Ac principles of operation
- 1. Automotive HeatingAutomotive Heating and Air Conditioningand Air Conditioning CHAPTER Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch SEVENTH EDITION Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Heating and Air-Conditioning Principles 3
- 2. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Learning ObjectivesLearning Objectives • Prepare for the ASE Heating and Air Conditioning (A7) certification test content area “A” (A/C System Service, Diagnosis and Repair). • Discuss the changes of states of matter. • Discuss the effect of heat and temperature on matter. continued on next slide
- 3. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Learning ObjectivesLearning Objectives • Discuss the two types of humidity. • Explain heating and cooling load. • Explain the three ways in which heat flows. • Describe the air-conditioning process. • Explain the purpose of an HVAC system.
- 4. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Changes of States of MatterChanges of States of Matter • A solid is a substance that cannot be compressed and has strong resistance to flow. • The molecules of a solid attract each other strongly, and resist changes in volume and shape.
- 5. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Changes of States of MatterChanges of States of Matter • A substance is solid at any temperature below its melting point. • A liquid is a substance that cannot be compressed. • The boiling point is the temperature at which a liquid substance turns to vapor.
- 6. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Heat and TemperatureHeat and Temperature • Temperature is the measure of the level of energy. • Temperature is measured in degrees. • Heat is measured in the metric unit called calorie and expresses the amount of heat needed to raise the temperature of one gram of water one degree Celsius.
- 7. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Two Types of HumidityTwo Types of Humidity • Absolute humidity is the mass of water vapor in a given volume of air. • Relative humidity (RH) is the percentage of how much moisture is present in the air compared to how much moisture the air is capable of holding at that temperature.
- 8. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Heating and Cooling LoadHeating and Cooling Load • Heating load is the term used when additional heat is needed. The actual load is the number of BTUs or calories of heat energy that must be added. • In most vehicles, heated coolant is circulated through a heat exchanger, called a heater core.
- 9. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Heating and Cooling LoadHeating and Cooling Load • One way to move heat, called cooling load, is with a block of ice. • A substantial amount of latent heat is required to change the state of the solid ice into a liquid.
- 10. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Figure 3–8 Winter presents a heat load where heat must be added for comfort (right). Summer presents a cooling load.
- 11. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Figure 3–9 Ice has a cooling effect because of latent heat of fusion which means that it absorbs heat as it melts.
- 12. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Figure 3–10 At one time, evaporative coolers were used to cool car interiors. Air forced through a water- wetted mesh produces evaporation and a cooling effect.
- 13. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Figure 3–11 Heat, from in-vehicle cabin air, causes the refrigerant to boil in the evaporator (left). The compressor increases the pressure and moves refrigerant vapor to the condenser, where the heat is transferred to ambient air. This also causes the vapor to return to liquid form.
- 14. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Three Ways Heat FlowsThree Ways Heat Flows • The simplest heat movement method is conduction, by which heat travels through a medium such as a solid or liquid, moving from one molecule of the material to the next. • Convection is a process of transferring heat by moving the heated medium, usually air or a liquid. continued on next slide
- 15. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Three Ways Heat FlowsThree Ways Heat Flows • Heat can travel through heat rays and pass from one location to another without warming the air through which it passes.
- 16. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Figure 3–12 Heat can be moved from the source by convection, conduction, or radiation.
- 17. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Air-conditioning ProcessAir-conditioning Process • The air-conditioning process works using a fluid, called refrigerant, which continuously changes state from liquid to gas and back to liquid. • Most states of matter can be changed from one state to another by adding or removing heat.
- 18. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Air-conditioning ProcessAir-conditioning Process • The three states of water are well known and include: 1. Solid ice 2. Liquid water 3. Vapor (gaseous)
- 19. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Figure 3–15 Ice is a solid form of water with a low temperature and slow molecular action.
- 20. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Figure 3–16 Water is warmer than ice and can flow to take the shape of any container.
- 21. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Figure 3–17 Adding heat to water produces steam, the gas state, with a much freer molecular action.
- 22. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Purpose of an HVAC SystemPurpose of an HVAC System • The goal in heating and air conditioning is to maintain a comfortable in-vehicle temperature and humidity. • Humid cold air feels much colder than dry air at the same temperature. • The act of cooling and dehumidifying air at the A/C evaporator causes water droplets to form on the evaporator fins.
- 23. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved Figure 3–18 When air comes into contact with the cold evaporator, excess moisture forms dew. This condensed moisture leaves the car through the evaporator drain.
- 24. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved SummarySummary • Heat is moved into or out of the passenger compartment to obtain a good comfort level. • Heat intensity is measured using the Fahrenheit or Celsius scales, and heat quantity is measured using calories and BTU. continued on next slide
- 25. Automotive Heating and Air Conditioning, 7e James D. Halderman | Tom Birch Copyright © 2015 by Pearson Education, Inc. All Rights Reserved SummarySummary • The comfort zone of most humans is between 68°F and 78°F (20°C and 26°C) and 45% to 50% humidity. • A/C systems reduce humidity by removing moisture (water) from the air. • HVAC systems clean air because particles are caught by moisture on the evaporator and by filters.