How to create waves/air flows?

Hi...

Im trying to figure out how can I make an air flow to explain the air conditioning work.

http://cloud.andersonid.com/image/05322C0s2h2S

I dont want to get the waves going back and forth, like this my crappy first try.

http://etypedit.com.br/demo1/demo1.html

I really need to know how can I get a smooth wave flow.

Thanks everyone!