I made a cheap, high capacity humidifier from a mist maker, storage crate, and 120mm fan (the fan blows into the crate, which pushes the mist out). This 4" flex pipe works fine to exhaust the mist when it is at this fully contracted state.
But humidifying one room isn't really why I made this: I wanted to be able to put it near the return air vent and humidify the entire townhouse. Unfortunately that vent is in the loft with no water access, so I've tried to connect 2 of these 8' ducts together to get up there and over to the vent. But when I do this, the vapor flow at the end is pretty weak, not nearly enough to humidify the whole townhouse. The vapor is condensing in the duct and falling back into the tank. I figure that if the fan had more static pressure it would be able to push the vapor fast enough to prevent it condensing. But I'm also trying to keep it fairly quiet, so I don't want to stick a big honking duct booster fan on there without knowing how powerful it needs to be. How do I calculate that?