629 / 2019-01-21 11:16:06

Experimental study on gas-solid two-phase flow field characteristics of spiral finned tube with different fin height and spacing

spiral finned tube; gas-solid two-phase flow; velocity distribution; concentration distribution; abrasion.

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Experimental study on gas-solid two-phase flow field characteristics of spiral finned tube with different fin height and spacing
Peng Zheng1, Fengzhong Sun*, Zhihang Han
1 School of Energy and Power Engineering, Shandong University, 17923 Jingshi Road, Jinan 250061, China; zhengp@mail.sdu.edu.cn, Tel: 18553836388, Fax: +86 0531 88395691.
* School of Energy and Power Engineering, Shandong University, Jinan 250061, China; sfzh@sdu.edu.cn.
Abstract: The coal is the mainly fuel of boiler in the power plant. The fly ash carried in the flue gas after coal combustion causes severe abrasion on the surface of boiler heat exchanger. Engineering practice witnesses that the heat-exchangers used of spiral finned tubes instead of that used of smooth tubes is an effective method lightening abrasion. In this paper, to study the mechanism of reducing abrasion of spiral finned tubes, the flow field characteristics of gas-solid two-phase flow around spiral finned tubes were studied by using three-dimensional particle dynamic analyzer (PDA) and glass beads as experimental particles in this experiment. The velocity and concentration of solid particles between two adjacent fins with different fin height and different fin spacing were observed under the hot condition. The results show that，in general, the distribution of particle concentration and velocity in the direction of fin spacing presents a parabolic distribution, that is, in the central zone ,the concentration and velocity of particles are relatively high, while in the zone near the wall, the concentration and velocity of particles are relatively low. In the direction of fin height, the particle concentration and velocity near the fin inlet were higher, while those near the base tube were lower. For the same measuring surface of finned tube with different fin height, the solid phase particle concentration at the top of the fin is basically the same. At the root of the fin, the particle concentration under the low fin increased obviously. The particle velocity distribution law is basically similar, that is, at the root of the fin, the particle velocity under the low fin is significantly higher than that under the high fin. The increase of fin spacing will result in the increase of particle concentration at the same fin height. The increase in the position close to the wall was not obvious, but the concentration of solid particles in the main flow area increased significantly. In the same working condition, when the spacing between fins increases, the velocity of solid particles near the wall does not change significantly, while in the main flow area, the velocity increases significantly. This study can be used for reference to optimize the structure of spiral finned tube to improve its performance.
Keywords: spiral finned tube; gas-solid two-phase flow; velocity distribution; concentration distribution; abrasion.