1. Lecture Objectives: Review Psychrometrics Introduce Air Handling Unit
Analyze swimming pool dehumidification example

2. HW1 Psychrometrics Due: September 18
Textbook (Thermal Environmental Engineering) problems:
8.1, 8.8, 8.13, 8.20
You have posted section 8 of this book

3. Psychrometric Chart Need two quantities for a state point
Can get all other quantities from a state point
Can do all calculations without a chart
Often require iteration
Many “digital” psychrometric charts available
Can make your own
Best source is ASHRAE fundamentals (Chapter 6)

5. Connection between W and Pw (W humidity ratio – Pw water partial pressure)
PV = mRT (Ideal Gas Law )
P = Pw + Pa
R = gas constant
P = pressure
V = volume
T = absolute temperature
W = humidity ratio
Subscripts: w is water vapor, a is dry air

6. Psychrometrics (Swimming pool example)

7. Swimming pool energy and mass balance

8. Evaporation Heat loss by evaporation: hm
Tpool
Tair
pool
W s W ≈ hm Ws
Tpool
Wair
pool
Depends on the air speed and even
more on the condition of the water surface
(people splashing in the water)
Further analysis can be conducted in the psychrometric chart

9. Air handling units (AHUs)
Major components
- …..

10. Major AHU Components Heat Exchangers Humidifiers Steam Air to air
Water
Water (mist)
AHU Fans
Air - water or air - refrigerate
Many more …

11. Positioning of AHUs Distribution systems Fresh air AHU For ventilation
AHU – Air Handling Unit
Distribution
systems
Fresh air
For ventilation
AHU
Primary
systems
Air transport
Electricity
Secondary
systems
Cooling
(chiller)
Heating
(boilers)
Building
(or Gas)
Gas

12. Process in AHUs
Example AHUs for swimming pools
MENERGA ThermoCond 19

13. Swimming pool heating

14. Dehumidification using outside air in Winter and Summer

15. More advance control
MENERGA
ThermoCond 29

16. Dehumidification using outside air in winter
Condenser in the air stream
Evaporator
Compressor of
the heat pump
Condenser in the swimming pool

17. Recirculation of air with dehumidification
catalog