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Coffee House => Coffee House Boards => CH / General => Topic started by: KennyR on May 16, 2004, 08:11:02 PM
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It's a warm day today and this summer will probably be even hotter than the last one, and the last one was a scorcher. Trouble is, my room is always the hottest in the house, because it's high up and has lots of electronics inside it.
Opening the windows isn't enough to cool it down on really hot days. I have one 60 watt fan, and was wondering, which way of using it cools down the room better:
- Pointing the fan out the window to blow out the hot air, sucking cool air in
- Pointing the fan in from the window to blow in cooler air, pushing the hot air away
Yes, I'm the scientist, but I can't figure this one out. My science knowledge tells me that pointing the fan out should work better, but experience says that pointing the fan in is better. But that could be that it just feels like it because it then blows air onto me. My thermometer can't seem to tell the difference either.
Anyone got a definitive answer?
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I think you're just mixing warm air with cold air. (btw else I think it's an extremely difficult question, considering all the 'aerodynamic' aspects of it)
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I guess the ideal solution is to suck air in at one end of the room and blow it out of the other.
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fan at window pointing in = cool air blowing in and slightly cooler warm air mixing about
fan at window pointing out = warm air blowing out and slightly cooler warm air moving about
That's the way my logic sees it, but that's in my universe where the pixies live :-D
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Depends, of course.
Pointing the fan *at* you will always feel better in the short term because it takes advantage of that natural evaporative cooling system you've inherited. If the air in the rest of the house is colder and can actually get up to you, you've a hope of a better overall improvement exhausting, though if not, the best is one of those $15 dual window fans with each independently reversible, so one can intake, one can output, at and least you're at parity with the outdoor temperature.
Or you could buy an air conditioner!
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that_punk_guy wrote:
I guess the ideal solution is to suck air in at one end of the room and blow it out of the other.
Actually, since it all works on pressure, one intake and one output is roughly equal to a single fan. If there's enough space for the air to move under its own pressure. When you have only one window, the exhaust/intake arrangement at least keeps you from blowing back in the hot air you've just exhausted, or vice versa, sort of. Maybe. ;-)
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I won't buy an air conditioner. I don't have anywhere to put it, and anyway, I can't run a 3kW device all day to keep me a bit cooler in good conscience.
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If the window will open at the top also, place the fan up there blowing out. Open the window at the bottom only slightly to allow some cooler air in, but making the fan push more hot air out, than the window opening is letting cool air in.
As the hottest air is also the highest in the room, this scenario will have the best cooling effect.
If there is another window in the room, open it at the bottom instead of the one with the fan in it.
Be sure to run it all night long and turn it off early in the morning. Do not turn it back on until the air in the room starts to get hotter than the outside air.
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One of the things I've been playing with is water as thermal mass... though the filled Arizona bottle collection only approximates a 10 gallon fish tank, and some of them have been dyed black, since it was more of a concern to try for a heat collector in winter.
It sort of helps, but the problem is keeping the water shaded, since once solar-heated (of course, turns out the shelf I'm using gets more sun in summer than winter) it takes a cold day to bleed the collected heat off. [If you're a true hippie, you want something more like 55 gallon drums or repurposed chunks of conduit, with anode rods so they don't rust out, and a floor strong enough to support them.]
Another interesting thing to note is that external shutters/shades/blinds are infinitely more efficient than the internal versions, which tend to act as solar heaters in the gap between themselves and the glass... I've toyed with the idea of cutting down the perforated shields they put over fluorescent lights in drop ceilings (the sort that are basically a white plastic grid, deep enough that, hung vertical, the edges would shade/reflect away a good chunk of incident light) and suction-cupping them or hanging them in front of windows outside, which might not look so bad, while cutting down the amount of energy that makes it in by a good fraction... Never managed to bother implementing it.
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@Kenny
If all else fails, keep the window open and use the fan to blow air on yourself. Airflow across your body will assist your natural cooling mechanism by increasing the rate of evaporation of sweat.
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What works best for cooling a room - fan pointing in or fan pointing out?
Fan pointing in.
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KennyR wrote:
I won't buy an air conditioner. I don't have anywhere to put it, and anyway, I can't run a 3kW device all day to keep me a bit cooler in good conscience.
:roll: :-P
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If everybody ran air conditioners in summer (even if we had enough power for them all, which we don't), it would only make the summers after that even hotter. And so they'd get bigger air conditioners...and it would get hotter still. And on... I know Americans would do just that, but the rest of the human race has got at least some instinct for self-preservation. Maybe.
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KennyR wrote:
If everybody ran air conditioners in summer (even if we had enough power for them all, which we don't), it would only make the summers after that even hotter. And so they'd get bigger air conditioners...and it would get hotter still. And on... I know Americans would do just that, but the rest of the human race has got at least some instinct for self-preservation. Maybe.
Well then I'll run an extra one in your honor, ;-) meanwhile I'm involved in a contest in a battle between my humidifier and dehumidifier to see which one wins :lol:
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Down here in the stifling south we figured it out a long time ago. Old "cracker" houses were vented at the top and bottom which allowed hot air to escape and be replaced by cooler air sucked from the shaded lower levels of the house. Go buy a special window fan which has movable sides to fill all the window space. Don't just stick a regular fan in a window, it'll just suck hot air in thru the window around the sides of the fan.
Put the fan on exhaust and open all doors to the cooler lower levels, but close all other windows in the room and on the upper floor if possible. Otherwise you'll just suck in more hot air.
Stay warm.
6
ps: search "cracker house" for a better description of how it works.
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What works best for cooling a room - fan pointing in or fan pointing out?
@ Sumner
Fan pointing in.
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Sorry not correct.
By blowing the air into the room, you are at the same time blowing the heat from the fan motor into the room.
By blowing it out, this extra heat never gets mixed with the room air.
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6 wrote:
Down here in the stifling south we figured it out a long time ago. Old "cracker" houses were vented at the top and bottom which allowed hot air to escape and be replaced by cooler air sucked from the shaded lower levels of the house. Go buy a special window fan which has movable sides to fill all the window space. Don't just stick a regular fan in a window, it'll just suck hot air in thru the window around the sides of the fan.
Put the fan on exhaust and open all doors to the cooler lower levels, but close all other windows in the room and on the upper floor if possible. Otherwise you'll just suck in more hot air.
Stay warm.
6
ps: search "cracker house" for a better description of how it works.
:-)
My Garage is a converted Cracker House. one big fan from Graingers in the attic pointed out, screen door on lower level left open. Whole building is a tunnel of cool air fron the lower level blowing out at the attic level.
A neat thing they do in the middle east, they suspend a piece of canvas above the roof to block the sun, and since the canvas is suspended above the roof, the heat from the sun hitting the canvas just blows away, rather than heating the roof.
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@ T_Bone
"A neat thing they do in the middle east, they suspend a piece of canvas above the roof to block the sun, and since the canvas is suspended above the roof, the heat from the sun hitting the canvas just blows away, rather than heating the roof."
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Hundred year old houses in the south are designed to work the same way.
High, steep angled roofs with large vents high on the gables allow the heat to escape before the attic heats up enough to transfer into the living space of the house.
Ever see a mobile home with an extra roof about two feet above the mobile home's flat roof and extending out a few feet past the sides? It's an indication the owner knows it will keep it cooler while at the same time protecting the home's flat roof from the eventual leaks they all get. There are quiet a few vacation houses like that at a large lake nearby
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For what it's worth, we cool an entire apartment (when it truly needs it) with a 1.8kw AC that runs on far less than a 50% duty cycle after the place has cooled down. *If* your local power is nuclear, there's theoretically no reason not to if you can afford it... except for the fact that the nukes and grid can't keep up with the load and they still end up having to drag out the 'emergency' dino-burning generators.
(Of course, the nuke plants do dump waste heat, too, hmm...)
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[Insert memory of being 'kind' and setting the AC up to 76 after the first 'blip' that heralded last summer's collapse... of course, if everyone else had done the same, I gather we probably still would've been screwed.]