has anyone experimented with very large heatpipes? I was thinking that if you could make a large enough heatpipe it might keep up with a bong, but without any required maintenance.
IMHO, I think using an evaporating chamber filled with aquarium wet/dry media & a fan blowing through it sounds promising.
Here's one example:
Typical wet/dry filter media is designed to give large amounts of surface area & long air/water contact times in a very compact volume. Having owned many salt-water aquariums with these filters, I know they result in huge amounts of evaporation (my 0.25cu ft chamber evaporated 2 gallons a day & I only used a tine aquarium air pump, not a fan:-). They also operate very quietly because the water slowly trickles through. Although I haven't heard of this idea being used yet, but it may work well.