Just like our own bodies, the inner workings of our homes and HVAC systems are complex. Hundreds of different pieces coming together to give us what we need to survive. Understanding the key working components can be as important as understanding the workings of our bodies.

With our bodies, these pieces include our nervous system, skeletal system, muscular system, and more. With our homes, it comes down to our air, heating, and cooling. Let’s unravel the mystery of heat exchangers and why they’re a major part of your home’s comfort.

Similar to the way a doctor can explain the complex needs of your health, we dedicate our time to translating the HVAC needs of the homes we service. As a part of that work, we’re constantly striving to make sure the words, phrases, and ideas known to our technicians are also clear to the customers they’re serving.

We’ve discussed a few different topics already: BTU, SEER, MERV, zoning systems, fresh air intake, and relative humidity. The topic for today’s post will be heat exchangers: what they are, why they matter, what varieties exist, and how they work.

What is a heat exchanger?

Part of your HVAC, heat exchangers have a pretty on-the-nose name. That’s because exchanging heat is exactly what they do. 

More specifically: a heat exchanger is an apparatus that exchanges or transfers thermal energy from one place to another. 

They’re used in homes, larger buildings, machines, and engines – though today’s post is only focused on their role in the heat management of your average home.

Why do I need to know about my heat exchanger?

The reason it’s important to know about your furnace’s heat exchanger is so you are better equipped to act if something goes wrong. There is no surefire sign of a faulty exchanger, but if your carbon monoxide detector is going off or your furnace is malfunctioning, you can recognize the exchanger as a potential cause and communicate that to any service provider hired to fix the problem.

Furnaces with faulty heat exchangers can lead to high CO2 levels, inconsistent combustion of fuel, and other potentially dangerous situations. The best way to avoid these situations is through scheduled, regular maintenance performed on your furnace.

What are the different types of heat exchangers and how do they work?

When heat is transferred, it’s typically done in one of three ways: conduction, convection, and radiation. The first two are what you’ll see in home HVAC, while the third accounts for situations like the way heat from the sun warms the planet. 

• Conduction heat transfer occurs when two materials, each at a different temperature, touch. If a hot coal is set on a cool stone, when you remove the coal you’ll be able to feel the residual, transferred heat from the coal. That’s conduction. 
• Convection heat transfer occurs when fluids cross paths and one stream carries heat away from the other. The simplest real life application of this is how food cools down when you blow on it. The air you blow (in this case quantified as fluid) essentially scoops up excess heat to carry it away.

Now you know the basic science behind heat transfer. What’s next are devices exchanging that heat themselves. There are two main varieties of heat exchanger typically used in residential applications:

• Coil heat exchangers use tubes that run back and forth to separate two fluids. One flows inside the tube and another on the outside. They use conduction through the walls of the pipe to allow the outside fluid to take heat from the inside one and then carry it away using convection. There are a number of different kinds of heat exchanger coils: condenser coils, evaporator coils, cold water coils, hot water coils, steam coils, and booster coils. While they all have different names and applications, they all use the aforementioned process in essentially the same way.

• Plate heat exchangers focus on the separation of fluids just like the coil exchangers, but their makeup is a bit more complex. Plate heat exchangers are made of thin metal plates built in a way to create separation between two fluids flowing through a HVAC system (your furnace, for example). The heat from the hotter of the two fluids is absorbed into one plate wall through convection and then uses conduction to reach the opposite side of the plate. Once it’s there, the second fluid, using convection, carries that heat away.

Heat exchangers operate with one focus: the way warmth enters and moves within your house. If heat isn’t staying inside your home or not entering the spaces it’s supposed to, that leaves you and your family feeling uncomfortable. 

Nobody wants that! If you’d like to learn more about how to improve your home’s heating, feel free to get in touch with the team at Welter Heating anytime!