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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

The Effect of the Circular Cylinder's Insertion Position on Heat Transfer Enhancement in Transition Flow

Get access (open in a dialog) DOI: 10.1615/IHTC15.hex.009362
pages 3643-3650

要約

The effect of the insertion position of circular cylinder on heat transfer enhancement ration in transition flow is researched. Firstly, the compound grid system is specially built for near-wall flow field around a cylinder under the transitional flow state. Secondly, numerical calculation is done with the typical cases of Reynolds number for the different position of the cylinder. The effect and reason of the insertion cylinder position on the enhancement of heat transfer near the wall are analyzed by using the flow field, Reynolds shear stress and turbulent heat flux, in order to find the optimal insertion position, and provide a theoretical basis for the development of high energy-efficient heat transfer equipment. Through the simulation results, the following figures are made and discussed: 1) Distribution of time means local Nussle number enhancement ratio (Nu) ??(Nu) ?_0 with C/D (where D is the cylinder diameter, C is the distance between the cylinder and the wall.) of increasing from 0 to 2.0 when Re=200. 2). The flow field with C/D of increasing from 0 to 2.0 when Re=200. 3). The section graph of the Reynolds shear stress -(uv) ? and the turbulent heat flux (v?) ? at the first and the second peak position. It is concluded from the simulation results: 1) The position of the (Nu) ??(Nu) ?_0 curve’s first peak is not changed with C/D, where always occurred at x/D=0; the value of the first peak decreases with increasing of C/D. Because the value of both -(uv) ? and (v?) ? at the first peak is zero, which is shown that the first position is not relation with instability of the flow field, but relation with the forced flow acceleration between the wall and the cylinder. 2) The position of the (Nu) ??(Nu) ?_0 curve’s second peak is moving to downstream direction with the increase of C/D, the value of peak increase with the increase of C/D, reaching to the max value at the C/D=1.0, and then decrease with the increase of C/D. According to the flow field, the second peak is caused by washing effects of the wall vortex island, and the position of vortex island and the strength of the wash effect is directly affected by C/D. Further, according to -(uv) ? and (v?) ? at the second peak, the contribution to heat