Flue-gas condensation

When we burn things like gas or oil to create energy to heat our homes or run our cars, there is a byproduct called flue gas that comes out of the exhaust pipe. Flue gas is made up of different chemicals like water vapor, carbon dioxide, and other gases.

Sometimes, people want to be more energy efficient and they use something called a "condensing boiler" to create heat. A condensing boiler is like a regular boiler but it has an additional feature that helps to capture some of the heat that would normally be lost in the flue gas.

To understand how that works, let's imagine you have a glass of ice water on a hot summer day. The glass gets all wet on the outside because of the condensation - or the process of turning water vapor (the stuff that's in the air) into liquid.

The same thing can happen with flue gas in a condensing boiler. The boiler has a special device called a heat exchanger that cools down the flue gas so much that the water vapor in it turns into liquid droplets. These droplets are then collected and drained out of the boiler.

Because the heat exchanger captures some of the heat that would normally be lost in the flue gas, condensing boilers are more energy efficient than regular boilers. They also produce less greenhouse gases because they help to capture some of the carbon dioxide that's produced during the burning process.