REFROIDISSEUR 101
Présenté par: Emilie Boyer, ing.17 Février 2021
AGENDA
Les trois (3) configurations de base d’opération & de tuyauterie
Le syndrôme du faible Delta T et ses causes, effets et solutions
Les attentions particulières à porter sur un concept/débit. L’impact des températures de l’eau refroidie & celle du
condenseur sur la consommation d’énergie du refroidisseur. Les considérations à porter sur la conception afin de
minimiser la consommation d’énergie du système sans affecter les performance
Questions
2
1) ‘’Constant Primary Flow (CPF)’’
2) ‘’Primary / Secondary’’
3) ‘’Variable Primary Flow’’
Configurations de base
Secondary Pumps
Load = Flow XDeltaTConstant Primary Flow (CPF)Dedicated Pumping
4
Secondary Pumps
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)
(63 l/s) 44 ºF(6.7 ºC)
(189 l/s) @ 6.7 ºC)
(1760 kW)
(189 l/s) @ 13.3 ºC)
Constant Primary Flow at Design
Primary
5
Flow 3000gpm (189 l/s)
Delta T 12oF (6.7oC)
Per Chiller System
Load 500 Tons (1760kW)
1500 Tons (5280kW)
56 ºF(13.3 ºC)
Secondary Pumps
53 ºF(11.7 ºC)
53 ºF(11.7 ºC)
53 ºF(11.7 ºC)
(63 l/s)
(1760 kW)
53 ºF
75%
53 ºF
(189 l/s) @ 6.7 ºC)
Constant Primary Flow at 75% Load
Primary
(189 l/s) @ 11.7 ºC) (11.7 ºC)
6
Flow 3000gpm (189 l/s)
Delta T 9oF (5.6oC)
Per Chiller System
Load 375 Tons (1320kW)
1125 Tons (3960kW)
44 ºF(6.7 ºC)
56 ºF(13.3 ºC)
Secondary Pumps
50 ºF(10 ºC)
50 ºF(10 ºC)
50 ºF(10 ºC)
(63 l/s)
(1760 kW)
50 ºF
50%
50 ºF
(189 l/s) @ 6.7 ºC)
Constant Primary Flow at 50% Load All Pumps & Chillers On
Primary
(189 l/s) @ 10 ºC) (10 ºC)
7
Flow 3000gpm (189 l/s)
Delta T 6oF (3.3oC)
Per Chiller System
Load 250 Tons (880kW)
750 Tons (2640kW)
44 ºF(6.7 ºC)
56 ºF(13.3 ºC)
Secondary Pumps
50 ºF(10.0 ºC)
50 ºF(10.0 ºC)
(63 l/s)
(1760 kW)
50 ºF
50%
50 ºF
(189 l/s) @ 8.3 ºC)
Constant Primary Flow at 50% Load 2 pumps on, 2 chillers on
Primary
Flow 2000gpm (126 l/s)
Delta T 6oF (3.3oC)
Per Chiller System
Load 250 Tons (880kW)
500 Tons (1760kW)
56 ºF(13.3 ºC)
44 ºF(6.7 ºC)
44 ºF)
44 ºF (6.7 ºC)
44 ºF(6.7 ºC)
1000- GPM63- l/s
1000- GPM63- l/s
?? GPM?? l/s
2000
2000
126
(189 (10.0 ºC)126 l/s) @ 10.0 ºC)
8
Secondary Pumps
53 ºF(11.7 ºC)
53 ºF(11.7 ºC)
53 ºF(11.7 ºC)
(1760 kW)
50%
(189 l/s) @ 8.3 ºC)
Constant Primary Flow at 50% Load All pumps on, 2 chillers on
Primary
Flow 3000gpm (189 l/s)
Delta T 6oF (3.3oC)
Per Chiller System
Load 375 Tons (1320kW)
750 Tons (2640kW)
56 ºF(13.3 ºC)
47 ºF)
(63 l/s) 47 ºF(8.3 ºC)
53 ºF(189 l/s) @ 11.7 ºC)
53 ºF(11.7 ºC)
9
53 ºF(11.7 ºC)
44 ºF (6.7 ºC)
44 ºF (6.7 ºC)
Secondary Pumps
50 ºF(11.7 ºC)
50 ºF(11.7 ºC)
50 ºF(11.7 ºC)
(63 l/s)
(1760 kW)
50 ºF(11.7 ºC)
50%
(189 l/s) @ 11.7 ºC)50 ºF
(189 l/s) @ 6.7 ºC)
Constant Primary Flow at 50% LoadAll pumps on, 2 chillers on with CHW reset
Primary
Flow 3000gpm (189 l/s)
Delta T 6oF (3.3oC)
Per Chiller System
Load 375 Tons 1320kW)
750 Tons (2640kW)
44 ºF(6.7 ºC)
56 ºF(13.3 ºC)
44 ºF)
50 ºF(11.7 ºC)
41 ºF (5.0 ºC)
41 ºF (5.0 ºC)
Need an automation System
12
Secondary Pumps
47 ºF(8.3 ºC)
47 ºF(8.3 ºC)
47 ºF (8.3ºC)
(63 l/s)
(1760 kW)
47 ºF(8.3 ºC)
25%
(189 l/s) @ 8.3 ºC)47 ºF
(189 l/s) @ 6.7 ºC)
Constant Primary Flow at 25% Load
Primary
11
Flow 3000gpm (189 l/s)
Delta T 3oF (1.7oC)
Per Chiller System
Load 125 Tons (440kW) 375Tons (1320kW)
44 ºF(6.7 ºC)
56 ºF(13.3 ºC)
Advantages Lowest installed cost
Less plant space than P/S
Easy to Control & Operate
Easy to Commission
Disadvantages Highest Plant Energy Cost (all pumps on always, possibly chillers as well)
12
Constant Flow Primary
1) ‘’Constant Primary Flow (CPF)’’
2) ‘’Primary / Secondary’’
3) ‘’Variable Primary Flow’’
Configurations de base
Primary (Constant) / Secondary (Variable)
PLoad = Flow XDeltaT
SLoad = Flow XDeltaT
Secondary Pumps
14
Primary (Constant) / Secondary (Variable)Headered Pumping
Secondary Pumps
15
But what controls the VSD’s?
16
What Controls the Flow of the Secondary Loop?
Valve Controls Leaving Air Temperature (LAT)
17
Valve Controls Leaving Air Temperature (LAT) Set Point = 55º (12.8º) LAT
T
18
As Valve Opens, Pressure in loop lowers As Valve Closes, Pressure in loop rises
19
T
Valve Controls Leaving Air Temperature (LAT) Set Point = 55º (12.8º) LAT
T
20
Valve Controls Leaving Air Temperature (LAT) Set Point = 55º (12.8º) LAT
T
21
Pressure Differential Sensor Controls Secondary Pump Speed
Differential Pressure sensor on last coil controls speed to Set Point (coil WPD+Valve PD+Piping PD+Safety) located at end of Index Circuit for best efficiency
Set PointP=25 ft (76 kPa)
P
22
Primary (Constant) / Secondary (Variable)Dedicated Pumping
Secondary Pumps
23
Primary (Constant) / Secondary (Variable)Rule of Flow
Primary flow must always be equal to or greater than Secondary flow.
Secondary Pumps
24
Primary/Secondary at Design
(63 l/s)
(1760 kW)
Secondary Pum3000 GPM @ 44
189 l/s @ 6.7 º
psºF
C
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)(189 l/s) @ 13.3 ºC)
50 ft (152 kPa) Head
Per Chiller System
Load 500 Tons (1760kW) 1500 Tons (5280kW)
Primary Secondary Bypass
Flow 3000gpm (189 l/s) 3000gpm (189 l/s) 0gpm (0 l/s)
Delta T 12oF (6.7oC) 12oF (6.7oC) ----
0 GPM @ 44 ºF0 l/s @ 6.7 ºC
3000 GPM @ 56 ºF(189 l/s) @ 13.3 ºC)
44.0 °F (6.7 °C)
100 ft (303 kPa) Head
100% Load = 100% Sec Flow
25
Primary/Secondary at 75% Load
(63 l/s)
(1760 kW)
Secondary Pumps2250 GPM @ 44 ºF
142 l/s @ 6.7 ºC
53 ºF(11.7 ºC)
53 ºF(11.7 ºC)
53 ºF(11.7 ºC)
56 ºF(13.3 ºC)
Per Chiller System
Load 375 Tons (1320kW) 1125 Tons (3960kW)
Primary Secondary Bypass
Flow 3000gpm (189 l/s) 2250gpm (142 l/s) 750gpm (47 l/s)
Delta T 9oF (5oC) 12oF (6.7oC) ----
750 GPM @ 44 ºF47 l/s @ 6.7 ºC
75%
2250 GPM @ 56 ºF(142 l/s) @ 13.3 ºC)
3000 GPM @ 53 ºF(189 l/s) @ 11.7 ºC)
44.0 °F (6.7 °C)
75% Load = 75% Sec Flow
26
Primary/Secondary at 50% Load
(63 l/s)
(1760 kW)
Secondary Pumps 1500 GPM @ 44 ºF
95 l/s @ 6.7 ºC
53 ºF(11.7 ºC)
53 ºF(11.7 ºC)
56 ºF(13.3 ºC)
Per Chiller System
Load 375 Tons (1320kW) 750 Tons (2640kW)
Primary Secondary Bypass
Flow 2000gpm (126 l/s) 1500gpm (95 l/s) 500gpm (32 l/s)
Delta T 9oF (5oC) 12oF (6.7oC) ----
500 GPM @ 44 ºF32 l/s @ 6.7 ºC
50%
1500 GPM @ 56 ºF(95 l/s) @ 13.3 ºC)
2000 GPM @ 53 ºF(126 l/s) @ 11.7 ºC)
44.0 °F (6.7 °C)
50% Load = 50% Sec Flow
27
Primary/Secondary at 25% Load
(63 l/s)
(1760 kW)
Secondary Pumps 750 GPM @ 44 ºF
47 l/s @ 6.7 ºC
53 ºF(11.7 ºC)
56 ºF(13.3 ºC)
Per Chiller System
Load 375 Tons (1320kW) 375 Tons (1320kW)
Primary Secondary Bypass
Flow 1000gpm (126 l/s) 750gpm (47 l/s) 250gpm (16 l/s)
Delta T 9oF (5oC) 12oF (6.7oC) ----
250 GPM @ 44 ºF16 l/s @ 6.7 ºC
25%
750 GPM @ 56 ºF(47l/s) @ 13.3 ºC)
1000 GPM @ 53 ºF(63 l/s) @ 11.7 ºC)
44.0 °F (6.7 °C)
25% Load = 25% Sec Flow
28
Advantages Easy to Control
Easy to Commission
Loop separation
Easier trouble-shooting
Lower Plant Energy (can sequence chillers and ancillary equipment)
Versatile – multi-circuit capability
Lower pump energy cost than CPF
Disadvantages Highest Installed Cost (Sec Pumps, Piping, etc.)
Potential for higher plant energy loss because of Low Delta Tsyndrome
29
Primary (Constant) / Secondary (Variable)
1) ‘’Constant Primary Flow (CPF)’’
2) ‘’Primary / Secondary’’
3) ‘’Variable Primary Flow’’
Configurations de base
Variable Primary Flow Load = Flow XDeltaT
Variable Primary Flow at 100% System Load
Two-way valves control capacity By varying flow of water in coils
Primary PumpsChillers Closed
31
Primary/Secondary System
Variable Primary System
Primary ChillersPumps
Four Differences?
32
Variable Primary Flow at Design
Variable Primary Flowat 100% System Load
Two-way valves control capacity By varying flow of water in coils
Per Chiller System
Load 500 Tons (1760kW) 1500 Tons (5280kW)
Primary Bypass
Flow 3000gpm (189 l/s) 0gpm (0 l/s)
Delta T 12oF (6.7oC) ----
56 ºF(13.3 ºC)
0 GPM @ 44 ºF0 l/s @ 6.7 ºC
3000 GPM @ 56 ºF(189 l/s) @ 13.3 ºC)
44.0 °F(6.7 °C)
3000 GPM @ 56 ºF(189 l/s) @ 13.3 ºC)
Primary Pumps 1000 GPM each
(63 l/s)
500 Ton (1760 kW)Chillers
3000 GPM @ 44 ºF189 l/s @ 6.7 ºC
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)
Closed
100% Load = 100% Flow
33
Variable Primary Flow at 75% Load
Variable Primary Flowat 75% System Load
Two-way valves control capacity By varying flow of water in coils
Per Chiller System
Load 375 Tons (1320kW) 1125 Tons (3960 kW)
Primary Bypass
Flow 2250 gpm (189 l/s) 0 gpm (0 l/s)
Delta T 12oF (6.7oC) ----
56 ºF
0 GPM @ 44 ºF0 l/s @ 6.7 ºC
2250 GPM @ 56 ºF
44.0 °F(6.7 °C)
2250 GPM @ 56 ºF
Primary Pumps 750 GPM each
(47 l/s)
2250 GPM @ 44 ºF142 l/s @ 6.7 ºC
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)
Closed
75% Load = 75% Flow
(142 l/s) @ 13.3 ºC) (142 l/s) @ 13.3 ºC) (13.3 ºC)
34
Variable Primary Flow at 50% Load
Variable Primary Flowat 50% System Load
Two-way valves control capacity By varying flow of water in coils
Per Chiller System
Load 375 Tons (1320kW) 750 Tons (2640 kW)
Primary Bypass
Flow 1500 gpm (95 l/s) 0 gpm (0 l/s)
Delta T 12oF (6.7oC) ----
56 ºF
0 GPM @ 44 ºF0 l/s @ 6.7 ºC
1500 GPM @ 56 ºF
44.0 °F(6.7 °C)
1500 GPM @ 56 ºF
Primary Pumps 750 GPM each
(47 l/s)
1500 GPM @ 44 ºF95 l/s @ 6.7 ºC
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)
Closed
50% Load = 50% Flow
(95 l/s) @ 13.3 ºC) (95 l/s) @ 13.3 ºC) (13.3 ºC)
35
Variable Primary Flow at 25% Load
Variable Primary Flowat 25% System Load
Two-way valves control capacity By varying flow of water in coils
Per Chiller System
Load 375 Tons (1320kW) 375 Tons (1320 kW)
Primary Bypass
Flow 750 gpm (95 l/s) 0 gpm (0 l/s)
Delta T 12oF (6.7oC) ----
56 ºF(13.3 ºC)
0 GPM @ 44 ºF0 l/s @ 6.7 ºC
750 GPM @ 56 ºF(47 l/s) @ 13.3 ºC)
44.0 °F(6.7 °C)
750 GPM @ 56 ºF(47 l/s) @ 13.3 ºC)
Primary Pumps 750 GPM(47 l/s)
750 GPM @ 44 ºF47 l/s @ 6.7 ºC
56 ºF(13.3 ºC)
Closed
25% Load = 25% Flow
38
Variable Primary Flow in Bypass Mode System flow below chiller min flow (250 gpm)
Variable Primary Flowat 25% System Load
Two-way valves control capacity By varying flow of water in coils
Per Chiller System
Load 50 Tons (176kW) 50Tons (176 kW)
Primary Bypass
Flow 250 gpm (95 l/s) 150 gpm (9.5 l/s)
Delta T 12oF (6.7oC) ----
56 ºF(13.3 ºC)
150 GPM @ 44 ºF
100 GPM @ 56 ºF(6.3 l/s) @ 13.3 ºC)
44.0 °F(6.7 °C)
250 GPM @ 48.8 ºF(15.8 l/s) @ 9.3 ºC)
Primary Pumps 250 GPM(15.8 l/s)
100 GPM @ 44 ºF6.3 l/s @ 6.7 ºC
9.5 l/s @ 6.7 ºCOpen
48.8 ºF (9.3 ºC)
37
Varying Flow Through Chillers - Issues
38
Issue 1 - During Normal Operation Chiller Type (centrifugal fast, absorbers slow)
System Water Volume (more water, more thermal capacitance, faster varianceallowed)
Active Loads (near or far from plant)
Typical VSD pump ramp rate setting of 10%/minute (accel/decel rates set to 600 seconds)
Issue 2 - Adding Chillers
Add chiller to sequence…operating chillers experience nuisance trips off-line(annoying)
Variable Primary System – Staging on chillers & changes in flow rateCurrent Situation – 1 chiller running
Variable Primary Flowat 100% System Load
Two-way valves control capacity By varying flow of water in coils
56 ºF(13.3 ºC)
44.0 °F (6.7 °C)
1000 GPM @ 56 ºF(63 l/s) @ 13.3 ºC)
Primary Pumps 500 GPM each
(32 l/s)
1000 GPM @ 44 ºF63 l/s @ 6.7 ºC
Closed
Per Chiller System
Load 500 Tons (1760kW) 500 Tons (1934kW)
39
Variable Primary System – Staging on chillers & changes in flow rateCurrent Situation –building load increases, valve opens, second chillerstarts
Variable Primary Flowat 100% System Load
Two-way valves control capacity By varying flow of water in coils
57 ºF(13.9 ºC)
45.0 °F (7.2 °C)
1100 GPM @ 57 ºF(69 l/s) @ 13.9 ºC)
Primary Pumps 550 GPM each
(35 l/s)
1100 GPM @ 45 ºF69 l/s @ 7.2 ºC
Closed
Per Chiller System
Load 275 Tons (967kW) 550 Tons (1934kW)
40
Advantages Lower Installed Cost (approx. 5% compared P/S)
No secondary Pumps or piping, valves, electrical, installation, etc.
Less Plant Space Needed
Best Chilled Water Pump Energy Consumption (most optimization-ready configuration)
VSD energy savings
Lower potential impact from Low Delta T (can over pump chillers if needed)
Disadvantages Requires more robust (complex and properly calibrated) controlsystem Requires coordinated control of chillers, isolation valves, controls andpumps Potentially longer commissioning times to tune the system Need experienced facility manager to operate/maintain properly Not for every type of chillers (centrifugal vs absorption)
41
Variable Primary Flow (VPF) System Arrangement
AGENDA
Les trois (3) configurations de base d’opération & de tuyauterie
Le syndrôme du faible Delta T et ses causes, effets et solutions
Les attentions particulières à porter sur le concept & le débit.
L’impact des températures de l’eau refroidie & celle du condenseur sur la consommation d’énergie du refroidisseur.
Les considérations à porter sur la conception afin de minimiser la consommation d’énergie du système sans affecter les performance
Questions
42
Low Delta T Syndrome
Secondary Pumps
Design Delta T = 12ºF
44°F
43
56°F
Major Causes of Low Delta T
44
Dirty Coils
Chilled Water Coil
T
45
Chilled Water Coil
Load = Flow X Delta T
46
Primary/Secondary at DesignIdeal Operation
(63 l/s)
(1760 kW)
Secondary Pumps3000 GPM @ 44 ºF
189 l/s @ 6.7 ºC
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)(189 l/s) @ 13.3 ºC)
Per Chiller System
Load 500 Tons (1760kW) 1500 Tons (5280kW)
Primary Secondary Bypass
Flow 3000gpm (189 l/s) 3000gpm (189 l/s) 0 gpm (0 l/s)
Delta T 12oF (6.7oC) 12oF (6.7oC) ----
0 GPM @ 44 ºF0 l/s @ 6.7 ºC
3000 GPM @ 56 ºF(189 l/s) @ 13.3 ºC)
44.0 °F (6.7 °C)
100% Load = 100% Sec Flow
12ºF (6.7ºC)
47
44 ºF(6.7 ºC)
Primary/Secondary at 67% LoadIdeal Operation
(63 l/s)
(1760 kW)
Secondary Pumps2000 GPM @ 44 ºF
126 l/s @ 6.7 ºC
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)(189 l/s) @ 13.3 ºC)
Per Chiller System
Load 500 Tons (1760kW) 1000 Tons (3518kW)
Primary Secondary Bypass
Flow 2000gpm (126 l/s) 2000gpm (126 l/s) 0 gpm (0 l/s)
Delta T 12oF (4.4oC) 12oF (6.7oC) ----
0 GPM @ 44 ºF0 l/s @ 6.7 ºC
2000 GPM @ 56 ºF(126 l/s) @ 13.3 ºC)
44.0 °F (6.7 °C)
67% Load = 67% Sec Flow
2000 GPM @ 56 ºF(126 l/s) @ 13.3 ºC)
44 ºF(6.7 ºC)
12ºF (6.7ºC)
48
Primary/Secondary at 67% LoadLow DeltaT
(63 l/s)
(1760 kW)
Secondary Pumps2400 GPM @ 44 ºF
152 l/s @ 6.7 ºC
54 ºF(12.2 ºC)
54 ºF(12.2 ºC)
54 ºF(12.2 ºC)(189 l/s) @ 13.3 ºC)
Per Chiller System
Load 500 Tons (1760kW) 1000 Tons (3518kW)
Primary Secondary Bypass
Flow 2000gpm (126 l/s) 2400gpm (152 l/s) 400 gpm (25l/s)
Delta T 10oF (5.6oC) 10oF (5.6oC) ----
400 GPM @ 54 ºF25.3 l/s @ 7.3 ºC
2400 GPM @ 54 ºF(152 l/s) @ 12.2 ºC)
44 °F(6.7 °C)
67% Load = 80% Sec Flow
2000 GPM @ 54 ºF(126 l/s) @ 12.2 ºC)
44 ºF(6.7 ºC)
10ºF (5.6ºC)
49
Primary/Secondary at 67% LoadLow DeltaT
(63 l/s)
(1760 kW)
Secondary Pumps2400 GPM @ 45.7 ºF
152 l/s @ 7.6 ºC
54 ºF ?(12.2 ºC ?)
54 ºF ?(12.2 ºC ?)
54 ºF ?(12.2 ºC ?)(189 l/s) @ 13.3 ºC)
Per Chiller System
Load 417 Tons (1467kW) 934 Tons (3286kW)
Primary Secondary Bypass
Flow 2000gpm (126 l/s) 2400gpm (152 l/s) 400gpm (25l/s)
Delta T 10oF (5.6oC) 10oF (5.6oC) ----
400 ? GPM @ 54 ºF ?25.2 ?+ l/s @ 12.2 ºC ?
2400? GPM @ 54 ºF ?(152? l/s) @ 12.2 ºC ?)
45.7 °F (7.6 °C)
67% Load = 80% Sec Flow
2000 GPM @ 54 ºF ?(126 l/s) @ 12.2 ºC ?)
45.7 ºF (7.6 ºC)
???
50
Primary/Secondary at 67% LoadLow DeltaT
(63 l/s)
(1760 kW)
Secondary Pumps2400 GPM @ 44 ºF
152 l/s @ 6.7 ºC
52 ºF(11.1 ºC)
52 ºF(11.1 ºC)
54 ºF(12.2 ºC)(189 l/s) @ 13.3 ºC)
Per Chiller System
Load 333 Tons (1172kW) 1000 Tons (3518kW)
Primary Secondary Bypass
Flow 3000gpm (189 l/s) 2400gpm (152 l/s) 600 gpm (38 l/s)
Delta T 8oF (4.4oC) 10oF (5.6oC) ----
600 GPM @ 44 ºF38 l/s @ 6.7 ºC
2400 GPM @ 54 ºF(152 l/s) @ 12.2 ºC)
44 °F(6.7 °C)
67% Load = 80% Sec Flow
3000 GPM @ 52 ºF(189 l/s) @ 11.1 ºC)
44 ºF(6.7 ºC)
10ºF (5.6ºC)
51
52 ºF(11.1 ºC)
Negative Effects of Low Delta T in P/S Systems
Consequences: Higher secondary pump energy
pumps run faster
Higher chilled water plant energy Ancillary equipment
Can’t load up chillers more than ratio Act DT / Des DT 10/12 = 83% or 417 tons
52
Variable Primary Flow at 67% LoadIdeal Operation
Variable Primary Flowat 100% System Load
Two-way valves control capacity By varying flow of water in coils
Per Chiller System
Load 500 Tons (1760kW) 1000 Tons (3518kW)
Primary Bypass
Flow 2000gpm (126l/s) 0gpm (0 l/s)
Delta T 12oF (6.7oC) ----
56 ºF(13.3 ºC)
0 GPM0 l/s
2000 GPM @ 56 ºF(126 l/s) @ 13.3 ºC)
44.0 °F(6.7 °C)
2000 GPM @ 56 ºF(126 l/s) @ 13.3 ºC)
Primary Pumps 666 GPM each
(42 l/s)
500 Ton (1760 kW)Chillers
2000 GPM @ 44 ºF126 l/s @ 6.7 ºC
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)
56 ºF(13.3 ºC)
Closed
67% Load = 67% Flow
53
Variable Primary Flow at 67% LoadLow DeltaT (can over-pump chillers)
Variable Primary Flowat 100% System Load
Two-way valves control capacity By varying flow of water in coils
Per Chiller System
Load 500 Tons (1760kW) 1000 Tons (3518kW)
Primary Bypass
Flow 2400gpm (152l/s) 400gpm (25 l/s)
Delta T 10oF (5.6oC) ----
54 ºF(12.2 ºC)
0 GPM0 l/s
2400 GPM @ 54 ºF(152 l/s) @ 12.2 ºC)
44.0 °F(6.7 °C)
2400 GPM @ 54 ºF(152 l/s) @ 12.2 ºC)
Primary Pumps 800 GPM each
(51 l/s)
1200 GPM(76 l/s)
ea Chiller Flow
2400 GPM @ 44 ºF152 l/s @ 6.7 ºC
54 ºF(12.2 ºC)
54 ºF(12.2 ºC)
54 ºF(12.2 ºC)
Closed
67% Load = 80% Flow
54
Major Causes of Low Delta T
55
Dirty Coils
Controls Calibration
Leaky 2-Way Valves
Coils Piped-Up Backwards
Mixing 2-Way with 3-Way Valves in the same system
Solution to (or reduce effects of) Low Delta T
Address the causes Clean Coils
Calibrate controls periodically
Select proper 2W valves and maintain them (fix leaky valves)
No 3W valves in design
Find and correct piping installation errors
Over deltaT chillers by resetting supply water down (P/S)
56
AGENDA
Les trois (3) configurations de base d’opération & de tuyauterie
Le syndrôme du faible Delta T et ses causes, effets et solutions
Les attentions particulières à porter sur le concept & le débit.
L’impact des températures de l’eau refroidie & celle du condenseur sur la consommation d’énergie du refroidisseur.
Les considérations à porter sur la conception afin de minimiser la consommation d’énergie du système sans affecter les performance
Questions
57
58
Chillers Equal Sized Chillers preferred, but not required
Maintain Min flow rates with Bypass control (1.5 fps for flooded and 1 gpm/ton forDX)
Maintain Max flow rates (12.0 fps) and max WPDs (45’ for 2P, 67’ for3P)
Modulating Isolation Valves (or 2-positionstroke-able) set to open in 1.5 to 2 min
Don’t vary flow too quickly through chillers (VSD pump Ramp rate – typical setting of10%/min)
Sequence
If CSD Chillers – Load-based sequencing…run chillers to max load (Supply Temp rise). Do not run more chillers than needed
Load-Based Sequencing of Chillers (CSD Example)
59
VPF Systems Design/Control Considerations
60
Chillers Equal Sized Chillers preferred, but not required
Maintain Min flow rates with Bypass control (1.5 fps)
Maintain Max flow rates (11.0 to 12.0 fps) and max WPDs (45’ for 2P, 67’ for3P)
Modulating Isolation Valves (or 2-position stroke-able) set to open in 1.5 to 2min
Don’t vary flow too quickly through chillers (VSD pump Ramp rate – typical setting of10%/min)
Sequence
If CSD Chillers – Load-based sequencing…run chillers to max load (Supply Temp rise). Do not run more chillers than needed (water-cooled, single compressorassumed)
If VSD Chillers – Energy-based sequencing…run chillers between 30% and 80% load (depending on ECWT and actual off-design performance curves). Run more chillers than load requires.
Energy-Based Sequencing of Chillers (VSD Example)
85ºF, 56%
75ºF, 48%
65ºF, 39%
55ºF, 32%
61
When to Employ CPF Next step above unitary products (introductory chilled water)
Low First cost, low budget projects where energy is secondary
Small speculative office buildings (small single chiller plants)
When to Employ VPF Plants that serve a few close buildings
Plants where full CPO, maximum efficiency is required
More sophisticated owner/operators
When to Employ P/S District Cooling Plants or Large (College) Campuses
Central Plants that serve loads far away on different schedules
Projects where energy is more important than first cost
Where separated water loops are more apropos
Where greatest reliability is required
62
Application Considerations
AGENDA
Les trois (3) configurations de base d’opération & de tuyauterie
Le syndrôme du faible Delta T et ses causes, effets et solutions
Les attentions particulières à porter sur le concept & le débit.
L’impact des températures de l’eau refroidie & celle du condenseur sur la consommation d’énergie du refroidisseur.
Les considérations à porter sur la conception afin de minimiser la consommation d’énergie du système sans affecter les performance
Questions
63
Pressure enthalpy curve Basic refrigeration cycle
Refrigerant rejects heat to atmosphere
Refrigerant absorbs heat from load
Lift(or Head Pressure)
Pres
sure
Enthalpy
Evaporator
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Condenser
Metering Device
Centrifugal chillers in today’s complex buildings How they work
Pres
sure
Enthalpy
Lift(or Head Pressure)
54° F (12° C)
44° F (7° C)
85° F (29° C)
95° F (35° C)
© 2020 Johnson Controls. All rights reserved.
How much energy is used?
Cooling Tower
5 hp/100 tons
Rul
es o
fthu
mb
Chilled Water Pump5 hp/100 tons
Condenser Water Pump5 hp/100 tons
Water-Cooled Chiller
75 hp/100 tons
Air-Cooled Chiller
140 hp/100 tons
500
ton
exam
ple Cooling Tower
25hp = 18kW
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Chilled Water Pump
25hp = 18kW
Condenser Water Pump
25hp = 18kW
Water-Cooled Chiller
0.56kW/tr = 280kW
Air-Cooled Chiller10 EER = 1.2kW/tr
= 600kW
How much energy is used?
Chi
lled
Wat
erPl
ant
Com
pone
nts
500
ton
Cen
trifu
gal
Chi
llerP
lant
Condenser Water Pump
Condenser Water Pump
1500 gpm @ 60 wpd
27.1 BHP
Cooling Tower
Cooling Tower Fan(s)
30 BHP
Chilled Water Pump
Chilled Water Pump
850 gpm @ 100 wpd
25.4 BHP
Water-Cooled Chiller
500 ton Centrifugal Chiller
361 BHP
Total = 82.5 BHP
© 2020 Johnson Controls. All rights reserved.
Chiller BHP = 4.4Xall other components
combined
Real world energy performanceHow does leaving chilled water temperature affect efficiency
Pres
sure
Evaporator
Condenser
Met
erin
gD
evic
e
∆ℎ
Energy / Enthalpy
Lift(or HeadPressure)
© 2020 Johnson Controls. All rights reserved.
© 2020 Johnson Controls. All rights reserved.
Real world energy performance Capitalizing on off-design conditions
Pres
sure
Energy / Enthalpy
Evaporator
Condenser
Met
erin
gD
evic
eReduces
energy consumption
Reduces compressor work
Lowershead pressure (lift)
RAISING chilled water temperature
Lift(or HeadPressure)
∆ℎ
∆ℎ Energy$aved
Water temperatures and chiller efficiency
1°Fcolder leaving chilled water temperature (lchwt)
or1°Fwarmer leaving chilled water temperature (lchwt)
2.2%Loss/gain to chiller efficiency
Cooling Tower5hp/100ton
Pumps (2x)10hp/100ton
Chiller70-75hp/100ton
Chiller Plant Efficiency Impacts Average Power Use
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Centrifugal plantsChilled water temperature and system efficiency
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Example System Assumptions ECHWT/LCHWT Efficiency (kW/ton)
Variance (% Efficiency)
500 tons 42 / 56 0.603 and 0.363 NPLVCentrifugal Chiller 44 / 58 0.572 and 0.337 NPLV + 5.4% / + 7.7%85 / 95 degree condenserwater (3 gpm/ton) 45 / 59 0.561 and 0.325 NPLV + 7.5% / + 11.7%
42 / 52 0.606 and 0.363 NPLVDelta T has little effect on chiller efficiency 44 / 54 0.574 and 0.338 NPLV
45 / 55 0.560 and 0.326 NPLV
With constant equipment cost, you will improve system efficiency with warmer CHW design temps.
54 deg air is achievable w/ 45 deg Chilled Water Regardless of Entering Air Conditions
What temperature chilled water do I need?
8000 CFM, 500 fpm
Inlet Air EAT(wb/db) EWT/LWTLAT CHWFlow
CoolingCoil(wb/db) gpm
100% OutsideAir 95/78 45/59 53.5 / 53.4 92.7 8-row & 10 FPI
Mixed Air 80/67 45/59 53.6 / 53.1 47.0 6-row & 10FPI
100% Return Air 75/62 45/59 53.9 / 52.7 30.0 6-row & 9FPI
Centrifugal chiller plantsChilled water temps & system efficiency
Warmer chilled water temps do not significantly impact airside performance or cost.
LCHWT/ECHWT LAT db / LAT wbMinimum Cooling
Coil Required First Cost vs. 42/56
42 / 56 53.5 / 52.7 5-rows 9 FPI
44 / 58 53.5 / 52.9 6-rows 9 FPI + $239
45 / 59 53.6 / 53.1 6-rows 10 FPI + $283
Air pressure drop difference: 42 vs. 45 CHW = 0.16” wpd
Example Airside Impact80 / 67 Entering Mixed Air Temp for AHU cooling coil 8,000 CFM AHUs @ 500 fpm
LAT = Sub 54 (54 db / 53.5 wb)
© 2020 Johnson Controls. All rights reserved.
Yearly system energy savings
Net System Energy Savings = $3,350, ~ 5.5% per year
Chiller: Chiller:
42 / 56 design, 0.363 kw/ton NPLV:45 / 59 design, 0.325 kw/ton NPLV:
$38,115 / year$34,125 / year
$3,990 reduction / year on Chiller
Airside: Airside:
42 / 56 design, 7.70 BHP per 8k CFMAHU: 45 / 59 design, 7.92 BHP per 8k CFMAHU:
$22,402 / year$23,042 / year
$640 extra / year on Airside
Assumptions: 500-ton chiller 3,000 yearly operating hours 350-ton average load $0.10/kwh 13 AHUs running at 8000 CFM (27-tons)
= 350-ton average load
© 2020 Johnson Controls. All rights reserved.
Airside BHP based on AF Fan at 4.0” TSP vs. 4.16” TSP (0.16” apd increase)
Annual Chiller Energy Cost = (Avg Load) (Run Hours) (NPLV kw/ton) ($/kwh)
Annual Airside Energy Cost = (Qty AHUs) (Run Hours) (BHP) (0.746 kw/bhp) ($/kwh)
What is the bestleaving chilled water temperature (lchwt)
for system efficiency?
The warmest temperature capable of providing your desired airside leaving air temp.
© 2020 Johnson Controls. All rights reserved.
Refrigeration cycleReal world energy performance
Pres
sure
Evaporator
Condenser
Met
erin
gD
evic
e
Lift(or HeadPressure)
∆ℎ
Energy / Enthalpy
© 2020 Johnson Controls. All rights reserved.
© 2020 Johnson Controls. All rights reserved.
Refrigeration cycleCapitalizing on lower leaving condenser water temperatures
Pres
sure
Energy / Enthalpy
Evaporator
Met
erin
gD
evic
e
Condenser
∆ℎ ∆ℎ
LOWERING condenser water temperature
Lowers head pressure
Reduces compressor work
Reduces energy consumption
Lift(or HeadPressure)
Energy$aved
Centrifugal chiller plantsCondenser water temperature and system efficiency
Entering condenser water temperature has minimal impact on efficiency
LEAVING condenser water temperature drives efficiency
Example:
3 gpm/ton 2 gpm/ton = 7.5% - 10%efficiency reduction
For every 1°F or 1°F the leaving CHW
temperature changes,
a chiller gains or looses≈ 1.5% - 2%in efficiency
Colderleaving condenser water temperature
saves energyandachieves airside performance
© 2020 Johnson Controls. All rights reserved.
Centrifugal plantsCondenser water temperature and system efficiency
Chiller500 tons54/44°F chilled water 85°F ECWT
Although you are using more energy on the Condenser Pump at 3 GPM/ton (6.3 BHP), you are saving over 4 times that energy (28 BHP) by making the Chiller more efficient
FL Efficiency = 0.574 FL Efficiency = 0.619
IPLV = 0.338 IPLV = 0.364
Chiller BHP = 361 Chiller BHP = 389
Parameters 3 GPM/ton (1500 GPM) 2 GPM/ton (1000 GPM)
Pump BHP = 27.1 Pump BHP = 20.8Condenser Pump60 ft WPD
© 2020 Johnson Controls. All rights reserved.
+28 BHPincrease
BHP change
-6.3 BHPdecrease
EB8
Diapositive 79
EB8 FL = Full load efficiency - (1%) - Ajouter slide Montréal ASHRAEEmilie Boyer, 2/8/2021
AGENDA
Les trois (3) configurations de base d’opération & de tuyauterie
Le syndrôme du faible Delta T et ses causes, effets et solutions
Les attentions particulières à porter sur le concept & le débit.
L’impact des températures de l’eau refroidie & celle du condenseur sur la consommation d’énergie du refroidisseur.
Les considérations à porter sur la conception afin de minimiser la consommation d’énergie du système sans affecter les performance
Questions
80
Centrifugal plantsCondenser water temps and system efficiency
800
Ton
Chi
ller
Sche
dule
Tow
erSc
hedu
lePu
mp
Sche
dule
Tower
Pump
Chiller
3 GPM/ton
3 GPM/ton
© 2020 Johnson Controls. All rights reserved.
Centrifugal plantsCondenser water temps and system efficiency
3 GPM/ton
Centrifugal plantsCondenser water temps and system efficiency 3 GPM/ton Rating
Centrifugal plantsCondenser water temps and system efficiency
10° ΔT
Centrifugal plantsCondenser water temps and system efficiency
3 GPM/ton 0.5727 0.3725 174032
Centrifugal plantsCondenser water temps and system efficiency
3 GPM/ton 0.3725
Summary
© 2020 Johnson Controls. All rights reserved.
RAISING leaving chilled water temperature saves energy Chiller gains/looses 2.0 – 2.5% efficiency with every degree
change in lchwt Negligible difference in chiller performance with higher
evaporator ΔT
LOWERING entering condenser water temperature saves energy Chiller gains/looses 1.5 – 2.0% efficiency with every degree
change in ecwt Major difference in chiller performance with higher condenser ΔT Leaving condenser water temperature sets chiller efficiency
HIGHER condenser flow saves chiller and system efficiency 3GPM/ton saves 7.5 – 10.0% efficiency vs 2 GPM/ton Review all component schedules during chiller selections
QUESTIONS?
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