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Imagine I have room that is very hot and it is colder outside. I want to cool it down using a fan.

Scenario 1

There is only one door. I have one fan.

Where should I put it and which way should it blow?

Room with a door

Scenario 2

I have two doors, one on each end. I still only have one fan.

Room with two doors

Scenario 3

Same as scenario 2, but I now have multiple fans.

For convenience, it is fine to assume that the room is a cuboid and that the fan emits no heat.

luispedro
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    A room with no windows very convenient – Argus Dec 03 '12 at 18:33
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    Hi luispedro, and welcome to Physics Stack Exchange! As specified in our homework policy and [FAQ#questions], this is a site for conceptual physics questions, not a place to get people to solve problems for you. If you'd like to edit this question to show what you've tried and what concept you got stuck on, I'll be happy to reopen it. – David Z Dec 03 '12 at 18:47
  • @Argus "first, assume the cow is a sphere..." – McGarnagle Dec 03 '12 at 18:49
  • @DavidZaslavsky This is not my homework. – luispedro Dec 03 '12 at 18:55
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    I will make my answer into a comment. The idea is to push air into the room, better with a centrifugal fan, http://en.wikipedia.org/wiki/Centrifugal_fan , which draws air efficiently, placed at the door. If it is the usual table fan which displaces air in front of it, it should be a bit outside the doors and aimed at the doors to push cool air in. – anna v Dec 03 '12 at 19:00
  • luispedro, I understand that this is not your homework. But still, you're asking people to solve a problem for you without showing the slightest bit of effort to work on it yourself. That sort of question is generally not considered appropriate here, homework or not. Try to figure it out yourself, and when you get stuck on some concept, then you can ask here. – David Z Dec 03 '12 at 23:26
  • @anna you know you're not really supposed to do that ;-) – David Z Dec 03 '12 at 23:27
  • @DavidZaslavsky: Most of the questions linked here on the right seem exactly like mine: here's an everyday thing, does anybody have a technical analysis of it? http://physics.stackexchange.com/questions/13795/if-i-put-3-bottles-of-water-next-to-each-other-in-the-fridge-which-one-is-cold?rq=1 http://physics.stackexchange.com/questions/3000/settling-of-rice-as-its-cooked?rq=1 http://physics.stackexchange.com/questions/11744/does-it-matter-how-you-order-your-tug-of-war-participants?rq=1 – luispedro Dec 04 '12 at 00:07
  • Those are old questions, they were asked before the scope of the site was really worked out. They wouldn't be appropriate here today. – David Z Dec 04 '12 at 00:16

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