1Low-GWP Refrigerant Workshop for IEA HPP's Annex 54: Heat Pumps for Low
GWP Refrigerants
Risk assessment of A2L refrigerants implemented in Japan
Eiji Hihara (University of Tokyo)
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Product Category Number of Unitsin 2016FY (x 1,000)
Refrigerant
Residential A/Cs 8,527.5 R410A ⇒ R32(almost 100%)
Commercial A/Cs 793.9 R410A ⇒ R32(only Small-size; 41%)
Gas engine-driven A/Cs 30.5 R410A
Water Chiller 12.9R410A, R134a⇒
R32,R1233zd,R1234ze,R1223yd
Commercial refrigerators 403.7R404 ⇒ R410A,
CO2,R448A,R463A
Refrigeration facility 29.7 R22 ⇒ NH3, (+CO2)
-in Japan-Conversion status for each product
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• Low Toxicity• Low Flammability
S:Safety
• Zero Ozone Depletion Potential (ODP)• Low Global Warming Potential (GWP)
E: EnvironmentPerformance
• High Seasonal Efficiency• Similar performance at high load
cooling
E: EnergyEfficiency
• Low Capital Cost• Low Operating Cost
E: EconomicFeasibility
S+3E
s
Key concept for refrigerant conversion
4Organization of the research committee for risk assessment of A2L refrigerants
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Japan Society of Refrigeratingand Air Conditioning Engineers,JSRAE
University of Tokyo
Tokyo University of Science, Suwa
Kyushu University
National Institute of Advanced Industrial Science and Technology,AIST
Japan AutomobileManufacturers Association, JAMA
Japanese Refrigerationand Air-conditioning Industry Association, JRAIA
Observers -NEDO-METI-KHK
Research on the safety of Mildly Flammable Refrigerants WG
Mini-Split Risk Assessment SWG(Ⅰ)(Ⅱ)
VRF Risk Assessment SWG
Chiller Risk Assessment SWG
Secretary: Fujimoto
Chair: Hihara
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A2L refrigerant risk assessment had difficulty and long period.
2011 2012 2013 2014 2015 2016 2017 2018
●ResidentialA/Cs
●CommercialA/Cs
●VRF
●Chiller
●Built-in Ref. Display Cabinets
●Others(Refrigeration
equipment)
R32 residential models launched.
R32 light commercial models launched.
Schedule of risk assessment for AC and others
New Risk assessmentfor A3 Refrigerant.
HFO centrifugal chillers launched.
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Trade-off relationship between GWP and flammability
R1234yf, R32, and R290 have much lower GWPs than R410A. R410A is nonflammable, but R1234yf, R32, and R290 are flammable.
Refrigerant R410A R32 R1234yf R717 R290Boiling temperature, ºC -51.4 -51.7 -29.4 -33.3 -42.1Critical temperature, ºC 71.3 78.1 94.7 132.4 96.7
GWP (100 years) 2088 675 4 <1 <3Burning velocity (cm/s) - 6.7 1.5 7.2 38.7
LFL [vol %] - 13.3 6.2 15 1.8UFL [vol %] - 29.3 12.3 28 9.5
Minimum ignition energy (mJ) - 15 500 21 0.246
Flammability 1 2L 2L 2L 3
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7Methodology of risk assessment
START
Identify user, intended use, reasonable foreseen misuse.
Estimation of risk
Hazard Identification
Risk Reduction
Evaluation of risk
Tolerable?
1
2
3
4
5
Validation and documentationYes
No
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8Identify products/system and life-stage for study
Residential A/C
Commercial A/C
VRF(multi A/C for commercial bldg..
Chiller
Commercial refrigerator
GHP
Industrial A/C
Identified Product/System
IdentifiedLife-stages
Logistic
Installation
Use(indoor)
Service
Disposal
Use(outdoor)
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Guide 51 ; Safety means freedom from unacceptable risks. Tolerable risk means accepted risk in a given context
based on the current values of society.
Examples of the current tolerable risk in Japan1. Chemical factory : 10-5 [accidents/(year-site)]2. Car : 10-7 [accidents/(year-unit)]3. Home appliance : 10-8 [accidents/(year-unit)]
for one million units in the market (106 unit)
Identify the tolerable risk
START
Identify user etc.
Estimation of risk
Hazard Identification
Risk Reduction
Evaluation of risk
Tolerable?
1
2
3
4
5
Validation and documentation
We concluded that the fire accident during use less than once a century would be acceptable.
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10Tolerable risk of each products
Product/System No. of units in market
Tolerable value Use Installation and
service
Residential A/C 1 × 108 1.0 × 10-10 1.0 × 10-9
Commercial A/C 7.8 × 106 1.3 × 10-9 1.3 × 10-8
VRF 1 × 107 1.0 × 10-9 1.0 × 10-8
Chiller 1.34 × 105 7.5 × 10-7 7.5 × 10-7
GHP 4.5 × 105 3.7 × 10-9 3.7 × 10-8
Display cabinet 4.9 × 105 2.0 × 10-8 2.0 × 10-7
Condensing unit 1.46 × 105 6.9 ×10-8 6.9 × 10-7
Tolerable value is dependent on the number of units in the market for each products
During installation and services, the tolerable value was increased by 10 times because the units are handled by trained professionals.
START
Identify user etc.
Estimation of risk
Hazard Identification
Risk Reduction
Evaluation of risk
Tolerable?
1
2
3
4
5
Validation and documentation
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11Methodology of Risk Assessment
[Probability of fire accident] = [Rapid leakage] × [High concentration] × [Ignition source]
Rapid leakage
Ignition
Existence of an ignition source
Concentration higher than lower flammability limit
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1. Rapid gas Leakage
2. Generating of Flammable volume
3. Existence of Ignition Source
and
and
Stove
AC type Residential Package VRF Chiller
Rapid Leak Rate 15kg/h 10kg/h 10kg/h burst 75kg/hProbability of leak 0.023% 0.0015% 0.0005% burst 0.0010%
market data (some data from IEC)
Stoves, Lighters, Sockets, Switches etc. were researched.
Estimation of incident probability
Ignition incident occurs when following three conditions occur simultaneously.
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Generated flammable volume-time integrationProbability of flammable volume=Space-volume x Total time
13FTA indoor space assumption13.
Flammable region
Floor-standing Indoor unit
Flammable gas region
Wall-mounted indoor unit
- Case of wall-mounted AC and floor-mounted AC -
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R32 Amount:1000 gFlow rate:250 g/min
• The small flammable region existed below the air outlet of indoor unit only.
• The flammable gas volume was small.• After leakage, the flammable region
vanished in less than a second.
Flammable region can only be seen near the unit
14.
- Case of wall-mounted AC -Flammable gas region
by the University of Tokyo Wall-mounted
Unit
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Refrigerant:R32Amount:1000 gFlow rate:250 g/min
• There was a large flammable region spread on the floor.
• The flammable region did not vanish for sometime.
Flammable region appears on the floor.
- Case of floor-mounted AC -Flammable gas region
by the University of Tokyo
Floor-mountedUnit
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16Study of flammability:TUSS16.
■ReferenceTHE INTERNATIONAL SYMPOSIUM on NEW REFRIGERANTS and ENVIRONMENTALTECHNOLOGY 2012
Pneumatic cylinder
Solenoid valve air
R1234yf Flammable
Flame
Flame propagation was not observed in the case of cigarette gas lighter with A2L gas
Result
LighterPush rod
300
1000
Refrigerantmixture
Study of ignition source- Cigarette Lighter -
Cigarette Lighter
by Tokyo University of Science at Suwa
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17Study of ignition:AIST17.Study of ignition source- Contactor, Sockets-
A2L gas did not ignite.But A2 and A3 gases ignited.
A2L
Contactor below 12kVA can be eliminated as ignition source for A2L gas.
by AIST by AIST
Magnetic contactor Hair Dryer
A3 A2
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2.30×10-4 (times/year/unit)by the results of the questionnaire survey
2. Volume and time of flammable gas
3. Ignition source
Flammable space
Indoor unit
1. Provability of rapid leakage
①AC magnetic switch (by AIST)
② Cigarette lighter (by TUS)
Electronic lighter is not a source of ignition.
③heating appliance (by TUS)
Flame propagation in the heating equipment is suppressed by convection.
Time and volume integration of flammable space9.8×10-3~3.7×10-2 m3・min (by U Tokyo)
Refrigerant: R32
When refrigerant leaksfrom a wall-mounted indoor unit, volume of flammable space is very small.
1) In the electromagnetic switch of 12kVA, flame propagation does not occur for R32.2) The possibility of ignition of Electrical components in the air-Conditioners and household appliances is extremely low.
Risk assessment of small split air conditionerSource: JRAIA
19Risk assessment of small split air conditionerTarget value
Results of risk assessment
3.着火源の存在
Ignition probability: 10-10 (times/year/unit) in use; 10-9 in service
Accident scenario
Ignition probability(times/year/unit)
Evalua-tion
At transportation 4.1х10-12 SafeAt installation 2.7х10-10 Safe
In operation Indoor unit:2.1х10-12
Outdoor unit:1.5х10-10SafeAlmost safe
In service 3.2х10-10 SafeAt disposal 3.6х10-11 Safe
Schedule2010~2013 2014 2015 2016
Consideration Fist Second assessmentConst. manual
Overseas operation
1) Wall-mounted split air conditioners are pretty safe in the lifecycle.
2) To improve the safety at the time of service and installation, a construction manual was issued.
Measures for safety
Source: JRAIA
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1.50×10-5 (times/year/unit)
2. Volume and time of flammable gas
3. Ignition source
Flammable space
1. Provability of rapid leakage
Risk assessment of floor-standing split air conditioner
Category Ignition source R32 Propane
Electric appliance
FireElectric equipmentAC switchLighting switch
△-××
〇〇〇〇
Smoking supplies
MatchOil lighterElectronic lighterFlame
○○×○
〇〇〇〇
Industrial tool
Metal sparkElectric toolRefrigerant recovery machineBrazing burner
○××
○
〇〇〇
〇
Body Spark of static electricity × 〇
Combustion appliance
HeaterWater heaterBoilerCooking device
△△△△
〇〇〇〇
Evaluation of ignition source for R32
When refrigerant leaksfrom a floor-standing indoor unit, volume of flammable space is notsmall.
Source: JRAIA
Refrigerant: R32
Time and volume integration of flammable gas1.43~1.55 m3・h (by U Tokyo)
21Risk assessment of floor-standing split air conditionerTarget value
Results of risk assessment
3.着火源の存在
Accident scenarioIgnition probability
(times/year/unit) Evalua-tion
At transportation 1.1х10-9 Safe
At installation 9.0х10-9 Safe
In operationIndoor unit:4.7х10-10
Outdoor unit:1.1х10-9SafeSafe
In service 4.3х10-9 Safe
At disposal 4.1х10-10 Safe
Schedule2013 2014 2015 2016
Consideration 1st 2nd assessmentConst. manual
Overseas operation
Source: JRAIA
Ignition probability: 10-9 (times/year/unit) in operation; 10-8 in service
・Mixing of leaked refrigerant with indoor air by a fan installed in indoor unit is required.
Measures for safety
22Risk assessment of VRF
2. Volume and time of flammable space
3. Ignition source
1. Provability of rapid leakage
Category Ignition source R32 Propane
Electric appliance
FireElectric equipmentAC switchLighting switch
○×××
〇〇〇〇
Smoking supplies
MatchOil lighterElectronic lighterFlame
○○×○
〇〇〇〇
Industrial tool
Metal sparkElectric toolRefrigerant recovery machineBrazing burner
○××
○
〇〇〇
〇
Body Spark of static electricity × 〇
Combustion appliance
HeaterWater heaterBoilerCooking device
○○○○
〇〇〇〇
○:Ignition,×:No ignition
(1) Evaluation of ignition source for R32
(2) Dangerous ignition source
In operation In service
Indoor Heater, cooking device, oil lighter Brazing burner
Outdoor Boiler, combustion heater Brazing burner
Ceiling cassette(0.8~10Hp)
Floor standing unit(1~20Hp)
Outdoor unit(5~56Hp)
Mechanical ventilation1.5 (times/h)
Natural ventilationClearance under Door: 10mm
No ventilation
Flammable volume [m3]
Time[min]
4.4E-03 5.3E-03 1.1E-02
158 ← ←
【Condition】Office:6.5*6.5*2.7mRefrigerant: 26.3kg (20Hp)
Indoor unit:5×10-6 (times/year/unit)Outdoor unit:1.48×10-3 (times/year/unit)
Refrigerant: R32
23Risk assessment of VRFTarget value
Results of risk assessment
3.着火源の存在
Accident scenarioIgnition probability
(times/year/unit) Evalua-tion
At transportation 7.8×10-17~1.8×10-16 Safe
At installation 1.9×10-9 Safe
In operation3.5×10-12 (Indoor)
1.9×10-11 (Outdoor)Safe
In service 8.7×10-11 Safe
At disposal 2.9×10-14 Safe
Measures for safety
Schedule2010~2013 2014 2015 2016
Location Safety measureRestaurant Leak detection, mechanical
ventilationKaraoke
(1) Indoor unit
Location Safety measure
Semi-underground Detector carrying, leak
detection, mechanical ventilationMachine
room
(2) Outdoor unit
In severe cases, safety measure is required.
1st 2nd assessment 3rd assessmentSafety guidelineAdd R1234yf, ze(E)
Ignition probability: 10-9 for indoor unit in use; 4×10-9 for outdoor unit in use 10-8 in service (times/year/unit)
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Conclusion
1. In Japan, the research committee was established in 2011 with collaboration of government, academia, and industry to initiate risk assessment of A2L. In March 2016, the research committee dissolved after concluding its research.
2. Based on the risk assessment, a new guideline of mildly flammable refrigerants for refrigerating equipment was drafted in 2016. R&D based on this guideline was conducted by each company.
3. The risk assessment for the safe use of flammable gases such as hydrocarbons are under study.
4. The final report on risk assessment of mildly flammable refrigerants can be freely downloaded from the following website.
http://www.jsrae.or.jp/jsrae/committee/binensei/risk_eng.html
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Thank you for your attention!
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