Best to fix the fan using rubber instead of metal screws, to avoid vibration. Different inlet and outlet will cause great changes in air flow resistance, of course, the bigger the better entrance opening. Do not near the inlet "220V AC Cooling Fan" placed a barrier object (such as a chip and interfaces), otherwise it will reduce the fan air flow. Fan space design. To fan efficiency, noise, must ensure that the distance between the fan and the fan casing is 5 ~ 10mm. Fan blades must be close to get a better efficiency.