A Numerical Study of Turbulent Flow and Heat Transfer of Dimples at Different Depths

Abstract

Abstract:

Abstract： Based on numerical simulations, the friction factors and heat transfer coefficients of four dimples with different depths were obtained by using the standard kω turbulence model, and the relations for the heat transfer and friction factors were also presented when the Reynolds number (Re) varies from 8 500 to 60 000. The results showed that the average heat transfer coefficient and the friction factor gradually increase with the increasing of the depth. They also increase as the Reynolds number increases. In the case of Re=8 500 and σ=0.1 or 0.3 (σ: the ratio of depth to face diameter), the average heat transfer coefficient and the friction factor are almost invariant, the average heat transfer coefficient increases 40% to flat plate channel. Compared with the depth of σ=0.1, a dimple depth of σ=0.3 achieves a heat transfer enhancement of more than 11% at the Reynolds number of 50 500. Compared to the flat plate channel, the average heat transfer performances of the dimpled channels increase by about 42.1% and 51.6%, friction factors increase 30% and 120%, respectively; and also the overall heat transfer coefficients increase by 10% to 35%; the heat transfer coefficient decreases as the increase of the depth. The distribution of local Nusselt number in the flow direction of shallow dimpled channel at a dimple depth of σ=0.1 and σ=0.2 is symmetric. However, it becomes asymmetric in deep dimpled channel at a dimple depth of σ=0.26 and σ=0.3. The reason may be the different vortex structures in shallow dimples and deep dimples.

Key words: dimple depth, vortex generator, gas turbine cooling, heat transfer enhancement, low pressure drop

CLC Number:

TK 47

YANG Yun,RAO Yu. A Numerical Study of Turbulent Flow and Heat Transfer of Dimples at Different Depths[J]. Journal of Shanghai Jiaotong University, 2017, 51(1): 18-.

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