If air conditioning only cooled air, most buildings would still feel uncomfortable.
So, what is really happening inside an AC system?
In Part 1, we explored what air is made of and why moisture plays such a big role in comfort. Now we shift focus to what actually happens inside an air conditioning system.
Air conditioning is not just about lowering temperature. It is about changing the condition of air in a controlled way.
Every system works by moving air from one state to another.
Process 1: Heating and Cooling
The simplest process changes only temperature.
Air passes over a heating or cooling surface, and its temperature rises or falls while moisture remains unchanged.
This is known as sensible heating or cooling.
It is straightforward but can require significant energy, especially when large volumes of air are involved.
Process 2: Cooling and Dehumidification
This is the most important process in air conditioning.
When warm air is cooled below a certain point, moisture begins to condense and is removed.
Now you know why water drips from air conditioners.
Cooling alone does not create comfort. Removing moisture is equally important.
Process 3: Mixing Air Streams
Most systems mix outdoor air with indoor air. The final condition depends on the proportion of each.
However, outdoor air often brings in heat and humidity, which increases the load on the system.
Proper mixing is essential for both comfort and energy efficiency.
Process 4: Evaporative cooling:
In dry areas, where the moisture content in the air is quite low, the cooling is done by using a water cooler. In the cooler, water is sprayed in the air stream to make it into finer particles & evaporate. This causes the temperature of the air to reduce, thus cooling it.
In this process the temperature of the air reduces & the moisture content increases.
Process 5: Chemical Dehumidification:
Have you ever wondered why the salt in the shaker got all soggy during rainy season? Well, the salt is a hydrophilic substance, i.e., it absorbs water/ moisture. So, when the moisture content in the air is higher in the rainy season, the salt absorbs the moisture & removes it from the air.
Using this property of hydrophilic materials like salt, silica gel is used in air conditioning systems to do dehumidification. High RH air is passed over a wheel having silica gel embedded on it to reduce its moisture content. This wheel of silica gel is reused by passing hot air over it which removes the moisture the silica gel & is regenerated.
How It All Works Together
A typical air conditioning system in Indian weather conditions follows a cycle:
- Mix fresh and return air
- Cool and remove moisture
- Adjust temperature if needed
- Supply air to the space
- Air absorbs heat and moisture
- Return and repeat
Each step is carefully designed to maintain comfort.
In Other Words
Air conditioning does more than cool the air. It removes moisture, brings in fresh air, and adjusts conditions to keep spaces comfortable.
If humidity is not controlled, a room can feel damp even when it is cool. True comfort comes from balancing both temperature and moisture.
Closing
This article is part of Aqua Chill’s HVAC Digest, focused on simplifying HVAC concepts and sharing practical industry knowledge.
To explore more about HVAC systems, industry trends, and real-world applications, connect with us or visit our website.