The Science behind HVAC

HVAC systems help us to stay warm in the cold and stay cool in the heat. They are ubiquitous in modern society and we may well wonder what we’d have done as a race without them. Tropical areas wouldn’t be able to survive the sweltering heat and the attack of mosquitoes without cooling systems. The people in extremely cold and icy areas of the world would be unable to survive without heating systems and most would die from hypothermia. Here’s an important question though? These systems that have done so much for us, how do they work? How is heat generated and distributed within a living space? How do air conditioners cool the air within our living spaces?
Science holds all most of the answers here. We will discuss a few basic scientific principles under the various units of HVAC that make the system work.
Heating- We all have a good idea about how heat gets generated. Fuels are burnt, energy is transferred. But how exactly does this energy get circulated around a room or living space? Heat transfer is achieved basically through three processes: Conduction, convection, and radiation.
Conduction: This is the transfer of heat by the vibration and collision of molecules through a solid body. Conduction is how the body of a metal pot feels hot when you’re cooking with it. The heat from the burner got transferred to the pot. Conduction depends on various factors such as the type of metal or material (heat capacity), size (heat transfer area) and others.
Convection: Convection is basically the transfer of heat through the movement of fluids. Fluids here refer to either liquid or gaseous materials. Convection occurs mainly by the bulk motion of the fluid. In simpler terms, imagine a kettle of boiling water gets spilt on the flow, as the water flows towards a nearby object (say your feet) It carries the heat along with it and makes you feel burned. That’s basically how convection works. Moving the heat through fluid.
Radiation: Radiation is the form of heat transfer that does not require a material medium through which the heat is transported. Rather, electromagnetic waves are the media through which radiant heat is transported. Radiation is how the heat from the sun gets to us on earth.
All of these phenomena have mathematical formulae to calculate the amount of heat transferred, but we do not want to scare away our non-science inclined readers

Ventilation- Like we described earlier, ventilation involves exchange of air, and it makes use of the principle fo diffusion. Diffusion involves the movement of molecules in air from a region of higher concentration to a region of lower concentration.

Air Conditioning
Refrigeration- Refrigeration works by taking a liquid (known as a refrigerant) through series of expansion and compression in an heat exchanger. The intermittent process allows for the removal of heat from the air inside the room and recirculating it out into the external air. This is why the air at the back of an air conditioner feels warm to the touch. More Info

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