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The 24th IIR International Congress of Refrigeration (ICR2015) Workshop: Research Project on Risk Assessment of Mildly Flammable Refrigerants
Experimental Evaluation of Physical Hazard of A2L Refrigerant Assuming Actual Handling Situations
20, Aug. 2015 (Thu), Pacifico Yokohama, JAPAN
Tomohiko IMAMURA and Osami SUGAWA
Dept. of Mechanical Engineering, Tokyo University of Science, Suwa, Japan
1. Introduction
Background & Objective (1/3)
Deregulation and utilization for A2L refrigerants
Probability of ignition and flame propagation
Damage by the combustion
Fundamental properties of combustion
Ref.: Saburi, T. et al., Risk Assessment of Mildly Flammable Refrigerants, 2014 Progress Report, p.69, 2015, http://www.jsrae.or.jp/committee/binensei/2014PR_e.pdf
Useful fundamental properties of combustion
have been obtained from
In the ideal environment (no concentration distribution) (no turbulence)
Physical Hazard
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➣Leaked refrigerant generally has a certain degree of concentration distribution.
We examined physical hazard by burning of A2L refrigerant
under several conceivable accident situations
based on these fundamental combustion behaviors.
1. Introduction
Background & Objective (2/3)
In the actual handling situation of air conditioning systems…
➣Ignition source is very various, and ignition behavior greatly affected by the turbulence and flow of the accumulated refrigerant.
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1. Introduction
Background & Objective (3/3)
Deregulation for A2L refrigerants
Risk assessment for A2L refrigerants based on the conceivable accident scenario is required.
Case1 Physical hazard evaluation in the case where an air conditioner containing an A2L-class refrigerant is simultaneously used with a fossil-fuel heating system in a general living space
Case2 Physical hazard evaluation in the service and maintenance
Case3 Physical hazard evaluation using VRF system
In the case of using a lighter in the refrigerant-leaked ambient: evaluation of ignition possibility
In the case that refrigerant leaks from a pinhole formed on the pipes or hoses
In the case that refrigerant leaks into an equipment used to service and maintenance like a collection device
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7
2-1: Use with Fossil-fuel Heating System
Objective & Experiments
Accident scenario: A wall-mount type room air conditioning system containing an A2L refrigerant is simultaneously used with a fossil-fuel heating system inside a general living space.
28
00
2800
21
00
40
0
Air conditioning system
FTIR FTIR
to vacuum
Logger
Amp.
cylinder
観測室
BD
Monitor
Unit: mm
stove(2.4 kW) Fan heater(3.2kW)
Measurement position of refrigerant and HF concentration
refrigerant
【Experiment】
Refrigerants:R32, R1234yf, R410A
Leak amount:800 g(generally installed in a commercial RAC)
Leak rate:10 g/min, 60 g/min
Heater:radiative stove(2.4 kW),oil fan heater(3.2 kW)
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【Results】
0200400600800
100012001400160018002000
R32 R1234yf R410A
HF
Co
nce
ntr
atio
n (
pp
m)
Varieties of Refrigerants
10g/min, AC-OFF10g/min, AC-ON60g/min, AC-OFF60g/min, AC-ON
➢ Hydrogen fluoride which is generated due to the combustion or thermal decomposition was confirmed. The concentration of generated HF is more than 3 ppm which is the permissible value, even R410A.
Heater: radiative stove
➢ Refrigerant concentration (<2 vol%) was much lower than LFL. Therefore no ignition and flame propagation to A2L refrigerants were observed.
2-1: Use with Fossil-fuel Heating System
Experimental Results
0
100
200
300
400
500
600
700
800
900
1000
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 20 40 60 80 100 120
HF
Co
nce
ntr
atio
n (
pp
m)
R3
2 C
on
cen
trat
ion
(vo
l%)
time (min)
10g/min, Refrigerant
60g/min, Refrigerant
10g/min, HF
60g/min, HF
AC-ON
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2. PHYSICAL HAZARD EVALUATIONS OF A2L REFRIGERANTS
2-2: Ignition and Flame Propagation Possibility by a Lighter
2-2: Ignition and Flame Propagation Possibility by a Lighter
Objective & Experiments
Accident Scenario: A service operative uses a portable lighter to smoke in a space in which an A2L refrigerant has leaked and accumulated.
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Type 1: piezo gas lighter
Push button
Fuel gas
air
・Fuel gas is discharged while a push button is pushed.
【Characteristic】
・Concentration of fuel gas is reached at least LFL at the outlet of fuel gas in the windbreak.
・Mixture in the windbreak consists of fuel gas, air, and A2L refrigerant while a push button is pushed.
・The energy of piezo spark is approximately 1~5 mJ.
Accident Scenario: A service operative uses a portable lighter to smoke in a space in which an A2L refrigerant has leaked and accumulated.
Type 2: Kerosene lighter
2-2: Ignition and Flame Propagation Possibility by a Lighter
Objective & Experiments
【Characteristic】
・Fuel gas is discharged while a cap of lighter is opened.
・Up-current of vaporized fuel is
appeared while a cap of lighter is opened.
・The energy of spark generated by rubbing a flint is much larger than that of piezo element.
Fuel is vaporized
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2-2: Ignition and Flame Propagation Possibility by a Lighter
Objective & Experiments
Accident Scenario: A service operative uses a portable lighter to smoke in a space in which an A2L refrigerant has leaked and accumulated.
【Experiment】
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Type 1: piezo gas lighter
Lighter
Push rod
Pneumatic cylinder
Solenoid valve air
300
1000
Refrigerant: R1234yf, R1234ze(E), R32
It was predicted that the concentration of n-butane/A2L refrigerants/air mixture is within the flammable range when the concentration of A2L refrigerants close to a gas lighter is less than LFL.
【piezo gas lighter】
One frame passed (1/30 sec)
Extinction Flame
R1234yf with LFL
Flame Extinction
No ignition and flame propagation to accumulated A2L refrigerant was confirmed.
2-2: Ignition and Flame Propagation Possibility by a Lighter
Experimental Results
One frame passed (1/30 sec)
Extinction Flame
R1234ze(E) with LFL
Flame Extinction
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2-2: Ignition and Flame Propagation Possibility by a Lighter
Objective & Experiments
Accident Scenario: A service operative uses a portable lighter to smoke in a space in which an A2L refrigerant has leaked and accumulated.
【Experiment】
Lighter 30
0
10
00
Neon transformer
Relay AC100V
High-speed camera
CCD
Digital video camera
Function Generator
Enegization time:50, 100, 500 ms
AC spark at 100 ms of energization time
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Type 2: kerosene lighter
【Kerosene cigarette lighter】
Ignition of a kerosene cigarette lighter was initiated by ac spark instead of the spark generated by rubbing a flint against a flint wheel directly.
Energization time:50 ms
Actual spark energy generated by rubbing:1.2 J
(Assuming that the composition of the flint alloy is 70wt% of cerium and 30wt% of Iron, and the mass of worn-down flint particle per one turn of flint wheel was 1.2×10-4 g)
Energization time:100 ms Energization time:500 ms
Refrigerant:R32,Refrigerant concentration at the lighter height:16 vol%
2-2: Ignition and Flame Propagation Possibility by a Lighter
Experimental Results 15/29
16
【Kerosene cigarette lighter】
Leak rate of refrigerant is small
The gas in the windbreak was sampled and GC-MS analysis was carried out.
5 10 15 20
Time since analysis start (min)
fuel gas only
R32 only
Significant peak of R32
Significant peak of fuel
5 10 15 20
Time since analysis start (min)
test 1test 2test 3test 4fuel gas onlyR32 only
The gas mixture in the windbreak consisted of vaporized kerosene and air even when the lighter was positioned in the accumulated R32. The use of a kerosene cigarette lighter in accumulated R32 might be capable of causing ignition of and flame propagation to R32.
Refrigerant cannot penetrate to the windbreak?
Fuel
Refrigerant
2-2: Ignition and Flame Propagation Possibility by a Lighter
Experimental Results 16/29
2. PHYSICAL HAZARD EVALUATIONS OF A2L REFRIGERANTS
2-3: Physical hazard of rapid leakage from a pinhole
2-3: Physical Hazard of Rapid Leakage from a Pinhole
Objective & Experiment
Accident Scenario: An A2L refrigerant leaks from a fracture or pinhole in the pipes or hoses such as that used to connect a car’s air conditioning system to a collection device.
Collection device
Car (example)
Pinhole, slit
Refrigerant
in the servicing and maintenance factory
18
Refrigerants:R32, R1234yf, R1234ze(E)
Pinhole: d=0.2, 1.0, 3.0, 4.0 mm
d
Slit: 1.0 x 4.0 mm
Mass flow rate:5.0-847 g/min
Ignition source:single spark, continuous spark, open flame
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【Experimental Results】
10.0 7.5 5.0
2.5
0 100 200 300
50
0
-50
Horizontal Distance (mm)
Heig
ht
(mm
)
12.5
(a) J20-11(R32, φ 4 mm, 0.30MPa, 540 g/min) Pinhole
Single spark
(a) Spark generated (t = 0s)
Pinhole
(b) t = 33 ms
Single Spark
Continuous spark Open flame
2-3: Physical Hazard of Rapid Leakage from a Pinhole
Experimental Results
The flammable zone was formed only in partial areas.
No ignition and flame propagation to the entire A2L refrigerant was observed.
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2. PHYSICAL HAZARD EVALUATIONS OF A2L REFRIGERANTS
2-4: Physical Hazard of Leakage into the Collection Device
2-4: Physical Hazard of Leakage into the Collection Device
Objective & Experiment
Accident Scenario: An A2L refrigerant leaked to inside of an equipment used for service and maintenance such as a collection device.
http://www.jraia.or.jp/htdocs_test2/product/flon/index.html
We examined…
➣leakage and ignition behaviors of A2L refrigerant in a model collection device.
➣especially the effect of slit fixed in the collection device to prevent the accumulation and ignition of leaked refrigerant.
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【Experiment】
Model collection device
cylinder
Concentration measurement system
1000
1000
1000
2-4: Physical Hazard of Leakage into the Collection Device
Experiment
Unit: mm
slit
Location of measurement of concentration: 0, 10, 25, 50, 75 cm above the bottom of model collection device Ignition source:DC spark discharge(energy: 16J,6Hz) Slit width:0 (close),1, 5, 10, 20 mm Varieties of refrigerant:R1234yf
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0
2
4
6
8
10
12
14
16
18
0 500 1000 1500 2000
con
cen
trat
ion
(vo
l%)
time (sec)
z=0cm z=10cm
z=20cm z=50cm
z=75cm LFL
0
2
4
6
8
10
12
14
0 500 1000 1500 2000
Co
nce
ntr
atio
n (
vol%
)
time (sec)
z=0cm z=10cmz=25cm z=50cmz=75cm LFL
Slit: 1mm Slit: 20mm
Slit: 0 mm Slit: 20 mm
2-4: Physical Hazard of Leakage into the Collection Device
Experimental results
The ignition possibility could be reduced by fixing slit having suitable width.
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3. Conclusions
Conclusions
We conducted the physical hazard evaluation on A2L refrigerant assuming conceivable accident scenarios experimentally.
➣Use with Fossil Fuel Heating System
➣Refrigerant concentration (<2 vol%) was much lower than LFL. Therefore no ignition and flame propagation to A2L refrigerants were observed.
➢ Hydrogen fluoride which is generated due to the combustion or thermal decomposition was confirmed. The concentration of generated HF is more than 3 ppm which is the permissible value, even R410A.
➣Ignition and Flame Propagation Possibility by a Lighter
➣When a piezo gas lighter was used in the accumulated R32 and R1234yf, no ignition and flame propagation was observed.
➣But when a kerosene cigarette lighter was used under the slow leak condition, ignition and flame propagation was observed.
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3. Conclusions
Conclusions
➣Physical hazard of rapid leakage from a pinhole
➣The flammable zone was formed only in partial areas.
➣No ignition and flame propagation to the entire A2L refrigerant was observed.
➣Physical Hazard of Leakage into the Collection Device
➣The ignition possibility could be reduced by fixing slit having suitable width.
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Acknowledgements
This study has been conducted a part of research project on the “Technology Development of High-efficiency Non-fluorinated Air Conditioning Systems” conducted by New Energy and Industrial Technology Development Organization (NEDO). The authors would like to sincerely thank Mr. Takanori Morimoto and Dr. Kyoko Kamiya of Japan Specialist in Law Engineering Corporation, and Mr. Shunta Nakamura, Mr. Shunsuke Mashimo, Mr. Takuro Sano and Mr. Kazutaka Yuzawa of undergraduate student of Tokyo University of Science, Suwa, for their kind supports with the experiments.
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