Adiabatic Process Psychrometric Chart
There are two common psychrometric design processes for evaporative humidification.
Sensible heating: red horizontal lines
Evaporative humidification: blue oblique lines
Heating + humidification (line A-B-C)
Pre-heating + humidification + post heating (line A-D-E-C)
Both processes have humidity ratio (Δx) increase:
from Xin (A) to Xout (C).
The Saturation Efficiency (η) or Cooling Efficiency is expressed in % and corresponds to the ratio between the entering dry bulb temperature and exiting dry bulb temperature over the wet bulb depression:
η = Real cooling/ Ideal cooling = (Tin – Tout ) / (Tin – Twb )
- Tin is the inlet air dry bulb temperature,
- Tout is the outlet air dry bulb temperature,
- Twb is the wet bulb temperature.
For the humidification process B-C: the pad efficiency is smaller, and its thickness is thinner.
For the humidification process D-E: the pad efficiency is higher, and its thickness is bigger.
Direct evaporative humidification adds humidity to the supply air.
Heating + Humidification
Pre-heating + Humidification + Post Heating