Best Case/PSU Fan Filter?

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

I heard that it's possible to make case/PSU fan filters out of acquarium
filters, dryer filters, faucet/door screens, or even women's nylons!
Which would probably be best while maintaining decent airflow?

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Mon, 16 May 2005 03:00:53 -0500, Jonathan Appleseed
<apple@mud.net> wrote:

>I heard that it's possible to make case/PSU fan filters out of acquarium
>filters, dryer filters, faucet/door screens, or even women's nylons!
>Which would probably be best while maintaining decent airflow?

Best at what? Trapping particles?

That is in direct opposition to maintaining decent airflow,
you'll have to pick what tradeoff you want to make per the
case, cooling needs, and filter area.

Filter area is one place you can really tweak the design.
That is, don't try to just put a fan-sized filter over only
the fan but a larger filter area, MUCH larger... as large as
possible. That will also reduce the cleaning interval if
there's a little extra margin for airflow.

Door screens are far too open to be of much benefit unless
you're only trying to keep larger insects out, they won't
even be effective enough at stopping pet hair. Nylons are
pretty good BUT also clog up faster. Ironically enough the
best filtration method might be having an air cleaner in the
room itself, not in the computer.

Even so, you'll have to decide how much you want to reduce
airflow and how much noise increase you can tolerate.
Consider that good filtration cuts airflow by well over 60%,
and poor filtration, well if it's bad enough it wasn't very
useful, the finer dust particals are the ones that get stuck
in every crevace either way while the larger ones are easy
to just blow out with compressed air.

The last filtered case I built used air-conditioner filter
material, it was a thin foam with plastic cross-braces in it
to aid in mounting it, since it was far larger than the
fans' housings. The borders of the filter panel were sealed
with foam weatherstrip tape on the front bezel.

Next time I build a "from-scratch" filtered solution I'll
use a large 1"-pleated paper fiber AC filter, similar to a
"3M filtrete" product but a generic version that filters
slightly less at about 1/4th the price, making it more
economical to throw away instead of bothering with cleaning.
(I don't think my computers are allergic to anything but
we'll see).
http://www.3m.com/us/home_leisure/filtrete/412_micro.jhtml

 

[Spajky]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Mon, 16 May 2005 03:00:53 -0500, Jonathan Appleseed <apple@mud.net>
wrote:

>I heard that it's possible to make case/PSU fan filters out of acquarium
>filters, dryer filters, faucet/door screens, or even women's nylons!
>Which would probably be best while maintaining decent airflow?

I use the latest .. ))
PS. there is no need for PSU (outakes) fan filter!
--
Regards , SPAJKY ®
mail addr. @ my site @ http://www.spajky.vze.com
3rd Ann.: - "Tualatin OC-ed / BX-Slot1 / inaudible setup!"

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Spajky writes:

> I use the latest .. ))

The latest what?

--
Transpose hotmail and mxsmanic in my e-mail address to reach me directly.

 

[Phisherman]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Mon, 16 May 2005 03:00:53 -0500, Jonathan Appleseed <apple@mud.net>
wrote:

>I heard that it's possible to make case/PSU fan filters out of acquarium
>filters, dryer filters, faucet/door screens, or even women's nylons!
>Which would probably be best while maintaining decent airflow?

There are many. A furnace filter has good flow, easily cut to size
and inexpensive. I use filters designed for a room air cleaner.

 

[Spajky]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Tue, 17 May 2005 06:25:52 +0200, Mxsmanic <mxsmanic@hotmail.com>
wrote:

>Spajky writes:
>
>> I use the latest .. ))
>
>The latest what?
(option!)=women's nylons
--
Regards , SPAJKY ®
mail addr. @ my site @ http://www.spajky.vze.com
3rd Ann.: - "Tualatin OC-ed / BX-Slot1 / inaudible setup!"

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

kony writes:

> Best at what? Trapping particles?
>
> That is in direct opposition to maintaining decent airflow ...

Not really. A very closely spaced mesh of extremely fine fibers can
catch a great many particles without having much effect on airflow. If
the filter is a mesh with spacing of 50 micrometres but the fibers in
the mesh are only 10 nanometres wide, you can stop 100% of 50-micron
particles and yet impede airflow by only 0.04%.

This is one reason why I've thought that nylons (stockings) might make
good filter material.

--
Transpose hotmail and mxsmanic in my e-mail address to reach me directly.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Mxsmanic wrote:

> kony writes:
>
>
>>Best at what? Trapping particles?
>>
>>That is in direct opposition to maintaining decent airflow ...
>
>
> Not really. A very closely spaced mesh of extremely fine fibers can
> catch a great many particles without having much effect on airflow. If
> the filter is a mesh with spacing of 50 micrometres but the fibers in
> the mesh are only 10 nanometres wide, you can stop 100% of 50-micron
> particles and yet impede airflow by only 0.04%.

Not after the 50 micron particles plugged up the 50 micron holes.

That's the problem with uniform, single plane, filters.

>
> This is one reason why I've thought that nylons (stockings) might make
> good filter material.
>

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

In article <pkfl81pn675kvioiq1uc0m6vshbunfpi0e@4ax.com>,
Mxsmanic <mxsmanic@hotmail.com> wrote:
>kony writes:
>
>> Best at what? Trapping particles?
>>
>> That is in direct opposition to maintaining decent airflow ...
>
>Not really. A very closely spaced mesh of extremely fine fibers can
>catch a great many particles without having much effect on airflow. If
>the filter is a mesh with spacing of 50 micrometres but the fibers in
>the mesh are only 10 nanometres wide, you can stop 100% of 50-micron
>particles and yet impede airflow by only 0.04%.
>
>This is one reason why I've thought that nylons (stockings) might make
>good filter material.
>
>--
>Transpose hotmail and mxsmanic in my e-mail address to reach me directly.


They all work, the difference is probably how often you have to
change/clean the filter.

I've managed very large systems for many years and they all have
filters in the air intakes. All of the filters have been thick mats,
not paper thin like a stocking. I imagine the depth allows lots of
dust to accumulate with a minimum of airflow restriction.

At home I buy a replacement air conditioner filter for a couple bucks
and cut it into pieces as needed and tape it to the case with a little
duct tape.


--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Wed, 18 May 2005 06:07:06 +0200, Mxsmanic
<mxsmanic@hotmail.com> wrote:

>kony writes:
>
>> Best at what? Trapping particles?
>>
>> That is in direct opposition to maintaining decent airflow ...
>
>Not really. A very closely spaced mesh of extremely fine fibers can
>catch a great many particles without having much effect on airflow.

Untrue.
Person after person has tested this and flow rate with even
a marginal filter is less than 50%. That is, unless you
already had such low flow rate that the measurement method
wasn't accurate down to that level thus extreme margin for
error.

It is certainly possible to still have acceptible flow rate,
I didn't mean to suggest anything to the contrary, BUT the
important distinction there is that requires higher fan RPM,
approaching a less than (very) quiet system. I'd rather
have quiet than dustless if forced to choose.


> If
>the filter is a mesh with spacing of 50 micrometres but the fibers in
>the mesh are only 10 nanometres wide, you can stop 100% of 50-micron
>particles and yet impede airflow by only 0.04%.

That is WAY off, unless of course you are also referring to
a filter surface area much, much higher than fan intake, but
frankly I dont' think it's even possible to achieve 0.04% no
matter how large, even if the entire front bezel were
nothing but a bulbous filter panel. I"m 100% sure it's
impossible as the mounting bracket for the filter alone with
NO filter in it will reduce flow by more than 0.04%.

It's up there past 50% flow reduction typically, but the
filter you mention might be past 80% flow reduction. It's
true that mesh can be very effective so long as you clean it
very frequently, but effective at stopping dust is _always_
going to impede airflow a proportional amount.


>
>This is one reason why I've thought that nylons (stockings) might make
>good filter material.

They do make decent filter material. They also drastically
lower flow rate. Take a pair and put a fan inside then tell
me if it was only 0.04%.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Mon, 16 May 2005 03:00:53 -0500, Jonathan Appleseed <apple@mud.net>
wrote:

>I heard that it's possible to make case/PSU fan filters out of acquarium
>filters, dryer filters, faucet/door screens, or even women's nylons!
>Which would probably be best while maintaining decent airflow?


I use a very cheap and effective material called Pellon (R). Look at the
pics on the web page below to get an idea how well it works, and how to
implement an effective filtration system.

http://webpages.charter.net/bobad/cool.htm

-- Bob

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Best is a compromise - filtration, size, airflow etc...

o Airflow resistance rises with filtration level
---- HEPA = sub-micron filtration and thus very high resistance
---- HEPA = high pressure radial (blowers) + 48-55dB(A) + few 10s cfm
o Airflow resistance rises with airflow
---- filter presents 15Pa resistance at low cfm, 45Pa at double that cfm
---- compensating for resistance by a merely faster fan is undermined

Coloco Centres filter via the HVAC plant - so racks don't have to...
o HVAC plant uses huge multi-kW high pressure radial (blower) fans
o Racks then try to keep the top (hot) part of the rack within spec

PCs impose several restrictions on cooling system...
o Fans are Axial -- PCs present low airflow resistance & demand high cfm
---- Axial fans -- small size, shallow depth, low noise, high cfm, low pressure
---- Radial fans -- large size, high depth, high noise, low cfm, high pressure
o Filters are omitted -- filter size limited by fan/case size & use of axial fans
---- Axial fans produce high airflow, but little pressure
---- Filter resistance exceeding an axial fans stall pressure results in zero airflow

PCs impose implementation restrictions on a filtered solution...
o All intake air must come through the filter
---- yet PC storage bays reduce the frontal area for filters
o Intake airflow must exceed exhaust fan airflow
---- positive case pressure prevents air intake thro non-filtered holes
---- again PC storage bays reduce the front area for fans

So there has to be a compromise...
o Dissipation of N watts limited to X temp rise requires a mass of air A
o Filters add resistance, reducing airflow, so increasing temp rise
o Balance via adjustments to filter system
---- increase filter size = less airflow velocity = less resistance
---- crease filter level = less resistance
o Balance via adjustments to cooling system
---- increase fan size, fan depth, fan speed
---- increase fan number re serial operation with exhaust fans

In practice?
o Most PC filters simply stop the fan blades dusting
o They will not prevent skived copper heatsinks from clogging
o They will increase the time between clogging - perhaps usefully

It is simpler to clean the CPU/GPU heatsink once in a while.
This is more of an issue with laptops - which use high density skived
copper heatsinks of low height, low airflow, non self-cleaning designs.

Heatsinks are frankly the sole device affected by "dust bunnies"
o Blow through, large fin, high velocity heatsinks are preferable
o Multi-fin (copper sheet flower) or asterisk (alloy extrusion) work well

Comes down to how much thermal dissipation you have.
o Easy to filter (& cool) a VIA C3 PC quietly
o Harder to filter (& cool) a Dual-Opteron 5-SCSI-RAID Twin-GPU Server

Most filters do merely stop fan blade dusting.
o Yes filters will stop the large particulates
o However higher heatsink fin density is a structure for dust matting
o In laptops fans can be roaring in 6 months from clogged heatsinks

In summary...
o Axial PC fans will lose ~40-60% of their airflow with a clean filter
---- the figure gets worse as the filter clogs, and HDs get hotter
o Fitting 38mm depth fans or larger fans can cause "fan count runaway"
---- velocity does not help -- resistance rises with higher airflow fans
---- area can assist -- it reduces airflow velocity, reduces resistance
---- fan count assists -- it increases fan area, reduces velocity & resistance

If you suffer hayfever, go buy a Honewell HEPA filter unit.
They use near operating theatre quality HEPA filter drums inside, they
are relatively quiet and are a better ROI than trying to filter a PC
--
Dorothy Bradbury

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

David Maynard writes:

> Not after the 50 micron particles plugged up the 50 micron holes.

The assumption is that you'd replace or clean the filters periodically.
No filter is going to let air through once it is clogged with particles.

--
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[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Mxsmanic wrote:

> David Maynard writes:
>
>
>>Not after the 50 micron particles plugged up the 50 micron holes.
>
>
> The assumption is that you'd replace or clean the filters periodically.
> No filter is going to let air through once it is clogged with particles.

That statement is a self fulfilling circular argument of the obvious. Of
course it won't let air through 'once it is clogged' but the point was how
quick and easy it is to clog uniform, 2 dimensional, media.

Irregular, 3 dimensional, media trap particles without creating such a
'perfect' occlusion of the porosity and have a larger effective surface
area. Not to mention there are other mechanisms for capturing particles
beyond simply "it won't fit through the hole', such as momentum (direction
change) and affinity.

A couple of common examples being the irregular, random fiber mat in
disposable air conditioning intake filters and the washable 'electrostatic'
filter of the same purpose.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

kony writes:

> I'd rather have quiet than dustless if forced to choose.

I'd rather have dustless than quiet. And cool has the highest priority
of all.

--
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[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Thu, 19 May 2005 06:37:40 +0200, Mxsmanic
<mxsmanic@hotmail.com> wrote:

>kony writes:
>
>> I'd rather have quiet than dustless if forced to choose.
>
>I'd rather have dustless than quiet. And cool has the highest priority
>of all.

Understandable.

Even so, a very course filter that doesn't eliminate dust
but greatly reduces it can still be beneficial. Not
"dustless" but greatly reduced dust levels. It is to a
certain extent the user's choice what to do, providing
they'll willing to make the modifications and/or improvise
rather than just buying the generic littel black plastic
filters with the foam insert that are most commonly sold at
PC parts suppliers. Those things are really horrible for
flow rate, last time I tried to put one of those on a 120x38
mm fan I'd guesstimate the flow was reduced to 20% of it's
former rate.

Dorothy make a good point about the axial fans maintaining
lower pressure. I keep meaning to find the time to hunt
down some really quiet radial or diagonal that're small
enough for PC uses, but if TOO much work goes into it you
might be as well off just dusting out the system every now
and again.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Indeed the Papst Diagonal Flow (DV) range are good re pressure:
o 172mm & 200mm form factors available
o Big noisy, heavy & expensive are the downsides
o Pressure of a radial fan in the package of an axial fan

You can get a reasonable solution using...
o 172x51mm Comair Rotron in 24V, lowest noise spec, run at 12V
o It will emit a tolerable level of noise, yet maintain good pressure

Ideally fit the PC into a ply/alloy flight case from Ebay:
o Extrusion & butterfly catch for the cover
o Heavy material for low frequency absorption (mass)
o Line with carpet rippled-foam-rubber underlay for high frequency
o Large enough to fit a decent size of filter on

Those cases aren't much - compared to some expensive PC cases.
Easily mount on wheels, use an old cheap PC case as skeleton.

Ensure the large exhaust fan is inset onto a sub panel so you
have a lined rear to absorb the noise - don't mount it on the rear.

Just use an external USB enclosure for removeable media.
USB allows hot plugging so only power up when needed.
--
Dorothy Bradbury

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Thu, 19 May 2005 06:37:40 +0200, Mxsmanic <mxsmanic@hotmail.com>
put finger to keyboard and composed:

>kony writes:
>
>> I'd rather have quiet than dustless if forced to choose.
>
>I'd rather have dustless than quiet. And cool has the highest priority
>of all.

I have 8 fans in my Athlon box, two in the PSU, one on the graphics
card, two on the HDD, one on the CPU, one at the rear of the case, and
one at the front. Have I missed anything?


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Thu, 19 May 2005 17:22:00 +1000, Franc Zabkar
<fzabkar@optussnet.com.au> wrote:

>On Thu, 19 May 2005 06:37:40 +0200, Mxsmanic <mxsmanic@hotmail.com>
>put finger to keyboard and composed:
>
>>kony writes:
>>
>>> I'd rather have quiet than dustless if forced to choose.
>>
>>I'd rather have dustless than quiet. And cool has the highest priority
>>of all.
>
>I have 8 fans in my Athlon box, two in the PSU, one on the graphics
>card, two on the HDD, one on the CPU, one at the rear of the case, and
>one at the front. Have I missed anything?


The system that I put the AC filters in the front & side,
has:,

3 x 92mm front case wall intake fans
1 x 80mm rear exhaust fan
1 x 80mm exhaust upper PSU
2 x 80mm & 1 92mm lower PSU
1 x 80mm CPU fan
2 (50/60mm) on-card video fans
1 x 120mm side-panel fan

So that's 12, and if it were a box I were overclocking a
lot, it'd have a mobo VRM fan too. The funny part is I
wasn't even trying to put a lot of fans in it, had simply,
previously optimized each part's cooling before they were
destined to be together as a single system.

Then again it's a full server with 14+ well-spaced bays...
wouldn't be very useful to have a giant case without a way
to cool it if/when full. It's merely quiet, not nearly
silent, makes overlapped lower frequency sounds vaguely like
a WWII bomber. That'd be too loud IMO, if it were a
primary-use "desktop" PC. Without the filters it could
easily be adjusted quieter with similar-if-not-same
resulting temps. That many drives results in a lot of
cables though, more cables makes it more of a pain to dust
out a system if/when filterless.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Franc Zabkar writes:

> I have 8 fans in my Athlon box, two in the PSU, one on the graphics
> card, two on the HDD, one on the CPU, one at the rear of the case, and
> one at the front. Have I missed anything?

I have only seven; maybe I need to add one.

--
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[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Thu, 19 May 2005 09:35:33 GMT, kony <spam@spam.com> put finger to
keyboard and composed:

>The system that I put the AC filters in the front & side,
>has:,
>
>3 x 92mm front case wall intake fans
>1 x 80mm rear exhaust fan
>1 x 80mm exhaust upper PSU
>2 x 80mm & 1 92mm lower PSU
>1 x 80mm CPU fan
>2 (50/60mm) on-card video fans
>1 x 120mm side-panel fan
>
>So that's 12, ...

I'm envious.

> ... and if it were a box I were overclocking a
>lot, it'd have a mobo VRM fan too.

I wonder if I can simulate the sound of five additional fans with my
soundcard ...

>The funny part is I
>wasn't even trying to put a lot of fans in it, had simply,
>previously optimized each part's cooling before they were
>destined to be together as a single system.
>
>Then again it's a full server with 14+ well-spaced bays...
>wouldn't be very useful to have a giant case without a way
>to cool it if/when full. It's merely quiet, not nearly
>silent, makes overlapped lower frequency sounds vaguely like
>a WWII bomber. That'd be too loud IMO, if it were a
>primary-use "desktop" PC.

Chances are that the combined thrust would walk it off the desk.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[Guest]

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Fri, 20 May 2005 17:09:38 +1000, Franc Zabkar
<fzabkar@optussnet.com.au> wrote:

>On Thu, 19 May 2005 09:35:33 GMT, kony <spam@spam.com> put finger to
>keyboard and composed:
>
>>The system that I put the AC filters in the front & side,
>>has:,
>>
>>3 x 92mm front case wall intake fans
>>1 x 80mm rear exhaust fan
>>1 x 80mm exhaust upper PSU
>>2 x 80mm & 1 92mm lower PSU
>>1 x 80mm CPU fan
>>2 (50/60mm) on-card video fans
>>1 x 120mm side-panel fan
>>
>>So that's 12, ...
>
>I'm envious.

You'd probably be more envious if you realized just how
little I paid for the case/PSU/fans. Nice set of gear that
only required some metalwork to get the 2nd PSU and filtered
fans implemented.


>
>> ... and if it were a box I were overclocking a
>>lot, it'd have a mobo VRM fan too.
>
>I wonder if I can simulate the sound of five additional fans with my
>soundcard ...

LOL.



>
>>The funny part is I
>>wasn't even trying to put a lot of fans in it, had simply,
>>previously optimized each part's cooling before they were
>>destined to be together as a single system.
>>
>>Then again it's a full server with 14+ well-spaced bays...
>>wouldn't be very useful to have a giant case without a way
>>to cool it if/when full. It's merely quiet, not nearly
>>silent, makes overlapped lower frequency sounds vaguely like
>>a WWII bomber. That'd be too loud IMO, if it were a
>>primary-use "desktop" PC.
>
>Chances are that the combined thrust would walk it off the desk.
>


Naw, I'm all about longevity, could've used fewer fans at
higher RPM but wanted longer cleaning intervals and more
redundancy in case there was a fan failure. Since it has a
couple of fairly important data archives on it in online
form, it seemed prudent to make it at least better than the
box it replaced.