Opie is correct. A sealed air system for the light is proper cooling. Passive may work if you suck the air out through your cool tube with a large enough blower.

Cool air in from the ground level and hot air out at the top.

But it's better to have your light system sealed and have a blower outside the grow area and use dryer vent pipes to connect all the air from the blower to the light then use a second piece of vent tube to take the air away from your plants.