Achieving Dry Outside Air in an Energy-Efficient Manner

1
Achieving Dry Outside Air in an Energy-Efficient
Manner
PSU
Stanley A. Mumma, Ph.D., P.E., Professor,
and Kurt M. Shank, M.S. Graduate Department of
Architectural Engineering College of
Engineering Penn State University _at_ University
Park, PA
Building Thermal and Mechanical Systems Laboratory
2
Presentation Outline

• Introduction and Objectives
• Potential Dedicated OA System Configurations
• Psychrometric Analysis of the DOAS
• Load and Hourly Energy Analysis of the
  Configurations
• Conclusions and Recommendations

3
Objective

• Develop a fundamental understanding of OA
  preconditioning equipment for dedicated OA
  systems composed of
• Passive desiccant wheels,
• Sensible heat exchangers,
• Deep dehumidification cooling coils.
• Present the design load and energy performance
  perspective.

4
Potential Configurations

• 1, Conventional Cooling Coil, Heating Coil, and
  Humidifier

Humidifier
HC
CC
OA
5

• 2, A Run around heat recovery system added to
  configuration 1.

Humidifier
HC
CC
OA
6

• 3, Passive Desiccant (Enthalpy) wheel added to
  the heating and cooling coils

RA
HC
CC
OA
EW
7

• 4, Enthalpy wheel, Cooling Coil and run around
  Heat Recovery

8

• 5, Dual Wheel DOAS Unit

State Point , typ
80F DBT, 55F DPT
RA
6
5
CC
3
0
1
2
4
55F DBT, 45F DPT
OA
45F
SW
PH
EW
9

• 6, Conventional All Air VAV System with air side
  Economizer.
• Illustration unnecessary

10
Design energy demand to treat10,000 scfm of OA
in Atlanta
Conf. CC load Tons Humid- ification k-Btu/hr Heating k-Btu/hr
1 94 238 465
2 85 238 465
3 51 0 108
4 43 0 108
5 43 0 0
6 85 238 0
11
Energy consumed to treat 10,000 scfm of OA in
Atlanta (3744 hr)
Conf. CC TH Reheat k-Btu Heating k-Btu Humid ification k-Btu
1 113,000 255,000 110,000 155,000
2 103,000 14,800 110,000 155,000
3 103,000 255,000 7,000 0
4 83,000 14,800 7,000 0
5 89,000 0 0 0
6 92,000 0 0 155,000
12
Four Regions on the Psych. Chart, w/ Atlanta Data
Region A, 1,635 hours
Region B, 784 hours
Region D, 214 hrs
5
6
Wet regions
3
4
Dry regions
Region C, 1,111 hours
70 80
45 55
13

• 5, Dual Wheel DOAS Unit

State Point , typ
80F DBT, 55F DPT
RA
6
5
CC
3
0
1
2
4
55F DBT, 45F DPT
OA
45F
SW
PH
EW
14
Region A, enthalpy wheel, cooling coil, and sen.
wheel
1
Key 1-2-6, enthalpy wheel 2-3, cooling coil 5-6,
3-4, sen. wheel
2
5
6
3
4
70 80F
45 55
15
Region B, cooling coil,and sen. wheel
Key 1/2-3, cooling coil 5-6, 3-4, sen. wheel
1,2
5
6
3
4
70 80F
45 55
16
Region C, enthalpy wheeland cooling coil
Key 1-2-5/6, enthalpy wheel 2-3/4, cooling coil
5, 6
2
3, 4
1
70 80F
45 55
17
Region D, enthalpy wheel,and sen. wheel
Key 1-2-6, enthalpy wheel 5-6, 3-4, sen. wheel
6
5
2
3
4
1
70 80F
45 55
18
Control Status of DOAS Equipment (See Tech Paper
4428)
Region Enthalpy Wheel, CTL CC, CTL Sensible Wheel, CTL
A Max speed and effectiveness Modulate to hold 45F Modulate to hold 55F
B Off Modulate to hold 45F Modulate to hold 55F
C Mod. Speed to reqd DPT Modulate to hold 55F Off
D Mod. Speed to reqd DPT Off Modulate to hold 55F
19
Conclusions

• The DOAS, configuration 5, exhibits superior
  demand and energy performance when compared to
  the other configurations analyzed.
• The DOAS assures verifiable ventilation delivery.
• Decoupled sensible and latent cooling contributes
  to improved comfort, health and productivity

20
Recommendation

• Make the transition to dedicated OA designs.
• Use configuration 5 to decouple the space
  sensible and latent loads.
• Save energy, improve quality of the spaces, and
  minimize litigation potential.