jason the filter freak June 22, 2007 June 22, 2007 In mostly inclosed hood, is it better to suck air out by having very few vents and an open back, or lots of veting and blowing into the tank (across the tank as opposed to venting out of the tank) What does anyone think here?
fab June 22, 2007 June 22, 2007 (edited) Here is a generality you can start with. It does not answer your question directly, but it lays the foundation for understanding the underlying issues in your question. Drawing (pulling) air horizontally across a tank provides the best laminar flow you will get over the tank. Blowing air across the tank will tend to produce turbulent flow. Laminar flow will move the heat away from the tank efficiently relative to turbulent flow across the tank. fab Edited June 22, 2007 by fab
DaveS June 22, 2007 June 22, 2007 Hmm, I might disagree with Fab. It's been a few years since my thermodynamics class but while he is right about sucking causing laminar flow I don't think in general this is what you want (if I read the question correctly). GENERALLY if you are looking to reduce heat in a tank by using a fan to increase evaporation, I'd think you would want turbulent flow. Laminar flow, while providing faster movement of a layer of air, would have a smaller amount of "useful" air being exposed to the surface of the tank and therefore provide less evaporation/cooling. In other words, imagine you had a 1 inch thick layer of air flowing over the tank. In laminar flow, the entire inch would travel faster across the top but only the 10th of the inch closest to the water would interact and absorb/evaporate any water. The rest would just fly over. (Please keep in mind I'm just making up numbers to explain the point). If the flow was turbulent, the entire inch of air would be "swirling about" so to speak, and therefore all the molecules would be available to evaporate water- and therefore cool the tank. Now given the fact that it's a mostly enclosed hood, that could very well be different. It's just that Fab's last sentence really struck me by surprise given that he's talking about general circumstances. This isn't meant to be a flame or anything, just wanted to post my take on things and see if I'm totally off.
Grav June 22, 2007 June 22, 2007 I agree with both Fab and Dave. Suck would draw more air / heat out of a confined space, but blow would create more evaporation. For TOTAL cooling: Suck if there is a glass top or anything else between the space and the water or if you do not have an auto-top-off system Blow if there is no glass and/or you want more evap so that you can add more Kalk.
SnowHeart June 25, 2007 June 25, 2007 So if one is looking to cool the water or increase oxygenation then blowing is better, but if you're looking to cool off lighting fixtures then sucking is better?
'Ric June 25, 2007 June 25, 2007 So if one is looking to cool the water or increase oxygenation then blowing is better, but if you're looking to cool off lighting fixtures then sucking is better? Yes, think of it this way: + If you want to get rid of hot AIR, you suck it out. Allow gaps or holes on the other side of the lights for cooler room temperature air to be drawn in to replace the hot air you suck out. + If you want to cool the WATER, you blow across the surface, just like you naturally do when you get a cup of tea that's too hot to drink. 'Ric
SnowHeart June 25, 2007 June 25, 2007 This is one of the most helpful science lessons I've ever had in five minutes or less. Awesome!
flowerseller June 25, 2007 June 25, 2007 Yes, think of it this way: + If you want to cool the WATER, you blow across the surface, just like you naturally do when you get a cup of tea that's too hot to drink. 'Ric Won't that cause evaporation and then make the tea stronger tasting?
'Ric June 25, 2007 June 25, 2007 Won't that cause evaporation and then make the tea stronger tasting? Technically, yes it would, but I would be amazed if even Gordon Ramsey's taste buds could tell the minute difference in taste without blowing on their tea 24/7.
dandy7200 June 25, 2007 June 25, 2007 blow Seriously, it causes more evaporation and cools much faster. Sucking only will draw the hot moist air out of the canopy after it has slowly evaporated on it's own. Also consider the fan you are using. If it is a computer fan or similar it is not meant to have moist air passing through it and will burn out rather quickly. I like the tea visualization, heres another one: Stand in front of a fan on a hot day, now go stand behind it.
HowardofNOVA June 25, 2007 June 25, 2007 Basically, I like both SUCK and BLOW! ....gets the job done right!! ah, blow moves the air and sucking removes it from the area! ....what?
jason the filter freak June 26, 2007 Author June 26, 2007 The fans I'm speaking of are the ones brk was selling for 20$ they're AC not DC... caution to anyone who has bought one of these, the wiring on the connectors is EXTREMELY fragile.
Grav June 27, 2007 June 27, 2007 Won't that cause evaporation and then make the tea stronger tasting? Chip, You totally kill me. Nobody on this form has the ability to make me LOL loud enough to wake my wife like you do... and it is usually something non-useful yet brilliantly to-the-point. Keep it coming.
dbartco June 27, 2007 June 27, 2007 The fans I'm speaking of are the ones brk was selling for 20$ they're AC not DC... caution to anyone who has bought one of these, the wiring on the connectors is EXTREMELY fragile. solder + heatshrink = safer. Do it right! do both on your hood.
treesprite June 27, 2007 June 27, 2007 I believe on this Nova Exteme, one fan sucks in on one end, and the other fan blows out on the other end
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