i have to get combine correct figure

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% EXAMPLE 3-3: Calculating the Voltage Losses for a Polarization Curve
% UnitSystem SI
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Inputs
R = 8.314; % Ideal gas constant (J/molK)
F = 96487; % Faraday’s constant (Coulombs)
Tc = 80; % Temperature in degrees C
P_H2 = 3; % Hydrogen pressure in atm
P_air = 3; % Air pressure in atm
A_cell=100; % Area of cell
N_cells=90; % Number of Cells
r = 0.19; % Internal Resistance (Ohm-cm^2)
Alpha = 0.5; % Transfer coeffi cient
Alpha1 = 0.085; % Amplifi cation constant
io = 10^-6.912; % Exchange Current Density (A/cm^2)
il = 1.4; % Limiting current density (A/cm2)
Gf_liq = -228170; % Gibbs function in liquid form (J/mol)
k = 1.1; % Constant k used in mass transport
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Convert degrees C to K
Tk = Tc + 273.15;
% Create loop for current
loop = 1;
i = 0;
for N = 0:150;
    i = i + 0.01;
    % Calculation of Partial Pressures
    % Calculation of saturation pressure of water
    x = -2.1794 + 0.02953 .* Tc-9.1837 .* (10.^-5) .* (Tc.^2) + 1.4454 .* (10.^-7) .* (Tc.^3);
    P_H2O = (10.^x);
    % Calculation of partial pressure of hydrogen
    pp_H2 = 0.5 .* ((P_H2)./(exp(1.653 .* i./(Tk.^1.334)))-P_H2O);
    % Calculation of partial pressure of oxygen
    pp_O2 = (P_air./exp(4.192 .* i/(Tk.^1.334)))-P_H2O;
    % Activation Losses
    b = R .* Tk./(2 .* Alpha .* F);
    V_act = -b .* log10(i./io); % Tafel equation
    % Ohmic Losses
    V_ohmic = -(i .* r);
    % Mass Transport Losses
    term = (1-(i./il));
    if term > 0;
        V_conc = Alpha1 .* (i.^k) .* log(1-(i./il));
    else
        V_conc = 0;
    end
    % Calculation of Nernst voltage
    E_nernst = -Gf_liq./(2 .* F) - ((R .* Tk) .* log(P_H2O./(pp_H2 .* (pp_O2.^0.5))))./(2 .* F);
    % Calculation of output voltage
    V_out = E_nernst - V_ohmic - V_act - V_conc;
    if term < 0;
        V_conc = 0;
        break
    end
    if V_out < 0;
        V_out = 0;
        break
    end
    figure(1)
    title('Fuel cell polarization curve')
    xlabel('Current density (A/cm^2)');
    ylabel('Output voltage (Volts)');
    plot(i,V_out,'b-o')
    grid on
    hold on
    disp(V_out)
end

Here i got grapgoc for v_out and when i changed it with v_ohmic and v_act i got correct output. But the problem is that I need to display 3 graphs in 1 graph.So i also did try it but didnt work well. I'm uploading the hand drawing of the figure it should be.

Answer 1

[Sulaymon Eshkabilov]

Here is how you can attain all three plots in one fig.:

...

plot(i,V_out,'b-o', i, V_act, 'r-d', i, V_ohmic, 'g--s')
disp(V_out), hold on
end
grid on
legend('V_{out}', 'V_{act}', 'V_{ohmic}')

[sevgul demir]

Thank you for reply me :) also i did try it and got the same result but the figure is not what we want ...

i have to show those 3 graph as like hand write figure :( but i dont know how...

Answer 2

[Sulaymon Eshkabilov]

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% EXAMPLE 3-3: Calculating the Voltage Losses for a Polarization Curve
% UnitSystem SI
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Inputs
R = 8.314; % Ideal gas constant (J/molK)
F = 96487; % Faraday’s constant (Coulombs)
Tc = 80; % Temperature in degrees C
P_H2 = 3; % Hydrogen pressure in atm
P_air = 3; % Air pressure in atm
A_cell=100; % Area of cell
N_cells=90; % Number of Cells
r = 0.19; % Internal Resistance (Ohm-cm^2)
Alpha = 0.5; % Transfer coeffi cient
Alpha1 = 0.085; % Amplifi cation constant
io = 10^-6.912; % Exchange Current Density (A/cm^2)
il = 1.4; % Limiting current density (A/cm2)
Gf_liq = -228170; % Gibbs function in liquid form (J/mol)
k = 1.1; % Constant k used in mass transport
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Convert degrees C to K
Tk = Tc + 273.15;
% Create loop for current
loop = 1;
i = 0;
for N = 0:150
i = i + 0.01;
% Calculation of Partial Pressures
% Calculation of saturation pressure of water
x = -2.1794 + 0.02953 .* Tc-9.1837 .* (10.^-5) .* (Tc.^2) + 1.4454 .* (10.^-7) .* (Tc.^3);
P_H2O = (10.^x);
% Calculation of partial pressure of hydrogen
pp_H2 = 0.5 .* ((P_H2)./(exp(1.653 .* i./(Tk.^1.334)))-P_H2O);
% Calculation of partial pressure of oxygen
pp_O2 = (P_air./exp(4.192 .* i/(Tk.^1.334)))-P_H2O;
% Activation Losses
b = R .* Tk./(2 .* Alpha .* F);
V_act = -b .* log10(i./io); % Tafel equation
% Ohmic Losses
V_ohmic = -(i .* r);
% Mass Transport Losses
term = (1-(i./il));
if term > 0
V_conc = Alpha1 .* (i.^k) .* log(1-(i./il));
else
V_conc = 0;
end
% Calculation of Nernst voltage
E_nernst = -Gf_liq./(2 .* F) - ((R .* Tk) .* log(P_H2O./(pp_H2 .* (pp_O2.^0.5))))./(2 .* F);
% Calculation of output voltage
V_out = E_nernst - V_ohmic - V_act - V_conc;
if term < 0
V_conc = 0;
break
end
if V_out < 0
V_out = 0;
break
end
figure(1)
title('Fuel cell polarization curve')
xlabel('Current density (A/cm^2)');
ylabel('Output voltage (Volts)');
plot(i,V_out,'b-o', i, V_act, 'r-d', i, V_ohmic, 'g--s', i, E_nernst, 'k--x', 'markerfacecolor', 'y')
disp(V_out), hold all
end
grid on
hold on
legend('V_{out}', 'V_{act}', 'V_{ohmic}', 'E_{nernst}', 'location', 'best')
gtext('V_{out}'),gtext( 'V_{act}'), gtext('V_{ohmic}'), gtext('E_{nernst}')

Click where you want to display the line name, e.g. V_out, V_act, V_ohm, E_nernst

[sevgul demir]

Thank you very much for your effort, but I have to say with regret that this result is very different from the graphic I was trying to make. :(

It looks like I need to add a new code or formula, but I don't know exactly. My attempts do not give the correct result.