Positive or negative?

[BrisoX]

So i'm planning to take NZXT Manta as my case. Also planned to take 2 Thermaltake Riing 140mm fans as intake, 1 Thermaltake Riing 120mm as exhaust fan and 2 Fractal HP-14 Venturi as exhaust on top of case pushing air out. is that good setup for air in case?

[ddddanil]

Positive pressure in preferred because you always can protect your fans from dust but you can't protect all your edges and so on. They have a TechQuickie video 'bout this.

[wildgg]

positive or negative arlfow does not depend on the amount of fans. but on the amount of air they move.

positive airflow would be best in your case.

[BrisoX]

5 minutes ago, ddddanil said:

Positive pressure in preferred because you always can protect your fans from dust but you can't protect all your edges and so on. They have a TechQuickie video 'bout this.

i've seen it yes. so with this setup i will have positive pressure

2 minutes ago, wildthing said:

positive or negative arlfow does not depend on the amount of fans. but on the amount of air they move.

positive airflow would be best in your case.

i thought maxing front intake and top fans on 40-50% and rear 120mm is 120 haha

[Cyracus]

10 hours ago, BrisoX said:

i thought maxing front intake and top fans on 40-50%

if they're the same kind of fans it's much simpler, not gonna look up the specs myself but either test which pushes more air, or take their numbers and put the ones that naturally push less air as exhaust. But negative pressure is technically better at cooling, and positive is better at dust management if the intakes are filtered, so best to shoot for slightly positive

[SSL]

2 hours ago, Cyracus said:

But negative pressure is technically better at cooling

 

Is there actually evidence of this one way or the other? Most statements I see about cooling seem to be based on unsubstantiated armchair theory.

[Cyracus]

1 hour ago, SSL said:

 

Is there actually evidence of this one way or the other? Most statements I see about cooling seem to be based on unsubstantiated armchair theory.

I've seen results from experiments that showed it, busy so can't dig anything up atm

[SSL]

1 minute ago, Cyracus said:

I've seen results from experiments that showed it, busy so can't dig anything up atm

 

I'll be here with bells on.

[LogicalDrm]

I would remove rear fan. You are good with 2 in, 2 out. If you have issues with CPU temps, you can try if having rear intake/exhaust helps.

[stconquest]

3 hours ago, SSL said:

 

I'll be here with bells on.

I can see negative air pressure being better at cooling the entire PC, not to any benefit to overall performance though.  The difference would normally be very little and worse for negative air pressure over time.

 

Negative air pressure draws in air from everywhere, effectively eliminating any hot spots or dead zones for heat to build up.  Alternatively, more dust would enter and cling to components resulting in heat build up on your parts.

 

Positive air pressure can control dust and be monitored for effectiveness.  I just look at my front filter and know when it is time to clean it, usually a month or so and my system is less positive due to dust clogging the filters.

 

Directed airflow and positive pressure (nearing equilibrium) seems to be my preferred set up, from experience.

[SSL]

54 minutes ago, stconquest said:

I can see negative air pressure being better at cooling the entire PC, not to any benefit to overall performance though.  The difference would normally be very little and worse for negative air pressure over time.

 

Negative air pressure draws in air from everywhere, effectively eliminating any hot spots or dead zones for heat to build up.  Alternatively, more dust would enter and cling to components resulting in heat build up on your parts.

 

Positive air pressure can control dust and be monitored for effectiveness.  I just look at my front filter and know when it is time to clean it, usually a month or so and my system is less positive due to dust clogging the filters.

 

Directed airflow and positive pressure (nearing equilibrium) seems to be my preferred set up, from experience.

 

Yeah, more armchair physics. But I'll join in, so it's fine.

 

Taking dead zones on their own; dead zones are a function of fan placement, not pressure. As long as there are no dead zones centered over components, it doesn't really matter whether or not any form.

 

Consider that with positive vs negative pressure, the overall CFM is not going to change assuming that the same fans are used at the same RPM in both configurations.

 

Further, consider that blowing fresh air over a heatsink will provide lower temperatures than pulling hot air away from a heatsink; this is because temperatures work as a function of delta over ambient. Therefore, cooler air flowing into the heatsink will result in cooler temperatures. Negative air pressure won't achieve this because the FPM will be very low at all parts of the case except for the immediate area around the exhaust fans.

[stconquest]

11 minutes ago, SSL said:

 

Yeah, more armchair physics. But I'll join in, so it's fine.

 

Taking dead zones on their own; dead zones are a function of fan placement, not pressure. As long as there are no dead zones centered over components, it doesn't really matter whether or not any form.

 

Consider that with positive vs negative pressure, the overall CFM is not going to change assuming that the same fans are used at the same RPM in both configurations.

 

Further, consider that blowing fresh air over a heatsink will provide lower temperatures than pulling hot air away from a heatsink; this is because temperatures work as a function of delta over ambient. Therefore, cooler air flowing into the heatsink will result in cooler temperatures. Negative air pressure won't achieve this because the FPM will be very low at all parts of the case except for the immediate area around the exhaust fans.

Physics are physics whether you sit in an armchair or stand at a lab table.

 

Observation is part of the scientific method so get off the rocker old man <<I don't know what that means either =D

 

I never said that cooling components are void of fans.  Fresh air would be directed over heat sinks whether running in positive or negative air pressure environments.

 

Seriously, I don't notice any change in temps when my system changes from positive to negative pressure initially.  When there is a 3-5 degree change, as I have not cleaned my filters in months, the temperature increase is due to dust buildup, not airflow.  This discovery uses the scientific technology of observation.

[SSL]

4 minutes ago, stconquest said:

I never said that cooling components are void of fans.

 

Did I say you did?

 

4 minutes ago, stconquest said:

Fresh air would be directed over heat sinks whether running in positive or negative air pressure environments.

 

Not at the same rate, which is key.

[stconquest]

6 minutes ago, SSL said:

 

Did I say you did?

You implied by referencing this:

 

6 minutes ago, SSL said:

Not at the same rate, which is key.

How is it not the same rate?  A fan on a set of CPU heat sink fins will push the same amount of air through those fins regardless of there being more positive or negative pressure in the case:  at least not to any degree of cooling advantage, and only until the dust from unfiltered air (negative pressure) clogs up those fins.

[SSL]

1 minute ago, stconquest said:

How is it not the same rate?  A fan on a set of CPU fins will push the same amount of air through those fins regardless of there being more positive or negative pressure in the case.  At least not to any degree of cooling advantage, and only until the dust from unfiltered air clogs up those fins.

 

Air from an intake blowing directly over a heatsink will be moving faster (and be marginally cooler) than air being drawn towards an exhaust. This is because the air entering a fan is being drawn from a larger area and being forced through an aperture. The air accelerates through the fan due to the Venturi effect and is moving faster on the other side, albiet in a narrower area, thus maintaining a balance in CFM.

 

As an analogy, think about water going down a drain vs water coming out of a pipe.

[stconquest]

5 minutes ago, SSL said:

 

Air from an intake blowing directly over a heatsink will be moving faster (and be marginally cooler) than air being drawn towards an exhaust. This is because the air entering a fan is being drawn from a larger area and being forced through an aperture. The air accelerates through the fan due to the Venturi effect and is moving faster on the other side, albiet in a narrower area, thus maintaining a balance in CFM.

 

As an analogy, think about water going down a drain vs water coming out of a pipe.

In principal, yes.  The environment of positive pressure should work better in directing more air through the fins as you describe.  In reality, it makes little difference to overall performance... until dust build up becomes the true factor for bad temperatures.

[SSL]

1 minute ago, stconquest said:

In principal, yes.  The environment of positive pressure should work better in directing more air through the fins as you describe.  In reality, it makes little difference to overall performance... until dust build up becomes the true factor.

 

A few degrees here and there can add up. It's certainly a win for passively cooled components, which negative pressure would leave out in the cold - or rather not.

[Cyracus]

I can't find anything atm, guess I'll have to do an experiment myself and I'll remember to contact you @SSL