Canopy fans, which direction and WHY?

[lilrobb]

I have heard very good reasons for either way (blowing in and blowing out) - who's got some SCIENTIFIC links that show which way works better?
I think the only one that can be ruled out is the mixed solution...

Poll attached just for the heck of it...

 

[grouper therapy]

Hot air rises .

Edit:

LilRobb;719098 wrote: I have heard very good reasons for either way (blowing in and blowing out) - who's got some SCIENTIFIC links that show which way works better?
I think the only one that can be ruled out is the mixed solution...

Poll attached just for the heck of it...

What is the purpose of the fans hot air removal or evaporation cooling?

 

[rdnelson]

Agree with Grouper Therapy with one addition. If you creat a lower pressure with in the canopy by having the fans blow out, it will draw air in through any cracks or openings in an effort to equalize the pressure. If the canopy is close to air tight but a gap is left around the tank the air flow will pass over the water surface drawing more gasses and increasing evaporation. It requires latent energy to cause evaporation which cools the water surface and therefore the tank. If you ever lived in Arizona, you know how well a swamp cooler works (at least until monsoon season hits).

 

[lilrobb]

grouper therapy;719106 wrote: What is the purpose of the fans hot air removal or evaporation cooling?

That's about the same - I only need to remove hot air to cool the tank, so whether I do that through removal of hot air or through evaporative cooling would be the same result - a cooler tank.

The argument with static pressure works for both directions - I personally take the blowing in option as that keeps my fan alive longer as no salt creep builds up...

 

[grouper therapy]

I believe that blowing air in is more likely to mix the hot air that has risen to the top of the canopy and mix it with the cool air near the water surface . Why not take advantage of the natural convection that has taken place which also creates a flow of through the canopy.
Fans are cheap enough.

Edit: When you say you want scientific evidence of which works better I'm not sure what you mean by "works better." Cooling only per cfm or watt used?

 

[rdnelson]

As for static pressure, the fans will be be trying to increase the pressure in a zone that already has a higher pressure thus working a bit harder. It wouldn't be much especially if the top of the canopy is open or has lots of cu/ft of vent available but still, it will work it a bit harder.

 

[tangaray]

Warm air has a lower density than cool air, so warm air rises within cooler air,[5] similar to

 

[rdnelson]

Well one thing I know for sure. We are a bunch of party animals aren't we??? LOL 11:20 on New Years Eve and we are on ARC discussing sucking or blowing. LOL I have an excuse. I am 52 and have a 20 year in the house with her boyfriend and a 15 year old who thinks she is 20. What's your exuses. LOL

 

[lilrobb]

I got a 3year old that crashed in front of the TV, I can't move without waking him...

 

[wbrown]

I got up at 0400 and kick started to Rooster so you party animals would get up on time.

Exhausting the air seems most logical to me, provided you have a place for air to intake. Salt creep can me mitigated by distance, so the farther you place the fans from the water and splashing, the less creep there will be. I've tried both methods, and short term blowing in over the water made the biggest change in water temps, this was with a small fan blowing over in an open top arrangement.
Longer term, or if I had a true canopy would probably lead me to duct the air to the outside with an inline fan. You can get soffit louvers in 2 1/4inch diameter at the home centers, paint to closely match your canopy and install for a less intrusive look.

 

[grouper therapy]

LilRobb;719111 wrote: That's about the same - I only need to remove hot air to cool the tank, so whether I do that through removal of hot air or through evaporative cooling would be the same result - a cooler tank.

The argument with static pressure works for both directions - I personally take the blowing in option as that keeps my fan alive longer as no salt creep builds up...

Some use fans for the expelling of moist air to prevent mold and mildew in their canopy is the reason I asked . My lights are fantastic and have solved any heat issues I may have had. That said I personally like to pull the air out from the upper half of the tank as well as allow the fresh air in the upper half of the tank as well thereby minimizing the flow of salty air over my high end light fixtures.

 

[itsamyheff]

I have always done the push/pull method. That way you draw air across just like a coil. Heat will dissipate in the flow of air. Thats my 2 cents and I am sticking to it. Happy New Year guys.

 

[lilrobb]

itsamyheff;719178 wrote: I have always done the push/pull method. That way you draw air across just like a coil. Heat will dissipate in the flow of air. Thats my 2 cents and I am sticking to it. Happy New Year guys.

Thermodynamically that is ineffective - if each fan moves 120cfm, if you put them in line they still only move 120cfm, if you put the parallel - they draw 240cfm...

 

[grouper therapy]

itsamyheff;719178 wrote: I have always done the push/pull method. That way you draw air across just like a coil. Heat will dissipate in the flow of air. Thats my 2 cents and I am sticking to it. Happy New Year guys.

I would think ALL fans are push /pull. If not then they become a vacum pump or a compressor.No?

Edit:

LilRobb;719182 wrote: Thermodynamically that is ineffective - if each fan moves 120cfm, if you put them in line they still only move 120cfm, if you put the parallel - they draw 240cfm...

Only if the blowing out fan is the only means of escape for the forced air.We are assuming air tight canopies if we are referencing inline.

Edit: Why would one not do the evaporation cooling in the sump away from the lights? I actually mounted a fan in the top of my canopy and found that the fan did not have to run at all , just creating a place for the hot air to escape was sufficient. My point is that maybe we would be better off not to run fans in the canopy if adequate non powered ventilation is provided and do the cooling elsewhere.

Edit: try this one Robb

 

[rdnelson]

grouper therapy;719185 wrote: Edit: Why would one not do the evaporation cooling in the sump away from the lights? I actually mounted a fan in the top of my canopy and found that the fan did not have to run at all , just creating a place for the hot air to escape was sufficient. My point is that maybe we would be better off not to run fans in the canopy if adequate non powered ventilation is provided and do the cooling elsewhere.

Haven't totally thought that through but I will say this. When designing Heating and Air Conditioning Systems, the supply is always put nearest the point of greatest heat transfer. As in, exterior walls near windows. The thought behind it is the room will stay more comfortable if the undesirable air is conditioned at the source rather than after it has circulated throught the space. That would lead me to believe that removing the heat at the source (the lights) would result in a more consistant temp throughout.

 

[grouper therapy]

For all who voted for air in I think you should run your bathroom fans the same way:sick:

 

[lilrobb]

You shower with saltwater?
That explains a lot...

grouper therapy;719203 wrote: For all who voted for air in I think you should run your bathroom fans the same way:sick:

 

[grouper therapy]

I like thought provoking threads. I have been thinking of ways to vent canopies I buikl without letting the light out . Got one I think but I need to try out on someones canopy(Robb) hint hint!

 

[lilrobb]

And I appreciate the comments here, keep 'em coming...

 

[grouper therapy]

LilRobb;719204 wrote: You shower with saltwater?
That explains a lot...

Come on! I can see how you Europeans get a little confused about showers.
Sorry man. I still love ya my brother.