Off[General::"spell1"]

To = 20;
ρ = 7290. ;
λ = 63.2;
cp = 256;
cm = 0.01;
mm = 0.1  cm;
ρel = 1.15*(10^(-5))*cm;
d = 0.1  mm;
xmax = 1.5  cm;
proud = 10;
Sk = ((Pi*(d^2))/4);
J = (proud/Sk);
QV1 = ρel*(J^2);
o = Pi*d;
α = 5;
σ = 5.67*(10^(-8));
ϵ = 0.8;
dQk = α*o*dx*(To - T[x, t]);
dQr = ϵ*σ*o*
          dx*((((To + 273))^4) - (((T[x, t] + 273))^4));
QV2 = ((dQk + dQr)/(Sk*dx)) // 
          FullSimplify;
rce = ρ*cp*D[T[x, t], t] == λ*D[T[x, t], {x, 2}] + 
            QV1 + QV2;
okr1 = T[0, t] == To;
okr2 = T[xmax, t] == To;
poc = T[x, 0] == To;
tmax = 0.001;
teplota[x_, t_] = 
        T[x, t] /. NDSolve[{rce, poc, okr1, okr2}, 
              T[x, t], {x, 0, xmax}, {t, 0, tmax}, 
              MaxStepSize -> {xmax/100, 
                  tmax/100}][[1]];
Plot3D[teplota[x, t], {x, 0, xmax}, {t, 0, tmax}, 
        PlotPoints -> 150];
Tepnakonci[x_] = teplota[x, tmax];
\(\(Plot[Tepnakonci[x], {x, 0, xmax}, PlotRange -> All, 
        AxesLabel -> {"x", "T[x,tmax]"}];\)
 (*Tepuprostred[t_] = teplota[xmax/2, t]; 
Plot[
        Tepuprostred[t], {t, 0, tmax}, PlotRange -> All, 
        AxesLabel -> {"t", "T[xmax/2,t]"}]*) 

\)