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

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

#31

Post by adrianN »

lstodd wrote: post #26
dgoldstein0 wrote: post #20

Earlier quoted context omitted.

This assumes there are enough bugs to be a problem. Some places this isn't the case. Also more likely to have bugs at lower floors of buildings as they tend to hang around trees and plants.

I'd worry more about dust. In a big city, just leaving windows quarter-opened for a week results in everything covered with a visible layer of dust and finely-ground rubber

Maybe you should move to a country with stricter air quality laws. I leave my windows open all summer and I can't observe any ground rubber in my apartment.

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

#32

Post by majewsky »

lstodd wrote: post #26
dgoldstein0 wrote: post #20

Earlier quoted context omitted.

This assumes there are enough bugs to be a problem. Some places this isn't the case. Also more likely to have bugs at lower floors of buildings as they tend to hang around trees and plants.

I'd worry more about dust. In a big city, just leaving windows quarter-opened for a week results in everything covered with a visible layer of dust and finely-ground rubber

Assuming you're either near a big road, or your city has a major problem with air pollution. I'm near a sort-of important road in a German city and I don't observe anything of this magnitude even though my windows are fully opened quite regularly. (Air pollution is not that bad in my city. Many other German cities are considering driving bans.)

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

#34

Post by croon »

taneq wrote: post #18

If this is because you want to feel cooler, place the fan so it blows cool air inwards onto you . You'll get far more benefit from having air blown on you than you will from just dropping the ambient temperature around you.

Assuming temperature in room is lower than your temperature (likely).

It only accelerates the speed at which your skin temperature moves to match the air temperature through convection.

If you can move air elsewhere to lower the temperature of the room, that is better long term.

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

#35

Post by amelius »

taneq wrote: post #18

If this is because you want to feel cooler, place the fan so it blows cool air inwards onto you . You'll get far more benefit from having air blown on you than you will from just dropping the ambient temperature around you.

Better yet: keep yourself wet while using the fan. The evaporation of water molecules cools you down.

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

#36

Post by jjcm »

kenhwang wrote: post #28
cbanek wrote: post #9

Like others have joked about, it's really about where you want the air and temperature to go. Let's say you have three fans in a computer case, one at the back, one at the front, and one on top of the CPU. If they all blow out of the case, then you've basically created a negative air pressure zone, and you will be sucking air through the vent holes elsewhere, and through any gaps in the case. This may have effects fo…

Just to add, for computer cases, you want it to be a high pressure zone because intake fans generally have filters in front to catch the dust before it gets into the case. Negative pressure means dust gets sucked in from the cracks.

Also while extremely trivial here, higher pressure air has a higher capacity to transfer heat.

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

#37

Post by realpeopleio »

My 4rd grade teacher was convinced of the science of using two fans to cool off the classroom: one blowing cool air into the classroom from the hallway and one fan blowing hot air out of the classroom through a window. The kids that sat near the fan blowing in the room from the hallway were quite content, but the kids by the window were always complaining and they would secretly turn the fan in the window around so it was also blowing in. This would infuriate our teacher when he would discover it and he would claim that the reason the classroom is hot is because the fans were no longer arranged to create air movement through the classroom. But the window kids weren't buying it.

So if sweaty 4th graders are any indication, have the fans blow on you regardless of whatever air movement is supposed to be made.

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