AIR CONDITIONING OF MOTOR VEHICLE

Necessity of Automobile Air-Conditioning: Due to varying conditions of heating, ventilating, cooling, dehumidification in the atmosphere at various places, it is necessary to be conditioned the air in the automobiles. To maintain human comfort and improve internal atmosphere in an enclosed space, proper control of freshness temperature, humidity and cleanliness of air is required. For this reason Automobile air-conditioning is necessary in the vehicles.

Construction and working of Passenger car Air – Conditioning:

The main components of Auto Air- Condition are:

1. Compressor

2. Magnetic clutch

3. Condenser

4. Receiver or dehydrator

5. Expansion valve

6. Evaporator

7. Such on throttling valve

Compressor: The compressor in the Auto Air- Condition system is belt-driven engine crankshaft pulley. A magnetic clutch engages the compressor shaft. When the voltage is applied to the compressor clutch coil was sufficient the compressor and pulley rotates together as one unit. When the voltage is interrupted the pulley, disengages automatically, causes compressor to stop. The low – pressured, high temperature, vaporized refrigerant enter in to the compressor and it increases the pressure of about 20kg/cm² and 100ºc temp, and pushes into the condenser. In the compressor the refrigerant never reaches its liquid state.

Magnetic Clutch: The electrically controlled magnetic clutch is housed in pulley assembly and a switch is on the controlling panel. This clutch is engaged or disengaged depending upon the temperature of the air. Bellow 40 ºF. The compressor cannot be operated. Above 55ºF this switch closes and completes the circuit to the compressor clutch.

Condenser: It is usually placed in front of the car and it is looks like a Fin-andtube radiator. The condenser receives heated and compressed gas from the compressor and is cooled by the air passing across the condenser. The refrigerant now in the form of high pressure liquid which is fed in to the receiver drier Unit.

Reservoir or Dehydrator: The refrigerant stored under pressure in the Receiverdrier. The drier removes any traces of moisture present in the system to avoid freezing of moisture at low temperature and thus clogging the lines. It causes running troubles.

Expansion Valve: In the expansion valve high pressure liquid is converted into low pressure liquid then the refinement flow in to the evaporator

Evaporator: The evaporator unit where the cooling effect is obtained is usually located inside the passenger compartment bellow the dash board. A high capacity blower circulates the air in the in the car interior across the evaporator coils, and the drops the temperature of the air inside the passenger compartment. The heat picked by the refrigerant goes back to the compressor in the vapour form, where the refrigerant is again compressed to a high pressure and the cycle starts again.

Suction throttle valve: It ensures that the refrigerant the evaporator says at such a pressure that the evaporator core surface temperature does not fall bellow the freezing point of water (0°c), thus preventing ice formation in the evaporator.