A heat exchanger can be found in many different pieces of equipment and applications used every day by the average person. These devices are used to help reduce the amount of energy that is lost when certain fuels are burned. These exchangers work by transferring the heat from one gas or liquid to another gas or liquid without allowing the two to interact in any way. The two fluids never have to directly touch each other.
While it may seem like an inefficient way of doing things, there are a number of applications in which it’s very important that the heat is transferred without any contact between the liquids. This transfer can be found in a number of places, including the following common uses.
A heating system that uses gas to power a boiler makes use of a heat exchanger. As the natural gas is burned, it heats up water in the pipes that are placed above the gas jets. Water then flows into this system of pipes, where it absorbs the heat. This is the heat exchange. The jets of gas that heat the pipes cool down while the water flowing through the pipes heats up. The gas never has to come in contact with the water. If it did, the water would extinguish the flames, halting the heating process.
On the other hand, some types of air conditioners actually use this process in reverse. Rather than pump heat into an area, they use heat exchangers to remove the heat from a space. The heat is absorbed into the water and is moved away to another area where it is released.
In other types of air conditioning, especially in central HVAC units, the heating and cooling system share some parts. One such part is the heat exchanger. When the system is in cooling mode, the exchanger is set very low so that no heat is added to the air. During the colder months, the system is put into heating mode and the exchanger is turned up, adding additional heat to the air.
Refrigerators work in a very similar fashion as an air conditioner or heat pump. The heat exchanger captures the heat from the refrigerator and transfers it out the back of the unit. This works in tandem with the cooling system to ensure that the interior of the refrigerator or freezer is kept at a constant temperature while using the least amount of energy needed to do so.
In power plants, a large amount of energy can be lost as the exhaust moves up and out of the system. The same is actually true in a number of engines as well. Rather than simply allow this energy to be lost, many of these systems have a heat exchanger installed that captures as much of the energy as possible. In most cases, the system has a number of fins installed in the exhaust pipe. When the gas moves past these fins, the water inside them is heated and is then cycled back into the engine or plant. While some energy is still lost, it’s much less than what would have been without the heat exchangers.