line not appear in plot

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amirul
amirul 2024-1-28
评论： Star Strider 2024-1-29
Ran in:
Below are my code, why the plot not appear. someone help
% PEM Electrolyzer Activation Overvoltage Plot
% Constants
ioa = 2e-9; % Anode exchange current density (A/cm2)
ioc = 2e-3; % Cathode exchange current density (A/cm2)
T = 297; % Temperature (K)
R = 8.314; % General gas constatnt (J/Kmol)
ctca = 0.5 ; % charge transfer coefficient anode
ctcc = 0.5 ; % charge transfer coefficient cathode
z = 2 ; % stoichiometric coefficient
F = 96485; % Faradays constant
% Operating current density range
i_density = linspace(0, 1.5, 100); % Current density range (A/m^2)
% Calculate activation overvoltage
a = R.*T/ctca.*z.*F;
b = R.*T/ctcc.*z.*F;
eta_activation = log((i_density/ioa).^(a))+(-log((i_density/ioc).^(b)))
eta_activation = 1×100
NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN
% Plot the results
plot(i_density, eta_activation,"b");
  2 个评论
Dyuman Joshi
Dyuman Joshi 2024-1-28
The plot is empty because all the values are NaN, see the edit above.

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回答（1 个）

Star Strider
Star Strider 2024-1-28
Ran in:
The ‘i_density’ vector begins with 0 and the log of 0 is -Inf.
Starting it instead with a very small value, and re-writing ‘eta_activation’ to use simple log identities produces finite results.
There is some variation in ‘eta_activation’, as demonstrated by the derivative plot (added) —
% PEM Electrolyzer Activation Overvoltage Plot
% Constants
ioa = 2e-9; % Anode exchange current density (A/cm2)
ioc = 2e-3; % Cathode exchange current density (A/cm2)
T = 297; % Temperature (K)
R = 8.314; % General gas constatnt (J/Kmol)
ctca = 0.5 ; % charge transfer coefficient anode
ctcc = 0.5 ; % charge transfer coefficient cathode
z = 2 ; % stoichiometric coefficient
F = 96485; % Faradays constant
% Operating current density range
i_density = linspace(1E-12, 1.5, 100); % Current density range (A/m^2)
% Calculate activation overvoltage
a = R.*T/ctca.*z.*F;
b = R.*T/ctcc.*z.*F;
eta_activation = log((i_density/ioa).^(a))+(-log((i_density/ioc).^(b))) % Original
eta_activation = 1×100
NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN
eta_activation = a*log(i_density/ioa) - b*log(i_density/ioc) % Rewritten
eta_activation = 1×100
1.0e+10 * 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166 1.3166
deta_activation_di_density = gradient(eta_activation,i_density) % Derivative
deta_activation_di_density = 1×100
1.0e-03 * 0 0 0 -0.0629 -0.1259 0.0629 0.0629 -0.0629 0.0629 0 -0.0629 0.0629 0 -0.1259 0 0 0 0 0.0629 0 -0.0629 0.0629 0 0.0629 -0.0629 0 0 -0.0629 0.0629 0
% Plot the results
figure
plot(i_density, eta_activation,"b");
xlabel('i\_density')
ylabel('eta\_activation')
figure
plot(i_density, deta_activation_di_density,"g");
xlabel('i\_density')
ylabel('$\frac{d(eta\_activation)}{d(i\_density)}$', 'Interpreter','latex')
.
  4 个评论
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amirul
amirul 2024-1-29
Thank you very much my friends. Appriciate it

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