1.6
Experimental Evaluation of Physical Hazard of A2L
Refrigerant Assuming Actual Handling Situations
The 24 th IIR International Congress of Refrigeration (ICR2015)
Workshop: Research Project on Risk Assessment of Mildly
Flammable Refrigerants
20, Aug. 2015 (Thu), Pacifico Yokohama, JAPAN
Tomohiko IMAMURA and Osami SUGAWA
Dept. of Mechanical Engineering,
Tokyo University of Science, Suwa, Japan
1. INTRODUCTION
1. Introduction
Background & Objective (1/3)
3/29
Deregulation and utilization for A2L refrigerants
Probability of ignition
and flame propagation
Physical
Hazard
Damage by the
combustion
Fundamental properties of combustion
Useful fundamental properties
of combustion
have been
obtained from
In the ideal environment
(no concentration distribution)
(no turbulence)
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
1. Introduction
Background & Objective (2/3)
4/29
In the actual handling situation of air conditioning systems…
➣Leaked refrigerant
generally has a certain
degree of concentration
distribution.
➣Ignition source is very
various, and ignition
behavior greatly affected by
the turbulence and flow of
the accumulated refrigerant.
We examined physical hazard by burning of A2L refrigerant
under several conceivable accident situations
based on these fundamental combustion behaviors.
1. Introduction
Background & Objective (3/3)
5/29
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
2. PHYSICAL HAZARD EVALUATIONS
OF A2L REFRIGERANTS
2-1: Use with Fossil Fuel Heating System
2-1: Use with Fossil-fuel Heating System
Objective & Experiments
7/29
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.
【Experiment】
2800
観測室
FTIR FTIR
refrigerant
to vacuum
stove（2.4 kW）
Fan heater（3.2kW）
400
2800
2100
Air
conditioning
system
BD
Monitor
cylinder
Logger
Amp.
Measurement position of
refrigerant and HF concentration
Unit: mm
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）
7
2-1: Use with Fossil-fuel Heating System
Experimental Results
Heater: radiative stove
10g/min, Refrigerant
60g/min, Refrigerant
10g/min, HF
60g/min, HF
AC-ON
0
20
40 60 80 100 120
time (min)
1000
900
800
700
600
500
400
300
200
100
0
HF Concentration (ppm)
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
HF Concentration (ppm)
R32 Concentration (vol%)
【Results】
8/29
2000
1800
1600
1400
1200
1000
800
600
400
200
0
10g/min, AC-OFF
10g/min, AC-ON
60g/min, AC-OFF
60g/min, AC-ON
R32
R1234yf R410A
Varieties of Refrigerants
➢ 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.
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
10/29
Accident Scenario: A service operative uses a portable lighter to smoke in a
space in which an A2L refrigerant has leaked and accumulated.
Type 1: piezo gas lighter
Push button
air
Fuel gas
【Characteristic】
・Fuel gas is discharged while a
push button is pushed.
・Mixture in the windbreak
consists of fuel gas, air, and
A2L refrigerant while a push
button is pushed.
・Concentration of fuel gas is
reached at least LFL at the
outlet of fuel gas in the
windbreak.
・The energy of piezo spark is
approximately 1~5 mJ.
2-2: Ignition and Flame Propagation Possibility by a Lighter
Objective & Experiments
11/29
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
Fuel is vaporized
【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.
2-2: Ignition and Flame Propagation Possibility by a Lighter
Objective & Experiments
12/29
Accident Scenario: A service operative uses a portable lighter to smoke in a
space in which an A2L refrigerant has leaked and accumulated.
Type 1: piezo gas lighter
Refrigerant: R1234yf, R1234ze(E), R32
【Experiment】
Solenoid valve
air
Lighter
300
Push rod
1000
Pneumatic
cylinder
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.
2-2: Ignition and Flame Propagation Possibility by a Lighter
Experimental Results
13/29
【piezo gas lighter】
Flame
Flame
One frame
passed
(1/30 sec)
Extinction
Extinction
R1234yf with LFL
Flame
Flame
One frame
passed
(1/30 sec)
Extinction
Extinction
R1234ze(E) with LFL
No ignition and flame propagation to accumulated A2L
refrigerant was confirmed.
2-2: Ignition and Flame Propagation Possibility by a Lighter
Objective & Experiments
14/29
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
【Experiment】
1000
Neon
transformer
Lighter
Digital video
camera
AC100V
Enegization time：50,
500 ms
300
CCD
Function
Generator
Relay
High-speed
camera
AC spark at 100 ms of
energization time
100,
2-2: Ignition and Flame Propagation Possibility by a Lighter
Experimental Results
15/29
【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
Energization time：100 ms
Energization time：500 ms
Refrigerant：R32，Refrigerant concentration at the lighter height：16 vol%
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)
2-2: Ignition and Flame Propagation Possibility by a Lighter
Experimental Results
16/29
【Kerosene cigarette lighter】
Refrigerant
Leak rate of refrigerant is small
Refrigerant cannot penetrate
to the windbreak?
Fuel
The gas in the windbreak
was sampled and GC-MS
analysis was carried out.
test 1
fuel 2gas only
test
The gas mixture in the windbreak consisted of vaporized
kerosene and
test
3only
R32
air even when the lighter was positioned in the accumulated R32.
test 4
Significant peak of
fuel gas only
The use of a kerosene cigarette lighter in accumulatedR32
R32 might be
R32
only
Significant
of
capable peak
of causing
ignition of and flame propagation to R32.
fuel
5
10 10
15 15
2020
analysis
start
(min)
Time Time
sincesince
analysis
start
(min)
5
16
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
18/29
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
Pinhole,
slit
Refrigerant
in the servicing and
maintenance factory
Car (example)
Refrigerants：R32, R1234yf, R1234ze(E)
Pinhole：
d=0.2, 1.0, 3.0, 4.0 mm
Slit: 1.0 x 4.0 mm
d
Mass flow rate：5.0-847 g/min
Ignition source：single spark, continuous spark, open flame
18
2-3: Physical Hazard of Rapid Leakage from a Pinhole
Experimental Results
Height (mm)
【Experimental Results】
(a) Spark generated (t = 0s)
50
12.5
0
2.5
10.0
-50
0
19/29
(b) t = 33 ms
5.0
7.5
Single spark
Pinhole
Pinhole
(a) J20-11（R32, φ 4 mm, 0.30MPa, 540 g/min）
100
200
300
Single Spark
Horizontal Distance (mm)
Continuous spark
Open flame
19
The flammable zone was formed only in partial areas.
No ignition and flame propagation to the entire A2L refrigerant
was observed.
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
21/29
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.
2-4: Physical Hazard of Leakage into the Collection Device
Experiment
22/29
【Experiment】
Unit: mm
1000
Concentration
measurement
system
1000
1000
cylinder
Model collection device
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
2-4: Physical Hazard of Leakage into the Collection Device
18
16
14
12
10
8
6
4
2
0
z=0cm
z=20cm
z=75cm
14
z=10cm
z=50cm
LFL
500
1000
time (sec)
1500
Slit: 0 mm
z=0cm
z=25cm
z=75cm
12
Slit: 1mm
0
23/29
Concentration (vol%)
concentration (vol%)
Experimental results
10
8
6
4
Slit: 20mm
2
2000
z=10cm
z=50cm
LFL
0
0
500
1000
time (sec)
1500
2000
Slit: 20 mm
The ignition possibility could be reduced by fixing slit
having suitable width.
3. CONCLUSIONS
3. Conclusions
Conclusions
25/29
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.
3. Conclusions
Conclusions
26/29
➣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.
26
ACKNOWLEDGEMENTS
Acknowledgements
28/29
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.
THANK YOU
VERY MUCH!
Lake Suwa, Japan, 2013.