Conjugate heat transfer in turbulent pipe flow with azimuthally non-uniform heating

Jonathan Neuhauser; Davide Gatti; Bettina Frohnapfel

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arXiv · 2610.12709

Conjugate heat transfer in turbulent pipe flow with azimuthally non-uniform heating

Jonathan Neuhauser·Davide Gatti·Bettina Frohnapfel

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Abstract

Turbulent conjugate heat transfer (CHT) in pipes with azimuthally non-uniform heating is studied theoretically and numerically with a focus on low-$\mathrm{Pr}$ fluids. While the influence of the solid properties is well documented for uniform heat flux, their effect under azimuthally non-uniform heating has not been explored systematically. We address this gap by combining spectral analysis of the problem -- which reduces arbitrary boundary conditions to a discrete set of azimuthal wavenumbers -- with well-resolved numerical simulations of thermally and hydraulically fully developed turbulent pipe flow at $\mathrm{Re}_τ\approx 180$ for $\mathrm{Pr} = \{0.025, 0.71\}$, representative of liquid metals and air. Two principal results emerge: (i) the global Nusselt number is independent of the azimuthal heat-flux distribution and exhibits only a minor dependence on the solid properties, resolving an open question for low-Prandtl-number fluids; (ii) CHT nevertheless strongly affects the azimuthally resolved mean temperature at low $\mathrm{Pr}$, where azimuthal conduction in the solid homogenises the interface heat flux, and governs the level of temperature fluctuations through the effusivity ratio (thermal activity ratio) $K$. Finally, an analysis of the turbulent Prandtl number $\mathrm{Pr}_{t}$ shows a strong anisotropy, particularly near the wall, and a dependence on the azimuthal wavenumber.

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Jonathan Neuhauser, Davide Gatti, Bettina Frohnapfel. 2026-10-08. Conjugate heat transfer in turbulent pipe flow with azimuthally non-uniform heating. https://arxiv.org/abs/2610.12709

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