Error using sym/subsindex (line 796)
显示 更早的评论
t1 = 588; %k
do = 3.5; % in
di = 3.0; % in
kp = 21.6; %W/(m*K)
ta = 294; % K
ts = 255.4; %k
h = 48.3; %W/(m^2*K)
deltar = 1; % in of calcium silicate insulation
e = .76;
at = pi*(do+2*deltar);
alm1 = (pi*(do-di))/(log(do/di));
alm2 = (2*pi*deltar)/log(do+2*deltar/do);
o = .0000000567; %W/(M^2*k^4)
d = .5; %do-di(in)
syms t2 t3 ki
eq1 = ki==.044+.0001144*(.5*(t2+t3)-283.333)
eq2 = 1/((d/(2*kp*alm1))+(deltar/ki*alm2))==(h*at(t3-ta)+e*o*at(t3^4-ts^4))/(t1-t3)
eq3 = (2*kp*alm1*(t1-t2))/((d)==h*at(t3-ta)+e*o*at(t3^4-ts^4))
[t2,t3,ki] = vpasolve([eq1,eq2,eq3],[t2,t3,ki],[0 inf;0 1])
t2 = double(t2)
t3 = double(t3)
ki = double(ki)
the error is in the eq2 line, eq1 seems to work fine.
4 个评论
Star Strider
2017-10-19
In your code, ‘at’ is a single scalar value. It is not a function or an array, yet you are addressing it as one or the other (probably as a function) in ‘eq2’ and ‘eq3’.
You need to decide what you want to do with it.
Nate Mahorner
2017-10-19
Nate Mahorner
2017-10-19
Star Strider
2017-10-19
The mystery nevertheless continues, since ‘s’ — either as a function or an array — appears nowhere in your code (that I can see).
Resolved it seems, regardless.
采纳的回答
Birdman
2017-10-19
0 个投票
You forgot to put an operator in front of your at variables in eq2 and eq3. Also, in the vpasolve function, choose your initial guess wisely. If you don't indicate an initial guess for your equations, MATLAB still finds answers. Hope this helps.
更多回答（1 个）
Walter Roberson
2017-10-19
0 个投票
You have at(t3-ta) and at(t3^4-ts^4) in that line, but at is not a function and and t3-ta and t3^4-ts^4 are not valid indices into the at variable
类别
在 帮助中心 和 File Exchange 中查找有关 Mathematics 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
