Effects of detached V-shaped ribs in cooling channels on turbulent flow and temperature distributions, heat transfer and friction factor

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Rib-roughening fluid-solid interfaces is an appropriate method for designing thermally effective heat-exchanger components. Structured surfaces enable the transfer of high heat flux rates between a coolant and the heated wall within the structural material temperature limits of heat exchangers. The objective of the present research project is the investigation of effects of rib-induced turbulent flow structures on heat transfer and flow resistance in a square channel rib-roughened by detached 60° V-shaped ribs on one channel wall for varying geometrical parameters and thermal-hydraulic conditions.The state of the art showed that the application of attached 60° V-shaped ribs causes efficient heat transfer enhancement. Rib-induced secondary flow motion increases the vertical mean flow velocity yielding enhanced convective heat transfer and high turbulent mixing. However, flow stagnation zones with deteriorated heat exchange occur in the vicinity of the concave rib-corners and in the recirculation regions of attached ribs. By detaching ribs from the wall, local heat transfer deterioration can be reduced. The displacement of the ribs from the wall induces a gap flow beneath the ribs. The flow exits the gap like a wall-jet flow and interacts with the wake flow. Thus, flow stagnation regions and the accompanied local heat transfer deterioration are minimized. It is assumed that the combination of these both favored attributes, i.e. that the application of detached 60° V-shaped ribs leads to increased thermal mixing, homogeneous solid-fluid surface temperature and enhanced local and global heat transfer and, thus, to a more effective performance than provided by attached ribs. The results will be obtained by a sophisticated measurement campaign (LDA, pressure sensores, IR-Thermography, thermocouples) and scale-resolving Large-Eddy-Simulations and will contribute significantly to the fundamental research of turbulent, thermal near wall flows. Furthermore, it is assumed that the results of the present project can initiate innovation and optimization in the research filed of heat transfer components.