gp1 pres_pem fuel cells
TRANSCRIPT
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United Arab Emirates UniversityCollege of EngineeringMechanical Engineering DepartmentGraduation Project I1st semester 2003/2004
Design of a Finned PEM Fuel cell
Advisor: Dr. Ayoub Kazim
Done by: Ahmed Al-Salami
Badr Ali Ahmed
Jassim Abdulla
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Overview:
Introduction.
Objectives.
Fuel Cells.
Fins.
Design & Analysis.
Assumptions.
Results.
Conclusion & Recommendations.
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Introduction
Summary of the project.
A fuel cell is a device that uses hydrogen (or
hydrogen-rich fuel) and oxygen to create
electricity by an electrochemical process.
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Objectives1. Study a PEM fuel cell.
2. Design a number of fins on the external plate of the PEM fuelcell.
3. Design of finned PEM fuel cell in terms of various geometry
and choose the best fin geometry in term of fin efficiencyand effectiveness.
4. Determine fin base temperature, heat transfer, efficiencyand effectiveness.
5. Couple the heat transfer equations of the fins with theelectrochemical equations of the fuel cells.
6. Perform economical analysis of a finned fuel cell.
7. Perform energy analysis on the fuel cell based on the firstlaw of thermodynamics.
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Types of Fuel Cells
Proton Exchange Membrane fuel cell (PEM).
Alkaline fuel cell (AFC).
Phosphoric-acid fuel cell (PAFC).
Solid oxide fuel cell (SOFC).
Molten carbonate fuel cell (MCFC).
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PEM Fuel Cell
PEM (Proton Exchange
Membrane).
Components of PEM.
PEM fuel cell process.
Anode: 2H2 --> 4H+ + 4e-
Cathode: 4e- + 4H+ + O2 --> 2H2O
Overall: 2H2 + O2 --> 2H2O
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Advantages:
Reliability.
Low Operating Cost.
Constant Power Production.
Clean Emissions.
Quiet Operations.
High Efficiency.
Choice of Fuels.
Storable.
Transportable.
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Disadvantages:
Safety.
Cost.
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Applications:
Stationery power
Automotive
Power Supply.
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Boundary conditions
1.Infinitely Long Fin.
2. Insulated Fin Tip.
3. Convection From Fin Tip.
4. Prescribed fin temperature .
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1. Infinitely Long Fin
TThpkAQ bcfinlong
fin
c
hA
hpkAfinlong
cfinno
fin
hA
kp
Q
Qfinlong
Rate of heat transfer :
Efficiency :
Effectiveness:
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2. Insulated Fin Tip
Rate of heat transfer :
Efficiency :
Effectiveness:
aLTThpkAQ bctipinsulated tan
ckAhpa /
alhA
kp
Q
Q
cfinno
fintanhtipinsulated
fin
c
hA
aLhpkA tanhtipInsulated
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3. Convection From Fin Tip
Rate of heat transfer :
Efficiency :
Effectiveness:
ckAhpa /
aLakhaL
aLakhaLTThpkAQ bcconv
sinhcosh
coshsinh.
aLak
haLaL
aLak
haL
sinhcosh
coshsinh
conv.
aLak
haL
aLakhaL
hA
kp
Q
Q
cfinno
fin
conv
sinhcosh
coshsinh.
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4. Prescribed fin temperature
Rate of heat transfer :
Efficiency :
Effectiveness:
(Watt)sinh
cosh
)(
aL
TT
TTaL
TThpkAQb
L
bcprescribed
aLaLTT
TTaL
b
L
finsinh
cosh
aL
TT
TTaL
hA
kp b
L
c sinh
cosh
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Flow chart
Re-design
Accept, and comparison between the
alternatives.
Select the best geometryof fin
Qno,fin Qfin, max Qfin
NO YES
Boundary Conditions
Assumption: h, k, Tb, Ta
Dimensions
L, r, x
Af Ac P
1
Design & Analysis
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Assumptions
Symbol Definition Value Unit Reference
h
Convection
heat transfer
coefficient
10 W/m2.oC Typical
237 for
Aluminum
Yunus A
Cengle, Heat
transfer.k
Thermal
conductivity401 for
Copper
W/m.oC
Yunus A
Cengle,Heat
transfer.
TaAmbient
temperature25
oC Assumed
TbBase
temperature65
oC Assumed
TLGiven
temperature30
oC Assumed
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Assumptions :
Steady state.
One-dimensional conduction.
Negligible radiation heat transfers effect.
The area of external plate is 10X10 cm2.
Material is aluminum.
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Cylindrical fin on the external plate
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Results
Qfin & Qfin, max Vs. Length
0.0500
0.1000
0.1500
0.2000
0.2500
0.0400 0.0500 0.0600 0.0700 0.0800 0.0900 0.1000 0.1100 0.1200
Length (m)
Qfin
(Watt)
0.1000
0.1500
0.2000
0.2500
0.3000
Qfin,m
ax(Watt)
Qfin Qfin,max
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Results
Efficiency & Effectiveness Vs. Length
0.7000
0.7500
0.8000
0.8500
0.90000.9500
1.0000
0.0400 0.0500 0.0600 0.0700 0.0800 0.0900 0.1000 0.1100 0.1200
Length (m)
65.0000
85.0000
105.0000
125.0000
145.0000165.0000
185.0000
Efficiency Effectiveness
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Results
Qfin & Qfin, max Vs. Diameter
0.03
0.23
0.43
0.63
0.00055 0.00155 0.00255 0.00355 0.00455 0.00555
Diameter (m)
Qfin(Watt)
0.042
0.442
0.842
Qfin,max
(Watt)
Qfin Qfin,max
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Results
Efficiency & Effectiveness Vs. Diameter
0.2
0.4
0.6
0.8
1
0.0008 0.0016 0.0024 0.0032 0.004 0.0048 0.0056
Diameter (m)
40
90
140
190
240
290
Efficiency Effectiveness
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Results
Maximum heat transfer rate at constant diameter = 2mm for cylindrical geometry.
Maximum heat transfer rate at constant length = 80mm for cylindrical geometry.
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Conclusion and Recommendations
References.
Test station of PEM fuel cell.
TK Solver software problems.
Heat transfer software's.
Boundary conditions information.
The coupling between the electrochemical analysis
and the fin design.
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