So I'm making a cooltube. I have a question

I found some instructions:

DIY: Best Cool Tube - Grasscity.com Forums

It talks about an open ended cool tube. Would that work? It would be an air intake obviously at the open end of the cool tube but seems like it would really fuck me over if I just left half of the glass tube open to the grow chamber and the other half being a duct leading to the 4" inline fan blowing air outside the chamber.

Or I guess since there would be that much air flowing across the bulb that it would effectively cool it down? I'm still kind of new to the idea of cool tubes and if they weren't being sold for hundreds of dollars I wouldn't believe that just running a little air over a hot bulb would cool the grow chamber so much.

Anyway the reason I ask is because I want one end of the cooling tube contraption (the intake end) to be open to the chamber to get some new air flow past the plants as well as just the bulb.

I put some duct and a carbon filter on the open end of my cooltube. That way I only need one fan. Temps were a little on the high side still cuz my space was so small and fan was not very powerful, but I had a pretty successful grow nonetheless.

I'm thinking about getting another fan, so I have one fan for the cooltube and one for exhaust. I thought about using duct on the intake side so that fresh air from outside the closet would flow past the light, then through more duct, finally to the fan and out the room. This would eliminate the problem of stinky air being blown out of the grow room, since the duct runs from one wall to the other.

But, I think you can also keep the one end open. Only problem is the smell.