1. Objectives
Psychometrics
Examples in AHUs

4. Humidification hw Specific enthalpy of water added to system
hg Specific enthalpy of saturated water vapor

5. Evaporative Cooling (air washing)

6. Air Washer Sprays liquid water into air stream
Typically, air leaves system at lower temperature and higher humidity than it enters

7. Air Washers/Evaporative Coolers
Heat and mass transfer is mutually compensating
Can evaluate based on temperature drop, humidification, or comparison to other energy exchangers

8. Evaporative Cooler 8

9. Cooling Tower
Similar to an evaporative cooler, but the purpose is often to cool water
Widely used for heat rejection in HVAC systems
Also used to reject industrial process heat

10. Processes in AHU and buildings

11. Systems: Single-Zone Air Systems
Zone – any space with a thermostat

12. Air conditioning 12

13. Reheat 13

14. Recirculation 14