high capacity chillers 97
Post on 21-Jan-2018
93 Views
Preview:
TRANSCRIPT
High Capacity Chillers:
Do we have Options?
by
Leslie T. Taniyama, V.P.Power and Systems Inspection Group – Hawaii Office
Phone (808) 955-6418
Email: psighi@aol.com
May 7, 2006
Power & SystemsInspection Group
Commercial Office High Rise Buildings,
Power & SystemsInspection Group
Commercial Office High Rise Buildings,Campuses,
Power & SystemsInspection Group
Commercial Office High Rise Buildings,Campuses,
Large Retail Malls and Stores
Power & SystemsInspection Group
Commercial Office High Rise Buildings,Campuses,
Large Retail Malls and Stores andAirports
Power & SystemsInspection Group
Commercial Office High Rise Buildings,Campuses,
Large Retail Malls and Stores andAirports
Power & SystemsInspection Group
Commercial Office High Rise Buildings,Campuses,
Large Retail Malls and Stores andAirports
Require Large Chilled WaterCentral Plants.
Power & SystemsInspection Group
Commercial Office High Rise Buildings,Campuses,
Large Retail Malls and Stores andAirports
Require Large Chilled WaterCentral Plants.
Power & SystemsInspection Group
What are the Choices:
Commercial Office High Rise Buildings,Campuses,
Large Retail Malls and Stores andAirports
Require Large Chilled WaterCentral Plants.
Power & SystemsInspection Group
What are the Choices:In Equipment?
Commercial Office High Rise Buildings,Campuses,
Large Retail Malls and Stores andAirports
Require Large Chilled WaterCentral Plants.
Power & SystemsInspection Group
What are the Choices:In Equipment?
And in Designs?
Power & SystemsInspection Group
Chiller Arrangements
The need to provide solutions for diverse building/facility operations
and its usage created various chiller arrangements.
Only recently has manufactures endorsed flow change through its
cooler/heat exchangers.
Centrifugal Chillers were reserved for the larger capacities over 250
Tons where rotary screw filled the lower capacities.
Recent developments in Centrifugal chiller designs, Screw chiller
designs and chiller plant configurations and designs have evolved to
allow for creative opportunities for energy efficiency and functional
improvements.
Power & SystemsInspection Group
Chiller Arrangements
Parallel Lead/Lag Chillers
Series Connected Chilled Water
Series-Series Counter Flow
Chiller Selections
Centrifugal Chillers
Screw Chillers
Hybrid – Centrifugal / Screw Combination
Power & SystemsInspection Group
Chiller Lift
The following analysis considers refrigerant lift calculations in the
comparisons of the chiller arrangements.
The reason why lift is considered, especially for centrifugal chillers, it
is somewhat proportional to the work performed by the compressor.
It is also more important for Centrifugal Chillers as lift control is crucial
in maintaining optimization of the inlet guide vane and vfd algorithms
of the chiller.
Screw compressors positively displaces refrigerant and is not as
concerned with surge conditions associated with centrifugal chillers.
Let’s look at the arrangements with the following conditions:
CWS = 75 °F, CWR = 85 °F
CHWS = 44 °F, CHWR = 54 °F
Power & SystemsInspection Group
CH-2 CH-1
Parallel Chiller Arrangement
CHWS = 44 °F
CHWR = 54 °F
CWS = 75 °F
CWR = 85 °F
CHWS = 44 °F
CHWR = 54 °F
CWS = 75 °F
CWR = 85 °F
Assumption: Condenser Approach = 1.5 °F = CWR – Condenser Refrigerant Temperature.
Evaporator Approach = 1.5 °F = CHWS – Evaporator Refrigerant Temperature.
Lift = Condenser Refrigerant Temperature – Evaporator Refrigerant Temperature = ~Work
= ( CWR – 1.5°F ) – ( CHWS – 1.5) = ( 85°F – 1.5 ) – (44°F – 1.5 ) = 83.5°F – 42.5°F
= 41°F for both chillers.
NOTE: If standard design of CWS = 85 °F, Lift = 51 °F.
Power & SystemsInspection Group
CH-2 CH-1
Series Chiller Arrangement
CHWR = 54 °F
CWS = 75 °F
CWR = 85 °F
CHWS = 44 °F
CWS = 75 °F
CWR = 85 °F
Assumption: Condenser Approach = 1.5 °F = CWR – Condenser Refrigerant Temperature.
Evaporator Approach = 1.5 °F = CHWS – Evaporator Refrigerant Temperature.
Lift = Condenser Refrigerant Temperature – Evaporator Refrigerant Temperature = ~Work
= ( CWR – 1.5°F ) – ( CHWS – 1.5)
CH1Lift = 83.5 - 42.5 = 43°FCH2Lift = 83.5 – 57.5 = 36°F.
CHW’ = 49 °F
Power & SystemsInspection Group
CH-2 CH-1
Series-Series CounterflowChiller Arrangement
CHWR = 54 °F
CWR = 85 °F
CHWS = 44 °F
CWS = 75 °F
Assumption: Condenser Approach = 1.5 °F = CWR – Condenser Refrigerant Temperature.
Evaporator Approach = 1.7 °F = CHWS – Evaporator Refrigerant Temperature.
Lift = Condenser Refrigerant Temperature – Evaporator Refrigerant Temperature = ~Work
= ( CWR – 1.7°F ) – ( CHWS – 1.5)
CH1Lift = 78.3 - 42.5 = 35.8°FCH2Lift = 83.3 - 47.5 = 35.8°F.
CHW’ = 49 °F
CW’ = 80 °F
Power & SystemsInspection Group
Let’s Review the Lift Differences
Chiller ArrangementParallel Lead/Lag Chillers
Series Connected Chilled Water
Series-Series Counter Flow
CH1-Lift*41.0 °F
CH2-Lift*41.0 °F
Power & SystemsInspection Group
Let’s Review the Lift Differences
Chiller ArrangementParallel Lead/Lag Chillers
Series Connected Chilled Water
Series-Series Counter Flow
CH1-Lift*41.0 °F
43.0 °F
CH2-Lift*41.0 °F
36.0 °F
Power & SystemsInspection Group
Let’s Review the Lift Differences
Chiller ArrangementParallel Lead/Lag Chillers
Series Connected Chilled Water
Series-Series Counter Flow
CH1-Lift*41.0 °F
43.0 °F
35.8 °F
CH2-Lift*41.0 °F
36.0 °F
35.8 °F
Power & SystemsInspection Group
Why should I be concerned about Lift?
Centrifugal Chiller 19XRV
0
10
20
30
40
50
60
70
0 1 2 3 4 5 6 7 8 9 10
Chiller Load
Re
frig
era
nt
Lif
t (D
P) Fully Loaded Chiller,
CWS=85CWR=95
Chiller Unloads,CWS=85CWR=90
Crosses Surge LineAnd goes into surge
Power & SystemsInspection Group
CH-2
CH-1
Rarely Would The Load Drop in Half.Right? ? ?
CHWR = 54 °F
CWS = 75 °F
CWR = 95 °F
CWS = 75 °F
CWR = 95 °F
CHWR = 44 °FCHWR = 54 °F
CHWR = 54 °F
1,000 GPM
n.c.
1,000 GPM
CHWR = 44 °F
Power & SystemsInspection Group
CH-2
CH-1
Let’s Lag On the CH2
CHWR = 54 °F
CWS = 75 °F
CWR = 95 °F
CWS = 75 °F
CWR = 95 °F
CHWR = 44 °FCHWR = 54 °F
CHWR = 54 °F
1,000 GPM
500 GPM
500 GPM
CHWR = 49 °F
CH-2 Valve Opens andCH-1 flow drops in HALF,Reducing load in half.
Power & SystemsInspection Group
Why should I be concerned about Lift?
Centrifugal Chiller 19XRV
0
10
20
30
40
50
60
70
0 1 2 3 4 5 6 7 8 9 10
Chiller Load
Re
frig
era
nt
Lif
t (D
P) Fully Loaded Chiller,
CWS=75CWR=85
Chiller Unloads slowly,CWS=65CWR=70
Does NOTCross Surge Line
Maintains Optimization
Power & SystemsInspection Group
Why should I be concerned about Lift?
Centrifugal Chiller 19XRV
0
10
20
30
40
50
60
70
0 1 2 3 4 5 6 7 8 9 10
Chiller Load
Re
frig
era
nt
Lif
t (D
P) Fully Loaded Chiller,
CWS=75CWR=85
Chiller Unloads slowly,CWS=65CWR=70
Does NOTCross Surge Line
Maintains Optimization
The lower the load is on the chiller,The lower the cooling tower water
Temperature needsTo be to maintain optimization.
Power & SystemsInspection Group
Carrier 19XRV Centrifugal Chiller w/ VFD500 N. Tons
Condenser Water and Load Characteristics
85
82.5
80
77.5
75
72.5
100%
75%
50%
25%
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
kW
/To
n
CWS Temp
Cap
acit
y (%
)
CWST vs 19XRV Chiller
Efficiency (kW/Ton)
1.000-1.050
0.950-1.000
0.900-0.950
0.850-0.900
0.800-0.850
0.750-0.800
0.700-0.750
0.650-0.700
0.600-0.650
0.550-0.600
0.500-0.550
0.450-0.500
0.400-0.450
Capacity (%)
CWS = 75 °F
Efficiency
kW/Ton
100% 0.461
75% 0.469
50% 0.498
25% 0.732
Power & SystemsInspection Group
Carrier 23XRV Screw Chiller w/ VFD500 N. Tons
Condenser Water and Load Characteristics
85
82.5
80
77.5
75
72.5
100%
75%
50%
25%0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
kW/Ton
CWS Temp
Lo
ad
%
CWST vs 23XRV Chiller Eff 23XRV
Efficie ncy (kW/Ton)
1.000-1.050
0.950-1.000
0.900-0.950
0.850-0.900
0.800-0.850
0.750-0.800
0.700-0.750
0.650-0.700
0.600-0.650
0.550-0.600
0.500-0.550
0.450-0.500
0.400-0.450
Capacity (%)
CWS = 75 °F
Efficiency
kW/Ton
100% 0.466
75% 0.437
50% 0.455
25% 0.601
Power & SystemsInspection Group
Let’s Review the Efficiency DifferencesOf the Centrifugal VFD Chiller and
The VFD Screw Chiller
19XRV 85 °F 82.5 °F 80 °F 77.5 °F 75 °F 72.5 °F
100% 0.586 0.552 0.520 0.490 0.461 0.434
75% 0.642 0.590 0.549 0.508 0.469 0.431
50% 0.727 0.665 0.609 0.552 0.498 0.450
25% 0.902 1.023 0.918 0.825 0.732 0.657
23XRV 85 °F 82.5 °F 80 °F 77.5 °F 75 °F 72.5 °F
100% 0.583 0.544 0.508 0.474 0.446 0.419
75% 0.573 0.534 0.496 0.466 0.437 0.406
50% 0.616 0.572 0.532 0.493 0.455 0.418
25% 0.859 0.784 0.715 0.657 0.601 0.550
CentrifugalVFD Chiller
ScrewVFD Chiller
Note: When a VFD operated centrifugal chiller
operates un-optimized, its efficiency worsens by as
much as 100% (0.469 kW/Ton vs. 0.820 k W/Ton).
Power & SystemsInspection Group
Chiller Lift Considerations
CWR = 85 °F
CWS = 75 °FAPPR = 4 °F
CHWR = 54 °F
CHWS = 44 °FAPPR = 4˚F
Cooler
Condensor
SRT = 40°F
SCT = 89 °F
35 psig
104 psig
Power & SystemsInspection Group
R134a PT Chart
top related