GP1 Pres_PEM Fuel Cells

7/31/2019 GP1 Pres_PEM Fuel Cells

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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


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


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


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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Documents

GP1 Pres_PEM Fuel Cells