HomeMechanical EngineeringAir-Conditioning System: It's Working Principle and Types of Air Conditioning system

Air-Conditioning System: It’s Working Principle and Types of Air Conditioning system

In this article, you will learn what is Air conditioning system with its working principle and classification or types of air conditioning systems. Download the PDF file at the end of this article.

Air Conditioning and Types

Nowadays the Air conditioning system is widely used in both domestic and commercial environments. Air cooling or air conditioning is the process of removing heat and moisture from inside the occupied space, to improve the comfort of occupants. This process is most commonly used to achieve a more comfortable interior environment, typically for humans.

Working of Air conditioning systems

The definition of air-conditioning is, A system for controlling the humidity, ventilation and temperature in a building or vehicle, typically to maintain a cool atmosphere in warm conditions.

While air conditioners can differ from model to model they are available in any range from small units that can cool a small bedroom to massive units installed on the roof of office towers that can cool an entire building.

Equipment Used in an Air Conditioning System

Following are the main equipment or parts used in an air conditioning system:

  1. Circulation fan: The main function of this fan is to move air to and from the room.
  2. Air conditioning unit: It is a unit, which consists of cooling and dehumidifying 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 at the proper point.
  4. Supply outlets: These are the grills, which distribute 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: The main function of the filters is to remove dust, “dirt and other harmful bacteria”s form the air.

Air Conditioner Working Principle

An air conditioner continuously draws the air from an indoor space to be cooled, cools it by the refrigeration principles, and discharges back into the same indoor space that needs to be cooled.

This continuous cyclic process of drawl, cooling, and recalculation of the cooled air keep the indoor space cool at the required lower temperature needed for comfort cooling or industrial cooling purpose. When you switch the air conditioner on, the thermostat control sends 120V of alternating current to the compressor and the fan motor.

The compressor act as a pump compressing the refrigerant in gas form into the condenser coils. Located the back of the unit. Where the gas is condensed into a hot liquid. The condenser coils dissipate the heat as the liquid travels through them.

air-conditioner systems diagram

Working

Once the liquid refrigerant has passed through the condenser coils and the capillary tube where it undergoes expansion. The liquid refrigerant passes through the evaporator coils. it travels to the evaporator coils located near the front of the unit.

As the refrigerant liquid enters these coils it expands into a gas which makes the coils cold. The gas flows through the coils to a suction line, attached to the compressor converts the gas back into a liquid and the cooling cycle continues.

At the same time, the fan motor rotates a blower wheel which draws in air to be cooled by the evaporator coils before recirculating it back into the room. It also operates the condenser fan blade which blows outside air through the condenser coils to cool them.

The air temperature is regulated by the thermostat control depending on the model. The control may be a thermostat switch and sensing bulb assembly or electronic control board that works with a sensor. The sensing bulb or electronic sensor is clipped to the front of the evaporator coils to monitor the temperature of the air entering the coils.

Once the room has sufficiently cooled the thermostat control shuts off the voltage to the compressor. Some models which use an event can operate the fan motor only to draw in cool air at night.

However, when the appliance is actively cooling the air the vent must be closed for the system to work properly. A slinger ring on the condenser fan blade picks up collected water at the bottom and sprays it on to the condenser coils to help the coils dissipate the heat. To prevent the water from dripping into the room the appliance should be tilted back slightly when they installed.

Types of Air Conditioning System

Following are the types of air conditioning system:

  1. Comfort air conditioning system.
  2. Industrial air conditioning system.
  3. Winter air conditioning system.
  4. Summer air conditioning system.
  5. Year-round air conditioning system.
  6. The unitary air conditioning system
  7. Central air conditioning system.

1. According To The Purpose

1.1 Comfort Air Conditioning system

In these types of air conditioning system, the air is brought to the required dry bulb temperature and relative humidity for human health, comfort, and efficiency. If sufficient data of the required is not available, then it is assumed to be 21°C dry bulb temperature and 50% relative humidity.

Ex. In homes, offices, shops, restaurants, theatres, hospitals, schools etc. are using air-conditioning systems to give comfort to people.

1.2 Industrial Air Conditioning System

In these types of air conditioning system, the inside dry bulb temperature and relative humidity of the air is kept constant for working of the machine and for the manufacturing process.

Textile mills, Paper mills, Machine part manufacturing plants, Toolroom, Photographic, etc. are using this type of air-conditioning system.

2. According To A Season of The Year

2.1 Winter Air Conditioning System

Air conditioner working principle In winter air conditioning system, the air is burnt and heated, which is generally followed by humidification.

Schematic for the system is arranged.

Winter Air Conditioning System

The outside air flows through a damper and mixes with the recirculated air. The mixed air passes through a filter to remove the dirt, dust, and impurities.

The air now passes through a preheat coil to prevent the possible freezing of water and to control the evaporation of water in the humidities. After that, the air is made to pass through a reheat coil to bring the air to the designed dry bulb temperature.

Now, the conditioned air is supplied to the conditioned space by a fan. From the conditioned space, a part of the air is exhausted to the atmosphere by the exhaust fans. The remaining part of the used air is again conditioned and this will repeat again and again.

2.2 Summer Air Conditioning System

Air conditioner working principle in summer air conditioning system. In this system, the air is cooled and generally dehumidified. A Schematic for a typical summer air conditioning system is arranged.

The outside air flows through the damper and mixed with recirculated air (which is obtained from the conditioned space). The mixed air passes through a filter to remove the dirt, dust and impurities.

Summer Air Conditioning System

The air now passes through a cooling coil. The coil has a temperature much below the required dry bulb temperature of the air in the conditioned space.

The cooled air passes through a perforated membrane and loses its moisture in the condensed from which is collected in the sump. After that, the air is made to pass through a heating coil which heats the air slowly.

This is done to bring the air to the designed dry bulb temperature and relative humidity. Now the conditioned air is supplied to the conditioned space by a fan. From conditioned space, a part of the used air is rejected to the atmosphere by the exhaust fan. The remaining air is again conditioned and this repeated for again and again.

The outside air is sucked and made to mix with recirculated air to make for the loss of conditioned air through exhaust fan from the conditioned space.

2.3 Year-Round Air Conditioning System

In a year-round air conditioning system, it should have equipment for both the summer and winter air conditioning. Schematic for a modern summer year-round air conditioning is arranged.

Air conditioner working principle In year-round air conditioning system. In this, the outside air flows through the damper and mixed with the recirculated air. The mixed air passes through a filter to remove dirt, dust, and impurities.

Year-Round Air Conditioning System

In the summer air conditioning system, the cooling operates to cool the air to the desired valve. The dehumidification is obtained by operating the cooling coil at a lower temperature than the dew point temperature.

In the winter air conditioning system, the cooling coil is made inoperative and the heating coil operates to heat the air. The spray type humidifier is also used in the dry season to humidify the air.

3. According To The Arrangement of Equipment

3.1 Unitary Air Conditioning System

  • In the unitary air conditioning system, the assembled air conditioner is installed in or adjacent to the space to be conditioned.
  • Unitary systems, the common type of one room conditioners, sit in a window or wall opening, with interior controls.
  • Interior air is cooled as a fan blows it over the evaporator.
  • The exterior air is heated as a second fan blows it over the conditioner.
  • In this process, heat is supplied from the room and discharge to the environment.
  • A large house or building may have several such units, permitting each room to be cooled separately.
The unitary air conditioning systems are of the following two types,
  1. Window unit
  2. Vertical packed units or PTAC systems
1. Window Unit

These types of conditioners have a small capacity of 1TR to 3TR and are mentioned through a window or wall. They are employed to condition the air of one room only. If the room is bigger in size, then two or more units are used.

2. Vertical Packed Units or PTAC systems

These type of air conditioner are bigger in the capacity of 5 to 20TR and are adjacent to the space to be conditioned. This unit is very useful for conditioning the air of a restaurant, bank or small office. PTAC systems are also known as wall split air conditioning systems or ductless systems.

These PTAC systems which are widely used in hotels have two separate units, the evaporative unit on the interior and the condensing unit on the exterior, with tubing passes through the wall and connect them together. This minimizes the interior system footprint and allows each room to be adjacent independently.

PTAC system may be adapted to provide heating in cold weather, either directly by using an electric strip, gas or other heaters, or by reversing the refrigerant flow to heat the interior and draw heat from the exterior air, converting the air into a heat pump.

While room air conditioning provides maximum flexibility when cooling rooms it is generally more expensive than a central air conditioning system.

3.2 Central Air Conditioning System

It is the most important types of air conditioning system, it uses when the required cooling capacity 25TR or more. It uses when the airflow is more than 300 m³/min or different zones in a building are to be air-conditioned.

Application of Air-Conditioning

Following are the application of Air Conditioning System:

  1. Using air-conditioner is common in food cooking and processing areas. Used in hospital operating theatres to provide comfortable conditions to patients. And many more industries like Textile, Printing, Photographic and much more.
  2. Air-conditioning system used as the commercial purpose for a human being. Example, in Theatres, Departmental store-room, etc.
  3. Many transport vehicles use air-conditioning systems such as cars, trains, aircraft, ships, etc. This provides a comfortable condition for the passengers.
  4. The air-conditioning system used in Television-centres, Computer centers, and museums for a special purpose.

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Conclusion

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Saif M
Saif M. is a Mechanical Engineer by profession. He completed his engineering studies in 2014 and is currently working in a large firm as Mechanical Engineer. He is also an author and editor at theengineerspost.com