heat and airflow info

[puffnstuff]

I am always reading threads about heat problems and I see a lot of mis-information so I just thought I should tell ya'll a little secret that goes against what you might believe. It doesn't matter how much air you have flowing over your bulb, it will still put out all of it's radiant heat. The air only cools the item's(metal and glass in the hood) that have been heated by the radiant heat. the air cool's by impacting on these heated surfaces and remove's the heat through conduction. The air particles come in contact with the surface and transfer the heat to the air and carry it away. This is why it is so important to have a fan blowing in your grow. It is to remove the heat from the plants through conductivity by impacting on the surface's. You can greatly increase the cooling effect of your airflow in your hood by causing the air to be disturbed instead of flowing straight through. The turbulance inside the hood will cause more air to impact on the interior surface of the hood and remove the heat. You can get away with FAR LESS AIRFLOW than people are useing around here.
puff

 

[4u2sm0ke]

okay....

 

[puffnstuff]

by "ok" I hope you meant,"so what does all this have to do with anything puff?". Ok so I rambled on about a couple things all jumbled together, sorry. Let me clairify, if I can. The main points are

1. more airflow gowing straight thru your hood is better than a little air, but you can cool them better if your air is turbulant and you dont need nearly as much air to keep the hood cool. turbulant air impacting on the surfaces is what does the cooling and it is the ONLY thing that the air does.
2. You CAN NOT stop the radiant heat from the bulb with air, no matter how much air you have flowing past the bulb.
3. radiant heat is absorbed by solid surfaces in the hood and glass. this heat must be removed in order to keep it from heating the room. The heat from the hood is spread to the room thru radiant heat just like the bulb heated it and from conduction of the air in the room impacting on the outside of the hot hood.
4. radiant heat that does get thru the glass and warms your plants ,and most of the radiated heat will go thru the glass, needs to be removed from the plants with a fan. The cooling of the plant tops is the major determining factor of how close can they be to the light, assumeing your glass is cool and not adding to the heat.

I hope this is more helpful. The main point is, dont just run out and throw more money at your heat problem. You dont need 700cfm to cool your hood. you dont even need 400cfm, well you may need 400 for 1000 watt, but I'll bet it can be done with 250 cfm, IF you make that air turbulant inside the hood, and insulate your ductwork. my hoods with 600watt hps are cool to the touch exept directly above the bulb. It is warm there but not very warm.
puff

 

[puffnstuff]

Oh, I should have also told you what fan I am useing. check the diy section for my 8 dollar inline fan thread. I also have 8" inline duct boost fans from lowes. The home made ones work a little better than lowes fans but are also a little louder. I was running one of each in series but have disconnected my home made ones now the I have 8" duct's. just did that today but I tested with either or both and the home made are better. I will be looking for 8" fans to make some larger versions just for fun next time I go shoppin'. Anyway, every one always say's inline duct boost fans are no good, but they do fine, IF you make your air turbulant. I made a little goodie to do this, but I am thinking of patenting it sooo.....latter.
puff