A. Single-phase liquid heat transfer

Figure 16095.6 shows, in an idealized form, the flow pattern and the variation of the surface and liquid temperatures in the regions designated by A, B, and C. The tube surface temperature in region A, convective heat transfer to single-phase liquid, is given by

\[\label{eq1} T_w=T_\ell(z)+\varDelta T_\ell \tag{1}\]

\[\label{eq2} \varDelta T_\ell=\dfrac{\dot{q}}{\alpha_{\ell o}} \tag{2}\]

where ΔT_ℓ is the temperature difference between the tube inside surface and the mean bulk liquid temperature at a length z from the tube inlet, and α_ℓo is the heat transfer coefficient to single-phase liquid under forced convection. The liquid in the channel may be in laminar or turbulent flow; in either case the laws governing the heat transfer are well established and the reader is referred to Section 168 for details. For turbulent flow the well-known Dittus-Boelter equation is often used: