Thermal Management of Low Profile Electronic Equipment Using Radial Fans and Heat Sinks

There is an increasing need for low profile thermal management solutions for applications in the range of 5-10 W, targeted at portable electronic devices. This need is emerging due to enhanced power dissipation levels in portable electronics, such as mobile phones, portable gaming machines, and ultraportable personal computers. This work focuses on the optimization of such a solution within the constraints of the profile and footprint area. A number of fan geometries have been investigated where both the inlet and exit rotor angles are varied relative to the heat conducting fins on a heat sink. The ratio of the fan diameter to the heat sink fin length was also varied. The objective was to determine the optimal solution from a thermal management perspective within the defined constraints. The results show a good thermal performance and highlight the need to develop the heat sink and fan as an integrated thermal solution rather than in isolation as is the traditional methodology. An interesting finding is that the heat transfer scales are in line with turbulent rather than laminar correlations despite the low Reynolds number. It is also found that while increasing the pumping power generally improves the thermal performance, only small gains are achieved for relatively large pumping power increases. This is important in optimizing portable systems where reduced power consumption is a competitive advantage in the marketplace. © 2008 by ASME