22 - Convection - Correlations for Heat Transfer Coefficient

Convection heat transfer associated with laminar flow in a circular pipe (Re \(<\) 2100) is less common than with turbulent flow. The correlations are simple, with Nusselt number being constant for fully developed flow (both hydrodynamically and thermally). \[\begin{aligned}  \ & \text{For uniform wall heat flux:} \qquad & \text{Nu} &= 4.36 \\ \ & \text{For uniform wall temperature:} \quad & \ \text{Nu} &= 3.66 \end{aligned}\] The \(L/D\) ratio for the entrance length required to reach fully developed flow is larger for laminar flow than for turbulent flow.