heatsink fan blowing in or out?

[hawksballer]

Sorry about this noobish question but this is the first time I have bought a fan and heatsink separately, should I put the fan blowing toward the CPU or away?

 

[BW86]

toward.

Or you can test it yourself and see what gives you better temps.

 

[MDE]

Normally it blows down onto the heatsink, or like BW86 said, test both ways and see which is better. What heatsink and fan did you get?

 

[hawksballer]

vantec tornado and a swiftech MCX6400-V

 

[BW86]

cool, post what temps you get when you get it all set up. Im curious in seeing what temps you get when the fans pointed toward the HS and away.

I would try if my temp probe wasnt all screwed up.

 

[AristoV300]

Toward the CPU. You should have an exhaust fan in the rear of the case to pull the hot air from the cpu.

 

[BBond]

I use a Swiftech MCX4000 with an 80mm to 120mm adapter and a 120mm Panaflo M1A fan. A high output fan (like my Panaflo or your Tornado) can get better temps sucking air off the heatsink instead of blowing, but you need an intake cover over the top half of the heatsink. I used an intake cover from an Alpha PAL HS. It fit the MCX4000 perfectly. Temps improved sucking vs blowing about 2 degrees Fahrenheit.

 

[VIAN]

I've noticed something interesting in my comp.

I've tested both ways and determined that sucking from the CPU was the best method for the following setup: two fans in the back, both the same strength as the CPU fan. Sucking from the CPU delivered 5 or more degrees cooler. But when I removed one of the fans in the back, the temperatures skyrocketed. So, I tested the blowing method and it worked cooler by 5 or more degrees.

I conclude that when you have 2 times the air being sucked out of the case, not including PSU, sucking is the best method. However, when you have less than that, assuming it will be just 1fan of equal strength to that of the CPU fan, blowing is the best method.

 

[wisdomtooth]

Two very general rules of thumb:

1) If your heatsink is shrouded, it might work better sucking air away from the CPU. The shroud defines a path for cool air to move uniformly through heatsink fins without escaping out the sides, allowing them to soak up as much heat as possible before being expelled out of the shroud by the fan.

2) If you are using low-speed fans without a shroud, it might work better blowing air at a CPU. Due to a lack of a shroud, a sucking slow-speed fan will pull air from everywhere around a heatsink, including from the sides where air does not pass much heatsink surface area before being expelled out the fan. This is inefficient. On the other hand, a slow-speed fan blowing at a heatsink will at least concentrate an air stream along the fins to move the maximum amount of air past the fin surface areas to transfer as much heat as possible.

Of course these are very general guidelines; your mileage may vary.