In a counterflow furnace, where does the air pass from?

In a counterflow furnace, the air moves from the top to the bottom of the furnace. This design is critical because it maximizes the heat exchange efficiency between the combustion gases and the incoming air. As the air descends through the heat exchanger, it absorbs heat from the hot gases that rise towards the top of the furnace. This counterflow arrangement ensures that the coldest air entering the furnace is heated as it moves downward, while the hottest gases exit, facilitating optimal thermal transfer.

This principle of counterflow is essential in ensuring that the air can achieve maximum temperature increase before it’s distributed into the living spaces, leading to improved efficiency and comfort levels in the environment being heated.