Ask HN: Do I place the fan so that it blows air inwards or outwards?

Re:Ask HN: Do I place the fan so that it blows air inwards o... by lmilcin on Monday May 28, 2018 @07:01AM (#17171764)

While this is technically true, the difference is very minor at the typical pressure ranges being used.

The highest performing PC fans create about 10mmH2O pressure while typically you can expect about 1mmH2O pressure compared to 10mH2O of the atmosphere. This translates to densening of the atmosphere around components by 0.1% or 0.01%, respectively.

Correct placement and design is by orders of magnitude more important than the increased efficiency due to higher density of air.

You could see much more effect by making your air more humid (humid air has higher heat capacity), which will be also much more pronuncable than the increased density due to pressure.

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Re:Ask HN: Do I place the fan so that it blows air inwards o... by mberger on Monday May 28, 2018 @10:13AM (#17172499)

TIL about mmH2O. Is this common in HVAC? I thought pressure was mostly in mmHg or bars(millibars).

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Re:Ask HN: Do I place the fan so that it blows air inwards o... by Cerium on Monday May 28, 2018 @10:35AM (#17172622)

Yes, fans usually have a specification on the pressure they can create in inches of water or millimeters of water.

I think it is because you can measure it yourself with just a tube and water- open end manometer.

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Re:Ask HN: Do I place the fan so that it blows air inwards o... by raldi on Monday May 28, 2018 @10:47AM (#17172676)

How?

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Re:Ask HN: Do I place the fan so that it blows air inwards o... by masklinn on Monday May 28, 2018 @11:19AM (#17172880)

Put bottom end of tube in water, put fan at top of tube drawing out, turn fan on, see how much the water climbs inside the tube?

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