Unable to perform assignment

Question

Michael Käufl 2020-1-13

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/500162-unable-to-perform-assignment

回答： Walter Roberson 2020-1-14

在 MATLAB Online 中打开

Hello Guys,

I've got this error message every time: Index exceeds the number of array elements (1).

Error in Neu_HTU>@(T_H2O,h_Luft)cp_H2O*Massenstromverhaeltnis*(1+(X_sat(i)-X(i))*cp_H2O*T_H2O(i)./Ch(i)) (line 112)

f1 = @(T_H2O,h_Luft) cp_H2O * Massenstromverhaeltnis *(1+(X_sat(i)-X(i))*cp_H2O*T_H2O(i)./Ch(i));

Error in Neu_HTU (line 114)

l1 = f1((T_H2O(i) ),(h_Luft(i) ));

Can anybody help me?

Cheers Michael

for i=1:ceil(T_H2O_aus/h)                                   % calculation loop
    T_H2O(i+1) = T_H2O(i)+h;
    
    X_sat(i) = 0.622 * p_sat_Antoine(T_H2O(i))/(p - p_sat_Antoine(T_H2O(i)));
    
    h_Luft_sat(i) = (cp_Luft + cp_Dampf * X_sat(i)) * (T_Luft_unten -273.15) + X_sat(i) * h_verdampfung;
    
    A(i) = 0.865^(2/3)*(((0.622+X_sat(i))./(0.622+X(i))-1)/(log((0.622+X_sat(i))./...
    (0.622+X(i)))));
    Massenstromverhaeltnis = M_H2O_ein/M_Luft*(1 - M_Luft/M_H2O_ein*(X_oben-X(i)));
    
    Ch(i) = h_Luft_sat(i) - h_Luft(i) + (A(i)-1)*(h_Luft_sat(i) - h_Luft(i) - (X_sat(i) - X(i)).*...
            (h_verdampfung + cp_Dampf*T_H2O(i))) - (X_sat(i) - X(i)).*cp_H2O.*T_H2O(i);
    
    %Funktion 1
    f1 = @(T_H2O,h_Luft) cp_H2O * Massenstromverhaeltnis *(1+(X_sat(i)-X(i))*cp_H2O*T_H2O(i)./Ch(i));
    
    l1 = f1((T_H2O(i)        ),(h_Luft(i)           ));
    l2 = f1((T_H2O(i) + 0.5*h),(h_Luft(i) + 0.5*h*l1));
    l3 = f1((T_H2O(i) + 0.5*h),(h_Luft(i) + 0.5*h*l2));
    l4 = f1((T_H2O(i) +     h),(h_Luft(i) +     h*l3));
    h_Luft(i+1) = h_Luft(i) + h/6*(l1+2*l2+2*l3+l4);
    
    %Funktion 2
    f2 = @(T_H2O,X) cp_H2O * Massenstromverhaeltnis * ((X_sat - X)./Ch);
    
    k1 = f2((T_H2O(i)        ),(X(i)           ));
    k2 = f2((T_H2O(i) + 0.5*h),(X(i) + 0.5*h*k1));
    k3 = f2((T_H2O(i) + 0.5*h),(X(i) + 0.5*h*k2));
    k4 = f2((T_H2O(i) +     h),(X(i) +     h*k3));
    X(i+1) = X(i) + h/6*(k1+2*k2+2*k3+k4);  
    %X_result = X(i+1); 
end

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Walter Roberson 2020-1-14

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/500162-unable-to-perform-assignment#answer_409988

在 MATLAB Online 中打开

T_H2O(i+1) = T_H2O(i)+h;

Okay, you are growing the vector T_H2O as you go, and if T_H2O(i) did not exist then you would not have gotten past that line. So we know that afterwards T_H2O(i+1) will exist.

f1 = @(T_H2O,h_Luft) cp_H2O * Massenstromverhaeltnis *(1+(X_sat(i)-X(i))*cp_H2O*T_H2O(i)./Ch(i));

This function accepts a parameter that for the purposes of the expression will be called T_H2O . This parameter will not necessarily have anything to do with the vector T_H2O that we established above will have at least at least i+1 elements. You need to mentally re-write the line as something like

f1 = @(FirstParameter,SecondParameter) cp_H2O * Massenstromverhaeltnis *(1+(X_sat(i)-X(i))*cp_H2O*FirstParameter(i)./Ch(i));        

Whatever first parameter you pass in is going to be indexed at i.

l1 = f1((T_H2O(i) ),(h_Luft(i) ));

You extract a single element from T_H2O and pass that as the first parameter to f1, passing in a scalar there. But f1 wants to access that scalar at index i.