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A/C SYSTEM THEORY

A/C SYSTEM THEORY. Sources which create Heat inside the vehicle. Sunlight. Other miscellaneous sources. Engine Heat. Road Heat, Transmission, Exaust system. Comfort inside. The comfort inside the passenger compartment is guarantee by : Proper temperature managment

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A/C SYSTEM THEORY

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  1. A/C SYSTEM THEORY

  2. Sources which create Heat inside the vehicle Sunlight Other miscellaneous sources Engine Heat Road Heat, Transmission, Exaust system

  3. Comfort inside • The comfort inside the passenger compartment is guarantee by : • Proper temperature managment • Low air humidity level • Good quality of the air, assured by cabin filter

  4. Heat = thermal energy Cold object = Low Energy Hot object = High Energy Kinetc energy of all molecules

  5. Temperature The temperature of a body indicates the heat concentration level contained in it: the measuring unit is the “grade” 100 0 COLD body Low energy level Low Temperature HOT body High energy level High Temperature

  6. Heat Movement WARM Object HIGH Temperature COOL object LOW Temperature HEAT Heat always moves from HOT to COLD. Whenever there is a temperature difference between two object, the heat energy will be trasferred from the warmer object to the cooler one, until both object have stabilized at the same temperature

  7. Methods of Moving Heat CONDUCTION: occurs by contact between two bodies without movement of matter (typical among solid) CONVECTION: occurs by movement of matter (typical in fluids) RADIATION: occurs between different bodies not in contact (typical infrared rays)

  8. Pressure Stratosphere Ozone barrier The atmospheric pressure in a given point of the atmosphere is the weight of the air column which goes from the above mentioned point to the higer limit of the same atmosphere. Common measuring unit: 1 Kg/ cm2 = 1 Atm = 1 Bar

  9. Changes of State Sublimation Solid state Liquid State Gaseous State Fusion Evaporation Solidification Condensation Solid and Liquid substances together are olso known as Fluid

  10. Temperature 100° Liquid+Vapour State The HEAT causes the change of state Vapour State The HEAT increases the temperature Liquid State The HEAT increases the temperature 20° Heat Evaporation = Heat Absorption at constant Temperature

  11. Temperature Scales CELSIUS (°C) -273 0 100 FAHRENHEIT (°F) -459 32 212 KELVIN (°K) 0 273 373

  12. Absolute and Relative Pressure Atmospheric Pressure R. P. (Kg/cm2) -1 0 1 2 3 4 5 6 A. P. (Kg/cm2) 0 1 2 3 4 5 6 7 Vacuum

  13. Refrigerant fluid The refrigerant fluid is a substance that absorb and transport the heat during circulation in the refrigeretor circuit. Comparison of the most important properties: R134a R12 Chemical formula CH2FCF3 CCL2F2 Boiling point at 1 bar abs. -26,5 -29,8 (°C) Critical pressure 39,45 41,1 (bar) Pressure of vapor at 25 °C 6,62 6,51 (bar) Ozone destruction potential (ODP) 0 1

  14. R134a - R12Pressure-Temperature relationship chart

  15. Refrigerator Circuit Condenser Expansion valve Compressor Evaporator

  16. A/C System working(evaporation) Incoming external air hot at high humidity level +30°C LIQUID Refrigerant Low pressure Low temperature Low heat q.ty 1 bar, - 20 °C, 500Kcal Subtraction of HEAT from air duting the refrigerant evaporation GASEOUS Refrigerant Low pressure Low temperature High heat q.ty 1 bar, - 20 °C,6.500Kcal Cold air at low humidity level +8 °C

  17. A/C System working Condenser GASEOUS refrigerant 18 bar 60 °C (with HEAT inside) HIGH PRESSURE (high temperature) DIS SUC Expansion Valve Compressor LOW PRESSURE (low temperature) LIQUID refrigerant 1 bar - 20 °C (without HEAT) HEAT absorption GASEOUS refrigerant 1 bar - 20 °C (with HEAT inside) Evaporator

  18. A/C System working(condensation) External air +30 °C GASEOUS Refrigerant High pressure High temperature High heat q.ty 16 bar, +60 °C,6.500Kcal Refrigerant yeld to external air the Heat during condensation LIQUID Refrigerant High pressure High temperature Low heat q.ty 16 bar, +60 °C, 500Kcal +45 °C

  19. A/C System working Condenser LIQUID refrigerant 18 bar 60 °C (without HEAT) GASEOUS refrigerant 18 bar 60 °C (with HEAT inside) HEAT discharge Engine side High pressure side (high temperature) External air Expansion Valve Compressor Low pressure side (low temperature) Passenger compartment GASEOUS refrigerant 1 bar - 20 °C (with HEAT inside) HEAT absorption LIQUID refrigerant 1 bar - 20 °C (without HEAT) Evaporator

  20. A/C System Condenser Compressor Evaporator Filter dryer Expansion valve

  21. Thanks for your attention

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