Trying to solve a set of equations in matlab result gives NaN instead of values,
ID: 3538881 • Letter: T
Question
Trying to solve a set of equations in matlab result gives NaN instead of values, can't figure out why. Code is pasted below:
clc
clear all
deltax=0.008;
kAL=237;
kCu=401;
h=60;
Tsur=20;
Ax=3.1416*(0.005/2)^2;
As=2*3.1416*(0.005/2)*0.008
T1=100;
T21=150;
syms T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 T13 T14 T15 T16 T17 T18 T19 T20
eq1=((kCu*Ax/deltax)*(T1-2*T2+T3))+(h*As*(Tsur-T2))==0;
eq2=(kCu*Ax*(T2-T3)/deltax)+(kCu*Ax*(T4-T3)/deltax)+(h*As*(Tsur-T3))==0;
eq3=(kCu*Ax*(T3-T4)/deltax)+(kCu*Ax*(T5-T4)/deltax)+(h*As*(Tsur-T4))==0;
eq4=(kCu*Ax*(T4-T5)/deltax)+(kCu*Ax*(T6-T5)/deltax)+(h*As*(Tsur-T5))==0;
eq5=(kCu*Ax*(T5-T6)/deltax)+(kCu*Ax*(T7-T6)/deltax)+(h*As*(Tsur-T6))==0;
eq6=(kCu*Ax*(T6-T7)/deltax)+(kCu*Ax*(T8-T7)/deltax)+(h*As*(Tsur-T7))==0;
eq7=(kCu*Ax*(T7-T8)/deltax)+(kCu*Ax*(T9-T8)/deltax)+(h*As*(Tsur-T8))==0;
eq8=(kCu*Ax*(T8-T9)/deltax)+(kCu*Ax*(T10-T9)/deltax)+(h*As*(Tsur-T9))==0;
eq9=(kCu*Ax*(T9-T10)/deltax)+(kCu*Ax*(T11-T10)/deltax)+(h*As*(Tsur-T10))==0;
eq10=(kCu*Ax*(T10-T11)/deltax)+(kCu*Ax*(T12-T11)/deltax)+(h*As*(Tsur-T11))==0;
eq11=(kCu*Ax*(T11-T12)/deltax)+(kAL*Ax*(T13-T12)/deltax)+(h*As*(Tsur-T12))==0;
eq12=(kAL*Ax*(T12-T13)/deltax)+(kAL*Ax*(T14-T13)/deltax)+(h*As*(Tsur-T13))==0;
eq13=(kAL*Ax*(T13-T14)/deltax)+(kAL*Ax*(T15-T14)/deltax)+(h*As*(Tsur-T14))==0;
eq14=(kAL*Ax*(T14-T15)/deltax)+(kAL*Ax*(T16-T15)/deltax)+(h*As*(Tsur-T15))==0;
eq15=(kAL*Ax*(T15-T16)/deltax)+(kAL*Ax*(T17-T16)/deltax)+(h*As*(Tsur-T16))==0;
eq16=(kAL*Ax*(T16-T17)/deltax)+(kAL*Ax*(T18-T17)/deltax)+(h*As*(Tsur-T17))==0;
eq17=(kAL*Ax*(T17-T18)/deltax)+(kAL*Ax*(T19-T18)/deltax)+(h*As*(Tsur-T18))==0;
eq18=(kAL*Ax*(T18-T19)/deltax)+(kAL*Ax*(T20-T19)/deltax)+(h*As*(Tsur-T19))==0;
eq19=(kAL*Ax*(T19-T20)/deltax)+(kAL*Ax*(T21-T20)/deltax)+(h*As*(Tsur-T20))==0;
S=solve(eq1, eq2, eq3, eq4, eq5, eq6, eq7, eq8, eq9, eq10,eq11, eq12, eq13, eq14, eq15, eq16, eq17, eq18, eq19)
T2_=eval((S.T2))
T3_=eval(S.T3)
T4_=eval(S.T4)
T5_=eval(S.T5)
T6_=eval(S.T6)
T7_=eval(S.T7)
T8_=eval(S.T8)
T9_=eval(S.T9)
T10_=eval(S.T10)
T11_=eval(S.T11)
T12_=eval(S.T12)
T13_=eval(S.T13)
T14_=eval(S.T14)
T15_=eval(S.T15)
T16_=eval(S.T16)
T17_=eval(S.T17)
T18_=eval(S.T18)
T19_=eval(S.T19)
T20_=eval(S.T20)
Explanation / Answer
clc
clear all
deltax=0.008;
kAL=237;
kCu=401;
h=60;
Tsur=20;
Ax=3.1416*(0.005/2)^2;
As=2*3.1416*(0.005/2)*0.008
T1=100;
T21=150;
syms T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 T13 T14 T15 T16 T17 T18 T19 T20
eq1=((kCu*Ax/deltax)*(T1-2*T2+T3))+(h*As*(Tsur-T2))==0
eq2=(kCu*Ax*(T2-T3)/deltax)+(kCu*Ax*(T4-T3)/deltax)+(h*As*(Tsur-T3))==0;
eq3=(kCu*Ax*(T3-T4)/deltax)+(kCu*Ax*(T5-T4)/deltax)+(h*As*(Tsur-T4))==0;
eq4=(kCu*Ax*(T4-T5)/deltax)+(kCu*Ax*(T6-T5)/deltax)+(h*As*(Tsur-T5))==0;
eq5=(kCu*Ax*(T5-T6)/deltax)+(kCu*Ax*(T7-T6)/deltax)+(h*As*(Tsur-T6))==0;
eq6=(kCu*Ax*(T6-T7)/deltax)+(kCu*Ax*(T8-T7)/deltax)+(h*As*(Tsur-T7))==0;
eq7=(kCu*Ax*(T7-T8)/deltax)+(kCu*Ax*(T9-T8)/deltax)+(h*As*(Tsur-T8))==0;
eq8=(kCu*Ax*(T8-T9)/deltax)+(kCu*Ax*(T10-T9)/deltax)+(h*As*(Tsur-T9))==0;
eq9=(kCu*Ax*(T9-T10)/deltax)+(kCu*Ax*(T11-T10)/deltax)+(h*As*(Tsur-T10))==0;
eq10=(kCu*Ax*(T10-T11)/deltax)+(kCu*Ax*(T12-T11)/deltax)+(h*As*(Tsur-T11))==0;
eq11=(kCu*Ax*(T11-T12)/deltax)+(kAL*Ax*(T13-T12)/deltax)+(h*As*(Tsur-T12))==0;
eq12=(kAL*Ax*(T12-T13)/deltax)+(kAL*Ax*(T14-T13)/deltax)+(h*As*(Tsur-T13))==0;
eq13=(kAL*Ax*(T13-T14)/deltax)+(kAL*Ax*(T15-T14)/deltax)+(h*As*(Tsur-T14))==0;
eq14=(kAL*Ax*(T14-T15)/deltax)+(kAL*Ax*(T16-T15)/deltax)+(h*As*(Tsur-T15))==0;
eq15=(kAL*Ax*(T15-T16)/deltax)+(kAL*Ax*(T17-T16)/deltax)+(h*As*(Tsur-T16))==0;
eq16=(kAL*Ax*(T16-T17)/deltax)+(kAL*Ax*(T18-T17)/deltax)+(h*As*(Tsur-T17))==0;
eq17=(kAL*Ax*(T17-T18)/deltax)+(kAL*Ax*(T19-T18)/deltax)+(h*As*(Tsur-T18))==0;
eq18=(kAL*Ax*(T18-T19)/deltax)+(kAL*Ax*(T20-T19)/deltax)+(h*As*(Tsur-T19))==0;
eq19=(kAL*Ax*(T19-T20)/deltax)+(kAL*Ax*(T21-T20)/deltax)+(h*As*(Tsur-T20))==0;
[T2_, T3_, T4_, T5_, T6_, T7_, T8_, T9_, T10_, T11_, T12_, T13_, T14_, T15_, T16_, T17_, T18_, T19_, T20_]=solve(eq1, eq2, eq3, eq4, eq5, eq6, eq7, eq8, eq9, eq10,eq11, eq12, eq13, eq14, eq15, eq16, eq17, eq18, eq19, T2, T3, T4, T5, T6 ,T7, T8, T9, T10, T11, T12, T13 ,T14,T15, T16, T17, T18, T19 ,T20)