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, JAPANTomohiko 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

PhysicalHazard

Damage by thecombustion

Fundamental properties of combustion
Useful fundamental propertiesof combustion

have beenobtained fromIn 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 veryvarious, and ignitionbehavior 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 evaluationin the case where an air
conditioner containing anA2L-class refrigerant issimultaneously used with afossil-fuel heating systemin a general living space

Case2
Physical hazard evaluationin the service andmaintenance

Case3
Physical hazard
evaluation using
VRF system

In the case of using a lighter in therefrigerant-leaked ambient: evaluation ofignition possibility
In the case that refrigerant leaks from apinhole formed on the pipes or hoses
In the case that refrigerant leaks into anequipment used to service andmaintenance 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 afossil-fuel heating system inside a general living space.
【Experiment】

2800

観測室

FTIR FTIR

refrigerant

to vacuumstove（2.4 kW）
Fan heater（3.2kW）
400

2800
2100

Air
conditioningsystem

BD

MonitorcylinderLoggerAmp.
Measurement position ofrefrigerant 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
02040 60 80 100 120time (min)

1000
900
800
700
600
500
400
300
200
100
0

HF Concentration (ppm)

2
1.8
1.6
1.4
1.2
10.8
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
010g/min, AC-OFF
10g/min, AC-ON
60g/min, AC-OFF
60g/min, AC-ON

R32R1234yf R410A
Varieties of Refrigerants➢ Refrigerant concentration (<2 vol%) was much lower than LFL.
Therefore no ignition and flame propagation to A2L refrigerants wereobserved.
➢ 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 aspace 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 apush button is pushed.
・Mixture in the windbreakconsists of fuel gas, air, andA2L refrigerant while a pushbutton is pushed.
・Concentration of fuel gas isreached at least LFL at theoutlet of fuel gas in thewindbreak.

・The energy of piezo spark isapproximately 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 aspace in which an A2L refrigerant has leaked and accumulated.

Type 2: Kerosene lighter
Fuel is vaporized【Characteristic】

・Fuel gas is discharged while acap of lighter is opened.
・Up-current of vaporized fuel isappeared while a cap oflighter is opened.

・The energy of spark generated
by rubbing a flint is muchlarger than that of piezoelement.

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 aspace in which an A2L refrigerant has leaked and accumulated.

Type 1: piezo gas lighter
Refrigerant: R1234yf, R1234ze(E), R32【Experiment】

Solenoid valve

airLighter

300

Push rod

1000

Pneumaticcylinder

It was predicted that the concentration of n-butane/A2L
refrigerants/air mixture is within the flammable range when theconcentration of A2L refrigerants close to a gas lighter is less thanLFL.

2-2: Ignition and Flame Propagation Possibility by a Lighter

Experimental Results

13/29【piezo gas lighter】
Flame
Flame

One framepassed(1/30 sec)

Extinction
Extinction

R1234yf with LFL

Flame

Flame

One framepassed(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 aspace in which an A2L refrigerant has leaked and accumulated.

Type 2: kerosene lighter【Experiment】

1000

Neon
transformer

Lighter
Digital video
cameraAC100V
Enegization time：50, 100,500 ms

300

CCD

Function
Generator

Relay

High-speed
cameraAC spark at 100 ms ofenergization time

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 insteadof 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?

FuelThe 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 vaporizedkerosene and
test
3only
R32
air even when the lighter was positioned in the accumulated R32.
test 4Significant peak offuel gas only
The use of a kerosene cigarette lighter in accumulatedR32
R32 might be
R32
only
Significant
ofcapable peakof causing
ignition of and flame propagation to R32.
fuel

5

10 10
15 15
2020
analysis
start
(min)
Time Timesincesince
analysisstart(min)516

2. PHYSICAL HAZARD EVALUATIONS
OF A2L REFRIGERANTS
2-3: Physical hazard of rapid leakage from apinhole

2-3: Physical Hazard of Rapid Leakage from a Pinhole

Objective & Experiment

18/29

Accident Scenario: An A2L refrigerant leaks from a fracture orpinhole 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 andmaintenance 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 mmdMass flow rate：5.0-847 g/min
Ignition source：single spark, continuous spark, open flame18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
10.0-50019/29(b) t = 33 ms

5.0

7.5

Single spark
PinholePinhole(a) J20-11（R32, φ 4 mm, 0.30MPa, 540 g/min）
100200300

Single Spark

Horizontal Distance (mm)Continuous spark

Open flame

19The 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 anequipment 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 modelcollection device.
➣especially the effect of slit fixed in the collection device toprevent the accumulation and ignition of leaked refrigerant.

2-4: Physical Hazard of Leakage into the Collection Device

Experiment

22/29【Experiment】
Unit: mm1000

Concentration
measurement
system1000

1000

cylinderModel collection device

slitLocation 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 Device1816141210864
20z=0cmz=20cmz=75cm14z=10cm
z=50cm
LFL

500

1000
time (sec)1500

Slit: 0 mm

z=0cm
z=25cmz=75cm12Slit: 1mm
023/29Concentration (vol%)concentration (vol%)Experimental results

10864Slit: 20mm

2

2000

z=10cmz=50cm
LFL

00

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 thanLFL. 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 theslow leak condition, ignition and flame propagation wasobserved.

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

28/29This 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 Morimotoand 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.