Seek for your Professional advice regarding Case Cooling

[456]

I am currently using a Lian Li PC-60 Case with a P4 stock CPU fan with a P4 1.7Ghmz CPU. All my IDe cables are rounded cables.

So based on the funamental concept that the more air comes through my case and my system should run cooler. I think my case should be better off with getting 83.1 CFM from 2 intake fans and exhaust with a 50.1 CFM fan at the rear.

Details:

Currently I have two intake fans (Sunon KD1208PTB3-6, 33.1CFM @, total of 66 CFM) and one exhaust fan of Sunon KD1208PTB3-6 as well.

If I want to improve the cooling of my case, should I use Choice 1 or Choice 2,please advise.

Choice 1. --- >
Intake fan (keep the two current 33.1 CFM fans)
Exhaust fan (replace with a a Sunon KD1208PTBX-6A 50.6 CFM fan)

Choice 2 --- >
Intake fan (keep one of the current 33.1 CFm fan and then replace the 2nd fan with a 50.6 CFM fan)
Exhaust Fan (replace with a a Sunon KD1208PTBX-6A 50.6 CFM fan)

Await for your professional advice.

TIA.

[newclockr]

In one of my machines, I changed the intake from a 48cfm to a 108cfm. The exhaust I left the 48cfm. There was only a 2c change in temps.

When I moved everything to a case with matching dual intake & exhaust fans, there was a 4-5c change. My conclusion was that intake & exhaust needed to be equal. Pumping more air in without being able to exhaust the same amount probably just recirculated the warm air. Along those same lines, you probably can't exhaust more air than you take in, defeating the airflow.

Does this make sense? Air FLOW....

newclockr (not a pro, but working on it.)

[456]

HI newclockr

This absolutely make sense to me. What about if I use the following combination:

Intake fan (keep one of the current 33.1 CFm fan and then replace the 2nd fan with a 50.6 CFM fan)

Total of 83.1 CFm for intake fans

Exhaust Fan (replace with a a Sunon KD1208PTBX-6A 50.6 CFM fan) with the exhaust fan from my Enermax Power Supply (around 25 CFM)

Total of 70.6 CFM

I really want to make the intake air flow equals to the exhaust one but my question is should I caluate the CFM of Power Supply exhuast fan into my calculation ??

PLease advise.

[richard_cocks]

IT is actually better to have intake slightly higher than exhaust in some way because then you get slightly higher pressure inside the case than out, meaning that the amount of dust you get in the case is reduced, and there should be enough holes int he case anyway that 10CFM can escape well enough.

[jmichna]

all these comments are interesting, and all have some truth to them, however, please be aware that the types of fans we are using have relatively low static pressures... they really cannot push more air into a closed box than is being exhausted. If anything, having slightly higher inflow than outflow will give you a really minor higher pressure differential... but we are probably talking a couple millibars of pressure if that much... I don't think this would be very effective at preventing dust from entering, and would not help cooling.
You are probably better served to have a negative pressure environment, more exhaust than inflow, so that you are pulling in cool(er) exterior from seams, vents, gaps, etc., beside the intake fans. The intake fans don't have to fight any higher pressure differential inside the case, so they are more efficient.
Also, think about air flow... intake from lower front , cooler air, exhausting out the top back... a blowhole exhaust on the top of your case is good... supplement your upper back exhaust with this.
Regarding dust... it happens. I blow out all my fans and heat sinks (cpu, ps, video card, chip set, slot blower, etc.) about every 6 weeks... this alone results in a drop of 2-3°C depending on how bad the dog and cat fur have gotten... I suggest people do this kind of housecleaning as routine maintenance.
I guess bottom line there's all kinds of ways to air cool... I've seen cases with nine (and more) case fans... front, side, top, back, all over... sounded like a terminal at a small airport.

My rig has 120mm front bottom intake, two 120mm rear top exhaust + ps exhaust at top back. Supplemented with narrow style squirrel cage slot blower next to video card gpu/gpu hs/fan. My cpu hs is Thermalright SK6/60-->80mm funnel/2900rpm 80mm fan (this is sone to be replaced with Thermalright AX7-BS + 3900rpm 80mm fan).
Think of all this as a good mental engineering and physics exercise.
Enjoy,
jmichna

[richard_cocks]

What I mean by higher pressure inside is that air will naturally flow out (that is what blowing really is, air moving from high to low pressure). And thus is air is flowing out not in through open holes, then dust won't be getting in that way and you can then have filters and such for your intake fans if dust is a real problem.

[jmichna]

Originally posted by richard_cocks
What I mean by higher pressure inside is that air will naturally flow out (that is what blowing really is, air moving from high to low pressure). And thus is air is flowing out not in through open holes, then dust won't be getting in that way and you can then have filters and such for your intake fans if dust is a real problem.
richard...
What I was trying to explain... maybe not real well... is that the fans we use are airflow-rated in an open environment, with essentially no "back pressure" (if you will) to fight against. That 50cfm fan may push that flow, but it does so with very little static pressure... it can't force air into a (more than just a marginally) higher pressure environment. You might get some positive pressure inside the case... but if you do it won't help cooling since you really are not moving the volume of air you expect INTO the case... yeah, you might reduce dust somewhat but....
Regards,
jmichna

[richard_cocks]

Really, you are going to get a net airflow of 0.

Yeah I suppse, it really depends on the torque of the fans pushing, they should be able to force some air from inside the case out through all the holes round the case. These places are where most the dust in a PC gets in as most ppl have just the PSU fan blowing outwards.

The otherway round, with a flow of air into the case through the holes, and the outward flow all through the fans, the dust will get in.
Both ways should manage to get the same amount of airflow in total (though it depends on fan position etc, if you have a radiator don't have an intake by it etc :D).

Also fans which are near the CPU and RAM should blow inwards, because you can blow across the memory and help cool that too.

But really every PC should be individually thought about because of what PCI cards etc they have, the location of the IDE cable and drives. also whether you choose drive bay held front air intake fans or card/slot coolers extracting air, it just depends what you want to achieve/what you want to cool, whether main prioity is CPU (try watercooling then) System temp (need very good airflow and ambient temp) or an overclocked vid card (have a slot cooler in the adjacent PCI slot if there is space, and a big fan pushing air in the otherside of it, get air circulating right round it :D) or whether your dual 15400RPM 120GIG HDDs are your pride and joy and you don't want them failing on you.

If ppl want some advice then post a screeny of your system's innards and your system/CPU temps then your PC's ideal airflow I am sure will provide much argument about what is best.

Hmm, this whole airflow thing I think has sparked my interest.

Back on topic; I certainly wouldn't advise a difference of more than about 10CFM between intake and outake, partially because one of your sets of fans will struggle or idle, and partially because your system's air won't be 'flowing' as such as more being wound up in turbulent air.

[newclockr]

456--

Looks like some slightly differing views posted! Truth is, each case and hardware config is different. Assuming you like to open your case and tweak a bit, best advice is to try different fan setups, reduce obstructions (round your cables, arrange your PCI cards, etc.) and check your temps with each change to find the best, lowest temps possible for your hardware.

As for dust--make a habit of blowing it out as often as necessary depending on your environment. Mine gets a blowjob at least once a month. One of my customers machines requires a dusting every two weeks. Others I've serviced have looked near new & unused with very little dust.

All of my machines have MBM5 installed with the on-screen display enabled, so I know if there's any change in temperature. I recently had a CPU fan die and was able to spot the problem before any damage was done. That little piece of freeware saved me a $$$CPU.

Good luck.