Chapter: Mechanical Engineering : Air Conditioning

Air Conditioning

Air Conditioning 1 Classification Of Air Conditioning 2 Window Type Air Conditioner

Air Conditioning

1 Classification Of Air Conditioning

2 Window Type Air Conditioner


Air Conditioning is the process of conditioning the air according to the human comfort, irrespective of external conditions.

Applications of Air Conditioning

Used in offices, hotels, buses, cars, etc.


Used in industries having tool room machines. Used in textile industries to control moisture. Used in printing press.


Used in Food industries, Chemical plants.




Air conditioning systems are classified as


1)   According to the purpose

·        Comfort Air conditioning.


·        Industrial Air conditioning. 2) According to Season of the year

·        Summer Air conditioning.

·        Winter Air conditioning.


·        Year round Air conditioning.


Types of Air conditioners

·        Room Air conditioners

·        Winter Air conditioners

·        Central Air conditioners


Functions of Air conditioners

·        Cleaning air.

·        Controlling the temp of air.

·        Controlling the moisture content.

·        Circulating the air.



·        Dry air: The atmospheric air which no water vapour is called dry air.


·        Psychometry: Psychometry is the study of the properties of atmospheric air.


·   3) Temperature: The degree of hotness  (or) Coldness is called the temperature.


·        Moisture: Moisture is the water vapour present in the air.


·        Relative humidity: Relative humidity is the ratio of actual mass of water vapour in a given volume to the mass of water vapour.


·        Dry bulb temperature: The temperature of air measured by the ordinary thermometer is called dry bulb temperature:


·        Wet bulb Temperature: The temperature of air measured by the thermometer when it is covered by the wet cloth is known as wet bulb Temperature.

·        Dew point Temperature: The temperature at which the water vapour starts condensing is called dew point Temperature








This is also called room air conditioner.

This unit consists of the following.


·        A cooling system to cool and dehumidify the air involves a condenser, a compressor and a refrigerant coil.


·        A filter to any impurities in the air. The filter is made of mesh, glass wool or fibre.


·        A fan and adjustable grills to circulate the air.

·        Controls to regulate the equipment operation.


·        The low pressure refrigerant vapour is drawn from the evaporator to the hermetic compressor through suction pipe.


·        It is compressed from low pressure to the high pressure and supplied to the condenser.


·        It is condensed in the condenser by passing the outdoor air over the condenser coil by a fan.


·        The liquid refrigerant is passed through the capillary into the evaporator.


·        . In the evaporator the liquid refrigerant picks up the heat from the refrigerator surface and gets vaporized.


·        A motor driven fan draws air from the room through the air filter and this air is cooled by losing its heat to the low temperature refrigerant and cold air is circulated back into the room.


·        The vapour refrigerant from the evaporator goes to the compressor from evaporator and the cycle is repeated.


·        Thus the room is air conditioned

·        The quantity of air circulated can be controlled by the dampers.


·        The moisture in the air passing over the evaporator coil is dehumidified and drips into the trays.


·        This water evaporator to certain extent and thus helps in cooling the compressor and condenser.


·        The unit automatically stops when the required temperature is reached in the room. This is accomplished by the thermostat and control panel.


Merits and Demerits of Window type air conditioner:

Merits :


A separate temperature control is provided in each room. Ducts are not required for distribution.


Cost is less.


Skilled technician is required for installation.



It makes noise.


Large hole is made in the external wall or a large opening to be created in the window panel. This leads to insecurity to inmates.


Split Type Air Conditioner - Layout


In split air type air conditioner noise making components like compressor and condenser are mounted outside or away from room.



·         Split type air conditioning system has two main components.


·         The indoor unit consists of power cables, refrigerant tube and an evaporator mounted inside the room.


·         Compressor is used to compress the refrigerant.


·         The refrigerant moves between the evaporator and condenser through the circuit of tubing and fins in the coils.


·         The evaporator and condenser are usually made of coil of copper tubes and surrounded by aluminium fins.


·         The liquid refrigerant coming from the condenser evaporates in the indoor evaporator coil.


·         During this process the heat is removed from the indoor unit air and thus, the room is cooled.


·         Air return grid takes in the indoor air.


·         Water is dehumidified out of air is drained through the drain pipe.


·         The hot refrigerant vapour is passed to the compressor and then to


·         the condenser where it becomes liquid. Thus the cycle is repeated.


·         A thermostat is used to keep the room at a constant, comfortable temperature avoiding the frequent turning on off.


Merits and Demerits of Split type air conditioner:


It is compact


Upto four indoor AHU’s may be connected to


It is energy and money saving. Duct is not used.


Easier to install.


It is noiseless, because rotary air compressor used is, kept outside. It is more efficient and powerful.


It has the flexibility for zoning.


DeMerits :

•        Initial cost is higher than window air conditioner


•        Skilled technician is required for installation.


•        Each zone or room requires thermostat to control the air cooling.


Applications of air conditioning:


•        Used in houses, hospitals, offices, computer centres, theatres, departmental stores etc.,


•        Air-conditioning of transport media such as buses, cars trains, aeroplanes and ships.


•        Wide application in food processing, printing, chemical, pharmaceutical and machine tool, etc.,



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