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The 24 th 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

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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

takarayamanbr
タイプライターテキスト
1.6
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長方形

1. INTRODUCTION

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

3/29

➣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.

4/29

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

5/29

2. PHYSICAL HAZARD EVALUATIONS OF A2L REFRIGERANTS

2-1: Use with Fossil Fuel Heating System

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)

7/29

【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

8/29

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.

10/29

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

11/29

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】

12/29

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

13/29

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

14/29

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

18/29

19

【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.

19/29

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.

21/29

【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

22/29

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.

23/29

3. CONCLUSIONS

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.

25/29

26

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.

26/29

ACKNOWLEDGEMENTS

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.

28/29

THANK YOU VERY MUCH!

Lake Suwa, Japan, 2013.