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When the fan oversizes the heatsink

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Insthink

Member
Joined
Dec 26, 2000
I got this fan
http://www.amkcomputer.com/amkpc/images/fop55.jpg

its a Sanyo Denky 90mm fan attached to a fop32 Globalwin heatsink

The fan is massive, but it doesnt run at high speed, its only massive so it can run at slow speed and still cool down nicely and be quiet.

I was wondering performance wise, should I cover the side of the fan that sticks out from the side of the heatsink? or made some kind of angle with tape so the wind created by the sides of the fan dont go outside of the heatsink but inside? if so, how much tape should cover the heatsink? halfway? or as little as possible.


Other question

Ive read a review for HSF here http://hardocp.com/reviews/cooling/roundup0601/index5.html

and I look at the temperatures and notice, wow they are high! yet most people CLAIM to have around 30-40 C with passive air cooling, whats going on?!


Reason im asking this is because right now im waiting for a exchange mobo, cause my epox was broke at second DDR slot, but I had the chance to run my AMD tbird 1.33ghz on it and notice I was getting 48C temperatures at standard voltage 1.83V i think.


Of course, after reading how to realy apply the artic silver II, i found out there was lots of dirt on my Heatsink from the past termal paste I badly removed and it was far from clean so I tought that it was the reason of high temperature, so it would be fixed once I clean it.


So even if I drop at maybe 45C with my HSF, how high is it safe for a CPU to reach? at upped voltage of 1.93V I would get close to 60C when playing games. Room temp is around 25-30C
 

Ridenow

Sneaky Moderator
Joined
Apr 17, 2001
Location
Springfield, IL
You have to be careful when you read about temps and be concerned about where and how they were measured. A lot of the motherboard probes are known to be inacurate. They are also on the bottom of the processor and the "accepted" method for testing is to drill a hole in the heatsink and epox in a probe. When I give my temps as around 42C I will say I used the Via monitor.
Some people would disagree with me, but I say over 50c is when you should be concerned.
As to your fan, I would not tape it off, all you would be doing is making the fan work harder. Sometimes you can make a funnel aparatus that can drop you temps a few degrees, but I would not bother.
 

cjtune

Member
Joined
Dec 18, 2000
Insthink, I think you meant ACTIVE air cooling. Passive air cooling is when hot air rises and cool air settles and so on...let's not get the terminologies confused.

Yeah, I agree with Ridenow. Different experimental conditions will yield different results but what's important is how a set of measurements relates (as in 'relatively') to another. Period.

The weakness of axial fans is then when they encounter even a slight impedence to airflow, their flowrates really go down. Even if you built and used a fandapter (that 'funnel device' as referred to by Ridenow), your 40cfm fan may be looking at say, 20-something cfm only. Better to get one of those high rpm Deltas -or is it time to consider the 'Hoot Chute'? But that 90mm fan of yours is a real beau so don't let it sit idle...
 

Hoot

Inactive Moderator
Joined
Feb 13, 2001
Location
Twin Cities
That fan is the Sanyo Denki 92x32mm 55cfm. My all-time favorite case fan. Quiet, yet powerful. Unfortunately, for use with the FOP HS, it's almost a total waste. The majority of airflow, in an axial fan, occurs in the outer 30% of the blades. Guess what part is not over top of the HS? That factor, combined with the huge dead zone under the hub, where the HS is the hottest and I'd say you got a mis-matched HS & F. Now, if you were to put a good design (not all are) fanadapter between that fan and the HS and you might have something.

Hoot