上次说comsol没熟，这个熟得还要慢

%jiaozi
function jiaozi
% --------------------------------------------------------------
% parameters
rho_out = 1050;
rho_middle = 1;
rho_in = 1050;

k_out = 0.4;
k_middle = 0.025;
k_in = 0.5;

Cp_out= 3000;
Cp_in = 4000;
Cp_middle = 2000;

thickness_out = 1e-3;
thickness_middle = 0.4e-3;
thickness_in = 14.6e-3;

Tw = 95;
T_ini = 25;
% --------------------------------------------------------------
% mesh:
x_mesh = [0.00005 0.0001 0.0005 0.001 0.05 [0.1:0.1:0.9], 0.95, 0.99, 0.995,0.999,0.9995,1];
x_out = x_mesh * thickness_out;
x_middle = x_mesh * thickness_middle;
x_in = x_mesh * thickness_in;
x_jiaozi = [0, x_in, thickness_in + x_middle, thickness_in + thickness_middle + x_out];

tmax = 600;
t = linspace(0,tmax,100);

% --------------------------------------------------------------
m = 0;
sol = pdepe(m,@jiaozi_pde,@(x)T_ini,@jiaozi_bc,x_jiaozi,t);
T = sol(:,:,1);
surf(x_jiaozi,t,T)

% --------------------------------------------------------------
function [c,f,s] = jiaozi_pde(x,t,u,DuDx)
if x < thickness_in
rho_jiaozi = rho_in;
Cp_jiaozi = Cp_in;
k_jiaozi = k_in;
elseif x < thickness_in + thickness_middle
rho_jiaozi = rho_middle;
Cp_jiaozi = Cp_middle;
k_jiaozi = k_middle;
else
rho_jiaozi = rho_out;
Cp_jiaozi = Cp_out;
k_jiaozi = k_out;
end
c = rho_jiaozi * Cp_jiaozi;
f = DuDx * k_jiaozi;
s = 0;
end
% --------------------------------------------------------------
function [pl,ql,pr,qr] = jiaozi_bc(xl,ul,xr,ur,t)
pl = 0; ql = 1;
pr = ur-Tw; qr = 0;
end
end