TITLE OF THE PROJECT:- AUTOMOBILE AIR CONDITIONING AIM OF THE PROJECT:- TO STUDY ABOUT AIR CONDITIONING SYSTEM OF AN AUTOMOBILE

PRESENTED BY:-INAMUL HASANBOP/10/AU/012JOHIRUL ISLAM TALUKDARBOP/10/AU/014NITUL DASBOP/10/AU/023

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.

AUTOMOBILE AIR CONDITIONING SYSTEM

MAIN COMPONENTS:-

1. COMPRESSOR2. CONDENSER 3. MEGNETIC CLUTCH4. ACCUMULATOR

/RECEIVER DRYER5. EXPANSION VALVE6. EVAPORATOR

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.

COMPRESSOR

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. CONDENSER

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.

MEGNETIC CLUTCH

ACCUMULATOR :-The accumulator is fitted between the

evaporator and the compressor. The function of the accumulator-

To ensure that the refrigerant leaves the accumulator as a vapour and not a liquid state for the compressor to induce.

To ensure it is free from dart, to stop any excessive wear premature failure to components.

To act as a temporary reservoir to supply the system under varying load condition.

ACCUMULATOR

EXPANSION VALVE:-The refrigerant goes from the receiver-drier to the expansion valve where a sudden expansion to a much lower pressure occurs. The expansion valve is operated by opposing pressures on either side of the diaphragm. If the evaporator outlet temperature is higher the refrigerant expands and exerts more pressure against the diaphragm, there by, providing a greater opening to the expansion valve and hence, a greater flow of refrigerant into the refrigerant into the evaporator for increased cooling. When the outlet temperature of the evaporator is low, the expansion valve starts closing

EXPANSION VALVE

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.

EVAPORATOR

TYPES OF CONTROL SYSTEM:-

In order to control the function and operation of a unit, there are four basic cycles and mechanical systems used. This systems are as follows-

A. Low side pressure controlB. Pressure operated by-passC. Solenoid operated by-passD. Electromagnetic clutch

LOW SIDE PRESSURE CONTROL:-In this system, an evaporator pressure controlled regulator valve is installed in the suction line. A constant pressure is kept in the evaporator by this valve. If the evaporator tends to go below a certain setting while holding the evaporator at constant pressure and temperature the valve would close.

This pressure control prevents the compressor from a producing a high vacuum at high speeds causing the compressor to loss its oil. A system with an automatic expansion valve having small bleeder hole in the orifice is used to overcome this problem. To prevent a high vacuum from forming, a small amount of refrigerant enters the suction line. In this system, the compressor is run continuously.

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.

SOLEOID OPERATED BYPASS:-

In order to open a solenoid valve and bypass the hot gas from the high pressure side to the low pressure side when the temperature of the evaporator falls to 0°C, a thermostat mounted on the evaporator is used. It is located in the return air flow with the sensing bulb. When the return air temperature is lowered, so that the thermostat is at the temperature of 0°C, the solenoid valve opens to allow hot gas from the condenser to bypass back into the suction line. This valve does not provide the throttling effect of a pressure operated valve since it is either closed or wide opened. In this system either a continuous operating compressor or a rotary compressor is used. When the circuit is closed or when the current is on, the solenoid is in a closed position. When the circuit is open, the valve also opens. Hence the thermostat opens on temperature drop.

ELECTROMAGNETIC CLUTCH:-

In certain automobiles air-conditioning systems a mechanism permitting the engine to run without the compressor running is used. To engage the compressor belt pulley to the compressor crankshaft or the disengage it a clutch is used. This clutch operated by electromagnetism by forcing the clutch disk against the pulley is known as magnetic clutch. Two types of magnetic clutches used are- revolving magnetic coil and stationary magnetic coil.

Theory

RefrigerantAir condition cycle

WORKING:-