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STUDY OF TRANSIENT HEAT TRANSFEROF A SOLID WITH PROTECTIVE FABRIC

UNDER HOT AIR JET IMPINGEMENT

MA Islam, AA Rezwan, S Hossain and AKMN Islam

Dept. of Mechanical Engineering

Bangladesh University of Engineering & Technology

Dhaka, Bangladesh

ICME 11-TH-042


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Outline

Motivation

Background of the Study

Methodology

Mathematical Model

Experimental Setup

Results

Comparison with the Standards

Further Improvement

ICME 11-TH-04220 December 2011


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Motivation

Fire Fighters against the Inferno



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Background

The most frequent injuries that the firefighters and alsothe employees working in many hazardous chemicalenvironment suffers are burns

The most obvious reason for their burn injuries is thehigh heat flux exposures

The present study focuses on the measurement of heatflux on a surface that can be imitated as a skin for ahigh heat flux exposure with a protective fabric support

How far can we prevent the fire burn wound?



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Skin



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Skin Burn Injuries

BurnInjuries

LayerInvolved

Appearance Texture Sensation Time toHealing

First

DegreeEpidermis Redness Dry Painful

1 week

or less

Second

DegreeDermis

Red with

clear blisterMoist Painful

2-3

weeks

Third

Degree

Extend

through

entire

Dermis

Stiff and

white /

brown

Dry,Leathery

PainlessRequires

excision

Fourth

Degree

Extends

through

skin,

subcutane

ous tissue

Charred

with escharDry Painless

Requires

excision



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Methodology


Thermocouple

Position

Schematic Diagram of the Experiment


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Mathematical Model

Semi- Infinite Solid Model

1

Boundary Condition T(x,0) = Ti

|=0



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Mathematical Model

The solution for the case

, 2

4

1erf

2

On the surface (x = 0) this equation reduces to

2

20 December 2011 ICME 11-TH-042


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Mathematical Model

Newtons law of cooling is used to calculate

the local heat transfer coefficient, h.

( (0,))

Nusselt Number



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Experimental Setup



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Experimental Setup: Heater Section

Cut-way View of Heater SectionICME 11-TH-04220 December 2011


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Experimental Setup: Fabric Holder

Connection

with the PicoSystem


Fabric Holder

Assembly

(Wooden

Frame)


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Experimental ConditionParameters Values

Jet Velocity (m/s)

Temperature (C)

Nozzle Dia (mm)

l/dr/d

19, 15

125

25.4

2, 4, 6-4.5 ~ 4.5

Environment Temp. (C) 25 ~ 32

Protective FabricAluminized glass fiber withvapor absorbent stitched with

Kevlar fiber (NAFFCO)

Base Plate Hardboard (Massonite)ICME 11-TH-04220 December 2011


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Protective Fabric


Brand: NAFFCO

Model: KA 800 (PO 300)

Aluminized glass fiber with vapor

absorbent stitched with Kevlar fiber

Exposed Surface

Inner Surface


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20

40

60

80

100

0 20 40 60 80 100 120 140 160 180 200

Temperature

(C)

Time (sec)

4.5

31.5

Center

-1.5

-3

-4.5

20

40

60

80

100

0 20 40 60 80 100 120 140 160 180 200

Temperat

ure(C)

Time (sec)

4.5

3

1.5

Center

-1.5

-3

-4.5

l/d = 2V = 19m/s

Without

FR Fabric

l/d = 2

V = 19m/sWithout

FR Fabric

Temperature Variation with Time



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0

0.5

1

1.5

2

2.5

3

3.5

4

0 30 60 90 120 150 180

SurfaceHeatFlux,

q(kW/m)

Time, t (sec)

Surface Heat Flux variation with Time

for different l/d Position

l/d=2

l/d=4

l/d=6

l/d=2 wf

l/d=4 wf

l/d=6 wf

V = 15 m/s



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0

0.5

1

1.5

2

2.5

3

3.5

4

0 30 60 90 120 150 180

SurfaceHeatFlux,

q(kW/m)

Time, t (sec)


for different Velocity

V=15 m/s

V=19 m/s

Dashed Line: With FR Suit

Solid Line: Without FR Suit

l/d = 2



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0

0.5

1

1.5

2

2.5

3

3.5

4

0 30 60 90 120 150 180

Su

rfaceHeatFlux,q(kW/m)

Time, t (sec)


for different Velocity

V=15 m/s

V=19 m/s

Dashed Line: With FR Suit

Solid Line: Without FR Suit

l/d = 6



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0

5

10

15

20

25

30

35

40

45

-4.50 -3.00 -1.50 0.00 1.50 3.00 4.50

Nu

r/d

Nusselt Number variation across Radial Position

for different Exposure Time

t=30s

t=65s

t=180s

l/d = 4

V = 19 m/s



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0

5

10

15

20

25

30

35

40

45

-4.50 -3.00 -1.50 0.00 1.50 3.00 4.50

Nu

r/d

Nusselt Number variation across Radial Position

for different l/d Position

l/d=2

l/d=4

l/d=6

Time = 65s

V = 19 m/s



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THE SAFETY COMPARISON

How far can we prevent the fire burn

wound?



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0

5

10

15

20

25

30

0 10 20 30 40 50

HeatFlux(kW/m)

Exposure Time (sec)

Human Tissue Tolerance to Pain Sensation

Stoll Criterion Without FR With FR

*Stoll, A. M. and Chianta, M. A. Method and Rating System for evaluations of Thermal Protection Aerospace Medicine,

Vol. 40, 1969

*ASTM Standard: F1060-05 Standard Test Method for Thermal Protective Performance of Materials for Protective Clothingfor Hot Surface Contact


l/d = 2

V = 19 m/s


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0

5

10

15

2025

30

35

4045

50

0 5 10 15 20 25 30

HeatFlux(kW/m)

Exposure Time (sec)

Human Tissue Tolerance to Second Degree Burn

Stoll Criterion Without FR With FR

*Stoll, A. M. and Chianta, M. A. Method and Rating System for evaluations of Thermal Protection Aerospace Medicine,

Vol. 40, 1969

*ASTM Standard: F1060-05 Standard Test Method for Thermal Protective Performance of Materials for Protective Clothingfor Hot Surface Contact


l/d = 2

V = 19 m/s


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Related Work

1. Lee, S., Park, C., Kulkarni, D., Tamanna, S., Knox, T.,2010, Heat and Mass Transfer in a Permeable Fabric

System under Hot Air Jet Impingement, Proc. Int.Heat Transfer Conf. (IHTC14)

2. Anguiano, R. M., 2006, Transient Heat Transferthrough Thin Fibrous Layer, M.Sc. Thesis, University

of Alberta, Emonton, Albarta, Canada

3. Torvi, D. A., 1997, Heat Transfer in Thin Fibrous

Materials Under High Heat Flux Conditions, Ph.DThesis, University of Alberta, Calgary, Alberta



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Future Work

Develop a model for computational technique

and validate the simulated result for the

improvement of protective fiber

Study the heat & mass transfer of the fire

resistive fabric under Steam Exposure

Study the heat transfer of the fire resistive

fabric under diffusion flame using different

flammable liquid



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Thank You

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