Transient Heat Transfer Under Graduate Thesis Part 1 Level 4 Term 1
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Transcript of Transient Heat Transfer Under Graduate Thesis Part 1 Level 4 Term 1
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Aashique Alam Rezwan
Sarzina Hossain
WORK PROGRESS
OF THE LEVEL 4 TERM I,
UNDER GRADUATE THESIS
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WEEK 1 & 2
Topic Selection & Discussion
Final Selected Topic:
Transient Heat Transfer Through Flame Resistance Fabrics
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WEEK 3
• Submission of Work Plane and other Materials
• Objectives:
1. To study the characteristics of heat transfer from a vertical hot jet of air impinging on
two types of horizontally mounted plate, a flat and a convex plate and to compare the two
results.
2. To study the performance of flame retardant fabrics in contact both with a flat and a
convex plate.
3. To compare the heat transfer characteristics of flat and convex plate (with and without
fabric).
4. Simulation of the heat transfer on flat and convex plate due to hot air impingement.
• Expected Outcomes:
1. Characteristics of convective heat transfer due to air impingement on a convex plate.
2. Characteristics of heat transfer of a flame retardant fabrics used by the local fire fighter.
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WEEK 4
• Discussion on Previous Work
• 1. In the flat plate experiment for nozzle to plate separation z/d<3 the maximum Nussult number occurs slightly off the stagnation point. Within this distance the flow parallel to the surface is accelerated. At the end of the accelerated flow region the pressure gradient increases which leads to sudden rise in the turbulence level. The velocity increases slightly off the centre. The result is a sharp increase in the heat transfer co-efficient, h and hence higher Nu.
• 2. For z/d=1 there is secondary peak. Secondary peaks occur in the wall jet as a result of rising turbulence & falling velocity.
• 3. It can be concluded that for z/d<3 there is no specific relation between r/d and Nu because high turbulence. For z/d>3 the Nusselt number exponentially decays with the increasing r/d.
• 4. As the time increases heat flux decreases.
• 5. As the nozzle to plate separation distance increases heat flux also decreases.
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WEEK 4 (CONTINUED)
• 6. For larger z/d separation the surface heat flux is fluctuating. This occurs due to the mixing of
surrounding air with hot fluid creates an eddy current which in turns create fluctuation in
reading.
• 7. When the experiment done with fabrics in contact with plate the maximum Nu occurred off
the centre but no secondary peak occurred. So it can be said that the turbulence effect is less
when fabrics is used.
• 8. Another non-contact testing is done where the fabric is 6mm away from the plate. This was
done to compare the energy transfer within the gap. The different FR fabrics give different result
but each of them proves to be more heat resistant when testing with air gap.
• 9. The results obtained using a shim stock testing is scattered with no definite pattern. They
have concluded that the testing apparatus was not perfect to test such situation.
• 10. Adding 6mm air gap contributes to reducing the heat transfer between the plate and warm
jet. As z/d become larger the Nu difference at centre became smaller. This is due to the
appearance of maximum value at the stagnation point.
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• Human Tissue Tolerance to Second
Degree Burn
• Stoll, A.M. and Chianta, M.A. “Method
and Rating System for Evaluations of
Thermal Protection” Aerospace
Medicine, Vol 40, 1969, pp. 1232-1238
WEEK 5
STUDY OF SKIN TOLERANCE
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• “Transient Heat Transfer Through Thin
Fibrous Layers”
• Performed by, Raul Munoz Anguiano
• Test Condition:
• Velocity of Air Jet: 13m/s
• Temperature: 102±4°
• Nozzle Diameter: 32mm
• Nozzle to Fabrics Distance: 128mm
WEEK 5 (CONTINUED)
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SIMULATION OF THE TEST PERFORMED BY THE
PREVIOUS AUTHOR
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WEEK 5 (CONTINUED)
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• “Heat and Mass Transfer in a
Permeable Fabric System Under Hot
Air Jet Impingement”
• Proceedings of the International Heat
Transfer Conference, August 8-13,
2010 © ASME 2010
• Test Condition:
• Velocity of Air Jet: 32m/s
• Temperature: 100°C and 200°C
• Nozzle Diameter: 20.6mm
• Nozzle to Fabrics Distance: 76.2mm
WEEK 5 (CONTINUED)
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ASTM STANDARDS FOR PROTECTIVE CLOTHING
• F2703-08: Unsteady-State Heat Transfer Evaluation of Flame Resistant Materials for
Clothing with Burn Injury Prediction
• Heat Flux: 84.6 kW/m2
• Gas Pressure: 55 kPa
• Optional Spacer: 6.4mm
• Minimum Sample Test: 5
• Time of Exposure: 60s
• F2700-08: Standard Test Method for Unsteady-State Heat Transfer Evaluation of Flame
Resistant Materials for Clothing with Continuous Heating
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WEEK 6
EXPERIMENT ON WIND TUNNEL
13.6
8.5
5.675
3.68
y = -2.31ln(x) + 6.9981
1
2
3
4
1 10 100
Rad
ial P
osi
tio
n
Velocity
Average Velocity Profile of the Wind Tunnel Exit
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WEEK 6
COMMENTS
• Centerline Velocity at maximum opening of Wind Tunnel: 4.2 m/s
• Maximum Velocity attained: 19.5 m/s
• Average Velocity attained within the experimental range: 4.75 m/s
• The exit velocity is not uniform due the presence of valve at the end. Velocity
at the outside periphery is higher due to the turbulence created by the valve
blade end. Thus only center portion of the tunnel cross-section is selected for
the upcoming experiment.
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PRIMARY DESIGN PARAMETERS
• Nozzle Diameters = 25.4 mm (1 inch)
• Inlet Velocity = 4.75 m/s
• Expected Jet Velocity = 73.62 m/s
• Inlet to Exit Pipe Length = 609.6 mm (24 inch)
• Pipe diameter (internal) = 63.5 mm (2.5 inch)
• Pipe Inlet Reducer = 101.6:63.5 mm (4:2.5 inch)
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PRIMARY DESIGN
NOZZLE
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PRIMARY DESIGN (CONTINUED)
NOZZLE PIPE ASSEMBLY
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PRIMARY DESIGN (CONTINUED)
NOZZLE PIPE ASSEMBLY
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PRIMARY DESIGN (CONTINUED)
NOZZLE PIPE ASSEMBLY
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PRIMARY DESIGN (CONTINUED)
NOZZLE PIPE ASSEMBLY
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PREDICTED VELOCITY ALONG THE SETUP
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PREDICTED VELOCITY ALONG THE SETUP
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PREDICTED TEMPERATURE ALONG THE SETUP
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PREDICTED TEMPERATURE ALONG THE SETUP
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PREDICTED TEMPERATURE ON THE WALL
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PREDICTED TEMPERATURE ON THE WALL
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PRESSURE DISTRIBUTION
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PRIMARY DESIGN
COMMENTS
• Primary Design Simulation shows a draw back in
experimenting with surface heating for air heater, that it
would require a tremendous amount of surface heat in
short length, under which the material can’t sustain.
Further calculation was recommended for better
design.
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ASTM STANDARD
Thermal Sensor
• Copper Slug Calorimeter
• Diameter = 4±0.05cm
• Mass = 18±0.05g
• Electrical Grade Copper
• Thermocouple: ANSI Type J
(Fe/Cu-Ni) or ANSI Type K(Ni-
Cr/Ni-Al)
• Wire Dia = 0.254 mm
Shutter
A manual or computer-controlled
shutter is used to block the heat
flux from the burner (placed
between the specimen holder
and the burner). Water cooling is
recommended to minimize
radiant heat transfer to other
equipment components and to
prevent thermal damage to the
shutter itself. ASTM Standard F 2703 - 08
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MATHEMATICAL MODEL PRESENTATION
Special Mid Term Session
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IMPINGING JET CHARACTERISTICS
Regions in submerged
impinging round jet:
• Initial Free Jet
• Core Region
• Decaying Jet Region
• Stagnation Region
• Wall Jet Region
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INITIAL FLOW REGION
Due to the application of
differential pressure across thin
flat orifice:
• Fairly flat velocity profiles
• Less turbulence
• A downstream flow contraction
(vena-contracta)
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INITIAL FLOW REGION
• The shearing at the edges
of the jet transfer
momentum outward
• More fluid is entrained
along with the jet
• Jet losses energy
• The velocity profile is
widened and decreased in
magnitude
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THE CORE REGION
• Unaffected by the
momentum transfer
• Higher total pressure
• Experience a drop in
velocity
• Dynamic pressure decays
as result of velocity
gradient presence in the
nozzle exit
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DECAYING JET REGION
Juckerman and Lior defines the end of the core region
as the axial position where the centerline flow dynamic
pressure reaches 95% of its original value.
• Begins at 4~8D from the nozzle exit
• Axial velocity component decreased
• Axial velocity and jet width vary linearly
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DECAYING JET REGION
• Decaying jet region & free jet region may not exist if
the nozzle lies within a distance of 2D from the target
• Elevated static pressure in the stagnation region
influence the flow immediately at the nozzle exit
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STAGNATION REGION
• Flow losses axial velocity and turns
• Builds up a higher static pressure on and above the wall
• Experiences high normal and shear stresses in the
deceleration region
• Stretches vortices in the flow and increases the turbulence
• Martin concluded that the region extends 1.2D above the wall
for round jets
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WALL JET REGION
• Flow moves laterally outward parallel to the wall
• Minimum thickness occurs within 0.75~3D from the jet axis,
then continually thickens moving farther away from the
nozzle
• Boundary layers begins within the wall, where its thickness
measures more than 1% of the jet
• Shearing layer influence by velocity gradient with respect to
both at the wall and at the fluid outside the wall
• Entrains flow and grows in thickness
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NOZZLE GEOMETRY TYPE ON JET IMPINGEMENT
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MAJOR PARAMETERS
• Nusselt Number, 𝑁𝑢 = 𝐷
𝑘𝑐
• Convective Heat Transfer Coefficient ℎ = −𝑘𝑐
𝜕𝑇
𝜕𝑛
𝑇𝑗𝑒𝑡−𝑇𝑤𝑎𝑙𝑙
• Recovery factor = 𝑇𝑤𝑎𝑙𝑙−𝑇𝑗𝑒𝑡
𝑈2
2𝐶𝑝
• Sherwood Number, 𝑆ℎ = 𝑘𝑖𝐷
𝐷𝑖, 𝑘𝑖 =
𝐷𝑖𝜕𝐶
𝜕𝑛
𝐶𝑗𝑒𝑡−𝐶𝑤𝑎𝑙𝑙
• Heat to mass transfer rate, 𝑁𝑢
𝑆=
𝑃𝑟
𝑆𝑐
0.4
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OTHER PARAMETERS
• Prandlt Number, Pr
•𝐻
𝐷: nozzle height to nozzle diameter ratio
• r/D: nondimensional radial position from center of the jet
• z/D: nondimensional vertical position measured from the wall
• Turbulence intensity, Tu
• Renolds Number, Re
• Mach Number, M
•𝑝𝑗𝑒𝑡
𝐷 : jet center to center spacing (pitch)
• Free Area, 𝐴𝑓
• Relative Nozzle Area, 𝑓
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EMPIRICAL CORRELATIONS
𝑁𝑢 = 𝐶 𝑅𝑒𝑛 𝑃𝑟𝑚 𝑓(𝐻 𝐷 )
• For Single Round Nozzle, Martin correlation
• 𝑁𝑢𝑎𝑣𝑔 = 𝑃𝑟0.42𝐷
𝑟
1−1.1𝐷 𝑟
1+0.1(𝐻 𝐷 −6)𝐷 𝑟 𝐹
• for 2,000<Re<30,000, F = 1.36 Re 0.574
• for 30,000<Re<120,000, F = 0.54 Re 0.667
• for 120,000<Re<400,000, F = 0.151 Re 0.775
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EMPIRICAL CORRELATIONS
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FLAME IMPINGEMENT
• Transfer heat very effectively and tends to have higher turbulence
• If some fuel travels through the stagnation region without complete
combustion, further reaction in the wall jet will release additional
thermal energy and improve uniformity
• Also transfer heat by radiation from the flame
• 60-70% heat transfer by convection [Malikov et al]
• Accumulation of soot may occur on the target which ultimately impede
heat transfer
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TRANSIENT HEAT TRANSFER
• Governing equation, 𝜕2𝑇
𝜕𝑥2=
1
𝛼
𝜕𝑇
𝜕𝑡
• Boundary condition, T(x,0) = Ti , T(0,t) = Ts
• Solving, 𝑇 𝑥,𝑡 − 𝑇0
𝑇𝑖 − 𝑇0= erf
𝑥
4𝛼𝑡
• For constant heat flux
• 𝑇 − 𝑇𝑖 = 2𝑞
𝛼𝑡
𝜋
𝑘𝐴𝑒𝑥𝑝
−𝑥2
4𝛼𝑡−
𝑞𝑥
𝑘𝐴1 − 𝑒𝑟𝑓
𝑥
4𝛼𝑡
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TRANSIENT HEAT TRANSFER
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GOVERNING EQUATIONS FOR THE FABRICS
• For gas phase in the Fabric Layer
• Mass Conservation Equation
• 𝜀𝜕𝜌𝑔
𝜕𝑡+
𝜕
𝜕𝑥𝜌𝑔𝑢𝐷 = 0
• Momentum Conservation Equation
•𝜕 𝜌𝑔𝑢𝐷
𝜕𝑡+
1
𝜀
𝜕 𝜌𝑔𝑢2
𝜕𝑥=
𝜕
𝜕𝑥𝜇𝜕𝑢𝐷
𝜕𝑥− 𝜀
𝑑𝑃
𝑑𝑥− 𝜀
𝜇
𝐾𝑢𝐷 −
𝜀𝜌𝑔𝐶𝐸
𝐾1/2 𝑢2
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GOVERNING EQUATIONS FOR THE FABRICS
• Energy Conservation Equation
• 𝜀 𝜌𝑐𝑝 𝑔
𝜕𝑇𝑔
𝜕𝑡+ 𝜌𝑐𝑝 𝑔
𝑢𝐷𝜕𝑇
𝜕𝑥=
𝜕
𝜕𝑥𝜀𝑘𝑔
𝜕𝑇𝑔
𝜕𝑥− ℎ𝑠𝑔
𝐴𝑠𝑔
𝑉𝑓𝑎𝑏𝑇𝑔 − 𝑇𝑠
• Energy Conservation Equation for Fabric Phase
• 1 − 𝜀 𝜌𝑐𝑝 𝑠
𝜕𝑇𝑠
𝜕𝑡=
𝜕
𝜕𝑥1 − 𝜀 𝑘𝑠
𝜕𝑇𝑠
𝜕𝑥+ ℎ𝑠𝑔
𝐴𝑠𝑔
𝑉𝑓𝑎𝑏𝑇𝑔 − 𝑇𝑠
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GOVERNING EQUATIONS FOR THE AIR GAP
• Mass Conservation Equation
• 𝑉𝑎𝑔𝑑𝜌𝑔
𝑑𝑡= 𝑚 𝑔,𝑖𝑛 −𝑚 𝑔,𝑜𝑢𝑡
• Where,
• 𝑚 𝑔,𝑖𝑛 = 𝜌𝑔𝐴𝑓𝑎𝑏𝑢𝐷|𝑥=𝐿𝑓𝑎𝑏
• 𝑚 𝑔,𝑜𝑢𝑡 = 𝐶𝑙𝑒𝑎𝑘𝜌𝑔
𝜇𝑔𝑃𝑎𝑝 − 𝑃𝑎𝑚𝑏
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GOVERNING EQUATIONS FOR THE AIR GAP
• Energy Conservation Equation
• 𝜌𝑉𝑐𝑝 𝑎𝑔
𝑑𝑇𝑎𝑔
𝑑𝑡= 𝑄 𝑔,𝑖𝑛 − 𝑄 𝑔,𝑜𝑢𝑡 + 𝑄 𝑓𝑎𝑏,𝑟𝑒𝑎𝑟 − 𝑄 𝑐𝑝
• 𝑄 𝑔,𝑖𝑛 = 𝑚 𝑐𝑝𝑇 𝑔,𝑖𝑛
• 𝑄 𝑔,𝑜𝑢𝑡 = 𝑚 𝑐𝑝𝑇 𝑔,𝑜𝑢𝑡
• 𝑄 𝑓𝑎𝑏,𝑟𝑒𝑎𝑟 = ℎ𝑓𝑎𝑏𝐴𝑓𝑎𝑏 1 − 𝜀 𝑇𝑠|𝑥=𝐿𝑓𝑎𝑏 − 𝑇𝑎𝑔
• 𝑄 𝑐𝑝 = ℎ𝑐𝑝𝐴𝑐𝑝 𝑇𝑎𝑔 − 𝑇𝑐𝑝
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THERMOPHYSICAL PROPERTIES OF FABRICS
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THERMOPHYSICAL PROPERTIES OF FABRICS
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WEEK 7
TYPICAL HEATING & FLOW ARRANGEMENT
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WALL TEMPERATURE REQUIRED FOR THE
DESIRED OUTLET TEMPERATURE
0
100
200
300
400
500
600
700
800
900
1000
0 0.5 1 1.5 2 2.5 3 3.5
Tem
per
atu
re
(°C
)
Length (m)
Wall Temperature Required with the Heating Zone Length
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NICHROME WIRE PARAMETERS
Week 7
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Ohms/ft at Room Temperature
Gauge Wire Diameter (mm) NiCr A NiCr C
10 2.591 0.06248 0.06488
11 2.311 0.07849 0.08151
12 2.057 0.09907 0.10290
13 1.829 0.12540 0.13020
14 1.626 0.15870 0.16480
15 1.448 0.20010 0.20780
16 1.295 0.24990 0.25950
17 1.143 0.32100 0.33330
18 1.016 0.40630 0.42190
19 0.914 0.50150 0.52080
20 0.813 0.63480 0.65920
21 0.7239 0.80020 0.83100
22 0.6426 1.01500 1.05500
23 0.5740 1.27300 1.32200
24 0.5105 1.60900 1.67100
25 0.4547 2.02900 2.10700
26 0.4039 2.571 2.670
27 0.3607 3.224 3.348
28 0.3200 4.094 4.252
29 0.2870 5.090 5.286
30 0.2540 6.500 6.750
31 0.2261 8.206 8.522
32 0.2032 10.160 10.550
33 0.1803 12.890 13.390
34 0.1600 16.380 17.010
35 0.1422 20.730 21.520
36 0.1270 26.000 27.000
37 0.1143 32.100 33.330
38 0.1016 40.630 42.190
39 0.0889 53.060 55.100
40 0.0787 67.640 70.240
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Approximate Amperes to Heat NiChrome Wire
Gauge
Wire
Diameter
(mm)
400°F
205°C
600°
316°
800°
427°
1000°
538°
1200°
649°
1400°
760°
1600°
871°
1800°
982°
2000°
1093°
10 2.591 16.2 23.3 29.7 37.5 46.0 56.0 68.0 80.0 92.0
11 2.311 13.8 19.2 24.8 31.5 39.0 48.0 57.0 67.0 78.0
12 2.057 11.6 16.1 20.8 26.5 33.5 40.8 48.0 56.0 65.0
13 1.829 9.80 13.6 17.6 22.5 28.2 34.2 41.0 48.0 55.0
14 1.626 8.40 11.6 15.0 18.8 23.5 29.0 34.6 40.5 46.0
15 1.448 7.20 10.0 12.8 16.1 20.0 24.5 29.4 34.3 39.2
16 1.295 6.40 8.70 10.9 13.7 17.0 20.9 25.1 29.4 33.6
17 1.143 5.50 7.50 9.50 11.7 14.5 17.6 21.1 24.6 28.1
18 1.016 4.80 6.50 8.20 10.1 12.2 14.8 17.7 20.7 23.7
19 0.914 4.30 5.80 7.20 8.70 10.6 12.7 15.2 17.8 20.5
20 0.813 3.80 5.10 6.30 7.60 9.10 11.0 13.0 15.2 17.5
21 0.7239 3.30 4.30 5.30 6.50 7.80 9.40 11.0 12.9 14.8
22 0.6426 2.90 3.70 4.50 5.60 6.80 8.20 9.60 11.0 12.5
23 0.5740 2.58 3.30 4.00 4.90 5.90 7.00 8.30 9.60 11.0
24 0.5105 2.21 2.90 3.40 4.20 5.10 6.00 7.10 8.20 9.40
25 0.4547 1.92 2.52 3.00 3.60 4.30 5.20 6.10 7.10 8.00
26 0.4039 1.67 2.14 2.60 3.20 3.80 4.50 5.30 6.10 6.90
27 0.3607 1.44 1.84 2.25 2.73 3.30 3.90 4.60 5.30 6.00
28 0.3200 1.24 1.61 1.95 2.38 2.85 3.40 3.90 4.50 5.10
29 0.2870 1.08 1.41 1.73 2.10 2.51 2.95 3.40 3.90 4.40
30 0.2540 0.92 1.19 1.47 1.78 2.14 2.52 2.90 3.30 3.70
31 0.2261 0.77 1.03 1.28 1.54 1.84 2.17 2.52 2.85 3.2
32 0.2032 0.68 0.90 1.13 1.36 1.62 1.89 2.18 2.46 2.76
33 0.1803 0.59 0.79 0.97 1.17 1.40 1.62 1.86 2.12 2.35
34 0.1600 0.50 0.68 0.83 1.00 1.20 1.41 1.60 1.80 1.99
35 0.1422 0.43 0.57 0.72 0.87 1.03 1.21 1.38 1.54 1.71
36 0.1270 0.38 0.52 0.63 0.77 0.89 1.04 1.19 1.33 1.48
37 0.1143 0.35 0.46 0.57 0.68 0.78 0.9 1.03 1.16 1.29
38 0.1016 0.30 0.41 0.50 0.59 0.68 0.78 0.88 0.98 1.09
39 0.0889 0.27 0.36 0.42 0.49 0.58 0.66 0.75 0.84 0.92
40 0.0787 0.24 0.31 0.36 0.43 0.50 0.57 0.64 0.72 0.79
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0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
100.00
110.00
120.00
130.00
140.00
150.00
160.00
170.00
180.00
190.00
200.00
210.00
220.00
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
Len
gth
(f
t)
Gauge
Characteristics Chart of NiCr A Volt 220V
205C
316C
427C
538C
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0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
100.00
110.00
120.00
130.00
140.00
150.00
160.00
170.00
180.00
190.00
200.00
210.00
220.00
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
Len
gth
(f
t)
Gauge
Characteristics Chart of NiCr C Volt 220V
205C
316C
427C
538C
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0.0000
50.0000
100.0000
150.0000
200.0000
250.0000
300.0000
350.0000
400.0000
450.0000
500.0000
550.0000
600.0000
650.0000
700.0000
750.0000
800.0000
850.0000
900.0000
950.0000
1000.0000
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
Res
ista
nce
(o
hm
s)
Gauge Size
Gauge Size - Resistance Of NiCr C
205C
316C
427C
538C
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REQUIRED LENGTH FOR THE AVAILABLE
WALL TEMPERATURE
0
0.5
1
1.5
2
2.5
3
3.5
0 100 200 300 400 500 600 700 800 900 1000
Len
gth
(m
(
Temperature (°C)
Required Length for the Wall Temperature to Raise the Flowing Fluid Temperature to 105°C
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RECOMMENDATIONS (WEEK 7)
• The design with only wall heating is complicated in a sense of
physical setup constrain
• For heating purpose, more reliable and higher heat transfer system
may be design
• Internal Fin type heat exchanger may be design with NiChrome
Wire heater
• From the NiChrome Wire Properties, 30 gauge wire with 316°C
heating can be recommended for design
• Further study required for designing other type of heat exchanger
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WEEK 8
BUDGET ESTIMATION Item Description Unit Price No. of Unit Required Total Price
Piping for Jet Impingement for both Air & Steam
2½ʺ GI Pipe
For heating space & flow
control
240/- per feet 5 ft 1200/-
1ʺ GI Pipe
For jet impingement both
in Air and Steam
80/- per feet 5 ft 400/-
4ʺ x 2½ʺ Socket
To reduce the flow
600/- 1 600/-
2½ʺ x 1ʺ Socket
To make the jet
300/- 1 300/-
1ʺ 90° Bends
To control the steam
60/- 5 300/-
Flange with 4ʺ hole
For setting up with the
wind tunnel
85/- per kg
Specimen Holder
½ʺ Plastic Pipe
To flow shield cooling
water
15/- per feet
Steel Sheet 28 gauge
For thermal shield
140/- per running feet 2 x 2 sq. feet 560/-
Wood Structure
Thermocouple
Measuring Plate
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BUDGET ESTIMATION (CONTINUED)
Type Size Wattage Rating Unit
Price
Rod Shape 8ʺ ~ 18ʺ 400W ~ 3000W 200/- ~
1200/-
12ʺ 2000W 450/-
12ʺ 1200W 350/-
8ʺ 400W 250/-
Ring Shape (Finned) 8ʺ 600W 400/-
U Shape 12ʺ 500W 350/-
Locally assembled Coil 4 feet
400/-
Heating Coil
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CALCULATION WITH INTERNAL FIN HEATER CONFIGURATION 1: TUBE BANKS PARALLEL TO THE FLOW DIRECTION
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• Initial Condition:
• Inlet Air Temperature = 30°C
• Heater Wall Temperature =
205°C
• Correlation: Nu=0.37 〖Re〗^0.8
for 17 < Re < 70000
• McAdams, W. H., Heat
Transmission, 3rd ed., New York,
McGraw-Hill, 1954
CALCULATION (CONTINUED)
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CALCULATION (CONTINUED)
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CONFIGURATION 2: TUBE BANKS ACROSS THE FLOW
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CALCULATION (CONTINUED)
• Initial Condition:
• Inlet Air Temperature = 30°C
• Heater Wall Temperature = 205°C
• Correlations: Knudsen and Katz suggested,
• Nu=C 〖Re〗^n 〖Pr〗^(1⁄3)
• For Tube Banks of 4 rows high and 6 rows deep,
• C = 0.27
• n = 0.63
• From Table 6-6 and Table 6-7
• [Zukauskas, A., Heat Transfer from Tubes in Cross Flow, Adv. Heat Transfer, vol 8, pp 93-160, 1972]
• Temperature Increased per Stage: 20.2°C
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WEEK 8
COMMENTS
• The calculation shows better heating can be achieved
with this type of arrangement.
• Further calculation on the same arrangement but
different configuration was recommended.
• Final design was encouraged to submit within the next
week.
• Simulating using CFD module was planned for the final
design.
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WEEK 9
• Provisional Advanced Bill was submitted for sanction
• Extended Abstract was submitted for participating in the
ICME 2011
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WEEK 10 SIMULATION OF THE TESTING EQUIPMENT DESIGNED
WITH ADIABATIC WALL CONDITION
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DESIGN CHECK 2
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DESIGN CHECK 2 (CONTINUED)
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DESIGN CHECK 3
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DESIGN CHECK 3 (CONTINUED)
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WEEK 10
COMMENTS
• The simulation showed a major drawback in the design that
- the surface temperature increased tremendously at the end of
the tube
- the temperature attained using fixed heat transfer is not
perfectly correct due to the physical constrain and the nature of
heat transfer in the air
• Further modification was recommended by using baffle or
extended chamber
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WEEK 11
REDESIGN
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REDESIGN (CONTINUED)
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REDESIGN (CONTINUED)
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REDESIGN
COMMENTS
• Temperature of the air attained is about 110°C - which is required for the testing of fabric
• But the surface temperature of the Fin/Tube Heater is maximum about 2437°C at some places - which will cause the heater to melt or break away before it reaches that high temperature
• Modification is recommended for the design
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FINAL DESIGN
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AIR JET IMPINGEMENT SETUP
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SECTIONAL VIEW OF SETUP
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SPECIMEN HOLDER
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FINAL DESIGN SIMULATION
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FINAL DESIGN (CONTINUED)
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FINAL DESIGN (CONTINUED)
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FINAL DESIGN (CONTINUED)
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FINAL DESIGN (CONTINUED)
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FINAL DESIGN (CONTINUED)
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FINAL DESIGN (CONTINUED)
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COMMENTS
• Air Temperature Expected: 120°C
• Maximum Surface Temperature of Heater: 630°C
• Jet Velocity Expected: 74 m/s
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CONSTRUCTION OF THE SETUP
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CONSTRUCTION
2½ INCH PIPE & REDUCER
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CONSTRUCTION (CONTINUED)
4 INCH PIPE WITH FLANGE
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CONSTRUCTION (CONTINUED)
2½ INCH PIPE & 1 INCH REDUCER
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CONSTRUCTION (CONTINUED)
FLANGE
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CONSTRUCTION (CONTINUED)
WOODEN FABRIC HOLDER
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CONSTRUCTION (CONTINUED)
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PLAN FOR NEXT TERM
• 1. Testing of the setup:
• (a) After establishing the structure, the data acquisition system will be assembled with it.
• (b) Then the calibration of testing equipment will be done.
• 2. Experiment on flame resistant fabric:
• Testing upon fabric will be performed by hot air jet impingement.
• 3. Calculation on the experimental value
• Calculation on the experimental value and later comparison on the result will be done .
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PLAN FOR NEXT TERM (CONTINUED)
• 4. Comparing experimental result with Computer simulation
• Computer simulation will be made using ANSYS CFX and ANSYS FLUENT. The
experimental result will be compared with the simulation. The mathematical model will be
verified by using the appropriate technique
• 5. Analysis on skin burning effect
• The result will be analyzed with the skin burning effect on heat flux and will be determined
whether the fabric can reduce the flame heating on skin
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PLAN FOR NEXT TERM (CONTINUED)
• 6. Study on steam impingement and steam exposures
• •Further study will be done on steam and a comparative study will be presented on steam
impingement technique.
• •The previous research on flame impingement shows that the significant difference
between the air impingement and steam impingement.
• •The momentum effect of steam is more acute than air.
• •Further, the condensation occurs in the stagnation point will cause more heat flux upon
the fabric material.
• •Some recommendations will be presented on steam modeling and experimental
constrained.
• •The effect of steam exposures can also be studied because in many cases, the steam
exposure may causes accident during working and emergency situation.
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Under Supervision of
Dr. Ashraful Islam
Professor, Department of Mechanical Engineering
Bangladesh University of Engineering & Technology
PREPARED BY
AASHIQUE ALAM REZWAN (06 10 012)
IN ASSOCIATION WITH
SARZINA HOSSAIN (06 10 063) SPECIAL THANKS FOR CONSTRUCTION WORK OF THE SETUP
A K M NAZRUL ISLAM (MASTER’S STD)