© Hitachi, Ltd. 2017. All rights reserved.
Cycle Simulation and Prototyping of Single-Effect Double-Lift Absorption Chiller
Hitachi, Ltd. Research & Development GroupThermal Fluidic Systems Research Department
May/17/2017
Tatsuo Fujii
© Hitachi, Ltd. 2017. All rights reserved.
1. Introduction2. Single-Effect Double-Lift (SEDL) absorption cooling cycle3. Cycle Simulation
Contents
1
4. Prototyping and Experiment5. Conclusions
2© Hitachi, Ltd. 2017. All rights reserved.
1. Introduction – activating low temperature heat –
Current status of driving temperatures of absorption chillers
Hot Water DrivenAbsorption Chiller
Temp.: 60°C 90°C 120°C 150°C 180°C~
Direct fired Absorption Chiller/Heater
Steam DrivenAbsorption Chiller
Double effectSingle effect
Not Available forCooling Use
(75°C)
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2. Single-Effect Double-Lift (SEDL) absorption cycle
High temp. Generator
Pressure
Temperature
Low temp.Generator
Evaporator
Auxiliary Generator
Absorber
Condenser
AuxiliaryAbsorber
AHX HHX
LHX
Heat Input
Heat Output
SEDL absorption cooling cycle
Ø Combination of single-effect and double-lift (half-effect) absorption cycle
Ø Consist of 7 phase changing heat exchanger and 3 solution heat exchanger
Ø Proposed by Schweigler et. al. in 1990’s
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3. Cycle Simulation
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3. Cycle Simulation – Modeling of SEDL cycle
Simulation model supported two-step evaporator and absorber (E/A).à Operated under 4 pressure levels
Strong solution
Refrigerant Weak solution
Cooling waterChilled water
Configuration of two-step E/A
E1
E2
A1
A2
pH
pM
pL1
pL2
Chilled water
Cooling water
Hot water (Heat source)
C AG
AA
AHX
E1
E2
HG
LG
HHX
LHX
A1
A2
Refrigerant liquid
Refrigerant vapour
Solution (Absorbent)
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3. Cycle Simulation – Computing strategy
Basically, cycle calculation is consist of three levels.
(3) Components levelEnergy and mass balance in each component in the same pressure level
(2) Same pressure levelMass balance in each pressure level pH, pM, pL1 and pL2
(1) Whole system levelEnergy and mass balance in the whole cycle
Input conditions
C AG HGC AG HG
COP,etc.
Chilled water
Cooling water
Hot water (Heat source)
C AG
AA
AHX
E1
E2
HG
LG
HHX
LHX
A1
A2
Refrigerant liquid
Refrigerant vapour
Solution (Absorbent)
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Chilled water
Cooling water
Hot water (Heat source)
C AG
AA
AHX
E1
E2
HG
LG
HHX
LHX
A1
A2
Refrigerant liquid
Refrigerant vapour
Solution (Absorbent)
48
49
50
51
52
53
54
55
56
94
95
96
97
98
99
100
101
102
2-step EA 1-step EA 2-step EA 1-step EA
Hot
wat
er te
mpe
ratu
re (T
HW
-out
)
(°C
)
Cap
acity
(QE)
, CO
P (%
)
Evaporator and absorber formation
QE COP THW-out
Chilled water: 13-8°C Chilled water: 15-7°C
THW-in: 95°C
3. Cycle Simulation – Effect of two-step E/A
As similar as conventional machines, two-step E/A configuration improved the capacity and COP. à We employed two-step E/A for the prototype chiller.
Calculation under the same heat exchanger size
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49
50
51
52
53
54
55
56
57
94
95
96
97
98
99
100
101
102
HG-LG-AGA-AA-C
HG-AG-LGA-AA-C
HG-LG-AGA-C-AA
HG-AG-LGA-C-AA
Hot
wat
er te
mpe
ratu
re (T
HW
-out
)
(°C
)
Cap
acity
(QE)
, CO
P (%
)
Hot water and cooling water flow order
QE COP THW-out
Hot water ->Cooling water ->
THW-in: 95°C,Chilled water in-out: 13-8°C
3. Cycle Simulation – Effect of water circulation –
Circulation methods for hot water and cooling water were examined and “HG-LG-AG” for the hot water and “A-AA-C” for the cooling water were selected.
Calculation under the same heat exchanger size
Chilled water
Cooling water
Hot water (Heat source)
C AG
AA
AHX
E1
E2
HG
LG
HHX
LHX
A1
A2
Refrigerant liquid
Refrigerant vapour
Solution (Absorbent)
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4. Prototyping and Experiment
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4. Prototyping and experiment – Cycle flow –
Prototype of SEDL chiller was designed with adoption of two-step evaporator and absorber, and optimized water circulating method.
Hot water (Heat source)
E1
E2
A1
A2
LHX HHX
AHX
LG AA AG C HG
Chilled water
Cooling water
This prototype can also be operated as a normal double-lift cycle.
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4. Prototyping and experiment – Whole system –
Experimental equipment(Hot/Chilled/Cooling water supply)
Prototype of SEDL chiller and experimental equipment are setup for performance test.
Hot water
Chilled water
Cooling water
(Return)
Prototype of SEDL absorption chiller
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4. Prototyping and experiment – SEDL chiller
Prototype chiller was manufactured, considering real product.
Prototype of SEDL absorption chiller
Evaporator
Auxiliary absorber
Solution heat exchangers
Absorber
Condenser
High temp. generator
Auxiliary generator
Low temp. generator
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4. Prototyping and experiment – Result (1) –
Basic performance data in DL and SEDL operations were measured.
Item UnitOperating mode
DL SEDL
Cooling capacity kW 42.0 106.1
Chilled waterInlet °C 15.0 12.0
Outlet °C 7.0 7.0
Cooling waterInlet °C 30.1 30.9
Outlet °C 34.5 36.6
Hot water(Heat source)
Inlet °C 60.0 88.7Outlet °C 56.3 53.0
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4. Prototyping and experiment – Result (2) –
The simulator was validated by comparing with experimental data.
40
45
50
55
55 60 65 70 75 80 85 90 95 100
Hot
wat
er o
utle
t te
mpe
ratu
re (
°C)
THW-out (SIM)THW-out (EXP)
0
20
40
60
80
100
120
55 60 65 70 75 80 85 90 95 100
Cap
acity
(QE)
, CO
P (
%)
Hot water inlet temperature (THW-in) (°C)
COP (SIM) COP (EXP)QE (SIM) QE (EXP)
Chilled water inlet: 13.0°C for SIM, 12.8~13.1°C for EXPCooling water inlet: 31.0°C for SIM, 30.7~30.9°C for EXP
Accuracy;THW-out: ±1°C (approx.)Capacity: ±5% of max. valueIn case of THW-in = 60°C, effect of heat leak increases relatively.
We are using this simulator considering this accuracy as enough level.
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5. Conclusions
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5. Conclusions – activating low temperature heat –
Current status of driving temperatures of absorption chillers
Hot Water DrivenAbsorption Chiller
Temp.: 60°C 90°C 120°C 150°C 180°C~
Direct fired Absorption Chiller/Heater
Steam DrivenAbsorption Chiller
Double effectSingle effect
(75°C)
SEDLAbsorption Chiller
Half effect
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0.000
0.001
0.002
0.003
0.004
0.005
0.006
Conventionalsingle-effect chiller
SEDL chiller(This work)
Hot
wat
er p
umpi
ng p
ower
(k
Wel/k
WC
ool)
0
20
40
60
80
100
120
140
Conventionalsingle-effect chiller
SEDL chiller(This work)
Coo
ling
capa
city
per
unit
hot w
ater
vol
ume
(MJ/
m3 H
W)
5. Conclusions – Comparisons with SE chillers
SEDL reduces hot water volume into about half amount, thus 1) increases cooling capacity per unit hot water volume (MJ/m3
HW), and 2) reduces pumping power for hot water (kWel/kWCool).
Chilled water: 12 -> 7°CCooling water:27 -> 33°CHot water inlet: 95°C
Flow rates of chilled water and cooling water are commonHot water inlet: 95°CHW pumping head: 20m
Cooling Capacity Pumping power
Í2 Í0.5
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5. Conclusions – remarks –
(1) A simulation program to study the effect of cycle configuration was developed. (2) A prototype SEDL absorption chiller with two-step E/A was also developed.
Patterns of circulating water were selected to maximize its cooling capacity.(3) The prototype performed at 106.1kW (30.2RT) in cooling capacity.
Chilled water of 7°C was obtained by using 88.7°C hot water, and its return temperature went down to 53.0°C.
(4) This prototype also could be driven in normal double-lift operation. 60°C hot water was used until 56°C and 7°C chilled water is produced.
(5) The simulation program appeared to have enough function and accuracy to predict the behaviour of SEDL absorption cooling cycle.
Through the development of SEDL chiller, following results are obtained.
This work is supported by New Energy and Industrial Technology Development Organization (NEDO), Japan.
© Hitachi, Ltd. 2017. All rights reserved.
Tatsuo FujiiMay/17/2017
Hitachi, Ltd. Research & Development GroupThermal Fluidic Systems Research Department
END
Cycle Simulation and Prototyping of Single-Effect Double-Lift Absorption Chiller
19
20© Hitachi, Ltd. 2017. All rights reserved.
Appendix A – Application image
Hot water network
Chilled water loopIndustrial waste heat, Power plant
SE/DL chillerHot water demand
Ø Wide temperature drop in hot water (i.e. 95 – 55 = 40 °C) reduces the hot water flow rate and pumping power of the system.
Gas-enginepower gen.
(CHP)
Ø Low temperature driven heat pump chillers are expected to be used in district heat, solar system and distributed energy systems.
Commercial demand
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Appendix B – Comparison with forerunner’s work
Ø Our project aims at reduction of hot water outlet temperature, hereby increase the application of hot water driven absorption chillers.
Cycle scheme
Cooling water temp. in/out (°C)
Hot water temp.
(°C)
1009080706050
Project Düsseldorf
Project Berlin
ZAE Bayern, 1998 This work
SE/DL
ASHRAE Transactions 104 (1998): 1420
27/35
Present Product
SE
(1990’s~)
31/37 27/35 31/36.4
: inlet : outlet
SE: Single effectDL: Double lift
27/33
For Asia For Europe
51°COutlet
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484950515253545556
94 95 96 97 98 99
100 101 102
Normal AHX*2 HHX *2 LHX *2 HHX *2LHX *2
HHX *2LHX *2AHX *2
Hot
wat
er te
mpe
ratu
re (T
HW-o
ut)
(°
C)
Cap
acity
(QE)
, CO
P (%
)
Solution heat exchanger formation
QE COP THW-outTHW-in: 95°C, Chilled water in-out: 13-8°C
Appendix C – Effect of solution heat exchangers –
Ø Referring simulation results, we selected “HHXÍ2 and LHX Í2”.
C AG
AA
AHX
E1
E2
HG
LG
HHX
LHX
A1
A2
Refrigerant liquid
Refrigerant vapour
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