performance considerations in adopting zero-odp and low-gwp refrigerants
TRANSCRIPT
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8/16/2019 Performance Considerations in Adopting Zero-ODP and Low-GWP Refrigerants
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Performance considerations in adoptingzero-ODP and low-GWP refrigerants
Eiji Hihara
The University of Tokyo
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Contents
• Introduction
• Performance of natural working fluids
• Performance of low-GWP refrigerants
• Conclusion
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Background1. R-1234yf is developed for mobile AC.
2. For residential and commercial AC, R-32, R-1234yf, mixture with R-1234yf are considered as candidates of next refrigerant.
3. The new refrigerant/refrigerant mixture must balance the systemefficiency, GWP, and safety.
Annual shipment inJapan
Current refrigerant Low-GWP refrigerant
Domestic refrigerator 4.3 million isobutane isobutane
Mobile air-conditioner 4.75million R-134a R-1234yf
Residential air-conditioner
7.75million R-410A ?
Commercial air-conditioner
7.44million R-410A ?
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Thermodynamic properties of low-GWPrefrigerants
R-410A R-32 R-1234yf
Chemical formula R32/R125(50%/50%)
CH2F2 CF3CF=CH2
Boiling temperature -51.6ºC -51.7ºC -29ºC
Critical temperature 72.5ºC 78.1ºC 95ºC
GWP(100years) 2088 650 4
Toxicity ASHRAE A ASHRAE A ASHRAE A
Flammability - ASHRAE 2L ASHRAE 2LLifetime in the air - 5.6 yeas 11 days
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Latent heat
Refrigerant Latent heatkJ/kg@25ºC
R410A 186.5R32 270.9
R1234yf 145.4
R22 182.7
Propane 335.7
Small latent heat of R-1234yf causes a large mass flow rate and alarge pressure drop.
25ºC
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Trade-off problem
Changing refrigerant is an important option to solveenvironmental problem.
Current refrigerant R-410A : GWP=2088
New low-GWP refrigerant R-1234yf: GWP=4
But the COP is very low for residential use.
Low GWP
Small latent heat
Large mass flow rate
Large pressure drop
Low COP
Trade-off
problem
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Contents
• Introduction
• Performance of natural working fluids
•
Performance of low-GWP refrigerants• Conclusion
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Fundamental heat pump cycle
1
23
4
P
h
subcooling : 5ºC
superheat : 5ºC
Temperature
Cooling conditionsEvaporating temp.: Teva
9ºC
Cooling conditions
Condensing temp.: Tcond 45ºCHeating conditionsEvaporating temp.: Teva
-3ºC
Heating conditionsCondensing temp.: Tcond
30ºC
Subcooling 5ºC
Superheat 5ºC
Compressor efficiency 1.0
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Performance of Heat Pump Cycles(direct-expansion fundamental cycle)
0 1 2 3 4 5 6 7 8 9
ammonia
propane
CO2
R22
R410A
R407C
COP
heating
cooling
0 5000 10000 15000 20000
ammonia
propane
CO2
R22
R410A
R407C
Capacity per suction vapor volume, kJ/m3
heating
cooling
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Revised heat pump cycles for ammonia,
propane, and carbon dioxide
Refrigerant Problem Revised cycle
Ammonia • Flammability• High temperature
of discharge gas
Liquid injection and
secondary refrigerantcycle
Propane • Flammability Secondary refrigerantcycle
Carbon dioxide • Low COP Internal heatexchange cycle
R22, R410A,R407C
Non Fundamental cycle
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Secondary Refrigerant Cycle
Fundamental cycle Secondary
refrigerant cycle
Cooling conditionsEvaporating temp.: Teva 9ºC 4ºC
Cooling conditionsCondensing temp.: Tcond
45ºC 45ºC
Heating conditionsEvaporating temp.: Teva
-3ºC -3ºC
Heating conditionsCondensing temp.: Tcond
30ºC 35ºC
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Transcritical Cycle
with Internal Heat Exchanger for CO2
1
23
4
P
h
heat exchange
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Liquid Injection Cycle for Ammonia
• In order to decrease the
discharge gas temperature, smallamount of liquid ammonia isinjected to the compressionprocess at the intermediatepressure.
•
5
1
23
4
67
1
x
x +1P
h216 P P P
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Brief summary
The performance of basic cycle of natural working fluids was comparedwith conventional refrigerants.
1. R22 has the highest COP.
2. Concerning ammonia, two-stage compression with liquid injection
cycle improves the COP and decreases the compressor dischargetemperature. But due to the flammability, the secondary refrigerantsystem reduces the COP.
3. For propane the potential performance is similar to R22, but thesecondary refrigerant system reduces the COP.
4. The COP of carbon dioxide is very low.
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Contents
• Introduction
• Performance of natural working fluids
• Performance of low-GWP refrigerants
• Conclusion
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ObjectiveCalculate cooling and heating COP using three pure
refrigerants and a mixture; R-410A, R-32, R-1234yf andR-32/R-1234yf(50%/50%).
Evaluate the performance of heat pump considering the
effect of the connecting tube.
Estimate total equivalent CO2 emission by using LCCPmethod.
Performance of low-GWP refrigerants is compared with thatof conventional refrigerants.
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Calculation Conditions
†)Based on JIS C 9612:2005
Test conditionRated cooling
capacity
Half cooling
capacity
Rated heating
capacity
Indoor dry bulb temp. [ºC] 27 20
Indoor wet bulb temp.[ºC] 19 -
Indoor air flow rate [m3 /min] 3.0
Outdoor dry bulb temp. [ºC] 35 29 7
Outdoor wet bulb temp.[ºC] - - 6
Outdoor air flow rate [m3 /min] 12.0
Capacity[kW] 1.3 0.65 1.6
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Heat Pump ModelIndoor Heat Excahnger
Outdoor Heat Exchanger
Suction Tube
Length: 7.5[m] I.D.:5.5[mm]
Discharge Tube
Length: 7.5[m] I.D.:5.5[mm]
Expansion Valve
CompressorFour way valve
Outdoor Unit
Indoor Heat Excahnger
Outdoor Heat ExchangerSuction Tube
Length: 1.0[m] I.D.:5.5[mm]
Discharge Tube
Length: 7.5[m] I.D.:5.5[mm]
Expansion ValveCompressor
Four way valve
Outdoor Unit
Cooling mode
Heating mode
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Heat exchanger modelIndoor heat exchanger Outdoor heat exchanger
Fin-tube HEX Air
Air
Row ColumnTotallength[m]
I.D.
[mm]
Finthickness[mm]
Finpitch[mm]
7/6 2 8.645 6.4 0.1 1.3
Row ColumnTotallength[m]
I.D.
[mm]
Finthickness[mm]
Finpitch[mm]
10 1 8.0 6.4 0.1 1.3
Fin-tube HEX
Refrigerant
Refrigerant
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1. On the rated cooling capacity condition, the COP of R-1234yf is about 60%of R-410A. The COP of R32 is the highest.
2. On the half cooling capacity condition, the difference becomes small.
3. The COP of R-32/R-1234yf mixture is better than that of R-1234yf.
COP on the rated & half coolingcapacity conditions
0
0.5
1
1.5
2
2.5
Rated coolingcapacity
Half coolingcapacity
C O P r
a t i o t o
R - 4 1 0 A
R-410AR-32
R-1234yfR32/R1234yf(50/50%)
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0.00.51.0
1.52.02.53.03.54.04.5
G[kg/s] ratio atrated capacity
Δ P[kPa] ratiothrough
evaporator atrated capacity
Δ P[kPa] ratiothrough suctiontube at rated
capacity
G[kg/s] ratio athalf capacity
Δ P[kPa] ratiothrough
evaporator athalf capacity
Δ P[kPa] ratiothrough suction
tube at halfcapacity
R
a t i o
t o
R 4 1 0 A R-410A
R-32R-1234yf R32/R1234yf(50/50%)
Mass flow rate and pressure drop incooling operation
• The COP of R-1234yf is very low due to its large pressure drop.
• The effect of pressure drop is not so large on the half capacity condition.
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LCCP Evaluation
Life Cycle Climate Performance
Climate impact is presented as an amount of equivalent CO2 emission.
LCCP is consists of two factors: direct impact and indirect impact.
Three different annual operation times for the heat pump areassumed.
normal: 1430h for cooling, 2889h for heating 1/2: 715h for cooling, 1445h for heating
1/3: 477h for cooling, 763h for heating
Direct Impact Indirect ImpactRegular emission of refrigerant duringoperation and end-of-life emissionsfrom the recovery of refrigerant at theend-of-life of the heat pumps.
Electricity consumption duringmanufacturing, operation andend-of-life of heat pumps.
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Comparison of total equivalent CO2 emission
• Direct impacts of R-1234yf and R-32 are negligibly small, because indirectimpact accounts for a substantial portion of total equivalent CO2 emission.
• R-32 and R-1234yf are better refrigerants than R-410A.
0
0.20.4
0.6
0.8
1
1.2
R - 4 1 0 A
R - 3 2
R
- 1 2 3 4 y f
R - 4 1 0 A
R - 3 2
R
- 1 2 3 4 y f
R - 4 1 0 A
R - 3 2
R
- 1 2 3 4 y f
Normal Time 1/2 Time 1/3
T o t a l e q u i v a l e n t C O 2 e m i s s
i o n
r a t i o
Indirect CO2 emission ratio of heating operation
Indirect CO2 emission ratio of cooling operation
Direct CO2 emission ratio
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Drop-in test of R-1234yf
APF
“Performance and Reliability Evaluation of a Room Air Conditioner with Low GWP Refrigerant,” TakashiOkazaki et al. Mitsubishi Electric Corporation
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Drop-in test of R32/R1234yf mixtures
“Experimental Study of Low GWP Refrigerants for Room Air-Conditioners ,” Hideki HARA et al. DAIKININDUSTRIES, LTD
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Thank you for your attention!
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