1. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-1 Heat always moves from hot to cold. In this example, it will travel from the fire to the cooler water and from the hand to the cooler ice.

2. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-2 Heat can enter a vehicle’s passenger compartment from several sources. The A/C system allows us to move excess heat out of the vehicle. (Courtesy of Toyota Motor Sales USA, Inc.)

3. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-3 The transfer of heat directly through a material is called conduction. (Courtesy of Chrysler LLC)

4. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-4 We move heat from the heater to the passengers or from the passengers to the A/C system by convection. Heat movement from the engine to the radiator using circulating coolant is also an example of convection.

5. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-5 Heated air next to the stove will rise and cooler air will move in to replace it. This creates a convection current to move the air and heat. (Courtesy of Chrysler LLC)

6. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-6 Heat is transferred from the sun to things on Earth through radiation. (Courtesy of Toyota Motor Sales USA, Inc.)

7. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-7 Radiant heat entering a vehicle through the windows can add a lot of heat to a car’s interior. (Courtesy of Chrysler LLC)

8. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-8 We can cause matter to change state by adding or removing heat.

9. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-9 A water molecule contains two oxygen atoms and one hydrogen atom; R-12 is a combination of one carbon, two chlorine, and two fluorine atoms; R-134a is a combination of two carbon, four fluorine, and two hydrogen atoms; and R-152a has two more hydrogen and two less fluorine atoms than R-134a.

10. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-10 Ice is a solid form of water with a low temperature and slow molecular action.

11. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-11 Water is warmer than ice and has a much freer molecular action.

12. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-12 Adding heat to water produces steam, the gas state, with a much freer molecular action.

13. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-13 Heat that causes a temperature increase is called sensible heat.

14. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-14 If we add 970 Btu of heat to 1 lb of water at 212°F,we will have 1 lb of steam at the same temperature.

15. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-15 If we start with 1 lb of water at 32°F, adding 180 Btu will increase the temperature to 212°F. It will take another 970 Btu (the latent heat of evaporation) to boil that pound of water.

16. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-16 In an A/C system, the refrigerant changes state and absorbs heat in the evaporator and releases heat as it changes state again in the condenser.

17. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-17 If we start with a 1-lb block of ice at 32°F, it will take 144 Btu (the latent heat of fusion) to melt all of the ice.

18. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-18 The amount of heat movement required to change 0°F ice to steam, or vice versa.

19. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-19 A refrigeration cycle absorbs heat as the refrigerant boils in the evaporator and removes heat as it changes state back to a liquid in the condenser.

20. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-20 The boiling point of a liquid changes as the pressure changes. Water will boil at 183°F with a pressure of 13 psi on a mountain. It will boil at 212°F at an atmospheric pressure of 14.7 psi. In a radiator at a pressure of 30 psi (absolute), it will boil at 250°F.

21. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-21 R-12 in a container is a saturated vapor with gas in contact with a liquid. The pressure in the container is in direct relation to the temperature (a); a chart can be used to determine the temperature if we know the pressure, or vice versa (b). (a. Courtesy of Chrysler LLC; b. Courtesy of Four Seasons)

22. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-22 The weight of the air in our atmosphere generates a pressure of about 15 psi at sea level. Atmospheric pressure and the boiling point of water are lower at higher altitudes (Courtesy of Chrysler LLC)

23. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-23 As shown on this compound gauge, pressures below atmospheric are commonly called a vacuum (a). A perfect vacuum is 29.92 inches of mercury (b). (a. Courtesy of TIP Instruments; b. Courtesy of Robinair, SPX Corporation)

24. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-24 The boiling point of water drops as pressure is reduced. At a near-perfect vacuum of 29.9199 δHg or 2.54 microns, the boiling point is 90°F.(Courtesy of Robinair, SPX Corporation)

25. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-25 The relative pressures between seven different measuring systems.

26. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-26 Depending on the combination of carbon, chlorine, fluorine, or hydrogen, a refrigerant is classed as an HFC, CFC, or HCFC. (Courtesy of TIF Instruments)

27. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-27 Comparison of the physical characteristics of R-12 and R-134a. (Courtesy of Zexel USA Corporation)

28. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-28 Refrigerant is commonly available in small or large (30- or 50-lb) containers. A 30-pound, disposable container of R-12 and small, 12-ounce can of R-134a is shown.

29. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-29 A refrigerant and its oil must be completely compatible with all of the materials and chemicals in the system.

30. Automotive Heating and Air Conditioning, Fifth Edition By Tom Birch © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 4-30 The boiling points for R-12, R-22, and R-134a vary depending on the pressure.