1. Objectives Humidifying - steam - adiabatic Cooling towers
AHU processes

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

3. Evaporative Cooling (air washing)

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

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

6. 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

8. Processes in AHU and buildings

9. Air conditioning

10. Single-Zone Systems
Zone – any space with a thermostat

11. Recirculation

12. Reheat

13. Evaporative Cooler

14. Air-to-air heat exchanger