Technical Seminar on Refrigeration Air Conditioning

2. INTRODUCTION The electrical energy is utilized by converting it into one form or other for getting suitable output from it. The utilization electrical energy for the refrigeration and air conditioning is fast replacing the old methods.

3. WHAT IS REFRIGERATION & AIR CONDITIONING ? The process of reducing the temperature of a body from the general level of temperature of surroundings is called refrigeration. Air-conditioning means control of temperature,humidity,purity and movement of air. The working conditions and comfort for human beings is improved by air-conditioning. The temperature is brought down during summer and increased during winter without causing any discount.

4. REFRIGERATOR This is the machine by which the temperature of substances is lowered by storing them in this machine.

5. PRINCIPLE A refrigerator works on the principle of cooling caused by evaporation. when we dip our finger in petrol or spirit,and the finger is taken out cooling is felt. This is because when petrol or spirit evaporates it draws heat from the finger thus cooling it.

6. REFRIGERANT The refrigerant is generally a gas which circulated through different stages to extract the heat from the substances. The various refrigerants used are carbon dioxide(CO2),sulphur dioxide(SO2),ammonia(NH3),Freon(F-12) and methyl chloride etc.

7. VAPOUR COMPRESSION CYCLE The main purpose of vapour compression cycle is to remove heat from the refrigerant by putting it into a stage for reuse. The various stages are 1.compression 2.condension 3.expansion 4.evaporation

8. APPLICATION The vapour compression refrigeration cycle is employed for the following purposes Domestic refrigerator, Water cooler, Air conditioner, Ice plant, cold storage etc.

9. DOMESTIC REFRIGERATOR The actual lay out of domestic refrigerator is shown in figure below.

10. ELECTRICAL CIRCUIT OF REFRIGERATOR The main parts of the electrical circuit are shown in figure below The various parts are 1. motor compressor unit 2. starting relay 3. thermostat 4. overload protector 5. cabinet light 6. drier assembly.

11. MOTOR COMPERESSOR UNIT The motor is a single phase capacitor start motor. The actual capacity of the motor depends upon the size of the refrigerator. But generally the horsepower of motors varies from 7/32 H.P. to 1/8 H.P. Mostly the motor and compressor are in one unit and is known a sealed unit.

12. STARTING RELAY The motor is operated by this relay which is also called motor protective relay. It essentially consists of a plunger on which a coil is wound . The figure below shows the arrangement:

13. THRMOSTAT A thermostatic switch is used on all the household refrigerators by which the temperature is controlled, and it is called thermostat. The construction of a thermostat used in a refrigerator is shown in figure below:

14. OVERLOAD PROTECTOR This is a thermal device which opens the circuit of the motor when overloaded and is called overload protector. The figure below shows the enlarged view of a overload protector.

15. CABINET LIGHT This circuit contains a lamp and a switch. The switch is called door switch and so installed that when the door is closed,the bulb remains off. When the door is opened, the bulb remains on.

16. DRIER ASSEMBLY This assembly is not employed on all the domestic refrigerators. This is a high resistance wire passing around the drier to remove the moisture from the refrigerator. This is connected across the supply by the thermostat.

17. AIR-CONDITIONER The room air conditioner is used to condition the air of a particular space occupied by the human beings i.e. office, room etc. It has automatic operation to control and maintain the humidity of air. There are two parts divided by a partition with a small opening at the top as 1.outdoor part 2.indoor part

18. AIR-CONDITIONER The complete operation of an air conditioner can be studied under these sub headings- 1.vapour compression cycle 2.air circulation 3.electrical circuit The figure below shows a room air conditioner