Aerodynamic and thermal investigation into axial flow fan cooling of electronic systems part II: unsteady flow measurements

摘要

In part I of this paper measurements of air velocity and surface temperature were presented for the case of a populated printed circuit board situated in the inlet flow to an axial fan. In part II, the board is placed in the exit fan flow and the measurements repeated. Both the flow and the heat transfer changed dramatically. The flow here is unsteady and swirling, giving rise to significantly higher heat transfer coefficients over the whole of the board. A simple method of understanding these flows is presented to help the system designer to use them to advantage. The implications for increased system reliability, due to both the measured low component temperatures and the lower operational temperature of the fan are significant.