{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

5 - MEM 415 FUEL CELL ENGINES Lecture#5-THERMODYNAMICS AND...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
2/7/2011 1 -- Lecture #5 -- MEM 415– FUEL CELL ENGINES THERMODYNAMICS AND POLARIZATION MEM 415– Lecture #5 Dr. E. Caglan Kumbur Assistant Professor of Mechanical Engineering Office: Curtis 160 Ph: 215.895.5871 e-mail: [email protected] -- Feb 7, 2011 -- Polarization and Performance Curve E 00 =E max (Ideal Case) = 1.23 V Polarization curve represents _______________________ , which is the key tool for evaluation of cell performance. Heat Dissipation Due to the resistances (in different forms) inside the cell . Cell dies after reaching some limiting current density. Useful Power • These losses can be categorized in __________________ MEM 415– Lecture #5
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2/7/2011 2 Polarization Curve Regions Region 1: Activation Polarization – Component of interest: Catalyst Layer Reason: Activation overpotential at the electrodes (Kinetic losses) Region 2: Ohmic Polarization – Component of interest: Electrolyte, Catalyst Layer, GDL Reason: Dominated by electrical and ionic conduction losses. Region 3: Concentration Polarization – Component of interest: Catalyst Layer, GDL Reason: Dominated by mass transport limitations. Region 4: Crossover Losses – Component of interest: Electrolyte Reason: Reactant crossover through the electrolyte. Region 5: Departure from maximum thermal voltage – Thermodynamics losses Reason: Departure from the maximum thermal voltage due to entropy change Ideal Gas Enthalpy- Constant Specific Heats- Summary of Last Lecture Gas phase specific heat Enthalpy and Internal Energy Calculation using Specific Heats- ! " # 2 1 ) ( 1 2 T T dT T c u u $ v dT du T c " ) ( % ) ( 1 2 1 2 T T c u u u # " # " & % P p dT dh T c " ) ( ! " # 2 1 ) ( 1 2 T T p dT T c h h ) ( 1 2 1 2 T T c h h h p # " # " & Entropy and Gibbs Function- MEM 415– Lecture #5
Background image of page 2
2/7/2011 3 work available maximum work electrical actual " th 2) 1) Thermo definitions: Summary of Last Lecture W e = - & G = n F E o !!! ( E nF G " & # Maximum Available/ Possible Voltage (Open Circuit Voltage) oo th H E E nF #& " " W e = - & H = - ! G = n F E ºº Maximum/Total Theoretical Voltage (Impossible in Reality !!) S T S T H E nF G G o & & # & & # & 1 work electrical Maximum S T & 1 H H E nF H H thermal & # " & " " & # " & " " work available Total 00 max , H t & # " Maximum thermodynamic efficiency 3) where x can be h, u, s, g, etc….. MEM 415– Lecture #5 Summary of Last Lecture Do the same process for & S, & U, & G… (products-reactants) D C B A d c b a % $ % $ ) * ) + , + , R R i P P i R P x v x v x x x - - # " # " & , , Reactants Products Where x can be h, u, s, g, etc….. Refer to your Thermo Book and Chapter 3 in your text book for detailed explanation !!!! MEM 415– Lecture #5
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2/7/2011 4 i u ref P P R P T s T s 0 ln ) , ( ) ( # " Change in Entropy and Gibbs Function D C B A d c b a % $ % $ ) * ) Reactants Products Entropy Summary of Last Lecture f Re - - # " # " & R i R i P i P i R p s s s s s ) ( ) ( , , % % - - # # # " R f i u ref R i P f i u ref P i P P R P T s P P R P T s ) ln ) , ( ( ) ln ) , ( ( Re 0 , Re 0 , % % ) ( ) ( 0 T h h Gibbs Function ref ref f s s g g # # # ) " ) ( 1 2 1 2 1 2 s s T h h g g # # # " # - - # " # " & R i R i P i P i R p g g g g g ) ( ) ( , , % % Refer to your Thermo Book for detailed explanation !!!!
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}