CHAPTER 13 Gas – Vapor Mixtures and Air-Conditioning

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

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

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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display 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.

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

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

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

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

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

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

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

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

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

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

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

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

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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display FIGURE 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.

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

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