The Graetz–Nusselt problem extended to continuum flows with finite slip. (9th January 2015)

• Record Type: Journal Article
• Authors: Haase, A. Sander; Chapman, S. Jonathan; Tsai, Peichun Amy; Lohse, Detlef; Lammertink, Rob G. H.
• Is Part Of: Journal of fluid mechanics. Volume 764(2014)
• Publication Date: 2015-01-09
• Subjects: boundary layers, -- convection, -- free shear layers; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2014.733
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract: Graetz and Nusselt studied heat transfer between a developed laminar fluid flow and a tube at constant wall temperature. Here, we extend the Graetz–Nusselt problem to dense fluid flows with partial wall slip. Its limits correspond to the classical problems for no-slip and no-shear flow. The amount of heat transfer is expressed by the local Nusselt number $\mathit{Nu}_{x}$, which is defined as the ratio of convective to conductive radial heat transfer. In the thermally developing regime, $\mathit{Nu}_{x}$ scales with the ratio of position $\tilde{x}=x/L$ to Graetz number $\mathit{Gz}$, i.e. $\mathit{Nu}_{x}\propto (\tilde{x}/\mathit{Gz})^{-{\it\beta}}$ . Here, $L$ is the length of the heated or cooled tube section. The Graetz number $\mathit{Gz}$ corresponds to the ratio of axial advective to radial diffusive heat transport. In the case of no slip, the scaling exponent ${\it\beta}$ equals $1/3$ . For no-shear flow, ${\it\beta}=1/2$ . The results show that for partial slip, where the ratio of slip length $b$ to tube radius $R$ ranges from zero to infinity, ${\it\beta}$ transitions from $1/3$ to $1/2$ when $10^{-4}<b/R<10^{0}$ . For partial slip, ${\it\beta}$ is a function of both position and slip length. The developed Nusselt number $\mathit{Nu}_{\infty }$ for $\tilde{x}/\mathit{Gz}>0.1$ transitions from 3.66 to 5.78, the classical limits, when $10^{-2}<b/R<10^{2}$ . A mathematical and physical explanation is provided for the distinct transition points for ${\it\beta}$ and $\mathit{Nu}_{\infty }$ .