If you look at the metal around the intake duct, this is where the air goes through and heats it up:

Here is an exhaust tip with the port pointed out so the hot air would be pulled out here by the exhaust:

What I am doing is similar but it is an experiment. I am not sure how well it will work but the idea is the flow is aligned to go in one tube by preference and pulled by the other by its sheer alignment. I have not actually run the engine long enough to test it yet but that is coming.
If it does work, it saves on plumbing. I don't have to run water lines from the water pump or use an extra pump.