The orientation effect of driven air flow on cooling performance of the cylindrical heat sink with a built-in horizontally-placed fan

This work continued previous study about the heat transfer of the LED graphite-composite heat sink with a built-in vertically-placed fan; it experimentally observed the heat transfer characteristics of the same heat sink but with a built-in horizontally-placed fan. Coupling with the vent channels of heat sink as well as forward and reverse rotations of motor fan, two flow-orientation modes in opposite flow directions could be formed. This study investigated the effect of the direction of the fan-driven air flow on the overall cooling performance of this type of LED heat sink when the configuration of vent channel and the size and power of motor fan were changed. The results indicate that compared with the configuration without motor fan, the Nu of the graphite-composite heat sink with a built-in fan was increased by 75%- 200%. The heat wink with downward flowing mode had slightly higher Nu than the one with upward flowing mode, especially under the operation of the smallest fan. The vent channels of heat sink closer to the bottom heating surface was more beneficial to the heat transfer enhancement, and more vent channels farther from the bottom heating surface would have minus effect on the heat transfer. Finally, the air flow velocity measurement and the smoke flow visualization were also performed. The flow and heat transfer characteristics can be used as reference for related heat sink development.