Chapter 9, Problem 9.19P

Interpretation Introduction

(a)

Interpretation:

To interpret the average power usage $\left(kW\right)$ per household and also estimate the number of apartment units that could be powered with the $13kW$ fuel cell.

Concept introduction:

The fuel cell operates at voltage of $26volts$ and current of $500amps$ and has maximum power of $13kW$. A single cell operates at $0.7volts$. A fuel cell is an electrochemical device which produces direct current $\left(DC\right)$ electricity by reacting Hydrogen $\left(H_2\right)$ with available Oxygen $\left(O_2\right)$ in the air.

Here,

$\begin{array}{l}{\dot{n}}_x=MolarFlowrateofChemicalSpeciesx,\\ {\dot{n}}_1=MolarFlowrateofHydrogenthatexitstheanode,\\ {\dot{n}}_2=MolarFlowrateofOxygenthatexitsthecathode,\\ {\dot{n}}_3=MolarFlowrateofWaterthatexitsthecathode.\end{array}$

Interpretation Introduction

(b)

Interpretation:

To interpret the flowrates of Hydrogen and Air required in $\frac{mol}{s}andSLPM\left(\frac{StdL}{\min }\right)$

Concept introduction:

The fuel cell operates at voltage of $26volts$ and current of $500amps$ and has maximum power of $13kW$. A single cell operates at $0.7volts$. Stoichiometric amount of moles of Hydrogen required

$\begin{array}{l}{\left(n_{H_2}\right)}_{stoich}=\frac{IN}{2F}\\ \\ here,\\ I=CurrentinAmp\\ N=NumberofCells\\ F=Faraday\text{'}sConstant=96485\frac{Coulombs}{molofelectrons}\end{array}$

The constant $2molelectronspermoloffuel$ which follows from the reaction at anode. The Hydrogen fed is $15\%$ excess of this amount and the air is fed in $200\%$ excess of amount required to consume all the Hydrogen.A fuel cell is an electrochemical device which produces direct current $\left(DC\right)$ electricity by reacting Hydrogen $\left(H_2\right)$ with available Oxygen $\left(O_2\right)$ in the air.

Here,

$\begin{array}{l}{\dot{n}}_x=MolarFlowrateofChemicalSpeciesx,\\ {\dot{n}}_1=MolarFlowrateofHydrogenthatexitstheanode,\\ {\dot{n}}_2=MolarFlowrateofOxygenthatexitsthecathode,\\ {\dot{n}}_3=MolarFlowrateofWaterthatexitsthecathode.\end{array}$

Interpretation Introduction

(c)

Interpretation:

Determine the molar flowrate of Hydrogen exiting from the anode and the molar composition of the cathode exit gas.

Concept introduction:

The fuel cell operates at voltage of $26volts$ and current of $500amps$ and has maximum power of $13kW$. A single cell operates at $0.7volts$. The Mole Flowrate of Hydrogen is $\left({\dot{n}}_{H_2}\right)=0.113\frac{mol{H}_2}{s}$. The Volumetric Flowrate of Hydrogen in Standard Liters per Minute is $152SLPM$. The Mole Flowrate of air is $\left({\dot{n}}_{Air}\right)=0.707\frac{mol}{s}$. The Volumetric Flowrate of air in Standard Liters per Minute is $951SLPM$.

The constant $2molelectronspermoloffuel$ which follows from the reaction at anode. The Hydrogen fed is $15\%$ excess of this amount and the air is fed in $200\%$ excess of amount required to consume all the Hydrogen .A fuel cell is an electrochemical device which produces direct current $\left(DC\right)$ electricity by reacting Hydrogen $\left(H_2\right)$ with available Oxygen $\left(O_2\right)$ in the air.

Here,

$\begin{array}{l}{\dot{n}}_x=MolarFlowrateofChemicalSpeciesx,\\ {\dot{n}}_1=MolarFlowrateofHydrogenthatexitstheanode,\\ {\dot{n}}_2=MolarFlowrateofOxygenthatexitsthecathode,\\ {\dot{n}}_3=MolarFlowrateofWaterthatexitsthecathode.\end{array}$

Interpretation Introduction

(d)

Interpretation:

To interpret the number of apartments could be safely powered with a $13kW$ fuel cell.

Concept introduction:

The fuel cell operates at voltage of $26volts$ and current of $500amps$ and has maximum power of $13kW$. A single cell operates at $0.7volts$. The Mole Flowrate of Hydrogen is $\left({\dot{n}}_{H_2}\right)=0.113\frac{mol{H}_2}{s}$. The Volumetric Flowrate of Hydrogen in Standard Liters per Minute is $152SLPM$. The Mole Flowrate of air is $\left({\dot{n}}_{Air}\right)=0.707\frac{mol}{s}$. The Volumetric Flowrate of air in Standard Liters per Minute is $951SLPM$ .The molar flowrate of Hydrogen exit from the anode is $0.015\frac{mol{H}_2}{s}$. The molar composition of cathode exit gas are $Oxygen=0.099\frac{mol{O}_2}{s}\&Nitrogen=0.558\frac{mol{N}_2}{s}$

The constant $2molelectronspermoloffuel$ which follows from the reaction at anode. The Hydrogen fed is $15\%$ excess of this amount and the air is fed in $200\%$ excess of amount required to consume all the Hydrogen .A fuel cell is an electrochemical device which produces direct current $\left(DC\right)$ electricity by reacting Hydrogen $\left(H_2\right)$ with available Oxygen $\left(O_2\right)$ in the air.

Here,

$\begin{array}{l}{\dot{n}}_x=MolarFlowrateofChemicalSpeciesx,\\ {\dot{n}}_1=MolarFlowrateofHydrogenthatexitstheanode,\\ {\dot{n}}_2=MolarFlowrateofOxygenthatexitsthecathode,\\ {\dot{n}}_3=MolarFlowrateofWaterthatexitsthecathode.\end{array}$

Interpretation Introduction

(e)

Interpretation:

To interpret the times when battery is being charged and the minimum total energy capacity of the battery in $kW\cdot hr$.

Concept introduction:

The fuel cell operates at voltage of $26volts$ and current of $500amps$ and has maximum power of $13kW$. A single cell operates at $0.7volts$ .The constant $2molelectronspermoloffuel$ which follows from the reaction at anode. The Hydrogen fed is $15\%$ excess of this amount and the air is fed in $200\%$ excess of amount required to consume all the Hydrogen .A fuel cell is an electrochemical device which produces direct current $\left(DC\right)$ electricity by reacting Hydrogen $\left(H_2\right)$ with available Oxygen $\left(O_2\right)$ in the air.

Here,

$\begin{array}{l}{\dot{n}}_x=MolarFlowrateofChemicalSpeciesx,\\ {\dot{n}}_1=MolarFlowrateofHydrogenthatexitstheanode,\\ {\dot{n}}_2=MolarFlowrateofOxygenthatexitsthecathode,\\ {\dot{n}}_3=MolarFlowrateofWaterthatexitsthecathode.\end{array}$