How to get better airflow?

[Vin]

hi there,

my current case has one 80mm fan (below the PSU) blowing air out of the case
(plus the regulars: one cpu fan and one exhaust fan on the back of the psu).
i've not added an intake fan in the front/bottom as there's no opening in my
case for any airflow, so a fan there would be totally ineffective.

i'm about to add THREE 80mm blowholes on the side panel one below the other;
with the first fan blowing air on top of the cpu/heatsink, the 2nd on the
northbridge and the third near the agp video card.

is this recommended? i don't want to create a turbulence effect as that
would negate the entire exercise.

also does anyone know whether the stock amd fan blows air on top of the
heatsink (inwards) or blows air away from the heatsink (outwards)?

any advise would be much appreciated.

best,
vin

 

[Ben Pope]

hi there,

my current case has one 80mm fan (below the PSU) blowing air out of
the case (plus the regulars: one cpu fan and one exhaust fan on the
back of the psu). i've not added an intake fan in the front/bottom as
there's no opening in my case for any airflow, so a fan there would
be totally ineffective.

i'm about to add THREE 80mm blowholes on the side panel one below the
other; with the first fan blowing air on top of the cpu/heatsink, the
2nd on the northbridge and the third near the agp video card.

is this recommended? i don't want to create a turbulence effect as
that would negate the entire exercise.

You'll probably find that a lot of the airflow will hit the motherboard and
disperse to the front as well as to the back of the case, since there are
not that many fans pulling the air out. You may find that there is a dead
spot in terms of flow at the front of the case, where your hard drives are.

Are you sure there are no holes at the front? Not even at the bottom? A
fan positioned at the front of the case, will usually pull air from just
behind the front panel at the bottom.

If there are really no holes at the front, you could put the fans towards
the front, and then create something to direct the airflow towards the back
of the case. Be sure there is adequate ventilation at the back of the case.

also does anyone know whether the stock amd fan blows air on top of
the heatsink (inwards) or blows air away from the heatsink (outwards)?

Dunno, but almost every single fan blows air onto the heatsink rather then
sucking it off (no jokes required!).

Regardless of all that you will notice a definate improvement in case
temperature with the three fans, it just may not be ideal.

Ben

 

[Hamman]

hi there,

my current case has one 80mm fan (below the PSU) blowing air out of the case
(plus the regulars: one cpu fan and one exhaust fan on the back of the psu).
i've not added an intake fan in the front/bottom as there's no opening in my
case for any airflow, so a fan there would be totally ineffective.

i'm about to add THREE 80mm blowholes on the side panel one below the other;
with the first fan blowing air on top of the cpu/heatsink, the 2nd on the
northbridge and the third near the agp video card.

is this recommended? i don't want to create a turbulence effect as that
would negate the entire exercise.

also does anyone know whether the stock amd fan blows air on top of the
heatsink (inwards) or blows air away from the heatsink (outwards)?

any advise would be much appreciated.

best,
vin

Go for the full air-cooling effect that i have:

2 8Cm case fan sucking in to the case over the AGP card
2 8Cm case fans on the top of the case taking air out
1 8Cm case fan on the front pulling air into the case
1 8Cm case on the usual back bit behind the heatsink

100% copper heatsink with an 6 to 8Cm adapter with yet another 8Cm fan on,
thermometer controlled

 

[kony]

hi there,

my current case has one 80mm fan (below the PSU) blowing air out of the case
(plus the regulars: one cpu fan and one exhaust fan on the back of the psu).
i've not added an intake fan in the front/bottom as there's no opening in my
case for any airflow, so a fan there would be totally ineffective.

First, we lack essential details of the system. There are two ways to
combat heat, to throw more fans/airflow into a system than necessary,
or to consider heat generation and supply only the airflow rate
needed. The latter is the quieter, less dusty solution.

For example, given a system that puts out around 300W of heat, if you
can accept a 10C rise over ambient you shoot shoot for roughly 55CFM
_realized_ airflow. Being conservative we might overshoot that by
quite a bit, since there's difficulty determining true airflow in the
application from fan free-air flow ratings. However, this assumes one
important detail, that all devices are properly heatsunk instead of
requiring excessive airflow to counter the cost-cutting measures
employed by some equipment manufacturers. Only you can assess the
heatsink situation.

i'm about to add THREE 80mm blowholes on the side panel one below the other;
with the first fan blowing air on top of the cpu/heatsink, the 2nd on the
northbridge and the third near the agp video card.

is this recommended? i don't want to create a turbulence effect as that
would negate the entire exercise.

Three fans should provide more than enough airflow, but will alter the
airflow characteristics of the case. Primarily you should consider
the hard drive(s), that if you have similar intake and exhaust rates,
there won't be any front and/or back pressure to move air past the
drive(s).

3 fans might be more than you actually need though, it could be
sufficient to use only one 92mm fan, axial, positioned to blow mostly
under the video card but a bit higher than the card too so air also
flows across the top of the card and towards the northbridge. It's
usually not necessary to dedicate an intake fan to the CPU-sink, since
decreasing ambient case temp and providing a stream of air nearby will
reduce the air being recycled through the 'sink fan, especially with
the rear fan in place. Is that rear fan mounted with a full-cutout
and/or a wire grill, or partially obstructed by a few small holes or
stamped-metal slots? Depending on the total heat produced it might be
enough to make sure that rear fan has no impedance to airflow, and
using a drill to create more "holes" in the chassis in front of the
hard drive area, so the backpressue is dropped. This would however
require disassembling the system to minimize risk and facilitate
cleanup of debris.

also does anyone know whether the stock amd fan blows air on top of the
heatsink (inwards) or blows air away from the heatsink (outwards)?

It blows in.

any advise would be much appreciated.

best,
vin

You might try putting a fan in the bottom-front of the side-panel, an
attempt to keep air flowing around the hard drives. Whether it would
be effective might depend on how open the bays are around the
drive(s). By placing a fan at the opposite end of the case from the
exhaust, the airflow moves past as many components as possible. A
second fan might be best placed as mentioned above, aligned with the
video card, mostly below and partly above it. You might be as well or
better off with two 92mm fans as three 80mm. The large a fan you use
the greater the airlflow/nose ratio prividing you choose fans with low
enough RPM @ 12V, or will be reducing fan speed by external control.

A little airflow goes a long way, two 92mm ~ 1400 RPM fans could be
optimal but of course it also depends on the external ambient temps.
An excessively hot computer room could demand higher airflow.

So far there's been no mention of filters... If you'll be using them
then factor in their effect, especially after becoming partly clogged
(if you won't be replacing and/or cleaning them very regularly). They
may drastically reduce airflow, requiring double or triple the number
of fans for the same flow rate. I recall one system I set up that had
slightly less airflow with two 120mm filtered fans than it's previous
two 80mm non-filtered fans. It might depend on the filter material of
course, these were using the standard, common filters available
everywhere, black plastic with thin-foam.


Dave

 

[Vin]

thanks for the detailed answer dave -- you've managed to address most of my
doubts. after reading your comments i've decided to:

a. install a blowhole in the side panel just above the agp slot (almost
parallel to the NB of the mobo) - this would blow cool air over the agp card
and the NB. And since the cpu heatsink/fan and the ram chips are pretty
close to this area, i'm guessing they might benefit from this intake fan
too.

(CONFUSED RAMBLINGS: Would adding 2 blowholes make a difference, with the
bottom one (parallel to the NB/AGP slot) blowing air into the case and the
top one (parallel to the cpu) blowing air out of the case. I ask this becase
the rear exhaust fan is very close to the cpu fan, therefore wouldn't an
intake blowhole parallel to the cpu create a haphazard airflow pattern?)

b. since my case doesn't allow me to install a fan in the front/bottom area
as most others, i'd be installing a blowhole in the side panel near the hard
drives (front middle of case) with it blowing air inwards.

c. replace my psu with one that has 2 fans (bottom and rear), which will
improve the exhaust of warm air from the system.

Would these changes be more advisable than simply adding 3 blowholes to the
side panel?

Also I'm not too keen on adding any filters to the fans as i've never
noticed any difference in the dust accumulation with my case open or closed.

best,
vin

PS: my rear exhaust fan (below the psu) doesnt have a cutout, only large
holes.

 

[dorothy.bradbury]

my current case has one 80mm fan (below the PSU) blowing air out of the
case

That sounds good - most likely near the CPU cooler:
o So reducing the amount of hot-air recirculation the CPU cooler does
o Increasing effectiveness of the cooler & off-loading heat from the PSU

(plus the regulars: one cpu fan and one exhaust fan on the back of the psu).
i've not added an intake fan in the front/bottom as there's no opening in my
case for any airflow, so a fan there would be totally ineffective.

There's no intake hole or grill at all?

Exhaust fans have 2 areas of resistance
o Case grills - on both intake & exhaust
---- case-punched slots/grills = 45-55% air resistance (brick wall)
---- round-wire grills = 8-15% air resistance
o Intake c/sectional area
---- not so much the grill, but the first inlet point feeding the case
---- often an oblong slot of small c/sectional area

It isn't always necessary to fit an intake fan:
o Intake fans are additive in pressure, not arithmetically in total cfm

Instead it can be simply a matter of freeing up the airflow path:
o Using round-wire grills in place of punched grills
---- this can require a sheet-metal nibbler to be used
o Ensuring the intake & exhaust c/sectional areas at least match
---- again by sheet-metal nibbler or hole-saw/punch

i'm about to add THREE 80mm blowholes on the side panel one below the other;
with the first fan blowing air on top of the cpu/heatsink, the 2nd on the
northbridge and the third near the agp video card.

That's a bit excessive.

o You have 3 fans in exhaust mode - say 25cfm each = 75cfm in total
o 300cfm cools 1500W, 75cfm cools 375W
---- at 100%-load CPU = 80W, Graphics = 50W, 2-10k-rpm HD = 50W
---- Total = 180W, and at most 250W for single CPU

is this recommended? i don't want to create a turbulence effect as that
would negate the entire exercise.

Turbulent flow is inevitable, and need not be noisy:
o Ensure intake fans have no obstruction on their intake side
---- and their exhaust side is free of anything of size for 30-35mm
---- a card is ok, but blowing at a flat card-cage fascia isn't
o Ensure intake fans use round-wire grills
---- small cost, but worth it re intake noise

Choice of fan will be important:
o Fans at front = nearest the ears = must be quietest
---- their use is additive in overcoming pressure, not directly cfm
o Few fans of quality rather than excessive in number
---- I'd try 3 phases of upgrade from grill to 2 fans, not 3

Also more holes = more holes for noise to escape from.
Case mounted fans are outside any soundproofing you use remember:
o CPU cooler / Soundproofing / Case-Fan / Ear )

also does anyone know whether the stock amd fan blows air on top of the
heatsink (inwards) or blows air away from the heatsink (outwards)?

Can vary - rack-mount heatsinks blow down on the heatsinks.
o Impingement cooling - blowing onto the heatsink surface.
o Blow-through cooling - blowing thro fins is quieter (eg, flower cooler)

You haven't mentioned if you have any fan exhaust ports above the PSU.
Sometimes these are present and should be filled before doing anything else.
Otherwise you have an airflow short-circuit to the PSU inlet defeating much
of the lower-intake upper-exhaust airflow path that designers assume.

I would try the following:
Phase 1)
o Fit an intake port on the case-side low-down near the front of the case
---- ideally facing away from your ears if possible
o Simply fit a grill in it, eg, 80mm
o Reassess your temperatures
---- you may be pleasantly surprised now there is a decent air-inlet port

Phase 2)
o Add a fan to this intake port
---- choose a low-noise quality fan, it's assistive, you're now blowing
socks off
o Reassess your temperatures

Phase 3)
o Create an intake port blowing onto the intake of the CPU cooler
---- this will provide a cool air feed to the fan
---- whilst not directly short-circuiting general airflow
---- since you will probably feed it at 25cfm, with 75cfm of exhaust fans

Phase 3 I wouldn't get too excited about, since you already seem to have
a rear case-mounted near-CPU exhaust fan. That is drawing the hot air away
from the CPU-cooler rather than it recirculating it - most recirculate 70%,
and
so must spin faster to compensate which results in considerably more noise.

You want to reduce the resistance the case offers to airflow.
If your case has a poor low-down-intake cross-sectional area - fix that.
You have ~75cfm of exhaust fans in there, but it must come in somewhere

Intake fans work to solve a problem of static pressure:
o A 25mm DC Axial fan creates little static pressure
---- a 32mm or 38mm fan creates more - but with MORE noise
---- two 25mm fans in series can often create more pressure with less noise
o Removing the obstruction to the intake airflow can be as effective
---- 75cfm will cool 375W

Then it's focus on quality of the fans re vibration - case induced noise
through substrate excitation (case sheet metal resonates) is notably on PCs.

 

[kony]

thanks for the detailed answer dave -- you've managed to address most of my
doubts. after reading your comments i've decided to:

a. install a blowhole in the side panel just above the agp slot (almost
parallel to the NB of the mobo) - this would blow cool air over the agp card
and the NB. And since the cpu heatsink/fan and the ram chips are pretty
close to this area, i'm guessing they might benefit from this intake fan
too.

Do you suspect that the NB is overheating?
Is the system unstable?
Isn't the CPU heatsink exhaust moving some air past the northbridge?

Given a reasonable ambient case temp, airflow from the CPU heatsink,
and a reasonably-sized northbridge cooler, it isn't normally necessary
to blow external air on the northbrige. If you're highly overclocking
the northbridge (regardless of, ignoring what the CPU is o'c to) and
hacked the board to raise the chipset voltage you may have special
needs, but ordinarily the northbridge only needs a fair-sized 'sink.
If the 'sink is too small you might replace it. I've accumulated many
old heatsinks over the years and usually just pull off the smallest
northbridge 'sinks and epoxy something larger onto it, though you need
to be SURE the two parts are fitting together well, near perfectly
flat, before permanently attaching a heatsink.

(CONFUSED RAMBLINGS: Would adding 2 blowholes make a difference, with the
bottom one (parallel to the NB/AGP slot) blowing air into the case and the
top one (parallel to the cpu) blowing air out of the case. I ask this becase
the rear exhaust fan is very close to the cpu fan, therefore wouldn't an
intake blowhole parallel to the cpu create a haphazard airflow pattern?)

Generally you don't want two fan near each other blowing in opposite
directions. If you ducted the intake fan to blow directly into the
CPU heatsink fan that might be an exception, but that's an awfully
elaborate setup for what may be minimal "useable" gains. The CPU is
going to benefit from more chassis airflow even if the fan isn't
pointed directly at it. If it's running too hot then odds are you
need a better heatsink, with a larger fan, but if it isnt' instable
then maybe we need more background about what your goal is.

b. since my case doesn't allow me to install a fan in the front/bottom area
as most others, i'd be installing a blowhole in the side panel near the hard
drives (front middle of case) with it blowing air inwards.

Yes, I'd be sure to plan additional airflow AROUND the needs of the
hard drive(s). Increasing air intake in that region, whether by
intake holes or fan, introduces cool air into the system, allow the
existing fans to move more air out of the system. Adding a single
intake fan next to the hard drive(s) might even be all you need,
though again we dont' know the exact motivation behind these
modifications.

c. replace my psu with one that has 2 fans (bottom and rear), which will
improve the exhaust of warm air from the system.

Generally I dislike depending on using the PSU to cool the system, but
sometimes it's necessary. A fan on the bottom usually has a great
benefit in helping to cool the motherboard as well as further reducing
CPU heatsink-recycled air. However, many dual-fan PSU now have slower
fans, don't move that much more air.

Would these changes be more advisable than simply adding 3 blowholes to the
side panel?

I'd start out with one hole, near the hard drive. No matter what else
you do you'll be wanting to keep air moving past the drive, so you
might as well add the fans incrementally.

Also I'm not too keen on adding any filters to the fans as i've never
noticed any difference in the dust accumulation with my case open or closed.

It depends on the environment, but the increased airflow will
certainly introduce more dust, and having a closed case helps to trap
that dust inside. Since your system seems to need added cooling I'm
guessing it didn't have much airflow to start with, so of course it
wouldn't get very dusty.

PS: my rear exhaust fan (below the psu) doesnt have a cutout, only large
holes.

Well, there's large holes, and then there's LARGE holes....
If it looks like over 1/3 of the area is obstructed then I'd cut out a
hole, and it'll be quieter too. If the case is sturdy enough and the
hole in the right place you might even be able to increase it's size
to accomodate the next larger sized fan. Of course this is a whole
lot easier with nibblers or a hole saw, sabre saw, files and other
such tools, so it's certainly not what everyone would want to do.


Dave

 

[Stacey]

hi there,

my current case has one 80mm fan (below the PSU) blowing air out of the
case (plus the regulars: one cpu fan and one exhaust fan on the back of
the psu).

One thing people ignore is where the PSU draws it's air. On AMD's site they
recomend PSU's that have the intake grill on the bottom NOT on the front of
the PSU case. This makes a BIG difference in the CPU's cooling and help rid
the case of heat. Not as "fancy" as a bunch of case fans but does as much
or more good and a lot quieter as you already have than fan in the case.

 

[PUMA F1]

You'll probably find that a lot of the airflow will hit the motherboard and
disperse to the front as well as to the back of the case, since there are
not that many fans pulling the air out. You may find that there is a dead
spot in terms of flow at the front of the case, where your hard drives are.

Are you sure there are no holes at the front? Not even at the bottom? A
fan positioned at the front of the case, will usually pull air from just
behind the front panel at the bottom.

If there are really no holes at the front, you could put the fans towards
the front, and then create something to direct the airflow towards the back
of the case. Be sure there is adequate ventilation at the back of the case.

Dunno, but almost every single fan blows air onto the heatsink rather then
sucking it off (no jokes required!).

Regardless of all that you will notice a definate improvement in case
temperature with the three fans, it just may not be ideal.

Ben

the AMD fans blow air onto the hestsink, I just found out and have a
bleeding index finger to prove it

 

[Matt]

hi there,

my current case has one 80mm fan (below the PSU) blowing air out of the case
(plus the regulars: one cpu fan and one exhaust fan on the back of the psu).
i've not added an intake fan in the front/bottom as there's no opening in my
case for any airflow, so a fan there would be totally ineffective.

i'm about to add THREE 80mm blowholes on the side panel one below the other;
with the first fan blowing air on top of the cpu/heatsink, the 2nd on the
northbridge and the third near the agp video card.

is this recommended? i don't want to create a turbulence effect as that
would negate the entire exercise.

also does anyone know whether the stock amd fan blows air on top of the
heatsink (inwards) or blows air away from the heatsink (outwards)?

any advise would be much appreciated.

best,
vin

First see:

http://www.amd.com/us-en/Processors/SellAMDProducts/0,,30_177_4458_3505^869^4348^1065,00.html

Then just cut one hole near the front bottom, hopefully in front of your
hard drives. You don't need to add any fans, I'll guess.

Make sure your heatsink is installed properly.