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

肋粗糙化流固界面是设计热效率高的热交换器元件的合适方法。结构化表面能够在热交换器的结构材料温度极限内在冷却剂和加热壁之间传递高的热通量率。本文研究了在不同几何参数和热工水力条件下，肋诱导湍流结构对方形通道内的传热和流动阻力的影响，结果表明，在方形通道的一个壁面上附加60 ° V形肋可以有效地强化传热。肋诱导的二次流运动增加了垂直平均流速，产生增强的对流换热和高湍流混合。然而，流动停滞区与恶化的热交换发生在附近的凹肋角落和附着肋的回流区。通过将肋与壁分离，可以减少局部传热恶化。肋从壁的位移引起肋下方的间隙流。该流像壁射流一样离开差距，并与尾流相互作用。因此，流动停滞区域和伴随的局部传热恶化被最小化。假设这两个有利属性的组合，即，分离的60° V形肋的应用导致增加的热混合、均匀的固体-流体表面温度和增强的局部和全局热传递，并且因此导致比由附接的肋提供的更有效的性能。结果将通过复杂的测量活动（LDA，压力传感器，红外热成像，热电偶）和尺度分辨大涡模拟获得，并将大大有助于湍流，热近壁流动的基础研究。同时，本计画之研究成果，也可作为热传元件研究领域之创新与优化之参考。

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.