rocky mountain ashrae - hydronic loop …...cv example: • coil requires 250 gpm • design dp for...
TRANSCRIPT
Hydronic Loop Performance: Design vs. Installed
Why design and modeling data don’t always
match a building’s actual performance
David Kandel
Rocky Mountain ASHRAE November 6, 2013
Agenda
Hydronic Loop Performance: Design vs. Installed • Design and Modeling Assumptions & Coil Behavior • Performance Problems
• Valve Sizing • Valve Authority • Coil Performance
• Potential Solutions
Valve Specs
• Design / Modeling Assumptions • Proper Valve Sizing • Stable System Pressures • Perfect Valve Authority
Valve / Coil Performance
Coil Performance C
oil P
ower
/ Fl
ow
Flow / Control Signal
ΔT
BTUh
Valve GPM
Resulting Coil Output
ΔT
Agenda
Hydronic Loop Performance: Design vs. Installed • Design and Modeling Assumptions & Coil Behavior • Performance Problems
• Valve Sizing • Valve Authority • Coil Performance
• Potential Solutions
Hydronic Valve Sizing
Pgpm Cv�
�
Example: • Coil Requires 250 GPM • Design DP for valve, 4 psi • DP of Valve not to exceed 5
psi
1252
2504
250 Cv ���
Hydronic Valve Sizing
Example: • Coil Requires 250 GPM • Design DP for valve, 4 psi • DP of Valve not to exceed 5
psi
1252
2504
250 Cv ���
Hydronic Valve Sizing
2GPM P ���
����Cv
Checking DP
Example: • Coil Requires 250 GPM • Design DP for valve, 4 psi • DP of Valve not to exceed 5
psi
Hydronic Valve Sizing
psi7.790250 P
2
����
����
2GPM P ���
����Cv
Checking DP
psi2.2170250 P
2
����
����
Piping Options
Coil Balance Valve
Control Valve
Coil Control Valve
Coil Flow Limiting Valve
Control Valve
No Balancing Device Oversized Control Valves
Coil Control Valve
Coil Control Valve
Near Pump: • High ΔP causes massive
overflow ΔP
35 psi
ΔP 8 psi
Far From Pump: • Oversized Valve cause
overflow • No Protection from pressure
changes
Traditional Balancing Valve Oversized Control Valves
Near Pump: • Major Valve Authority issues • No Protection from pressure
changes
Balance Valve
Balance Valve
Far From Pump: • Minor Valve Authority issues • No Protection from pressure
changes
Coil Control Valve
Coil Control Valve
ΔP 35 psi
ΔP 10 psi
Flow Limiting Valve Oversized Control Valves
Near Pump: • Major Valve Authority issues • No Protection from pressure
changes below full flow
Far From Pump: • Minor Valve Authority issues • No Protection from pressure
changes below full flow
Coil Control Valve
Coil Control Valve
ΔP 35 psi
ΔP 10 psi
Flow Limiting Valve
Flow Limiting Valve
Agenda
Hydronic Loop Performance: Design vs. Installed • Design and Modeling Assumptions & Coil Behavior • Performance Problems
• Valve Sizing • Valve Authority • Coil Performance
• Potential Solutions
15
Valve Authority
Branchp�
valvep�Coil
Balance Valve
branch
valve
ppA
��
�
16
Valve Authority
Valve Opening (%)
Flow
(%)
branch
valve
ppA
��
�
Balance Valve
Balance Valve
Coil Control Valve
Coil Control Valve
ΔP 20 psi
ΔP 10 psi
4 psi 4 psi 2 psi A = 0.4
4 psi 4 psi 12 psi A = 0.2
17
Valve Authority
0 40 60 80 100
20
40
60
80
100
10
30
50
70
90
10 20 30 50 70 90
Valve Opening (%)
0.2
1
Valve Authority Distortion
Flow
/ C
oil O
utpu
t (%
)
Valve Opening (%)
Flow
(%)
branch
valve
ppA
��
�
18
Valve Authority
0 40 60 80 100
20
40
60
80
100
10
30
50
70
90
10 20 30 50 70 90
Valve Opening (%)
0.2
Valve Authority Distortion
Flow
/ C
oil O
utpu
t (%
)
Agenda
Hydronic Loop Performance: Design vs. Installed • Design and Modeling Assumptions & Coil Behavior • Performance Problems
• Valve Sizing • Valve Authority • Coil Performance
• Potential Solutions
100
90
20
40
60
80
10
30
50
70
Coo
ling
Out
put (
%)
0 40 60 80 100 10 20 30 50 70 90
Water Flow (%)
110 120 130 140 150
Cooling Output %
Water ΔT
Wat
er Δ
T
Power Saturation Point
Waste Zone
Understanding Coil Behavior
Operating in the Waste Zone 1. Pumping more Water 2. Reduced Delta T 3. No additional BTUs
Coils Heat Transfer Coefficients
• Air film coefficient of sensible heat transfer between air and the external surface of the coil
• Water film coefficient of heat transfer between the internal coil surface and the coolant fluid within the coil
• Unit conductance of the coil material Based on a coil design with a clean, non-fouled surface
Coil Degradation
Heat Transfer of Coil Degrades Over Time • Damage to coil or fins • Air-side fouling • Water-side fouling
Coil Degradation
Coil Performance C
oil P
ower
/ Fl
ow
Flow / Control Signal
ΔT
BTUh
Valve GPM
Resulting Coil Output
ΔT
Coil Performance
Coil Degradation
Was
te Z
one
Coi
l Pow
er /
Flow
Flow / Control Signal
ΔT
Coil Performance
Coil Degradation
Was
te Z
one
WW
More GPM to produce the same BTU
Coi
l Pow
er /
Flow
Flow / Control Signal
ΔT
Coil Degradation Cost of Operating in the Waste Zone
Coil Degradation Cost of Operating in the Waste Zone
55 gpm
320 kBTU/hr
325 kBTU/hr
65 gpm
1 2
Coil Degradation Cost of Operating in the Waste Zone
1 2 BTUh 320,000 325,000 1.6% GPM 55 GPM 65 GPM 18% Pump hp Hp increase = (65/55)3 65%
3
1
2
1
2���
����
�GPMGPM
HPHP
?
1 2 Δ BTUh 320,000 325,000 1.6% GPM 55 GPM 65 GPM 18%
Agenda
Hydronic Loop Performance: Design vs. Installed • Design and Modeling Assumptions & Coil Behavior • Performance Problems
• Valve Sizing • Valve Authority • Coil Performance
• Potential Solutions • Pressure Independent Valves • Delta T Limiting • Direct BTU Control
Pressure Independent Valves Better Performance • No Issues with oversizing • Perfect Valve Authority • Stable control, part load and full load
Pressure Independent Valves PI Valve Technologies
Mechanical Regulator Flow Meter
Pressure Independent Valves PI Valve Technologies
Mechanical Regulator Flow Meter
Delta T Limiting BTU Monitoring
BTU Meter
Delta T Limiting BTU Monitoring
BTU Control Maximizing Load to Flow Ratio
Coil Performance C
oil P
ower
/ Fl
ow
Flow / Control Signal
BTUh
Valve GPM
Resulting Coil Output
Hydronic Loop Performance: Design vs. Installed • Design and Modeling Assumptions & Coil Behavior • Performance Problems
• Valve Sizing • Valve Authority • Coil Performance
• Potential Solutions • Pressure Independent Valves • Delta T Limiting • Direct BTU Control
Questions?