Effects of detached V-shaped ribs in cooling channels on turbulent flow and temperature distributions, heat transfer and friction factor
Final Report Abstract
This DFG project deals with the enhancement of convective heat transfer in square cooling channels with one wall structured by detached V-shaped ribs. Experiments were carried out in a specially manufactured test section in a gas loop. The velocity distributions and flow dynamics were systematically measured using laser-Doppler-anemometry and hot-wire anemometry and IR thermography measurements were used to determine the surface temperature distribution of the structured channel wall for different fin configurations in a Reynolds number range of 2,0 ⋅ 10^3 ≤ Rekr ≤ 7,0 ⋅ 10^3. In addition, the thermal flow field was determined numerically using large-eddy simulations. The results provide deep insights into the thermal flow dynamics by means of extensive measurements in combination with scale-resolving large-eddy simulations. It was shown that for detached V-shaped ribs, a geometry-induced secondary flow occurs above and below the rib. It depends on the clearance-to-rib-height ratio and, thus, different flow configurations develop within the inter-rib spacing for varying clearance-to-rib-height ratios. The variations of the geometry-induced secondary flow with the clearance-to-rib-height ratio significantly influence the spatial development of the separating shear layers and the associated turbulent flow structures. For comparatively small wall clearance-to-rib-height ratios ( c/kr ≤ 0.5), the rib-induced wall wards turbulent transport as well as the downward advective mean transport due to the secondary flow penetrate to the immediate vicinity of the channel bottom wall. Detaching the ribs increases the convective heat transfer and thermal performance for an effective cooling. The maximum wall surface temperature decreases sharply as a result of a flow-related suppression of recirculation areas and stagnation points in the area of the rib rear side and the surface temperature is homogenized. For comparatively large clearance-to-rib-height ratios, the upward vertical mean flow velocity in the rib wake suppresses the fluid transport down to the wall. Therefore, the convective heat transfer reduces, while the wall surface temperature homogenizes.
Publications
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Laser-Doppler- und Hitzdraht-Anemometrie-Messungen entlang V-förmiger angehobener Rippen in einem quadratischen Kanal. tm - Technisches Messen, 90(5), 310-322.
Ruck, Sebastian; Arbeiter, Frederik & Digel, Leon
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LDA-Messungen entlang V-förmiger angehobener Rippen in einem quadratischen Kanal, 29. Fachtagung Experimentelle Strömungsmechanik, Ilmenau (2023)
Sebastian Ruck
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Numerical investigation of the convective heat transfer in a square channel rib-roughened by detached V-shaped ribs, 9th Thermal and Fluids Engineering Conference (TFEC), Corvallis (2024)
Sebastian Ruck
