Side exhaust without vertical riser (i.e. no chimney)

Thanks for hearing my novice question! Reading Erica and Ernie's wonderful book now, as well as doing online research, but can't seem to find explanation about basic chimney dynamics....
Why is an external, vertical chimney even necessary? I want to run the end of the heat exchange pipe (with downward pitch) right out the wall of the yurt, with no vertical riser.... shouldn't the cool, moist air readily flow out of the lowest point of the system? Why try to get it to rise vertically at all... I am new to the idea of "overdraft," but couldn't this be compensated for by putting a 90 or greater bend at the end?

thanks again,

Joe

The downdraft condensation exhaust type has been attempted, to no avail. Nature of the mass, you can't get lower temps than the mass is at. So, if your point is to heat the yurt, you have exhaust gases hotter than ambient. These won't go down

https://en.wikipedia.org/wiki/Stack_effect

http://www.mha-net.org/docs/v8n2/wildac12b.htm

Build it with an upward pitch. The air coming out may not be totally cool. From all I've read you need to create the draft in some way. I know from experience in extremely cold weather it's sometimes hard to get a draft going.