally obtained at steady and unsteady fan operation conditions, and the particle image velocimetry (PIV) optical flow measurement technique is applied to analyze the flow inside a transparent experimental model of a heat sink channel. Different fan operation conditions are compared based on the coefficient of performance (COP). Flow in the different heat sink channels strongly differ, depending on the relative position of the channel with respect to the fan and due to a partial obstruction of channels by the fan housing. Moreover, the symmetry in the channels is broken due to the fan induced swirl. These observations can explain discrepancies in the thermal characteristics of numerical models that assume uniform symmetrical and parallel airflows as well as equal distribution across the channels. The gained insight will help to design a feedforward/feedback control system which adjusts fan speed and incorporates a combination of forced and natural convection phases in order to improve the cooling system performance for steady and unsteady heat input conditions.