How an air conditioner works? – Principle, Classification

You may be wondering how an air conditioner works, so “topairconditioner” is here to tell you all about air conditioners.

The air conditioner is an electronic device that gives you the best comfort during scorching summer.

It’s one of the best devices which gives you cold and fresh air if you compare the air conditioner with other devices like a cooler, fan, etc.

The air conditioner has only the best scientific structure to give you the best air experience, or it helps to purify the air in your surroundings.

As you know, in India, the summer starts from earlier March and lasts till June. The average temperature continues around 32 – 40 °C in the summer.

The air conditioners have designed to maintain the room temperature at the optimal level to keep cooling the room. then the best air conditioner is the only option for you

They also have to remove air dust and little particles from the room. That’s why the best air conditioner is all you need in your place.

Let’s find out how an air conditioner works?


The functioning of How an Air conditioner works-

So, let’s begin in a simple way to understand how the function of the air conditioner works.

Every air conditioner has two interconnected coils inside them that frequently flowing refrigerant fluid inside them to maintain cold air in the room.

As I have already mentioned above that, there are two coils in an air conditioner,

So the coil which is inside the room/house is known as Evaporator.

And when the coil which has placed outside of the room/house is known as Condensor.

How an air conditioner works

The fundamentals of an air conditioner working principle is simple.

As per the working principle of the air conditioner, the room temperature should be lower to keep the evaporator cold, And the Condensor should be hot more than the surroundings.

With these situations, the refrigerant fluid, which is frequently flowing, will inspect the heat from the room and eject out to the surroundings.

How an air conditioner works

Fundamental Principle of How an air conditioner works –

Let’s see how this rule has executed in practice.

Two more components should be inside your air conditioner to accomplish this goal.

That is Compressor and Expansion Valve.

The work of the Compressor is to increase the pressure of the refrigerant.

How an air conditioner works


The Refrigerant is handled by the compressor in its gaseous state so that the compressor increases the pressure of the refrigerant, and compress the gas. The pressure rises as well as the temperature increase.

The Temperature of the compressor outlet should not be lower than the temperature of the surroundings.

That’s why through the condenser hit exchanger, if you hot gas passes so that results you can immediately eject the heat.

While this heat ejection stage, the gas compressed through the Condensor to the liquid and a circulating fan in the condenser makes this work simple.

How does an air conditioner works
Expansion Valve

In the Condensor, An expansion valve has fitted at the exit of the Condensor.

The main object behind it is to reduce the refrigerant flow, so it reduces the pressure of the fluid.

So now, the trick here is that you might be aware that it is possible to boil the liquid only by decreasing the pressure around it.

This event happens on the inner of the expansion valve along with the pressure falls down one part, and the liquid gets evaporated.

However, some energy supplied to it for this evaporation, and when it happens, the energy comes from the inner side of refrigerant until the temperature drops.

It is how the cold refrigerant has produced inside of air conditioner.

This low-temperature refrigerant should add a temperature lower than the room temperature. So bypassing the room’s air over the evaporator coil, the room temperature will drop.

The refrigerant gets converted to vapor during this hit absorption process.

What is TON?

You might have heard a term called TON associated with the air conditioner.

The TON represents how many hits an evaporator can absorb from the room. In simple words, it represents an air conditioner’s hit removal capability.

In this way, achieve the fundamental rule of an air conditioner.

The temperature is lower than the room temperature in the coil inside the room. And the temperature is more than the atmosphere temperature in the loop outside the room.

In an actual air conditioner, the compressor sites near to condenser and the expansion valve sites near to evaporator.

There are some practical issues with the design near to the evaporator coils; the air temperature will be quite low.

It will lead to water condensation on the evaporator coils, and that’s why it needs a pipe to remove this water condensate.


Modern air conditioners use scroll compressors instead of the reciprocating type because of the silence and excellent speed control.

Do you know how your air conditioner can maintain almost steady room temperature irrespective of the load?

This problem has finished through inverter technology. It is the best modern air conditioner.

What is Inverter Ac?

The modern air conditioner uses the variable speed motor technology called Inverter Technology. Inverter technology helps for better temperature control just by adjusting the motor speed.

The compressor speed or refrigerant flow rate and cooling capacity can be control accurately.

Here comes an exciting design challenge for the air conditioner.

The compressor of the air conditioner designed to handle only Vapor and a small fraction of liquid content can affect its performance and damage.

For these reasons, it is the desire that the Evaporator converts all of the liquid to the vapor.

And even it increases the temperature of the vapor by 5°C to 8°C after the conversion.

How does it make sure that the fluid which enters the compressor is truly Vapor?

This condition has maintained through a special kind of expanse value called Thermostatic Expansion Valve (TXV).

What is TXV?

The Thermostatic Expansion Valve (TXV) is similar to the expansion value we saw earlier, but here the temperature of the bulb controls the needle.

The bulb has connected to the evaporator’s exit, and the refrigerant inside of the bulb is separated from the primary refrigeration cycle by a diaphragm.

When the bulb is hot, the refrigerant inside will evaporate, and the needle moves down.

We know the sudden cooling of the refrigerant has achieved across the expansion value with the help of restriction.

The narrower the restriction, the colder the outlet refrigerant will be.

Let’s consider a bad situation for the compressor.

Assume the evaporator temperature is not so low.

So the evaporator absorbs deficient heat, and all the liquid in it won’t convert into the vapor.

Thus, the refrigerant which leaves for the compressor will not be superheated.

This low temperature at the evaporator exit will immediately have sensed by the bulb and will cause the needle to move upward and makes the restriction narrower.

The narrow restriction causes a good temperature drop, thus evaporated will receive much cooler fluid, and it can absorb a great amount of heat.

It will make sure that all the liquid has converted to vapor.

Thus, the complex task of having vapor only conditions at the compressor has automatically maintained by the (TXV).

Let us clear up a common misconception at this stage.

TVX do not control the room temperature.

They just make sure that the compressor poorly receives refrigerant performed.

The speed of the compressor controls the refrigerant flow rate and the room temperature due to their simplicity and efficiency TXV widely used in the industrial and domestic applications.

So now, let’s move forward a little bit deeper.


Factors affecting comfort Air conditioning

  1. Temperature of Air
  2. Humidity in Air
  3. Purity of Air
  4. Motion of Air


These are the factors that affect your air in the room while your ac is on. These could be the reasons behind your bad experience of cooling air.

Let’s dig into these topics one by one.

1. The temperature of Air

In air conditioning, temperature control means the maintenance of any desired temperature within the encase phase, even if the outside air temperature is above or below the desired room temperature.

It is accomplished either by the edition of removal of the heat from the inclose phase as and downloaded.

It has noted that a human being feels comfortable when the air is at 21°C with 56% relative humidity.

2. Humidity in Air

So the control of humidity of air means decreasing or increasing the moisture content of the air during summer or winter, respectively, to produce comfortable and healthy conditions.

The control of Humidity is not only necessary for human comfort, but it also increases the efficiency of the workers, employees, etc.

In common, the respective humidity must be at least 60% in the Summer Air Conditioning System.

And on the Other hand, If you will talk about the Winter Air Conditioning System, then it should not be less than 40%.

3. Purity of Air

It is also one of the essential factors which affect the comfort of the human body.

It has noticed that people do not feel comfortable while breathing contaminated air even if it is within the acceptable temperature in humidity ranges.

Thus, to keep the air fresh, it is clear that proper filtration cleaning and purification in the air is one of the significant rules.

4. Motion of Air

The action or circulation of air is another significant factor that should have controlled.

To keep a constant temperature throughout the conditioned space, Therefore, it is necessary to keep the equidistribution of air to be air-conditioned.


What is Air conditioning system?

The system effectively controls conditions like the temperature in air, purity of air, the humidity of the air, etc. To produce desired upon the occupants of the space is known as an air conditioning system.


Equipment used in an Air Conditioning System

So, there is various equipment used in Air Conditioning System. Let’s dig into all the point given below step by step –

Equipment used in an Air Conditioning System

  1. Circulation fan
  2. Air Conditioning unit
  3. Supply duct
  4. Supply outlets
  5. Return outlets
  6. Filters
1. Circulating fan

The primary function of the circulating fan is to move air to the end of the room.

2. Air conditioning unit

It is the units that consist of cooling and de-humidifying processes for Summer air conditioning or heating and humidification processes for Winter air conditioning.

3. Supply duct

It directs the conditioned air from the circulating fan to the space to be air-conditioned that proper point

4. Supply outlets

So these are the only thing that distributes the conditioned air evenly in the room.

5. Return outlets

These are the openings in a room surface which allow the room air to enter the return duct.

6. Filters

So, the main function of the filter is to remove dust, dirt or other harmful bacteria from the air


What is the Classification of Air Conditioning System?

  1. According to Purpose
  2. According to the season of the year
  3. According to the arrangement of equipment
  4. According to the fluid media used in the thermal distribution system

So there are four types of classification of air conditioning systems. Let’s dig into every classification step by step.

1. According to purpose

In this type of air conditioning system, which has based on purpose like where the air condition system is going to use or the uses of the air conditioning system.

So, there are two types for this classification in which you can understand it in a better way.

  1. Comfort Air Condition System
  2. Industrial Air Condition System
A) Comfort Air Condition System

In which, the air is conducted to dry-bulb temperature and associated humidity for human health, comfort, and efficiency. It is called the Comfort Air Conditioning System.

If the satisfactory data of the demanded condition has not given, then it is assumed to be 21 ° C dry temperature and 50% relative humidity.

Example:- The comfort air may be adapted for homes, offices, shops, restaurants, theatres, hospitals, schools, etc.

B) Industrial Air Condition System

In an industrial air conditioning, the inside the dry-bulb temperature and relative humidity of the air is kept constant for the proper working of machines and adequate research and manufacturing process.

The industrial air conditioner is very beneficial because some of the sophisticated electronic and other machines need a particular dry bulb temperature and relative humidity. Sometimes these machines also require a specific psychrometric process.

Example:- This type of air conditioning system is using in textiles mills, paper mills, machine parts, manufacturing plants, tool rooms, photo processing plants, etc.


2) According to the season of the year

These are the air conditioning systems depend on the season i. e. winter, summer, etc. This air conditioner is used for an individual, family, etc.

Let’s move on to how we can understand this type of air conditioning system one by one.

A) Summer Air Conditioning System

It is the most important type of air conditioning system, in which the air is cooled generally dehumidified.

Winter air conditioning system

It is the diagram for the summer air conditioning system, and I will explain in detail below.

So, when the outside air flows to the damper which is obtained from the Conditioned space. And it mixes up with Recirculated air.

The mixed air passes through a filter to remove the dirt, dust, and other harmful bacterias.

Now the air passes through the cooling coil; the coil has a temperature much below the required dryable temperature of the air in the Conditioned space.

The cooled air passes through a Perforated Membrane and loses its moisture in the condensed form, which is collected in the Sump.

After that, the air has made to pass through a Heating coil which heats the air slightly.

It is how air is brought to the designed dryable temperature ane relative humidity.

Now, the conditioned air is supplied to Conditioned space through a Fan.

The Conditioned space, apart from the used air, is exhausted to the atmosphere by the exhaust fans or ventilators.

The remaining part of the air is used known as Recirculated air is again conditioned shown in the above picture, and the process is repeated.

So, outside air is sucked and made to mix with Recirculated air to make up for the loss of conditioned air through the exhaust fan or ventilation from the Conditioned space, and this process is repeated.

So this how the Summer air conditioning system works.

B) Winter Air Conditioning System

In the Winter air conditioning system, the air is heated, which is generally accompanied by humidification.

Winter air conditioning system

As you can see in the picture when the outside air flows through the Damper and mixes up with the Recirculated air which is obtained through the Conditioned space and mix air passes through a filter to remove dirt, impurities, etc.

Now, the air passes through a Preheat coil to prevent the possible freezing of water and to control the evaporation of water in humidifier.

After that, the air is allowed to pass through a Reheat coil to bring the air to designed dryable temperature.

The conditioned air is supplied to the Conditioned space through a Fan.

Apart from the used air is exhausted to the atmosphere by the exhaust fans or ventilators and

The remaining part of the air is used known as Recirculated air is again passed through the Conditioned space by mixing it with the outside air to make up for the loss of conditioned air through the exhaust or ventilation from the Conditioned space.

So, this is all about how the Winter air conditioning system works.

Let,s move on to the last one.

C) Year Around Air Conditioning System

The year air conditioning system should have equipment for both the summer and winter air conditioning.

year air conditioning system

So, in the diagram, we can see that the outside air flows through a Damper which is coming from the Conditioned space and mixes up with Recirculated air.

The is air passes through the Filter to remove dirt, dust, and other impurities.

In the Summer Air Conditioning System, the Cooling coil operates to the air to the desired value.

The dehumidification is obtained by operating the Cooling coil the temperature lower the due point temperature i. e. apparats due point.

And in winter, the Cooling coil is made inoperative, and the Heating coil operates to heat the air.

The spry type of Humidifier is also made to use in the dry season to humidity the air.

So this is the Year-round air conditioning system all about.

3) According to the arrangement of equipment

This one of the types of classification of air conditioner systems, so let’s dig into this point in detail.

To understand this classification of the arrangement equipment, we have two points to understand it easily.

  1. Unitary Air Conditioning System
  2. Central Air Conditioning System

Below is a detailed explanation of these two types in detail.

A) Unitary Air Conditioning System

In the Unitary air conditioning system, factory assembled air conditioners are installed in or adjacent to space to be conditioned. These systems are tested as per standard specifications and are available in the form of package units of varying capacity and type. Each package consists of refrigeration or heating units with fans, filters, controls, etc.

The unitary air conditioning system is of the following two types.

  1. Window Units
  2. Verticle Packed Units

Let’s look into these types step by step.

i) Window Units

These are self-contained units of the small capacity of 1TR to 3TR, and these are mounted in a window or through the wall. They are employed to condition the air of one room only. If the room is bigger, two or more units are installed.


ii) Verticle Packed Units

These are also self-contained units of the bigger capacity of 5 to 20TR and these are installed adjacent to the space to be conditioned. This is very useful for conditioning the air of a restaurant, bank or small office.

The unitary air conditioning system may be adapted for winter, summer, or year-round air conditioning.

Depending upon the requirement these are available in the form of window air conditioners, split air conditioners, heat pumps, ductable systems with air-cooled or water-cooled condensing units, etc.


So, the example of Unitary air conditioning systems such as A typical window type air conditioner or a typical package unit with the remote condensing system.

B) Central Air Conditioning System

Let’s try to understand Central Air Conditioning System from the following points in detail.

  1. The name central system or equipment is also commonly called an applied system or applied machinery.
  2.  Central station equipment is associated with installations where the cooling plant has located in the basement or the penthouse on the roof of the multi-story buildings.
  3. It serves the are handling equipment and air distribution systems throughout the building.
  4. Although size is not necessarily the crossover point between the unitary and central station, it has acknowledged that central station equipment starts at 25 TR or more.
  5. The central air conditioning is also adapted when the airflow is more than m³/min or different zones in a building are to be air-conditioned.
4) According to the fluid media used in the thermal distribution system
  1. All Air System
  2. All Water System

This is one of the classifications of the air conditioning system, I will take you to its explanation, and I will give you in detail.

So, let’s dig into these points step by step.

A) All Air System

In all systems, the air is used as the media that transport energy from the Conditioned space to the Air conditioning plant.

This air extracts (or supplies in case of winter) the required amount of sensible and latent heat from the conditioned space.

The return air from the conditioned space is conveyed back to the plant, where it again undergoes the required processing thus completing the cycle.

All air systems can be further classified into:

a) Single duct system – The single duct system can be provided with either cooling or heating using the same duct, but not both heating and cooling simultaneously. These can be further classified into:

  • Single duct, constant volume, single-zone system
  • Single duct, constant volume, multiple-zone system
  • Single duct, variable volume system

So let’s dig into these classifications, and we will look very aspects in detail and step by step.


i) Single duct, Constant Volume, Single-zone system

Single duct, Constant Volume, Single-zone system

As you can see in the image, outside air interest into the Cooling coil, and then air enters the Heating coil after which through a Fan and Humidifier it enters the Conditioned space and again the air returns back through the Dampers to the Air cooling system.

If you look into the image, there are two sensors i. e. T or H

In this system, the conditioned space (T) which is linked through the sensors that maintained the temperature. And through the (H) sensor, the humidity of the Conditioned space is maintained.

So, as per image, there is only one duct for either cooling process or heating process both can be done through this system.

Now we will understand the Applications of single duct, constant volume, single-zone system –

  • Space with uniform loads, such as more extended open areas with small external loads, e.g. theatres, auditorium, departmental stores.
  • Spaces were requiring precision control such as laboratories.
  • The single, multiple zone system can be used in larger buildings such as factories, office buildings, etc.


ii) Single duct, Constant Volume, Multiple-zone system

You can better understand it with the image, and then I will explain it to you in detail.

Single duct, Constant Volume, multiple-zone system

As per the diagram, the air is entering through the Damper to the Cooling coil, and it flows to the Heating coil too.

Then again the air enters through the Fan and Humidifier it enters into Zone 1, Zone 2, and Zone 3.

If you observe that there is a Reheat coil, So here the Reheat coils are provided to temperature as per the requirement of that particular Zone.

After passes through these various Zone, the air is again sent back to the air conditioning system.

So, it is the Single duct, Constant volume, Multiple zone systems, where we can see that there are various zones and these multiple zones can be maintained at the different temperatures as per the requirement.

Now, we will find what the advantages of the Single duct, Constant volume, multiple zone systems with Reheat coils in detail are.

a) Advantages of Single duct, Constant volume, multiple zone systems with Reheat coils –

  • Relatively small space requirement.
  • Excellent temperature and humidity controlled over a wide range of zone loads.
  • Proper ventilation and air quality in each zone are maintained as the supply air amount is kept constant under all conditions.

b) Disadvantages of Single duct, Constant volume, multiple zone systems with Reheat coils –

  • High energy consumption for cooling, as the first cooled to a very low temperature and is then heated in the Reheat coil.
  • Simultaneous cooling and heating are not possible.


ii) Single duct, Variable volume system

    Single duct, variable volume system

    In the diagram, we can see that it is too similar to the Single duct, Constant volume, Multiple zone systems as I have explained before.

    And here is different is that, hear we are having Dampers at the starting of each and every zone.

    So through the Dampers, the volume which is entering into a particular space can be controlled.

    That’s why this system is called as Single duct, Variable volume system.

    Now let’s move the merits and demerits of this system

    a) Advantages of Single duct, Variable volume system –

    • Lower energy consumption in the cooling system as air is not cooled to very low temperature and then Reheated as in the Constant volume system.
    • Lower energy consumption also results due to lower fan power and input due to lower flow rate, when the load is low.


    b) Dual duct system – The dual duct system can provide both cooling and heating simultaneously. These can be further classified into:

    • Dual duct, constant volume system
    • Dual duct, Variable volume system

    Let’s dig into this point in detail, and we’ll look it step by step.


    i) Dual duct, Constant volume system

    Dual duct, constant volume system

    There are two ducts in Image, one duct is having the Cooling coil associated with it and the second one is with Heating coil associated with it.

    So, the air is coming out Cooling coil and Heating coil are mixed at a particular point (mixing box) before entering into the specific zone.

    The temperature is maintained according to the requirement of the particular zone (that is called a mixing point).

    As per the image, we can see that there are two zones; therefore, there are two Mixing points.

    So, after the conditioning of a particular zone, the air is again sent back in the form of return air to the air conditioning system, and again it is sent back to the system as per the requirement of that particular zone.


    i) Dual duct, Variable volume system

    These systems are similar to the dual duct, constant volume system with the only difference that instead of maintaining constant flow rates to each zone, the mixing boxes reduce the airflow rate as the load on the zone drops.

    So, as you can see in the image given above, the Dampers will be provided on the place of Mixing box in case of a variable constant system to control the volume which is sent to the Zone as per the changes in the load.

    B) All Water System

    The fluid used in the thermal distribution system is water, i.e. water transports energy between the conditioned space and air conditioning plant.

    It consists of a basic fan coil unit, connectors, radiators, etc.


    So, the above diagram is given for all the water systems.

    As you can see in the image, the location of the Heating coil or Cooling coil is given at the corner site, and as per the requirement of the system.

    Through the pump, the water is supplied to a water supply line in which entered the zones as Zone1 or Zone2 through the Flow control valves.

    And after conditioning of air in that particular zone, the water is sent back through the Return water line again to the Heating or Cooling coil.

    In the image, there is a PRV (Pressure Reducing Valve) to reduce the pressure of the water, if it is not at the level of Return water line.

    So, there is water is the medium that transports energy between the conditioning space in the air conditioning plant.

    In every Zone, There is a basic fan coil unit which will transport the energy from the water to air in the Conditioned space.

    So, let’s move on to the basic fan coil unit for cooling purposes and take a look in detail, and I will explain it step by step.

    basic fan coil unit for cooling purposes

    As per the image, Warm air from conditioned space enter through the bottom area, and it passes through air Filter to remove dirt, dust, etc. And then it enters to the Fan area.

    As you can see in the picture, Connection for cold water is given, and the Finned tube cooling coil is provided with a straight opposite site of it.

    Here, heat transfer between water and air takes place, where the water takes up heat from the air, and air comes to a lower temperature.

    So, the Condensate water drain line is in the above-given image where the condensate is collected.

    Now, cold air is taken out from the top area, which is Cold air to conditioned space.

    C) Air Water System

    Air and water are used for providing conditions in the conditioned space.

    Air water system

    So, this is the layout of the basic Air-water system.

    Ap per the image, you can see the Central plant for secondary water an on the opposite Central plant for primary air.

    Though the Central plant for secondary water there is Secondary water line and through Central plant for primary air, there are Primary air ducts.

    And on the right bottom side, that should be Conditioned.

    There is Room unit in the Conditioned space where water enters into the air conditioning system.

    It cools the air at a particular temperature, and then air is circulated in the circulating space.

    So, the primary and secondary are circulated int he Conditioning space, and then again Secondary it enters into the air conditioning system to acquire the required temperature.

    This process gets repeated so either heating-cooling process can be done through these air conditioning systems asper th requirement of the conditioning space.

    If cooling required cooling is required than cool air is allowed to enter into this air conditioning system.

    And on the other hand, if heating is required than hot air is allowed to enter into this air conditioning system and the air is cooled or heated as per the requirement, and it is recirculating in the air conditioning system.

    So, this all about the Air-water system.

    What is the election Criteria for Air conditioning system?

    1. Capacity, Performance, and Spatial requirements.
    2. Initial and Running costs.
    3. Required system Reliability and Flexibility.
    4. Maintainability
    5. Architectural constraints.

    The relative importance of the above factors varies from case to case.

    My thoughts –

    I have explained the principle of the air conditioner on which an air conditioner works and functions of the air conditioner. And the fundamental rules in which whole structure works.

    I have also covered all about factors that affect the functioning of an air conditioner such as Humidity of air, Purity of air, etc.

    The necessary equipment is best for the functioning of an ac. And the classification of the air conditioner.

    Here is all reason how does an air conditioner works and If you want any help from our team.

    Feel free to contact us through the contact form, and you can comment down below how this article helps you.


    Also, read

    Window ac vs Split ac: Which is better for you? [Updated]

    What are inverter ac and Its benefits – 2020


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