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Journal of Enhanced Heat Transfer
Numerical Predictions of Fluid Flow and Heat Transfer in Corrugated Channels Using Time-Dependent and Time-Independent Flow Models
The Key Lab of Education Ministry for Enhanced Heat Transfer and Energy Conversion, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
Four different models, including the steady (time-independent) laminar, the unsteady (time-dependent) laminar, the steady turbulent, and the unsteady turbulent flow model, are used to predict the heat transfer and flow behavior in multi-cycle corrugated channels having the same geometries as those tested by Ali and Ramadhyani (1992) for Reynolds numbers between 145 and 4095. The Nusselt number (Nu) and apparent fanning friction factor (fapp) are calculated and compared for different models and with the Ali & Ramadhyani experimental data. The comparisons suggest that the laminar flow model can be used for Reynolds numbers below 600 while the turbulent flow model should be adopted when the Reynolds number exceeds 600. The unsteady and the steady laminar flow model yield almost the same Nu and fapp for Re ≤ 600, and so do the unsteady and the steady turbulent flow model for Re > 600. So, it is appropriate to use the steady model to predict the Nu and fapp of a corrugated channel. Furthermore, it is found that the local Nusselt number changes sharply near each corner of the corrugated channel: the minimum appears slightly upstream from the corner while the maximum occurs somewhat downstream from the corner. For laminar flow in a multicycle corrugated channel, the upstream cycle yields higher Nu than the downstream cycle; for turbulent flow in the same channel, however, the downstream cycle gives higher Nu than the upstream cycle.
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