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Heat pump example
Heat Pump
Consumes heat energy Rejects heat energy
A recreation center
Ice Rink Swimming pool
Electric power for a compressor
EvaporatorCondenser
85-89oF 30oF
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
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:
http://www.handsdownsoftware.com/
Connection between W and Pw(W humidity ratio – Pw water partial pressure)
• PV = mRT (Ideal Gas Law )
• P = Pw + Pa
w
a
a
w
TRVP
TRVP
a
w
R
R
P
P
m
mW
a
a
w
w
w
w
PP
PW
622.0
R = gas constantP = pressureV = volumeT = absolute temperatureW = humidity ratio
Subscripts: w is water vapor, a is dry air
Evaporation
• Heat loss by evaporation:
pool W s W Tair
Tpool
hm pool WsTpool Wair
Further analysis can be conducted in the psychrometric chart
≈
Depends on the air speed and even more on the condition of the water surface (people splashing in the water)
Dehumidification using outside air in winter
Condenser in the swimming pool
Evaporator
Condenser in the air stream
Compressor of the heat pump
Recirculation of air with dehumidification
catalog