Air Conditioning Circuit

1. Air Conditioning Circuit Columbia Basin College Automotive Technology

2. The Basic Cycle • Heat is picked up by the Evaporator Fins • Heat picked up by the liquid refrigerant as it evaporates. • Heat-laden refrigerant vapor is pumped by compressor into the condenser • The refrigerant in the condenser is given up to the less-hot air passing across the condenser coils as it condenses back to a liquid

3. Transfer of Heat Relies on Pressure Change • Low Pressure of 21-35 lbs - Temp of 21-28 degrees F • High Pressure of 180-220 lbs - Temp of 88-100 degrees F • Anytime there is a pressure change there is a temperature change • Anytime pressure & temp changes there is a change of state

4. Pressure’s Effect on Gases and Vapors • Pressure affects the temperature of gases and vapors by raising it’s boiling point. • Compressing a gas or vapor increases its temperature because the same amount of heat is concentrated into a smaller space. • The temperature of the gas or vapor can be raised without adding extra heat.

5. Refrigerant Changes State • Low Pressure side - Liquid to a Vapor • Low side tubing is often cool enough to collect frost or water droplets on high humidity days. • High Pressure side - Vapor to a Liquid • Tubing diameter is often smaller than on the low side • Hotter than the low side tubing

6. Temperature - Pressure Relationship • Heating refrigerant causes it to expand. Different refrigerants have different expansion rates. • When confined in a enclosed place, a increase temperature is always accompanied by an increase in pressure. • For a given temperature, a corresponding pressure will exist in a container of R-12 or R134a

7. Basic A/C System • Two copper coils • one coil is evaporator • one coil is condenser • Between coils is a compressor • Fans page 68C

8. Compressor • Pulls in low-pressure vapor • Pumps out high-pressure vapor • Provides a endless cycle of cooling • Condenses, Evaporating and heating • Raises pressure and temperature of refrigerant entering condenser to a point where it can transfer heat to outside air through the condenser

9. SERVICE VALVES

10. A/C Service Connectors

11. Condenser • Located in front of radiator • Compressor pumps high pressure vapor into condenser where ram air passing over coils carries off heat • The heat loss causes the refrigerant to become a high-pressure liquid.

12. Expansion Valve or Fixed Orifice Tube • Provides a restriction in refrigerant flow which the compressor can build up a pressure in the condenser. • Compressor suction lowers pressure in the evaporator • Regulates pressure differential between the high and low sides. • Keeps evaporation and expansion of refrigerant and most efficient level.

13. Evaporator • Function is opposite of condenser • Evaporator coils remove heat and humidity from the air being circulated in passenger compartment. • When liquid refrigerant absorbs heat, it again becomes a vapor under low pressure • Has a tray to collect moisture from fins

14. Fans • One fan to circulate air through evaporator fins • One fan to circulate air through condenser fins

15. High Pressure Side • High side includes • Discharge side of Compressor • High Pressure vapor lines to condenser • Condenser • High Pressure liquid lines to orifice valve • Inlet side of orifice Valve

16. Low Pressure Side • Includes: • Orifice • Low Pressure Liquid lines • Evaporator • Low Pressure Vapor Lines • Suction side of Compressor • Outlet side of orifice valve