The Dust Acumulation Test

[Intrepid]

I have started a test of which type of preassure causes the most acumulation of dust. Here is how it works, I have 2 fully gutted PSUs each now has a 92mm panaflow fan on it running at 5V both are connected to my silent miniATX testing PSU that sits atop the two boxes. in each box is a fresh blank CD shiny side up. the only diference is that one has air bieng pushed into it, the other has air bieng sucked from it. so one has a - presure and the other has a + preassure. the fans are ducted to fit on and will run 24/7 until it is time to remove the lids and see which CD has the most dust settled on it. Tthe good thing about these PSUs is plents of holes and cracks for air to move in adn out. this may not be the perfect sim but should answer the question. I am doing this becasue i have heared argiments that negetive pressure is better thna positive, adn vice versa.

Here is the setup as it is, running right now.

[big_bertha]

well if you know jack **** about physics you will know that positive pressure is better (assuming you filter the fan air)

if you dont it is exactly the same.

and you will have to leave it on for a month to see. good luck mate... and use a black light to see all the dust better

[MajinSSJVegetto]

Big Bertha, just to tell you, knowing the physics doesnt mean "jack ****".

Real life is almost ALWAYS different than physics will tell you.

Experiments help. This is a interesting one, I can't wait to see results.

[big_bertha]

my prediction is that there will be a layer of crud in both cases. when someone tells you that positive airflow doesnt deposit dust, it is incorrect. what they mean is if you filter incoming air and have no other place for it to enter than it will be cleaner inside.

you seemed a little harsh with your reply and on rereading my post i looked a little as well. didnt mean it. just seen this argument a million times. lets see how the "real world" test pans out

[Intrepid]

in real life the fans arent typicly filtered and i have herred that positive presure can leave stagant pockets where negetive pressure forces air to move thru all crevises of the case preventing sudt from settling.

I have also head all the arguments for positive pressure, much more prolific on these boards.

EDIT also I plan to leave it there till say christmas, you can headge your bets till then and i'll take plenty of pics with hte best camera i can find. there are CDs in ther, blanks, those will be more likely to show the dust than just a blank inside of a steel box.

[BoonieRat]

It may affect where the dust settles, but who cares where the dust settles?,it's about STOPing dust :D. is the CD the same as electro~staticly charged componants?. do the test with a working PSU or it's pointless. who has an empty PSU case with a CD in it in their Case? LoL!. it's all about controlling where the air enters the case, on filtering the air, ...

[Intrepid]

i would have used active PSUs if one of those hadent exploded. and i am only doing this to see simply if positive or negetivep ressure alowes more dust to settle, regardles of other factors. its a simple test thatdidnt take long to set up, so you cna factor in other this sepratly.

[big_bertha]

did you put a filter on the fan for the positive air pressure test?

[Intrepid]

if one was filtered and 1 wasnt it would offset the test, i'll filter the next test in about a month or two.

[RedDeathDrinker]

What about a control sample?

Use a box with some air holes, and put a blank CD in there as well, to monitor dust buildup without any fans or pressure difference......

This should be an interesting test. I'll be waiting for the results at Xmas!

[TimDgsr]

Originally posted by MajinSSJVegetto
Big Bertha, just to tell you, knowing the physics doesnt mean "jack ****".

Real life is almost ALWAYS different than physics will tell you.

Experiments help. This is a interesting one, I can't wait to see results.


the only reason physics doesn't work in real life scenarios is because people are leaving out variables. hate the player not the game.

[wildfrogman]

This will be pretty interesting seeing how it turns out. I read somwhere that the reason people get more dust build up with negative pressure is mostly just a few simple reasons. One is most cases have cracks~vents etc and you have a more even flow of air and some that gets sucked from the ground that is really dusty. Two, that the airflow is more even and sort of spreads out and delevers more air across the pcb~electronics~case surface so more dust gets caught on the surface of whats being cooled. Thats most of it that i remember but it makes sense. All major companies~big business and such are designed on negative airflow. And server~high end stuff that compayes paid a ton of money to engineer the airflow and such have to be doing somthing right.

[Carnil]

Originally posted by BoonieRat
It may affect where the dust settles, but who cares where the dust settles?,it's about STOPing dust :D.

I care about where the dust settles. I'd much rather have dust settle on the fan blades, the intake vents, or just about anywhere but the heatsinks. If dust is on the heatsink, it's insulating it, and the CPU will run hotter.

[Intrepid]

Well I had to stop the test pre-maturly. but it has ben enough time. i needed those 92mm fans for my case. and the box with negetive poressure had almost no dust settled on the CD, but the one with positive pressure had a lot of dust settled in there. thus concludes that


negetive pressure is better for cooling!

[FunkDaMonkMan]

OR!! like my rig.. with positive pressure and filters... i get ZERO... ZERO dust :D

[Skulemate]

That's a curious conclusion considering the aim was to see how much dust settled.

[TimDgsr]

Originally posted by Intrepid6546
negetive pressure is better for cooling!

in the situation you used it in :)

[Intrepid]

Ok i'll refine this.

In situations where there are holes in the casing other than the fan holes positive air pressure allows more dust to settle inside the case in the absense of filters.

To test with filters on each would probably yeild the same results only about five months later.

One good thing than to achieve near perfect airflow for lnog term systems would be to have filters at all air entry points and have a negetive case pressure.

[NeoMoses]

Well stated, Intrepid.

[grunjee]

Hmmmmm. Now I'm not sure what the answer is.

[country_3030]

That would mean you would have to seal every little place where dust could enter then put filters on the fans.

[Stumpjumper5200]

Wait a sec, negative pressure might be better for dust reduction........saying it's better for cooling is a whole other experiment. Sounds like an interesting one though.

BTW - I love how people call it "negative pressure" when it's really just more exhaust airflow then intake :D The real pressure drop is probably .0000001psi

[Intrepid]

well for you stumpjumper a single output fan, probably the one cooling your rad or block, will keep your case at negetive pressure and be silent.

[Crash893]

i think its a good test but i dont think posative air pressure would help keep out dust


it works in bio suits becase the air coming in is filtered so dust cant get in the cracks
but in computers the air is not fileterd and your essantuall blowing it in .

still want to see the results of the test.

[Stumpjumper5200]

I think the best way to keep dust out would be to filter the intakes and have more intake CFM then exhaust CFM, that way the "extra" air will blow OUT of the cracks.

[Intrepid]

having positive pressure (more intake than output) will cause there to be a pocket of stagnent air in the midle of the case allowing sudt to settle, which is what happened in hte positive pressure simulation. in the negeting pressure (more output adn input) the air moved constantly thru all of the case and dust was not allowed to settle.
it seems the best thing would be to have ALL of the holes or cracks in the case filtered or sealed (idealy) and have one or two fans pulling air out of the case, one back and one top.

[TimDgsr]

Originally posted by Intrepid6546
having positive pressure (more intake than output) will cause there to be a pocket of stagnent air in the midle of the case allowing sudt to settle, which is what happened in hte positive pressure simulation. in the negeting pressure (more output adn input) the air moved constantly thru all of the case and dust was not allowed to settle.
it seems the best thing would be to have ALL of the holes or cracks in the case filtered or sealed (idealy) and have one or two fans pulling air out of the case, one back and one top.

i'd like to think that the ideal setup would be exact intake and exhaust pressure. like sandwiching a rad.

[Stumpjumper5200]

True, you would want things to be equal, but in staying with the whole dust prevention theme, you would need the setup I described above (theoretically at least)