There is a pipe of 32mm in diameter. Water flows from left to right. There are two branches in that pipe. To one of them connected input of water heat exchanger, to another - output of water heat exchanger. Pipe inside of heat exchanger has size of 3/4 inch. That means there is reduction of diameter. Is it possible to create circulation without water pump in that heat exchanger by playing with pipe size, angles of branches, etc.?
I need water to get into heat exchanger, so that it could boil water inside.