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Idea for cpu cooling. Is it stupid?

DT4K

DT4K

Diamond Member
This may be a bad idea, but I want some opinions.
1. Cut a hole in the top of your case
2. Put a 120mm fan blowing in
3. Put in some kind of plastic shroud or tube that takes the air coming in from the 120mm fan and funnels it directly to the heatsink

This would allow you to use a fairly quiet fan and still get a ton of air blowing on the heatsink. It would also mean the heatsink would be getting cooler room air instead of the warmer air inside the case. If you don't think this would work, tell me why.
 
That could work, but i am not sure the air would be under enough pressure to effectively cool the heatsink. I could be wrong though.
 


<< and what will be replacing the hs air? >>



I'm not sure what you mean. The idea is that the big fan would be constantly blowing cool air into the case and directly on the heatsink, then you would have 1 or 2 exhaust fans in the back to pull warm air out of the system. I don't know about the pressure. It just seemed that by using a 120mm fan and directing it to the heatsink, you could get a lot more airflow to take the heat away without generating a lot more noise. It's kind of an extension of the idea of using a 60mm to 80 mm fan adapter to get more air blowing on the heatsink. The advantage would be that your blowing cool room air directly on the heatsink instead of the air that's moving around inside your case.
 
My reasoning is there are now 120mm-80mm fan adaptors and people have said that there would not be enough back pressure, or something to that effect, for it to work properly. Like i said above, i could be wrong. The only way to find out if it would work would be to try it!
 


<<

<< and what will be replacing the hs air? >>



I'm not sure what you mean. The idea is that the big fan would be constantly blowing cool air into the case and directly on the heatsink, then you would have 1 or 2 exhaust fans in the back to pull warm air out of the system. I don't know about the pressure. It just seemed that by using a 120mm fan and directing it to the heatsink, you could get a lot more airflow to take the heat away without generating a lot more noise. It's kind of an extension of the idea of using a 60mm to 80 mm fan adapter to get more air blowing on the heatsink. The advantage would be that your blowing cool room air directly on the heatsink instead of the air that's moving around inside your case. >>



That big fan would have to have a somewhat high cfm since it is not directly over the hs, btw, Dell use to do something similar to what you said.
 
I have seen some plastic shrouds on some cases, but I don't know if they are meant to blow air down or suck it away. It seems like if you have a 120mm fan blowing into a tube that narrows to 60mm at the end, it would create higher pressure at the 60mm end. I guess the only way to find out is to try. If I have some spare time, I will experiment a little. If it doesn't work, I can always turn the fan around and have an exhaust blowhole on top. Any ideas what to use for the tube? it would need to be a 90 degree angle and be 120mm diameter on one end and 60mm on the other.
 
There was a commercial attempt at a ducted heatsink, you can check it out here. I think that if you want to run a ducted setup, a centrifugal blower would be a better choice because they typically lose less output when working against a pressure gradient.

In general, however, if your goal is to reduce noise, cutting holes in the case is not always a good solution because it gives internal sounds an easy way out. I would look first at heatsinks which can accept quiet-running 80mm fans by design.
 
I think Dell computers come with only case fan and the air is routed with a shroud. Not sure whether it blows or sucvks though.
 
Interesting idea...but any system with a blowhole in the top makes me kind of laugh. Having the shroud taper to a smaller opening would help kick in the venturi effect, but i really have no idea if it would work. The back pressure people talk about is probably the movement of heated air rising from the HS, which the fan would have to counter. U know, this is a good question for the Highly Technical gang. They would eat it up!
 


<< Not sure whether it blows or sucvks though. >>


Dell blows and sucks. You knew that was coming...
I've heard of a few case mods that do the same thing. I've heard It's fairly effective.
 
If you can find a heatsink ~120mm wide (mounted), go for it. Remember, make the fan suck, because you DON'T want to work against rising air. Oh yeah, make the shroud the entire height of the heatsink, and cover all sides except for the opposite side. Does that make any sense? 😕
 
That is exactly what my dell 400 celeron uses for cooling. Not sure if it would work on CPU's that run hotter like the tbirds. It is quiet though.
 
Wouldn't it be a little easier to cut a blowhole on the side of the case, directly parallel to the CPU heatsink then duct that? That way, you won't have to have insanely high static pressure to overcome the 90 degree angle of a top blowhole.

Another option is to put multiple fans in the same wind tunnel. It won't increase CFM, but it will increase static pressure.
 
I personally have one of the monster hp cases(don't know model) from the 9900 series of computers. It comes with a duct that runs from the rear grill straight over the HSF and it keeps my cpu below 45C load. I personally like having a rear intake with duct and having the PS be the outtake. You could also use a blow hole for more air flow since the hot air will be rising. Neurofreeze has a good option as well putting a fan at the side of the case, I'd personally put it a little closer to the front so if you use it with a rear exhaust you'd make a circular path that would pass through the HS instead of blowing over the top(Sorry don't know how to explain that better.)
 
no it is not a stupid idea. Rather than having the fan mounted at the top of the case, however, it would make more sense to have the rear fan bracket adapted, so you can pout the fan there, and then use a shroud to force air over the heatsink. OEM companies use this, and it is also used in Server rackmount cases. (Check out Anand's article about his new servers)

Normally it would be ideal to have the fan blowing into the case, so air is being blown over the heatsink. That way the airflow would be more concentrated. However, if done correctly, having the fan set to draw air from the case and exhaust it out could work well, as long as there is a tight seal around the heatsink with a relatively small area for air to be drawn into.
 
If the fins of the heatsink are oriented vertically, you won't have have a 90-degree bend if you duct it to a top-mounted blowhole.
 
I had a 92mm fan on the side, and i ducted it directly to my cpu(used a CPU fan too) and that dropped my cooling significantly, unfortunatly, i took it off cause i didn't fasten it very well, and it fell off and i'm afflicted with a disease called lazy 😀 should work if you do it 'right", good luck in your cooling adventure!
 
Just remember, whichever way your new fan goes, make sure you have the same amount of air blowing INTO the case as OUT of it. Otherwise, you'll be fighting an uneven pressure gradient.
 
Does anyone know if any company makes a counter-rotating fan. I would like to try a normal fan and a c-r fan and see if it would make more of a difference than two similar ones stacked.
 
Wouldn't it be better to put the inhole at the bottom of the case, instead of the top so it doesn't have to fight rising hot air? Less turbulence and such?
 
It is not stupid and it is a good idea. Already you can buy kits that do this but they are for rear 80mm fans taking are in and feeding it right to the 60mm fan on the heatsink. Exactly what you are proposing but on a different scale and location. Check out the The WHISPER solution for sale at Directron

Your idea would be better due to the 120mm fan.
 
i was thinking about making a tube that goes from outside my window (helpful during the sub-zero winters, and cool evenings) and directly over the CPU heatsink/Fan...would REALLY lower CPU temps when it's like -5 degrees outside.
 


<< i was thinking about making a tube that goes from outside my window (helpful during the sub-zero winters, and cool evenings) and directly over the CPU heatsink/Fan...would REALLY lower CPU temps when it's like -5 degrees outside. >>



Your room would look like a nuclear reactor 🙂 But that would sure as heck cool the CPU down! 🙂
 
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