Lecture Objectives:

1
Lecture Objectives

• Review Psychrometrics
• Introduce Air Handling Unit
• Analyze swimming pool dehumidification example

2
HW1

• Psychrometrics
• Due February 10, 2015
• Textbook (Thermal Environmental Engineering)
  problems
• 8.1, 8.8, 8.13, 8.20
• 3.2, 3.5
• 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)

4
(No Transcript)
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)
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Swimming pool energy and mass balance
8
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
9
Air handling units (AHUs)
Major components - ..
10
Major AHU Components
Humidifiers
Heat Exchangers
Steam
Air to air
Water
Water (mist)
AHU Fans
Air - water or air - refrigerate
Many more
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Positioning of AHUs
AHU Air Handling Unit
Distribution systems
Fresh air For ventilation
AHU
Primary systems
Air transport
Electricity
Secondary systems
Cooling (chiller)
Heating (boilers)
Building
Gas
(or Gas)
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Process in AHUs

• Example AHUs for swimming pools

MENERGAThermoCond 19
13
Swimming pool heating
14
Dehumidification using outside air in Winter and
Summer
15
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