I remember my neighbor telling me about a guy who studied air movement. He used a round tube and wanted to move air between floors for heating and cooling. He tried pulling it and he tried pushing it through the pipe to figure out which way worked best and which was more efficient. There was a difference, but for the life of me I can't tell you which way worked better. I think I must be getting that old timers thing.
PS Sorry Matt if we kind of hi jacked this thread. I liked the original topic of generating electric from heat. Sorry if we wondered a bit from the topic at hand.