\(-\kappa\frac{\partial T}{\partial y}\left(x,0\right)=h_{f}\left[T_{f}-T\left(x,0\right)\right];\ \ T\left(x,\ \infty\right)=T_{\infty},\ C\left(x,0\right)=C_{w},\ C\left(x,\infty\right)=C_{\infty}.\) (7)