用matlab解复杂方程组eq1=sym('(Tg-302)/(1/23.26+0.01/1.1)+h*(Tg-Tf)+hwg*(Tg-Tw)=0.7*600');eq2=sym('h*(Tg-Tf)+h*(Tw-Tf)=q');eq3=sym('1.128*V*1005*(Tf-302)/0.75/4.6/2.2=q');eq4=sym('Tf=0.75*To+0.25*302');eq5=sym('h*(Tw-Tf)+1/(1/8.72+0.2/0.49)*(Tw

Question

用matlab解复杂方程组
eq1=sym('(Tg-302)/(1/23.26+0.01/1.1)+h*(Tg-Tf)+hwg*(Tg-Tw)=0.7*600');
eq2=sym('h*(Tg-Tf)+h*(Tw-Tf)=q');
eq3=sym('1.128*V*1005*(Tf-302)/0.75/4.6/2.2=q');
eq4=sym('Tf=0.75*To+0.25*302');
eq5=sym('h*(Tw-Tf)+1/(1/8.72+0.2/0.49)*(Tw-299)+hwg*(Tw-Tg)=0');
eq6=sym('0.6*4.6*0.3/sqrt(1+1)*sqrt(2*9.8*2.5*(Tf-302)/302)=V');
eq7=sym('5.67*10^8*(Tg^2+Tw^2)*(Tw+Tg)/(1/0.8+1/0.94-1)=hwg');
eq8=sym('0.0267*Nu/2.5=h');
eq9=sym('4.9+0.0606*(V/4.6/0.04*0.04/0.000016*0.701*2*0.04/2.5)^1.2/(1+0.0909*(V/4.6/0.04*0.04/0.000016*0.701*2*0.04/2.5)^0.7*0.701^0.17)=Nu');
[Tg,h,Tf,hwg,Tw,q,To,Nu,V]=solve(eq1,eq2,eq3,eq4,eq5,eq6,eq7,eq8,eq9);
运行后提示：Warning:Explicit solution could not be found.
> In solve at 140
In sym.solve at 49
方程组应该有大于0的解.
方程中有什么问题,应该怎么解方程组?

Answer 1

再检查一下方程,用fsolve
function hhh
To=400
Tf=0.75*To+0.25*302
V=0.6*4.6*0.3/sqrt(1+1)*sqrt(2*9.8*2.5*(Tf-302)/302)
Nu=4.9+0.0606*(V/4.6/0.04*0.04/0.000016*0.701*2*0.04/2.5)^1.2/(1+0.0909*(V/4.6/0.04*0.04/0.000016*0.701*2*0.04/2.5)^0.7*0.701^0.17)
h=0.0267*Nu/2.5
q=1.128*V*1005*(Tf-302)/0.75/4.6/2.2
eq1=sym('(Tg-302)/(1/23.26+0.01/1.1)+h*(Tg-Tf)+hwg*(Tg-Tw)=0.7*600');
eq2=sym('h*(Tg-Tf)+h*(Tw-Tf)=q');
eq5=sym('h*(Tw-Tf)+1/(1/8.72+0.2/0.49)*(Tw-299)+hwg*(Tw-Tg)=0');
%eq7=sym('5.67*10^8*(Tg^2+Tw^2)*(Tw+Tg)/(1/0.8+1/0.94-1)=hwg');
[Tg,Tw,hwg]=solve(eq1,eq2,eq5,'Tg,Tw,hwg');
Tg=subs(Tg),Tw=subs(Tw),hwg=subs(hwg)
hwg1=5.67*10^8*(Tg^2+Tw^2)*(Tw+Tg)/(1/0.8+1/0.94-1)
x0=[Tg h Tf hwg Tw q To Nu V]
%x0=[11.2698 0.9291 455.5052 -1.8440 -11.2698 113.7074 487.3698 97.0550 0.0031]
fsolve(@myfuns,x0)
function eqs=myfuns(x)
Tg=x(1);h=x(2);Tf=x(3);hwg=x(4);Tw=x(5);q=x(6);To=x(7);Nu=x(8);V=x(9);
eq1=(Tg-302)/(1/23.26+0.01/1.1)+h*(Tg-Tf)+hwg*(Tg-Tw)-0.7*600;
eq2=h*(Tg-Tf)+h*(Tw-Tf)-q;
eq3=1.128*V*1005*(Tf-302)/0.75/4.6/2.2-q;
eq4=0.75*To+0.25*302-Tf;
eq5=h*(Tw-Tf)+1/(1/8.72+0.2/0.49)*(Tw-299)+hwg*(Tw-Tg);
eq6=0.6*4.6*0.3/sqrt(1+1)*sqrt(2*9.8*2.5*(Tf-302)/302)-V;
eq7=5.67*10^8*(Tg^2+Tw^2)*(Tw+Tg)/(1/0.8+1/0.94-1)-hwg;
eq8=0.0267*Nu/2.5-h;
eq9=4.9+0.0606*(V/4.6/0.04*0.04/0.000016*0.701*2*0.04/2.5)^1.2/(1+0.0909*(V/4.6/0.04*0.04/0.000016*0.701*2*0.04/2.5)^0.7*0.701^0.17)-Nu;
eqs=[eq1;eq2;eq3;eq4;eq5;eq6;eq7;eq8;eq9];