Making hot air rise faster in flue gas funnel

mellotango

Hi, and thanks for your expert opinions in advance. I'm working on a theorical scenario of a flue gas funnel. Assuming hot air is rising from a funnel at a constant rate. Would the hot air rise faster if water droplets were sprayed at the top of the funnel, hence lowering the air temperature at the top part of the funnel? Would this lead to an increased air pressure differential at the bottom of the funnel vs the top of the funnel, leading to hot air rising faster, and hence, creating a more powerful updraft?

pukb

If water droplets were sprayed at top of funnel, it would cool down air much faster and hence air becomes heavier much earlier and hence its speed reduces.

Andre

Try it the other way around, vaporize the water at the bottom. That will cool the air, but your heat source could neutralize that and reheat it. Now, the moist and warm air is even less dense, because of the molecular weight of H2O (~18) is lower than average air (~29).

So as the air rises, expands and cools adiabatically, the water vapor will condense eventually, forming clouds, and adding the latent energy back to the air, reducing the adiabatic cooling rate signifiantly, boosting the convection.