Originally Posted by yellowtoblerone
you're saying there has to be an exhaust fan at the end in addition to a 60mm fan on the northbridge for the exhaust pipe to have adequate cooling effect?
Yes because the air coming in from the NB side would "crash" against the 90* angle and possibly even rebound hot air due to such a small space. You will need something sucking the hot air out to keep adequate CFM flowing through the tube mechanism
However if you had reversed the flow to have the hot air dumped into the case and use this tube as an intake for clean cold air, it will reduce the NB temps, and you could make an exhaust port above the fan to help vent the hot air. The plus to this is because your are in a Pull effect, there is not as much of a concern about the sharp angle - hence why I suggested an exhaust fan on the outside for the other configuration - the pull effect of a fan has bettter cooling abilites for various reasons, mainly due to deadspots in fans as a major.