19-02-2013, 10:55 AM
AUTOMOBILE AIR CONDITIONING
AUTOMOBILE AIR.pptx (Size: 2.03 MB / Downloads: 200)
INTRODUCTION:-
In 1939 Packard marketed the first mechanical automotive air conditioning system which worked on a closed cycle. The system used a compressor, condenser, receiver drier and evaporator to operate the system. The only system control was a blower switch. The major problem with the system was that the compressor operated continuously and had to help the belt removed to disengage the system which was generally during the winter months. Over the period 1940-41 a number of manufacturers made vehicles with air conditioning system but this were in small volume and not designed for the masses. In 1954-55 Nash kalvinator introduced air conditioning for the mass market. It was an air conditioning unit that was compact and affordable with controls on the dash and an electric clutch.
Due to varying condition of heating, ventilating, cooling and dehumidification in the atmosphere at various places, the air conditioning of automobile’s is very essential. To maintain human comfort and improve internal atmosphere in an enclosed space, proper control of freshness temperature, humidity and cleanliness of the air is required.
COMPRESSOR:-
This is a heart of air conditioning system . The function of the compressor is compress and calculate superheated refrigerant vapour around a closed loop system.The compressor is driven by engine driven pulley system . At the front of the compressor is a magnetic clutch which when given power engages the compressor. The compressor draws in refrigerant vapour from the suction side which is the outlet of the accumulator or the outlet of the evaporator .Any liquid or dirt allow to enter the compressor will cause damage.
CONDENSER:-
The function of condenser is to act as a heat exchanger to dispel the heat energy contained in superheated the refrigerant. Condenser is basically a fin-and-tube radiator , usually placed in front of car’s radiator . The condenser receives heated and compressed refrigerant vapour from the compressor and is cooled by the air passing across the condenser. The refrigerant is now in the form of a high pressure liquid which is fed to the receiver drier unit.
MEGNETIC CLUTCH:-
The electrically controlled magnetic clutch is housed in pulley assembly and the system selector switch controlling the clutch operation is mounted on the control panel inside the passenger compartment. In the off or on vent position , the compressor and its clutch are off. In other four positions of the selector switch the clutch is engaged or disengaged depending upon the condenser remain open and the compressor cannot be operated.
EVAPORATOR:-
The evaporator is another little radiator that does just the opposite task as the condenser . As the super-cool liquid is passed through its tubes, air is forced through and gets really cold, right before it hits face. As it warms up again, the refrigerant starts turning back into a gas.
PRESSURE OPERATED BY-PASS:-
In this system the pressure operated bypass valve is connected between the compressor discharge(high side) and compressor low side or suction line. When the pressure difference reaches the valve setting, the valve is set to open and bypass hot vapour from the high side to the low side. The valve will close or open if the suction, line pressure decreases or increases respectively. To maintain a certain pressure in the evaporator, hot gas(vapour) is fed into the low pressure side. In this system, a continuously operated compressor is used.