Developed and quasi-developed macro-scale heat transfer in micro- and mini-channels with arrays of offset strip fins subject to a uniform heat flux

Abstract

In the present work, we examine to what degree the heat transfer can be described as developed on a macro-scale level in typical micro- and mini-channels with offset strip fin arrays subject to a uniform heat flux, considering flow entrance and side-wall effects. Full-scale numerical heat transfer simulations are conducted to determine the extent of the developed macro-scale heat transfer region within the arrays. We find that the onset point of developed heat transfer increases linearly with the Péclet number and channel width. However, the thermal development lengths remain limited relative to the overall channel length. Therefore, the local macro-scale heat transfer coefficient can be modeled by developed Nusselt number correlations with discrepancies below 25% in both the developed and developing heat transfer regions. We observe that quasi-developed heat transfer prevails over nearly the entire entrance region of the channel and significantly contributes to the main heat transfer characteristics, particularly the eigenvalues and amplitudes of the dominant temperature modes. Additionally, we analyze the impact of channel side walls on the temperature field's periodicity and the macro-scale temperature profile, which we characterize through an effective heat transfer coefficient. Our comprehensive numerical data covers various fin height-to-length ratios up to 1, fin pitch-to-length ratios up to 0.5, and channel aspect ratios ranging from 1/5 to 1/17, encompassing Reynolds numbers from 28 to 1224. Two sets of Prandtl number and thermal conductivity ratio are investigated, corresponding to the combinations of copper/air, and copper/water.

This article may be downloaded for personal use only. Any other use requires prior permission of the author and Elsevier Publishing. This article appeared in International Journal of Heat and Mass Transfer 236, 126285 (2025) and may be found at https://doi.org/10.1016/j.ijheatmasstransfer.2024.126285, 62 pages, 20 figures

References in corpus (5)

• Friction factor for steady periodically developed flow in micro-and mini-channels with arrays of offset strip fins
• Developed and quasi-developed macro-scale flow in micro- and mini-channels with arrays of offset strip fins
• A macro-scale description of quasi-periodically-developed flow
• Quasi-periodically developed flow in channels with arrays of in-line square cylinders
• A Mathematical Description of the Quasi-Periodically Developed Heat Transfer Regime in Channels with Arrays of Periodic Solid Structures