1. Lecture Objectives: Finish heat pump example Review Psychrometrics
Swimming pool example

2. Heat pump example A recreation center Heat Pump Ice Rink Swimming pool
Condenser
Evaporator
85-89oF
30oF
Consumes heat energy
Rejects heat energy
Electric power
for a compressor

3. Ice Rinks
Energy flow

4. Challenges for this problem
Circulating fluid
Adjustment of evaporation and condensation temperatures
Adjustment of capacity for design condition
Control of capacity for non design conditions
Need to study load profiles
Design sophisticated control
Provide backup system

5. Psychrometrics (Swimming pool example)

6. 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)
Or electronic version at:

8. 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

9. Swimming pool energy and mass balance

10. 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

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

12. Swimming pool heating

13. Dehumidification using outside air in Winter and Summer

14. More advance control
MENERGA
ThermoCond 29

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

16. Recirculation of air with dehumidification
catalog