1.4

ICR2015 Workshop on Risk Assessment ofMildly Flammable Refrigerants, August 20, 2015

4. Fundamental and Practical Flammability
Properties of 2L Refrigerants

Kenji TAKIZAWA
National Institute ofAdvanced Industrial Science and Technology (AIST)

Overview
1. Background
2. Fundamental flammability properties
3. MIE and quenching distance
4. Flame extinction diameter
5. Summary2

1. Background- Importance of evaluating low flammability
2. Fundamental flammability properties

3. MIE and quenching distance
4. Flame extinction diameter
5. Summary3Flammability properties, indices of fire risksRisk*  combination of probability of occurrence of harm and severity of that harm
Probability of fire

Severity of fire
FuelOxydizer
Burning velocity

IgnitionsourceHeat of combustion

Pressure rise rate
Heat release rate

Flammability limits
Minimum ignition energy (MIE)Autoignition temperature・・・・・・・・*ISO/IEC Guide 51, Safety aspects-Guidelines for their
inclusion in standards (1999)

4

Class 3

ISO Flammability Classification*

50Su,max, cm s-1

High severity

What is class 2L refrigerant?

4030

R290

Class 2R152a

20100R717

R1234yf
510R3215Class 2L
20

LFL 3.5 vol% or Hc 19 MJ kg-1
→Class 3
In Class 2, BV 10cm s-1→Class 2L
No flame propagation→Class 1

25LFL, vol%Low probability

Class 2L is the least flammable refrigerant classLow GWP 2L refrigerants are now considered as promisingalternatives
Flammability properties should be studied to characterize 2L for
further understanding their practical risks*ISO 817, Refrigerants— Designation and safety classification (2014)

5Objectives
Practical fire risk
Leak analysis

Flammability characteristics
Physical hazard

Fundamental, Definition
Ignition test of oil lighter

LFL, UFL

Reaction rate

Propagation
ratew  (uSu)2

Probability offire
MIE

Burningvelocity

Severity of
fire
Pressure riserate

Today’s presentation
Heat release
rate

Quenching
distance
Safety of electric parts

Venting

OthersTherm. decomp.

Diesel explosion

 Draw relationships between fundamental, various characteristics, and practicalrisks for wide variety of flammable refrigerants

6

1. Background

2. Fundamental flammability properties
 Flammability limits
 Burning velocity

40 cm s-1

3. MIE and quenching distance

4. Flame extinction diameter

5 cm s-1

5. Summary

1.5 cm s-1

7

Flammability limits measurement
ASHRAE method* (1)Results of R290/Nitrogen/ Air

Test apparatus

Not exceed 90°arc
AC15kV90゜

Conc. of R290, vol%12

Non flammable

108

Exceed90°arc

6Flammable420

Non flammable
020

40

60

80

100

N2/(N2+R290), vol%

Flame propagation is determined by 90 degree criterion measured from the pointof ignition to the walls of the flask*ANSI/ASHRAE Standard 34, Designation and safety classification of re8

Flammability limits measurement
ASHRAE method (2)Results for R1234yf (CH2=CFCF3)

At 35 C and 0% RH

90Burning velocity measurement in microgravity (g)By removing gravity, we obtain “ideal” spherically-propagating flame

10-m drop tower in AIST

Apparatus in the inner capsule in the outer capsuleFlame propagation can be expressed by established spherical flame models
10Flame propagation in g
R1234yf (CH2=CFCF3), Su,max = 1.5 cm s-1
1G

g

By using g environment, we obtainspherically-propagating flame without affecting buoyancy nor wall quenchingSu from highly to only mildly flammable compounds by a single test method11

Humidity effects on flammability
Monthly average weather of four capitals

R1234yf flame with and without moisture

Temperature, ºC

2ASHRAE humidity
1.5ASHRAE humidity

ASHRAE humidity

0% RH

3ASHRAE humidity

Humidity effect on Burning velocity

 Humidity level in the current
standard is not high enough forhigh humidity areas of the world
 We are studying comprehensively
onhumidity
effectson
flammability

Stoichio. Su ,cm s-1

Relative Humidity, %RH

R1234yf

R1234ze(E)IncreaseBecomeflammable

R32

10Slightly
decrease

5N.F.
0Dry

Moist

DryMoist

DryMoistHumidity increased Su of R1234s

12

Summary of Part 2
2L flame (R1234yf)

Measurable Su range
Typical methods This workin g

Su, cm s-1

in 1G

Nobuoyancy

1050Target
・R717
・R32

g SV method

Buoyancy

Vertical tube

15

SV method

Nozzle burner

dr/dt

・R32/HFO blend
Practically・Flam/nonflam blend
important
・R1234yf

R290 flame in 1G

By using g environment, we evaluate Su from highly to only mildly
flammable compounds
131. Background
2. Fundamental flammability properties

3. MIE and quenching distance* Potential ignition sources Difficulty in MIE measurement
 Ignition and quenching of minimum flame Quenching distance measurement
 Estimation of MIE
QD measurement of R1234yfin g

4. Flame extinction diameter

5. Summary*See also, K. Takizawa et al., Quenching distance measurement ofhighly to mildly flammable compounds, Fire Safety J., 71, 58 (2015).

14

Background: potential ignition sources of refrigerants
Indoor unit2L refrigerants were not ignited by spark of hairdryer (1200W, ca. 0.2-0.4J)
15Potential ignition sources of refrigerants
Outdoor unit
Ignition test using MC(60A、220V load)

Example of AC outdoor unit
Inverter
MCCompressor

Electromagnetic contactor (MC) is an important potential ignition source that may
exist in high concentration refrigerantR32 and R1234yf were not ignited by spark of AC220V and 60A load (ca. 4J >Emin)To understand these results, ignition and quenching characteristics for 2L shouldbe accumulated
16

Wide variations of published MIE values
106
1.E+061051.E+05

Published MIE value, mJ

MIE, mJ

Difficulty in MIE measurement104
1.E+04

For 2L refrigerants,
variation of MIE is three orders!

103
1.E+03102
1.E+02

R1234yf101
1.E+01100
1.E+0010-1
1.E-01
00

R152a

R290
Lewis&Von Elbe*

R32 R717
10203010Max S20-1 30u, cm s
Su,max, cm/s

4040

 Variation of reported MIE values is very wide, which makes it difficult to use
MIE as a flammability index
 To obtain reliable MIE is important to improve the current situation*B. Lewis, G. von Elbe, “Combustion, Flames and Explosions of Gases”, third ed. (1987).

17Ignition and quenching of minimum flame(3) d  dq

(2) d = dq

(1) d < dqHeat lossddd

Heat generation

Extinction
Terms

Minimum flame diameter Quenching distance (dq)Definition

Ignition

To supply to the combustible mixture sufficientenergy to create a kernel of hot gas that satisfies
the necessary condition for self-propagation

Quenching
distance (dq)

Critical size that the inflamed volume must justexceed in order to propagate unaided

Self-sustained propagation

Equationdq = a (/CP0Su)

Minimum ignition The amount of energy that the spark must supply Emin = (1/6)  dq3 0 CP Tenergy (Emin)for the hot kernel to attain this critical size (dq)

 We estimate MIE by obtaining QD and employing heat loss theory18

Quenching distance measurement

DC spark

Acrylic cylinder

Electrodes withparallel plates+Micrometer-R290, d =1.7 mm

Considering wide use of the test method and values, we tested various conditions:
1. Compound

2. Configuration of parallel plates

R290
R600aR152aHFO-1243zfHFC-143
R152a/134a (50/50 v/v)
HFC-254fb
R717
R143aR32
R1234yf

 Vertical position*

3. Type of ignition spark・AC spark Horizontal positiond Under microgravity

Neon transformer
Duration of 100 ms
Energy of 2.5 J・DC sparkDuration of 1-10 ms
Energy of 0.1-5 J*ASTM E582-07 “Standard Test Method for Minimum Ignition Energyand Quenching Distance in Gaseous Mixtures” (2007)

19

QD measurement in g-R1234yf, 10 vol%-dqd = 24.7mm

d = 24.9mm

Not ignited

Ignited20

Results of QD

15R71710dq ,mmR1234yf

20+ ASTM configuration
Parallel plates in thehorizontal directiongless flammable

25mmdqdq,, mmless flammable-Relationship between QD and BV-dq,h+ dq,v
dq in g
R1234yf
R290

R290

R717

5R32001020
30Su0, max,cm ss-1-1
Su0,max, cm

40

more flammable(uSu0,max)-1 (102 kg-1 m2 s) less flammableObtained a single continuous function between dq and Su from highly to only
mildly flammable compounds
Su <10 cm s-1dq 5 mm21Estimation of MIE
Exp. values in this study

Su, dq



R290



Emin  1 / 6 d q  2 3 bC p Tb  Tu R717
R32

This study：

R1234yf

Theoretical eq. of Emin

Comparison between
estimation and experiment

ASTM configuration

dq-2

Parallel plates in thehorizontal directionδMinimum flame Reported Emin are at most 3 orders of magnitude different Our estimation agreed with lower value of reported Emin for all the compounds
without adding any modifications
 Emin was essentially proportional to the cube of dq22

1. Background- Importance of evaluating low flammability
2. Fundamental flammability properties
3. MIE and quenching distance

4. Flame extinction diameter-Index of safe design of electric parts

5. Summary

R152a flame goes out throughopening of MC23

Measurement of flame extinction diameter d*Acrylic cylinder
PTFE plate of 1mm in thicknessdhR1234yf, g (9.4%, d = 10mm)

R290 (4.5%, d = 1.25mm)
Opening“Go”

Opening“No go”
24Results of flame extinction diameterd* of 2L refs as a function of hQD

Ｒ-32/NH3/254fbの比較

8R-32
R32

7R-717
R717

HFC-254fb
HFC-254fb

6d*, mm,mmd*Comparison of d* (@h = 9mm)

5MC for 65A:
13.23.0 mm(Go)43Socket:
7.02.3 mm

2(No go)10010203040h,h , mmmm

506070 R290 flame can pass the opening of socket R32 flame cannot pass the opening of MCd* was positively related to dq, negatively related to Su
With increasing h (growing flame sphere), d* decreased and converged25Summary of part 4
Flammability
characteristics

Extinction diameter (d*), mm

10Structureof electric parts

8Go

Leakof refrigerant

64 No go

R32
Opening of MC
MC2Compressor
0R290
d*(R32) > D(MC)

Outdoor unit

 Based on our experiment and theory, we can identify potential ignition sources offlammable refrigerants-R290 flame having a high BV can pass the opening of socket-2L flame having a low BV cannot pass the opening of MC26

Summary
1. Evaluation of low flammability becomes practically important because
the less flammable a material is, the more widely it will be accepted
We are trying to develop evaluation methods and give the values to help
development of good materials
Sumax vs GWP 100yr

Fuel
R290

40403030Su0,max, cm s-1

Su0,maxSumax, cm s-1

R32
R600a

2020

R152a
R32R717

R134a
R410A

1010Low GWP & Low Flammability
R74400
11AMOLEA1)

DR-552)

R125
Current refrigerant

GWP, 10
10100
100
GWP
100yr
GWP,-1000
1000

10000
10000
1) AMOLEA: R1123/32 (45/55)
2) DR-55: R32/125/1234yf (67/7/26)

27

2. In the NEDO project, we studied ignition and extinction of refrigerants
 We measured QD for various compounds by various conditions andobtained a single correlation between Su and dq
 Based on this correlation, we estimated Emin as a starting point

Thank you!
dq,h+ dq,v
dq in gdq ,mm

less flammable We will further study ignition and extinction characteristics applicable topractical risk assessment of 2L refrigerants

2L
R1234yf
R290

R717(uSu0,max)-1

less flammable28