Lecture Objectives:

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Lecture Objectives

• Finish heat pump example
• Review Psychrometrics
• Swimming pool example

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

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Psychrometrics (Swimming pool example)
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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/

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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
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Swimming pool energy and mass balance
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Evaporation

• Heat loss by evaporation

Tpool
Tair
pool
W s
W
hm

Wair
Tpool
Ws
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
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Process in AHUs

• Example AHUs for swimming pools

MENERGAThermoCond 19
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Swimming pool heating
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Dehumidification using outside air in Winter and
Summer
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More advance control
MENERGA ThermoCond 29
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Dehumidification using outside air in winter
Condenser in the air stream
Evaporator
Compressor of the heat pump
Condenser in the swimming pool
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Recirculation of air with dehumidification
catalog