1. CHAPTER 13 Gas – Vapor Mixtures and Air-Conditioning

2. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-1 FIGURE 13-1 The C p of air can be assumed to be constant at 1.005 kJ/(kg · °C) in the temperature range - 10 to 50°C with an error under 0.2 percent.

3. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. FIGURE 13-2 At temperatures below 50  C, the h = constant lines coincide with the T = constant lines in the superheated vapor region of water. 13-2

4. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-3 FIGURE 13-4 For saturated air, the vapor pressure is equal to the saturation pressure of water.

5. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-4 FIGURE 13-5 Specific humidity is the actual amount of water vapor in 1 kg of dry air, whereas relative humidity is the ratio of the actual amount of moisture in the air to the maximum amount of moisture air can hold at that temperature.

6. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-5 FIGURE 13-6 The enthalpy of moist (atmospheric) air is expressed per unit mass of dry air, not per unit mass of moist air.

7. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-6 FIGURE 13-8 Constant- pressure cooling of moist air and the dew-point temperature on the T-s diagram of water.

8. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-7 FIGURE 13-11 The adiabatic saturation process and its represen-tation on a T-s diagram of water.

9. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-8 FIGURE 13-12 A simple arrangement to measure the wet- bulb temperature.

10. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-9 FIGURE 13-14 Schematic for a psychrometric chart.

11. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-10 FIGURE 13-15 For saturated air, the dry-bulb, wet- bulb, and dew- point temperatures are identical.

12. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-11 FIGURE 13-20 Various air- conditioning processes.

13. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-12 FIGURE 13-21 During simple heating, specific humidity remains constant, but relative humidity decreases.

14. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-13 FIGURE 13-22 During simple cooling, specific humidity remains constant, but relative humidity increases.

15. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-14 FIGURE 13-23 Heating the humidification.

16. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-15 FIGURE 13-24 Schematic and psychrometric chart for Example 13–5.

17. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-16 FIGURE 13-25 Schematic and psychrometric chart for Example 13–6.

18. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-17 FIGURE 13-27 Evaporative cooling.

19. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-18 FIGURE 13-29 When two airstreams at states 1 and 2 are mixed adiabatically, the state of the mixture lies on the straight line connecting the two states.

20. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-19 FIGURE 13-31 An induced-draft counterflow cooling tower.

21. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13-20 Photo credit: Yunus Çengel FIGURE 13-33 A spray pond.