"Ghostrider" <-00-@fitron.142> wrote in message
news:uQvjCejyHHA.3916@TK2MSFTNGP02.phx.gbl...
>
> Vanguard wrote:
>
>> "Jim" wrote in message
>> news:469e8d15$0$20609$4c368faf@roadrunner.com...
>>
>>> I've got an Antec case with a 120mm fan in the back for exhaust.
>>> I've just added a front "intake" fan. Both fans are identical and
>>> have 3 speed settings. Is it OK to set both to high, or should one
>>> fan be set faster than the other for better airflow?
>>
>>
>>
>> The exhaust fan can only exhaust as fast as air can get in. The
>> intake fan can only intake as fast as air can get out. If the
>> potential exhaust rate is higher than the potential intake rate (for
>> all avenues of intake and exhaust) you will have negative pressure
>> inside the case which promotes the collection of dust. If the
>> potential intake rate is higher than the potential exhaust rate, you
>> will have positive pressure inside the case which promotes the
>> movement of dust to reduce its collection.
>>
>> In general, you want a higher potential intake rate than the
>> potential exhaust rate. Also, in general, you won't be able to
>> measure either. The airflow rate spec for fans is their FREE flow
>> rate; i.e., without any restrictions, like a grill or against a case
>> that can disturb linear airflow into the intake side of the fan.
>>
>> Get Speedfan or a temperature monitor utility included for your
>> motherboard. Then test it yourself. The run through the 9
>> combinations of speeds for the fans and monitor the resultant
>> temperature (wait 10 to 15 minutes for temperatures to somewhat
>> stabilize).
>>
>> Front=low, Rear=low
>> Front=low, Rear=medium
>> Front=low, Rear=high
>>
>> Front=medium, Rear=low
>> Front=medium, Rear=medium
>> Front=medium, Rear=high
>>
>> Front=high, Rear=low
>> Front=high, Rear=medium
>> Front=high, Rear=high
>>
>> While this lets you determine which combination gives you the coolest
>> temperature, having the coolest temperature may not be necessary if
>> another combo is quieter and gives a temperature within spec for the
>> CPU. You'll probably get the coolest temperature with both fans at
>> high but also the most noise.
>>
>> With Speedfan, and if the fans have 3 leads (power, ground, and
>> sense), you can control the fan speeds to give you a reasonable
>> temperature and to up fan speeds when temperatures exceed your
>> configured thresholds. That way, the fans would be quiet most of the
>> time but probably will speed up when you play a game (but the game is
>> probably far more noisy than when you are writing e-mails so the game
>> drowns out some of the increased fan noise). Most fans can have
>> their speed control by changing their duty cycle but I don't know
>> about your 3-speed fans. I'm guessing they simply add another inline
>> resistor and are basically 12-volt fans, and probably can be
>> duty-cycle controlled by Speedfan.
>>
>
> All this work for a computer case that is unsealed, full of holes and
> openings? The only important thing is to insure that the differential
> favors air intake versus air exhaust, the degree of the differential
> being the convectional cooling that is desired or required whereby the
> Laws of Thermodynamics takes over at the heatsink/fan to ventilating
> air
> level. It's the airflow...not the fan speed...that is important.
And the OP can measure the effect of changing airflow by monitoring the
resultant temperature(s). It is NOT required that the case, CPU,
memory, disk, and other areas be ran at room temperature. They just
need to be within operating environmental spec. I've seen lots of users
giggle at having their CPUs run at 40C when their host would run just as
well at 55 to 60C. The OP doesn't need to make more noise with
high-flow fans running at max speed when slower and quieter is
sufficient.
The OP already added the front 120mm fan, so "all this work" is already
done and in the past. Now the OP needs to figure out how to achieve
sufficient cooling at minimal noise. Speedfan, or any other temperature
monitoring utility, will help.
--
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