Development of centrifugal chiller and heat pump using...
Transcript of Development of centrifugal chiller and heat pump using...
© 2017 MITSUBISHI HEAVY INDUSTRIES THERMAL SYSTEMS, LTD. All Rights Reserved.
2017.5.17
Development of centrifugal chiller and heat pump using low GWP refrigerant
Ryosuke Suemitsu1*, Naoya Miyoshi1, Yasushi Hasegawa1,
Kazuki Wajima1, Yoshinori Shirakata1, Kenji Ueda1
1Mitsubushi Heavy Industries Thermal Systems, Ltd.
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Today’s Presentation
1. Introduction
2. Development of centrifugal chiller using low GWP refrigerant
3. Development of centrifugal heat pump using low GWP refrigerant
4. Conclusions
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1. Introduction
Paris Agreement (in December 2015, COP21)
Every country shall update and submit the own country’s reduction goal every 5 years.
Montreal Protocol “Kigali Revision” (in October 2016)
Mandatory of the HFC production and the step-by-step reduction
There is a need to transfer
to low GWP refrigerants.
1 5,000 100 1,000 (USRT)
Capacity(kW)
Centrifugal Chiller
Co
oli
ng
s
ou
rce
He
ati
ng
so
urc
e
Centrifugal heat pump
Shopping center/mall Clean room
Tall building Building
Capacity and temperature needs
1990s 2000s 2010s
HFCs (Ex. R-134a) GWP:100~4,000
Paris Agreement
Montreal Protocol (2016)
The next-generation
alternative refrigerant GWP: low
Transition of refrigerant
We use R-134a as the refrigerant of centrifugal chillers and heat pumps.
3.5 350 3,500
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1. Introduction
We need to take into consideration the following requirements to select alternative refrigerants;
Environmental conditions: GWP ≦ 150, ODP ≦ 0.001, allowable concentration ≧ 800 ppm.
Low toxicity and low flammability Physical properties: The design pressure must not be excessively high, because of the price of machines.
Cycle efficiency is equivalent to that of R-134a.
Cost
Refrigerant HFC Olefins
134a 1234yf 1234ze(E) 1233zd(E)
Global Warming Potential (GWP) *5thIPCC 1300 <1 <1 1
Ozone Depletion Potential (ODP) 0 0 0 0
Allowable concentration [ppm] 1000 500 800 800
Toxicity low low low low
Flammability non low low non
Safety class *ASHRAE34 A1 A2L A2L A1
Saturated pressure (@38℃)[kPaG] 861.9 866.4 624.3 100.8
Theoretical COP *@ET=5,CT=38,η=0.9 6.58 6.31 6.56 6.93
Price / R-1233zd(E) rated value - 2.5 1.5 1
Comparison of R-134a and olefins
R-1234ze(E) and R-1233zd(E) meet our requirements.
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1. Introduction
We selected R-1234ze(E) and R-1233zd(E) for centrifugal chillers.
A R-1234ze(E) type has been developed
for the capacity from 300 to 5000 USRt.
A R-1233zd(E) type has been developed
for the capacity from 150 to 700 USRt.
There are still some candidate refrigerants for centrifugal heat pumps.
1234ze(E) 1233zd(E)
1 5,000 100 1,000 Capacity (USRT)
(kW)
Centrifugal Chiller
Co
oli
ng
s
ou
rce
H
ea
tin
g s
ou
rce
Centrifugal heat pump
Shopping center/mall Clean room
Tall building Building
Capacity and temperature needs
3.5 350 3,500
some candidate refrigerants
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R-1233zd(E)’s cycle efficiency is better than R-134a,
and the cost is better than R-1234ze(E).
However,
the specific gas volume
is about five times larger than R-134a.
Advanced and compact design is made
to replace with centrifugal chillers using R-1233zd(E).
Refrigerant HFC Olefins
134a 1234ze(E) 1233zd(E)
Standard boiling point [℃] −26.1 −19.0 18.3
Saturated pressure (@6℃)[kPaG] 260.7 167.3 −39.1
Saturated pressure (@38℃)[kPaG] 861.9 624.3 100.8
Saturated vapor specific volume (@6℃)[m3/kg] 0.056 0.069 0.277
Theoretical COP *@ET=5,CT=38,η=0.9 6.58 6.56 6.93
Price / R-1233zd(E) rated value - 1.5 1
2. Development of centrifugal chiller
Refrigerant
Comparison of R-134a and olefins for chiller
R-1234ze(E)’s physical properties
are similar to R-134a.
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Compressor
Improvement of aerodynamic design
CFD analysis was performed to optimize the impeller, the inlet guide vane, and the path form of refrigerant gas.
Compared with R-134a,
the volume of compressor reduces to 140%.
the adiabatic efficiency is improved by 3% for the same capacity.
Refrigerant 134a 1233zd(E)
Saturated vapor specific volume (@6℃)[m3/kg] 0.056 0.277
About five times larger
Impeller
Inlet guide vane
Path of refrigerant gas
Outline drawing
of centrifugal compressor
Ref. inlet
Ref. outlet
Reduce
to 140%
compared
with R-134a
2. Development of centrifugal chiller
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Compressor
Direct-connected motor
For R-1233zd(E), the impeller is
directly mounted on the motor shaft,
For R-134a, the impeller is rotated
by the motor via a step-up gear.
as the lower vapor sound speed can be achieved
even if the capacity is same.
A compact compressor unit with a motor
Improved performance by reducing the losses as the result of eliminating the step-up gear and minimizing the number of compressor bearings
2. Development of centrifugal chiller
Refrigerant 134a 1233zd(E)
Saturated vapor sound speed (@6℃)[m/s] 146.7 135.8
Lower
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Evaporator and condenser
The shell & tube type heat exchanger, and flooded type evaporator Since the specific gas volume is larger, and the differential pressure between the condenser and evaporator is smaller than R-134a, pressure drop should be carefully considered.
We analyzed the actual chiller and measured the verification test
Evaporator Condenser
2. Development of centrifugal chiller
Inlet
Chilled water
Ref. outlet
Ref. inlet
Outlet
Inlet
Cooling water
Ref. outlet
Ref. inlet
Outlet
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Evaporator and condenser
Compared with R-134a,
The volume of the evaporator and condenser reduce to 120%.
The outside heat-transfer coefficient of evaporator registers no more than 10% decrease, and the coefficient of condenser registers no more than 20% decrease at the rated condition.
Test results of evaporator Test result of condenser
2. Development of centrifugal chiller
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Model Existing Developed
Rated capacity 200 USRt (703 kW)
Refrigerant R-134a R-1233zd(E)
Chilled water temp. 12.0°C → 7.0°C
Chilled water flow rate 120.7 m3/h
Cooling water temp. 32.0°C → 37.0°C
Cooling water flow rate 141.5 m3/h 139.6 m3/h
Power consumption 115.0 kW 111.3 kW
COP 6.1 6.3
Dimensions L×W×H 3.7×1.5×1.8 m 3.8×1.6×1.7 m
Installation area 5.55 m2 5.83 m2
Shipping weight 3.9 ton 4.3 ton
The COP is improved by 3% compared with an existing type that had the same capacity, under the rated capacity conditions.
The installation area reduces about 105% that of the existing type for the capacity from 150 to 700 USRt.
Model machine verification
*machine rated value = 200 USRt
Test machine appearance
2. Development of centrifugal chiller
Comparison of specification
Performance Result
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3. Development of centrifugal heat pump
Industrial customers have required us heat pumps to use high temperature heat.
We have been developing a high temperature heat pump
heating pressurized water to the temperature from 160°C to 200°C
The target COP is 3.5 with the aim of boiler replacement.
Refrigerant
The operational temperature must be considered. This requires the following;
Stability at high temperature: Prevention of isomerization and decomposition.
Standard boiling point: The size of compressor should not be too small for the adiabatic efficiency. The design pressure should not be too high for the manufacturing.
Critical point: The critical temperature should be higher than the operating temperature to improve the efficiency of the cycle.
Lubricant oil
The lubricant oil must maintain the stability at high temperature, requiring the temperature-dependent viscosity and solubility in the refrigerant.
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Refrigerant HFC Olefins
134a 1234ze(E) 1233zd(E)
Standard boiling point [°C] -26.1 -19.0 18.3
Critical temperature [°C] 101.1 109.4 166.5
Saturated pressure (@90°C)[MPaA] 3.244 2.476 0.833
Saturated vapor specific volume (@30°C)[m3/kg]
0.0266 0.0328 0.1175
Theoretical COP *@ET=25,CT=91,η=0.9 2.00 2.04 2.46
3. Development of centrifugal heat pump
Test condition Result
R-1233zd(E)
: Mineral oil
Temperature [°C]
Duration [h]
Air/moisture [ppm]
Acid Value [kOH/g]
50:50 150 168 100/100 <0.01
50:50 150 168 500/100 <0.01
50:50 150 168 1000/1000 0.03
50:50 200 168 500/1000 0.02
50:50 200 336 500/1000 0.01
R-1233zd(E) meets our requirements
Stability: at up to 150°C
but, poor at 200°C…
We still have
some candidate refrigerants.
Mineral oil was selected
Stability of R-1233zd(E): Thermal stability for 90°C applications
Enough solubility and viscosity: Kinetic viscosity and solubility are 125% and 112%, compared with requirements for the bearings of up to 160°C applications.
Refrigerant and lubricant oil First step; We investigated the replacement with a low GWP refrigerant in a 90°C application.
Accelerated thermal stability testing for 90°C applications
Comparison of R-134a and olefins for 90°C applications
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Aerodynamic shape of compressor The compressor was designed for a high head and large volume flow rate
to reduce the number and the capacity.
The compression ratio is larger by 40%, compared with a chiller.
The flow rate is larger by 39%, and
the adiabatic efficiency is improved by 3.5%, compared with an existing type.
3. Development of centrifugal heat pump
Equipment design Heat pump cycle
We adopted the compression bleeding cycle for the temperature from 160°C applications.
The bleeding cycle is highly efficient
by using some of the refrigerant gas
to discharge from the low stage compressor
for intermediate heating.
The compressors have two-stages compression. Two-stage compression bleeding cycle
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3. Development of centrifugal heat pump
Future work
The heat pumps operating at high temperature using low GWP refrigerants are going to be developed through the stages, 90°C, 160°C, 200°C.
The development of refrigerants and lubricant oil are being conducted in parallel with that of the heat pump.
We focus to introduce a model to heat pressurized water to 200°C in practical applications by 2023.
Application
Heat pumps heating water to the temperature from 160°C to 200°C are suitable for industrial applications, for example, chemical reaction and dried processes.
We have been investigating the details to propose a heat system for industrial processes. ex) heat and energy balance operating time temporal axis of thermal demand and heat source
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4. Conclusions and Acknowledgements
A centrifugal chiller using low GWP refrigerant have been developed.
A R-1234ze(E) type have been developed for the capacity from 300 to 5000 USRt.
A R-1233zd(E) type have been developed for the capacity from 150 to 700 USRt.
A centrifugal heat pump using a low GWP refrigerant is being developed.
In the experiments, R-1233zd(E) was selected for a heat pump heating water to 90°C. The design have been completed and we are preparing for drop-in testing.
The developments of heat pumps heating water to 90°C, and higher temperatures are going to be carried out, with a final goal of operation at 200°C.
This work is supported by New Energy and Industrial Technology Development
Organization(NEDO).