dP(ft) 83
dP (ft)
35
dP (ft) 41
105
140
180
188
AHU 3
1,800
GPM
Tout(F)= 50
Tin (F)= 40
9000
Managing
Delta T
in Buildings
AHU 2
Tout(F)= 50
1,800
GPM
Tout(F)= 50.0
1,800
GPM
AHU 1
192.5 FT
5,400
77
Tret (F)=
GPM
309 HP
270
221
50.0
Tsup(F)=
HX Building Side
Building Pump
HX DC Side
DC
Pump
1
Presented By:
Henry W. Johnstone, P.E.
President and Director of Mechanical Engineering
GLHN Architects & Engineers, Inc.
MBH
DC
Pump
1
Chiller 1
Chiller 2
40
Water Cooled
Air Conditioning
COP 7
0.6 kW/Ton
2.25Gal/Tonhr @ 5 Cycle
Steam cycle -450 Gal/MWH
Combined cycle -250 Gal/MWH
Building Cooling Load
Qc
W
Qh
Supply Air
ASHRAE Summer
Comfort Zone
Outdoor Air
Return Air
Flow Energy
Dry Bulb Wet Bulb Humidity
Flow
Content
Moisture Content
Airflow Enthalpy
ExtractedAir
Energy
Extracted
Moisture
O Air Type
O
3
3
btu/lbair(MBH)
gr/lb
(MBH)
(gal/hr)
(gal/hr)
( F)
( F)
(ft /min)
air
(ft
/min)
Outside
100.00
87.00
176.33
51.80 1838,500
1,500
325 12
19
Return
80.00Outside
63.94
63.70
29.14
1,084
41
1,500
Supply
55.00Return
54.00
60.81
22.60 2438,500
1,500
142 2
841
39
7
8,500
Difference
(Coil
Cooling)
183
12
243
2
Total Cooling
10,000
426
14
Air Type
The Coil Story
Cooling Coil
q (heat exchanged) = m (mass flow) Cp (specific heat) dT (log mean)
load (BTUH) = 500 x flow (gpm) x Dt WTR (°F) on the water side
and
load (BTUH) = 1.08 x flow (CFM) x dT AIR (°F) on the air side
The Coil Story
85
80
TEAT
75
Air Side
Temperature
70
65
Q
60
TLWT1
TLAT
dq
55
50
45
TEWT1
Water Side
40
35
1
2
Location
The Coil Story
85
80
TEAT
Temperature
75
Air Side
70
65
TLWT2
TLAT
60
55
50
45
TLWT1
TEWT1
Water Side
TEWT2
40
35
1
2
Location
The Coil Story
That Simple?
•
•
•
•
•
Dehumidification- Dewpoint
Airside Velocity- Wetability
Materials, Fin Configuration, Circuiting
Fouling
Water Velocity- Flow Regime - Turbulators
The Coil Story
That Simple?
• Dynamics
– Load Variations
– Control Loop Stability
TC
T
LAT
flow
temperature
pressure
MBH
CFM
EDB/EWB
The Coil Story
Specific flow rate, gpm per ton
Flow Rate as a Function of Water Temperature Difference (dT)
8
7
6
5
4
3
2
1
0
0
2
4
6
8
10
12 14
16 18
20 22
Water temperature difference, F deg
Q(gpm)
=
Load (Tons)
24
dt(oF)
24
The Coil Story
1200
1000
800
flow
600
dP
HP
400
Distribution System
hL = f L V 2
D 2
200
0
1
2
3
4
5
6
7
Pump Work (hp) = Head (ft) x flow (gpm)
3960 x eff
OR
Pump Work = k (flow)3
8
9
10
The Coil Story
20
EWT WRT LWT Flow MBH
18
40 18.1 58.1 120 1089
4.44 10.06 14.50 1902
90.8
41 16.6 57.6 132 1089
5.00
9.22 14.22 2092
90.8
14
42 15.0 57.0 146 1089
5.56
8.33 13.89 2314
90.8
12
43 13.4 56.4 163 1089
6.11
7.44 13.56 2584
90.8
10
44 111.7 55.7 186 1089
6.67
6.50 13.17 2948
90.8
7.22
5.56 12.78 3455
90.8
LWT
WTR
16
WTR
8
45 10.0 55.0 218 1089
EWT
dT
LWT
Flow
TR
6
46
8.3 54.3 263 1089
7.78
4.61 12.39 4169
90.8
4
47
6.5 53.5 336 1089
8.33
3.61 11.94 5326
90.8
2
0
0
40
4.44
41 42 43
5
5.56
6.11
44 45 46
6.67
EWT
7.22
47 48
7.78
8.33
EDB/EWB =
85/67
ACFM = 30,000
dP (ft) 13
82
85
98
100
AHU 3
1,000
GPM
Tout(F)= 58
Tin (F)= 40
9000
MBH
Case 1: 40 F EWT/58 LWT 18 F dT
Flow = 1,000 GPM
Case 2: 46 F EWT/54 LWT 8 F dT
Flow = 2,250 GPM
dP (ft) 13
82
85
dP (ft) 63
97
100
101
113
176
AHU 3
1,000
AHU 3
GPM
2,250
Tout(F)= 58
Tin (F)= 40
9000
77
Tout(F)= 54
Tin (F)= 46
9000
MBH
145.5 FT
GPM
9 HP
GPM
MBH
30.8 FT
1,002
188
2,252
108
106
77
GPM
97 HP
HX Building Side
Building Pump
222
213
HX Building Side
Building Pump
HX DC Side
Case 1: one coil
40 F EWT/58 LWT 18 F dT
1,000 GPM
31 ft dP
9 HP
HX DC Side
Case 2: one coil
46 F EWT/54 LWT 8 F dT
2,250 GPM
145 ft dP
97 HP
dP(ft) 83
dP (ft)
11
dP (ft)
dP (ft) 13
86
97
110
16
35
dP (ft) 18
41
90
100
113
106
135
124
176
AHU 3
AHU 3
1,000
1,200
1,800
GPM
Tout(F)= 58
Tin (F)= 40
9000
GPM
Tout(F)= 57
50
Tin
40
(F)= 42
Tin (F)=
9000
MBH
GPM
1,000
GPM
Tout(F)= 54
1,200
1,286
GPM
GPM
Tout(F)= 54.0
1,200
1,286
GPM
GPM
AHU
AHU 11
AHU 1
89.0 FT
FT
166.5
63.0 FT
3,000
77
GPM
56 HP
MBH
AHU
AHU 22
AHU 2
1,000
128
184
140
77
77
124
Tret (F)=
3,600
4,371
GPM
GPM
95 HP
HP
216
166
243
143
210
Tsup(F)=
52.4
40
HX
Side
Building Side
HX Building
HX Building Side
Building
Pump
Building Pump
Building Pump
HX DC Side
Case 1: three coils
All at 40 F EWT/58 LWT 18 F dT
3,000 GPM
63 ft dP
56 HP
HX
Side
DC Side
HX DC
Case 2:
3: three
three coils
coils
Case
All at
at 42
40 FF EWT/57
EWT in LWT 15 F dT
All
2 at 54
LWT 14 F dT
3,600
GPM
1 atft dP
50 LWT 10 F dT
89
4,371GPM
95
HP
167 ft dP
216 HP
-20.0
dP(ft) 83
dP(ft) 43
dP (ft)
dP (ft)
dP (ft) 21
18
135
131
110
92
35
dP (ft) 41
105
140
180
AHU 3
1,286
AHU 3
GPM
1,800
Tin (F)= 40
Tout(F)= 54
GPM
Tout(F)= 50
Tin (F)= 40
MBH
9000
9000
AHU 2
Tout(F)= 54
1,286
GPM
Tout(F)= 54.0
1,286
GPM
1,800
GPM
Tout(F)= 50.0
1,800
GPM
AHU 1
101.5 FT
77
Tret (F)=
192.5 FT
GPM
116 HP
MBH
AHU 2
Tout(F)= 50
AHU 1
3,857
5,400
152
179
Tsup(F)=
54.0
40
77
Tret (F)=
GPM
309 HP
270
221
50.0
Tsup(F)=
HX Building Side
HX Building Side
Building Pump
Building Pump
HX DC Side
HX DC Side
3900 GPM
DC
Pump
1
188
Chiller 1
Impact on DC Loop
5400 GPM
DC
Pump
1
DC
Pump
1
Chiller 1
Chiller 2
40
District Diagram
AHU 3
AHU 3
AHU 3
AHU 3
AHU2
AHU2
AHU1
AHU1
76.1 FT
3,600
GPM
55.0
40
HEAT EXCHANGER
76.1 FT
3,600
GPM
55.0
HEAT EXCHANGER
40
AHU2
AHU1
76.1 FT
3,600
GPM
55.0
40
HEAT EXCHANGER
AHU 3
AHU 3
55
mr5
1,200
GPM
40
ms5
55.0
AHU 3
AHU2
AHU2
mr4
55.0
1,200
GPM
55
GPM
AHU1
55
40
ms4
AHU2
AHU1
mr3
55.0
1,200
40
ms3
AHU1
76.1 FT
76.1 FT
3,600
mr2
3,600
GPM
55.0
GPM
55.0
HEAT EXCHANGER
40
ms2
HEAT EXCHANGER
40
76.1 FT
3,600
GPM
55.0
HEAT EXCHANGER
40
Impacts on Building Operation
• Design Intent - Customer Satisfaction
– Space Humidity and Temperature Control
• Building Energy Consumption - Cost
– Pump and Fan
– Hot Calls and Maintenance
• DC Interface-Contractual Obligation
– Building Leaving Water Temperature/Flow
Impacts on DC Operation
• Plant Operation
– Chiller Staging
– Plant Energy Efficiency
– Thermal Energy Storage Capacity
• Distribution Capacity
– Opex – Pumping Energy
– Capex – Ton per inch of pipe diameter
Solutions
• Supply Side dT Erosion
– Bypass
– Fouling at HX and Coils
• Return Side dT Erosion
–
–
–
–
–
Air Side Terminal Design and Diagnosis
Separate Control on Sensible and Latent
Leaving Air Setpoint Control
Chilled Water Valve Control: Pressure Independence
Monitoring and Intelligence
• Analysis
– Design and Operation
Heat Exchanger Fouling
• Coil Air Side
• Coil and HX Water Side
• Chiller Evaporator
Terminal Design
• Dedicated Outdoor Air
– Exhaust Air Heat Recovery
– Separate Sensible and Latent
• Series Latent and Sensible
• Elimination of Reheat
• Data Acquisition
– Real Time Load Analytics
Pressure Independent Control
T
F
AHU1
T
F
AHU1
T
VFD
HX Building Side
Building Pump
F
HX DC Side
P
VFD
DC
Pump
Chiller Plant
P
Summary
Diligence
Data
Analysis
Technology
Persistence
Questions?
[email protected]