AIR CONDITIONING

BCDUNIT-V

Prof S S JAHAGIRDARBE (CIVIL), ME(ENV.),PhD(persuing)NK Orchid college of Engg. and Tech. , Solapur

Definition

Process of treating the air so as to control simultaneously its temperature, humidity, purity and distribution to meet the requirements of controlled space.

Requirements of a conditioned space

1) Comfort and health of occupants

2) Needs of certain industrial processes

3) Efficient working of commercial premises/offices

Functional classification Comfort air conditioning : -

Aim at giving max human comfort to occupants/users of conditioned space

Industrial air conditioning : - The coditioning creates, controls and maintains such an environment inside the conditioned space, that it would suit best to the needs of industry.

Classification based on season/Temperature

1) Summer air conditioning In summer outside temp is more

and hence cooling of air is required Consists of i) Air cleaningii) Air coolingiii) Dehumidificationiv) Air distribution/circulation

2) Winter air conditioning In winter outside temperature is

low hence heating of air is needed for comfort.

Cycle of operations consists of i) Air cleaningii) Air heatingiii) Humidificationiv) Air distribution/circulation

Essentials of air conditioning system

1) Temperature control Effective temp = 200C to 230C in

summer Effective Temp = 180C to 220C in

winter For Indian conditions 250C with

60% relative humidity to 300C with 45 % relative humidity, with air velocity not exceeding 10 m/min

2) Humidity control

During summer dehumidification is done so that relative humidity is 40 to 50%

During winter humidification is done so that relative humidity is 50 to 60 %

3) Air Velocity control

High velocity of conditioned air may cause greater temperature difference between outside and inside.

Velocity = 6 to 9 m/sec is desirable

4) Air Quality control

Air should be free from odour, toxic gases, bacteria and other micro-organisms

Essentials of air conditioning system

1. Filtration2. Heating (in winter)3. Cooling (in summer)4. Humidification5. Dehumidification6. Air circulation or distribution

1) filtration Should be capable of removing dust,

ash, smoke, bacteria etc Should be capable of holding

moderate amount of dust without affecting the efficiency

Should offer low resistance to flow of air

Workable under sufficient range of velocities.

Should afford easy cleaning manually or mechanically

2) Heating

Heating is necessary in winter so as to compensate heat loss from room.

Pre heating of incoming air may be done by passing over air furnaces or coils through which hot water is circulated.

3) Cooling

Cooling of incoming air is necessary in summer.

Principle of mechanical refrigeration is used.

4) Humidification

Humidification or addition of water is necessary in winter when air because of low temp has less humidity.

Incoming air is passed through pans of water or wet cloth strips

5) Dehumidification

In this process certain amount of water is extracted from air.

This is done in summer where incoming air is cooled.

Adsorbents can be used to adsorb excess moisture from air

6) Air circulation or distribution

END