If you’re like most people, you often take your Hamilton Township, NJ, home’s HVAC system for granted. It’s hard not to. Modern HVAC systems are reliable and efficient, working when you call on them. But have you ever stopped to think about the science behind HVAC systems? Many fascinating scientific concepts work together to make indoor heating and cooling possible. Here’s everything you need to know about how those concepts apply to common heating and cooling systems.
The Scientific Basics of HVAC
Broadly speaking, two scientific principles are involved in modern HVAC systems. Together, they make it possible to move heat from place to place, convert energy into heat, and expel it. The two categories are as follows.
Thermodynamics
Thermodynamics is the science of the relationships between heat energy and other forms of energy. All HVAC systems rely on some basic thermodynamic principles to function. Those principles guide the design of HVAC systems and play a role in their efficiency.
Fluid Mechanics
Fluid mechanics is the study of how various forces interact with fluids and gasses and their effects. It’s a foundational branch of physics, without which air conditioning couldn’t exist. Fluid mechanics plays a role in how HVAC manufacturers design their systems. It governs things like flow rates, pressures, volume, and velocity as they pertain to refrigerants.
The Science Behind Furnaces
Furnaces, be they natural gas or oil-burning, rely on the combustion process to generate heat. Scientifically speaking, combustion is the rapid combination of a fuel with oxygen. During combustion, the atomic bonds in the fuel get broken, releasing energy. Some of that energy gets released as heat and some as light. The reason we use oil and natural gas for furnaces is that they’re relatively energy-dense. That means the combustion of either of those fuels releases quite a bit of energy. Of the two, natural gas is more energy-dense, containing 55 Megajoules per kilogram. Heating oil, by comparison, contains 46.2 Megajoules per kilogram. For reference, the wood you’d burn in a fireplace only contains 16 Megajoules per kilogram.
All of that potential energy would be useless, however, if it weren’t for the second law of thermodynamics. This is because combustion releases heat and gaseous byproducts, including carbon monoxide. As a result, your furnace can’t simply burn fuel and release its byproducts into your home. Instead, it must vent those byproducts outside while transferring the heat energy into your home’s air. This is possible because the second law of thermodynamics states that heat energy will spontaneously flow toward colder substances.
To take advantage of that, furnaces use a heat exchanger, which is a set of coils with metal fins attached. The hot combustion gasses pass through the coils, heating the fins. As this happens, your furnace uses a large fan to circulate air from your home across those fins. Thanks to the second law of thermodynamics, the heat spontaneously moves from the fins into the cooler air. Then, your furnace exhausts the somewhat cooler gas into the outdoors.
If you own a high-efficiency furnace, however, the combustion gasses pass through two heat exchangers. This allows for the maximum amount of heat transfer into your home’s air. As a result, the exhaust gas from a high-efficiency furnace should remain at or below 140 degrees Fahrenheit. By contrast, the exhaust gasses leaving a standard furnace may be as hot as 400 degrees Fahrenheit.
The Science Behind Air Conditioning
Air conditioners also rely on the same heat exchange process and science that makes a furnace work. This is why a home’s furnace and AC system often share an indoor unit. That helps minimize system size and allows for shared components like blower fans and ductwork. However, air conditioners don’t use combustion since their job is to remove heat, not add it.
To remove heat from your home, an air conditioner uses the refrigeration process, which relies on fluid mechanics. Specifically, the refrigeration process takes advantage of the relationship between pressure, temperature, and boiling point in liquids and gasses. Generally speaking, when you increase pressure on a fluid or gas, it heats up, and its boiling point increases. When you decrease pressure, the opposite happens.
Your air conditioner uses the same heat transfer principles your furnace uses but in reverse. It starts with an expansion valve, which lowers the temperature and pressure of your AC’s refrigerant. The cold refrigerant can then absorb heat from your home’s warm air inside a heat exchanger. As it does this, your air gets colder, and the refrigerant warms up until it boils into a gas.
The warm, gaseous refrigerant then travels outside to your AC’s outdoor unit. There, a compressor increases its pressure, raising its temperature some more. After leaving the compressor, the refrigerant ends up between 120- and 140 degrees Fahrenheit. Then, the second law of thermodynamics makes another appearance. By passing the hot gaseous refrigerant through another heat exchanger, it can shed its heat into the outdoor air. Just as long as the outside air temperature is lower than the refrigerant temperature, your AC will work. Then, the process starts over again, and the cycle continues until your home is as cool as you want it.
The Science Behind Heat Pumps
It may surprise you to find out that the air conditioners you’ve always known are a type of heat pump. However, the term heat pump, as it applies to HVAC, refers to a very specific type of system. It can serve both your home’s heating and cooling needs. In cooling mode, a heat pump works just like an air conditioner, as described above. In the winter, though, it takes advantage of the same scientific principles to heat your home. It does this by running the refrigeration cycle in reverse.
Remember that the second law of thermodynamics states that heat energy spontaneously moves to colder areas or substances? Well, that works at any temperature. Compressing a refrigerant will raise its temperature just as well in the winter as in the summer. So, to heat your home, a heat pump only needs two things. One is a reversing valve to change the flow of refrigerant. The other is a refrigerant capable of getting colder than the outdoor air in winter. Having both allows a heat pump to tap into an essentially free source of heat for your home. Since there’s no fuel involved, air-source heat pumps typically operate at between 250% and 350% efficiency. That blows every other type of heating system away, save for geothermal. Those are heat pumps, too, but they use underground refrigerant loops to collect or expel heat.
Your Trusted Heating and Cooling Specialists
If you want the finest heating and cooling systems available for your Hamilton Township home, Christian Brothers Air Conditioning Plumbing Electrical can help. We’ve served the local community since 2011, offering complete HVAC, indoor air quality, and commercial services. Whether you need work performed on a furnace, AC, heat pump, or boiler, we can handle it. And our transparent pricing means you’ll never have to guess what you’re getting into by working with us. So, if you need HVAC services in Hamilton Township, contact Christian Brothers Air Conditioning Plumbing Electrical today!
