【eq2】...Tf)+hwg*(Tg-Tw)=0.7*600');eq2=sym('h*(Tg-Tf)+h*(Tw-Tf)=q')...

【eq2】...Tf)+hwg*(Tg-Tw)=0.7*600');eq2=sym('h*(Tg-Tf)+h*(Tw-Tf)=q')...

【答案】 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];

感谢回答