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首页> 外文期刊>Journal of Mechanical Science and Technology >An investigation of local heat transfer characteristics in a ventilated disc brake with helically fluted surfaces
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An investigation of local heat transfer characteristics in a ventilated disc brake with helically fluted surfaces

机译：带有螺旋凹槽表面的通风盘式制动器的局部传热特性研究

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摘要

Local Nusselt numbers in the cooling flow passage of the automobile disc brake with helically fluted surfaces are presented. The flat surface in the flow passage is modified to the helically fluted surface for the purpose of enhancing the heat transfer rate, thereby reducing the thermal stress and deformation in the disc brake. Thermochromic liquid crystals and shroud-transient technique are used to measure spatially-resolved surface temperature distributions, which are used to deduce local Nusselt numbers. The Reynolds number Re ranges from 30,000 to 70,000, the helix angle θ is fixed at 45° and the dimensionless streamwise distance z/d ranges from 1.5 to 4.5. The results show that in general, local Nusselt numbers monotonically decrease with a distance away from both windward and leeward crests of the helical flute and reach a minimum value near its valley for all Re’s and z/d’s tested. The local Nusselt numbers on the helically fluted grooves are maximum 51.6 to 93.7% higher than values measured on the flat surface. The heat transfer enhancement magnitudes become more pronounced with smaller Re and z/d. The largest enhancement occurs at the windward side of the helical flute at z/d=1.5 and Re=30,000. It is also found that at Re=30,000 the average Nusselt numbers on the helically fluted surface are maximum 37% higher than those on the flat surface. The numerical results show that with 10 braking cycles, the temperatures with helically fluted surface are maximum 44.3%, 36.8%, and 36.6% lower than those with the flat surface in the inlet, the center, and the outlet, respectively.
机译：给出了具有盘形凹槽表面的汽车盘式制动器的冷却流道中的局部Nusselt数。为了提高传热率，将流道内的平面改形成螺旋槽面，从而减小了盘式制动器的热应力和变形。热致变色液晶和覆盖物瞬变技术用于测量空间分辨的表面温度分布，用于推断局部Nusselt数。雷诺数Re在30,000至70,000的范围内，螺旋角θ固定为45°，无因次流向距离z / d在1.5至4.5的范围内。结果表明，总体而言，局部Nusselt数随螺旋长笛的迎风峰和背风峰的距离而单调减小，并且在所有Re和z / d测试中，其最低谷附近均达到最小值。螺旋凹槽上的局部Nusselt值比在平坦表面上测得的值大51.6％至93.7％。 Re和z / d越小，传热增强幅度越明显。最大的增强发生在z / d = 1.5和Re = 30,000的螺旋槽的上风侧。还发现，在Re = 30,000时，螺旋凹槽表面上的平均Nusselt数最多比平坦表面上的平均Nusselt数高37％。数值结果表明，在10个制动周期中，螺旋形凹槽表面的温度分别比进口，中心和出口处平坦表面的温度分别低44.3％，36.8％和36.6％。

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