Any benefit to adding a fan duct between the heatsink and rear exhaust fan?

[ProtoflareX]

I was researching ways to keep the inside of a case as cool as possible and came across the method of placing a fan duct between the heatsink and rear exhaust fan of a case. According to what I read, doing this will reduce both CPU temps and the temps of the surrounding hardware moderately. Now, I could be completely wrong, but this method seems a little archaic, and I have some reservations about its effectiveness in the modern day, as I rarely hear of people doing this. Do you guys think this is still a worthy method of keeping the inside of a case cool, or should it be forgone?

[schwellmo92]

Sounds like a bad idea, how will other heat inside the case exhaust if the rear exhaust fan is covered?

[ProtoflareX]

2 minutes ago, schwellmo92 said:

Sounds like a bad idea, how will other heat inside the case exhaust if the read exhaust fan is covered?

I figured it would escape through the top exhaust fans. I guess I should have mentioned that I'm planning to install two 140mm fans as top exhausts.

[schwellmo92]

2 minutes ago, ProtoflareX said:

I figured it would escape through the top exhaust fans. I guess I should have mentioned that I'm planning to install two 140mm fans as top exhausts.

You're going to have terrible airflow with a setup like that, do you have like 6 fans for the intake? You should have like double the amount of intakes as exhaust.

[aisle9]

That something I've seen done on really, really old computers with hot CPUs (think Pentium 4, Pentium D), but it does more harm than good imo. It seems like a good idea. Keep the hot CPU air out of the rest of the case. What actually ends up happening is the air from the rest of the system gets exhausted right through the CPU cooler, which raises your CPU temps, which raises ambient temps in the case, and that air is then pulled back through the CPU cooler...see the problem? If I had a dollar for every 2004-ish Dell that came to me with a dead Socket 478 Pentium 4, I'd have enough for a couple of extra value meals at Mickey D's, and my thinking is that their cooling method has a lot to do with that.

 

IMO, you're much better off having a cooler that stands alone. If it's a tower cooler, have the CPU cooler fan running and an exhaust fan mounted on the back panel of the case to pull that exhaust right out. If it's a downdraft cooler and you have a fan mount up top, place a fan there as well as on the back panel to get that hot air out. Putting a duct between the cooler and the case exhaust was never really a great idea to begin with, imo.

[ProtoflareX]

2 minutes ago, schwellmo92 said:

You're going to have terrible airflow with a setup like that, do you have like 6 fans for the intake? You should have like double the amount of intakes as exhaust.

The setup I'm planning on is two 200mm fans as intakes, two 140mm fans as top exhausts and one 120mm fan as a rear exhaust.

[ProtoflareX]

3 minutes ago, aisle9 said:

That something I've seen done on really, really old computers with hot CPUs (think Pentium 4, Pentium D), but it does more harm than good imo. It seems like a good idea. Keep the hot CPU air out of the rest of the case. What actually ends up happening is the air from the rest of the system gets exhausted right through the CPU cooler, which raises your CPU temps, which raises ambient temps in the case, and that air is then pulled back through the CPU cooler...see the problem? If I had a dollar for every 2004-ish Dell that came to me with a dead Socket 478 Pentium 4, I'd have enough for a couple of extra value meals at Mickey D's, and my thinking is that their cooling method has a lot to do with that.

 

IMO, you're much better off having a cooler that stands alone. If it's a tower cooler, have the CPU cooler fan running and an exhaust fan mounted on the back panel of the case to pull that exhaust right out. If it's a downdraft cooler and you have a fan mount up top, place a fan there as well as on the back panel to get that hot air out. Putting a duct between the cooler and the case exhaust was never really a great idea to begin with, imo.

Very informative post, looks like this idea is getting marked with a big "X".

[aisle9]

9 minutes ago, schwellmo92 said:

You're going to have terrible airflow with a setup like that, do you have like 6 fans for the intake? You should have like double the amount of intakes as exhaust.

2 in, 1 out is adequate for most systems. Once you get to or above 4 fans, the 2-1 ratio no longer stands. With 4 fans, your strongest two in and your weaker two out will do just fine. At 5 fans, 3-2 usually, but there are reasons to go 2-3 . At 6 fans, 4-2 or 3-3. At 7, what the hell are you doing that requires 7 fans?

 

Every airflow setup should be tailored to the individual case. If you want to go hardcore about it, you can calculate based on CFM and static pressure, taking into account the placement of drive cages and filters, to figure out what a proper fan setup would look like. If you're a normal human being, the ratios suggested above are perfectly adequate. If you want to get technical, I believe negative pressure is actually ever so slightly better for cooling, but positive pressure is better for dust buildup, so it usually wins out.

[dfsdfgfkjsefoiqzemnd]

That sounds like an okay setup fan-wise.  A bit overkill perhaps, but I've done way worse myself. 

Don't do the duct though. @aisle9 is completely right in that it will make matters worse.  IF you insist on using a duct, make it an intake duct.

[schwellmo92]

This is really good info on airflow and also takes in to account you graphics card setup (negative pressure is bad with a blower).

https://www.silverstonetek.com/techtalk_cont.php?tid=wh_positive&area=en

[ProtoflareX]

2 minutes ago, schwellmo92 said:

This is really good info on airflow and also takes in to account you graphics card setup (negative pressure is bad with a blower).

https://www.silverstonetek.com/techtalk_cont.php?tid=wh_positive&area=en

This is only tangentially related to what I made this thread for, but it's something that I never decisively determined as I was researching case airflow. What kind of case pressure is ideal for an internal exhaust graphics card?

[schwellmo92]

13 hours ago, ProtoflareX said:

This is only tangentially related to what I made this thread for, but it's something that I never decisively determined as I was researching case airflow. What kind of case pressure is ideal for an internal exhaust graphics card?

Positive pressure is better always IMO.

[LogicalDrm]

18 hours ago, ProtoflareX said:

This is only tangentially related to what I made this thread for, but it's something that I never decisively determined as I was researching case airflow. What kind of case pressure is ideal for an internal exhaust graphics card?

Doesn't matter. "Pressure" or what it refers to is only important when you have issues with dust. Neutral pressure is overall best if you could achieve it. Much more important thing is having constant airflow over all parts which need to be cooled, with as little pockets of air as possible.

 

Going back to original question, airduct for exhaust isn't really needed. As air moves from fan to fan, your exhausts will already catch all of the airflow coming from CPU heatsink. Any methods of directing airflow inside the case will have very minimal impact on cooling. Airduct on intake side would help, but only in sense that you can direct cool air to component needing it most.