Why would you aim the PSU fan towards the vent roof?

[Twisted4000]

Here's what I mean: you know that some PC cases come with these case vent things on top of the PSU? Why would you want to aim the PSU's fan towards that? Doesn't the PSU's fan aim down towards the mobo and CPU to help cool down the system?

Just wondering...

[i7@980XFTWt]

The only reason I can think of would be that there is good enough cooling in the computer so they added a fan to cool down the roof of the tower. I know it sounds stupid but from what you have described it seems like the only possible answer.

[HansBerg]

Well that depends on the PSU. The CoolerMaster I have has the fan pointing downwards into the computer case. Now does the fan draw the hot air from the computer into the PSU and it escapes through the vents on the back of the PSU or is the fan drawing air in through those vents and blowing it onto the computer tower where it is then drawn out of the tower by the tower extracter fan on the back of the computer case.
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The case I have also has a vent in it with a tube attached that goes to the CPU fan which draws cool air from the outside into the case to supply that air directly to the Heatsink fan.
Some fans draw air into the case and others extract the air.
Maybe the PSU fan you are talking about is either drawing in air or extracting it.
Put o small piece of tissue paper on it and see which way it goes. Don't use such a small piece of tissue that will get sucked into the PSU