4. Heat Transfer Coefficient

Unlike thermal conductivity \(k\), the heat transfer coefficient is not a material property. Rather it depends on geometry, fluid properties, motion, and in some cases temperature difference, \(\Delta T=(T_s-T_\infty)\). That is \[h = f(\text{geometry, fluid motion, fluid properties}, \Delta T)\]

\[q = -k\left.\frac{\partial T}{\partial y}\right|_{y=0} = h(T_s-T_\infty)\]

\[h =\frac{-k}{T_s-T_\infty} \frac{\partial T(x,0,z)}{\partial y}\]