What is Air Conditioner and how it works???
What is Air Conditioner and how it works???
Hello Everyone. Welcome to our site. Today we will see Air Conditioner definition, their working principle , How its works, what are its major parts and its functions. So, lets starts.
If you’re feeling the summer heat, you might be enticed to switch on the machine - your air conditioner.
“Air conditioning is the process of removing heat and moisture from an occupied space to improve the comfort of occupants.”
Air conditioners are often used to improve comfort and indoor air quality. Air conditioner pulls off the heat and making the air inside the Home, Office, Auditorium or Shopping mall makes you to feel pleasantly chill. Air conditioning is used to cool and dehumidify the rooms equipped with heat emitting devices such as high power lights in studio’s, server rooms, control rooms, and to store some Digital data archives, UPS battery rooms, etc. Air conditioning and refrigeration, both are same thing but with a little difference. Both are rely on the laws of chemistry.
What are the types of air conditioners ?
Window ac, Split ac, Floor standing ac, Package ac, Portable ac, Concealed ac, Cassette ac, VRV/VRF and Chillers.
Working principle of Air Conditioner.
Air conditioner is running on the basis of Vapor Compression Refrigeration Cycle. It consists of 4 main parts.
Evaporator coil, Compressor, Condensor coil and Expansion valve.
Vapor compression refrigeration system uses refrigerant as a medium and it undergoes various phase changes like liquid to gas, gas to liquid thereby removing heat from the occupied space. Here’s a schematic diagram of how most a/c units works.
1 Low pressure, Low temperature saturated vapor
2 High pressure, High temperature superheated gas
3 High pressure, Medium temperature saturated liquid
4 Low pressure, Low temperature liquid
Indoor blower blows the room air( ~30°C) over the evaporator coil. Low pressure liquid refrigerant in the evaporator absorbs heat energy from the room air and evaporates to gas. Here I consider r22 gas, its boiling point is -40.8°C. Which means there’s now more heat in the refrigerant, and less in the air.
The blower fan blows that colder air into your room. So now your A/C has to do two things: One, removed the heat absorbed by the refrigerant to outside, and two, it has to condense the refrigerant back into a liquid so it can be used again. Here is the use a compressor to do those things. The low pressure and low temperature saturated vapor enters the Compressor and is compressed to high temperature and high pressure superheated gas.
When a gas is compressed, its volume decreases and its pressure increases. When pressure increases then temperature also increases. Next to the compressor is Condensor. The fan in the outdoor unit removes the latent heat from the superheated gas and condense to high pressure and medium temperature saturated liquid all way the refrigerant passes through the condensor coil.
Usually outside air temperature and condensor coil surface temperature will be same and no heat transfer occurs. So, the refrigerant temperature should be more than the outside temperature. This job is perfectly done by the compressor. It then passes to the expansion valve.
The expansion valve regulates the flow of refrigerant. There is a bulb and diaphragm which restricts the flow. A detailed explanation on working of Expansion valve will be post in upcoming sessions. Depends on the cooling demand from evaporator coil, the expansion valve opens and reduce the high pressure liquid to low pressure liquid refrigerant to evaporator. This cycle continues in a loop, over and over until your home reaches the temperature.
Refrigerants
From simple split units to even large industrial chillers, the working rule all are same. And that is because they pass the refrigerant between all the major components of the evaporator, the compressor, the condenser and finally the expansion device. When we say refrigerant what we mean is may be a fluid which will be easily boiled from a liquid into a vapor, and even be condensed from a vapor back into a liquid. And this cycle or process need to be repeated again and again without failure.
Even we could use water as refrigerant that will work and is utilized in absorption chillers. Because of the reason why don’t we typically use water in common refrigeration units is, there are specially made refrigerants designed specifically for the task and so they are able to perform much better. While the refrigerant could be practically any substance, there are some chemicals that do the job better than others, and these refrigerants have a good history.
The properties of refrigerant should be
1. a low boiling point,
2. good at conducting heats,
3. easily absorbs heat as it boils,
4. cheap in price,
5. Easily available,
6. non-flammable and non-toxic as possible.
Some of the more commonly used refrigerants are R22, R407c, R134a, R600a and R410a.
As you’ll see on the above table, these refrigerants have extremely low boiling points compared to water. So they need a very low heat to boil and evaporate into a vapor and this suggests they can extract heat sooner. You can see that at atmospheric pressure the boiling point of water is 212 °F or 100 °C, but R22 has a boiling point -41.44 °F or -40.8 °C or. So we can use room temperature to boil these and take the warmth faraway from the space and expelled that to the atmosphere.
Compressors
Compressors used in air conditioner and refrigeration systems are named as hermetic, open and semi-hermetic compressors. These are describe on how the compressor and motor drive are placed in relation to the gas or vapor being compressed.
In hermetic and most semi-hermetic compressors, the compressor and motor driving the compressor are integrated, and operate within the single system. The motor is meant to work in, and be cooled by, the refrigerant gas being compressed.
The hermetic compressors uses a one-piece or two piece welded steel casing that cannot be repair, if it fails it is simply replaced with a new unit. A semi-hermetic compressors uses a large cast metal shell with gasketed covers that can be opened to replace motor and compressor components.
The advantage of a hermetic and semi-hermetic is that there is no way for the gas to leak out from the system. Open compressors depends on shaft seals to withstand the internal pressure and these seals require a lubricant such to retain their sealing properties.
Hermetic compressors are used in low capacity units. Semi-hermetic compressors are utilized in mid-sized to large refrigeration and aircon units, where it is cheaper to repair the compressor instead of installing a new one.
Various types of compressors are
1. Centrifugal
2. Reciprocating
3. Rotary screw
4. Rotary scroll
5. Rotary vane
All these types will be detailed in the next coming sessions. Otherwise you will be bored to read all in one article.
How to measure capacity of air conditioner ?
Air conditioners capacity is measured in Tonnage or Ton.
1 ton = 12,000 Btu/hr.
Btu/hr – British thermal unit.
“Thanks for reading and please share this post with your friends and support us. We’ll see in another interesting post.”
Author
Engr.Ahmed Hussain
Comments
Post a Comment