重力驱动颗粒流横掠倒置滴形管管外流动传热特性的数值研究

doi:10.11949/0438-1157.20190557

摘要/Abstract

摘要：

采用离散单元方法（DEM）模拟了重力驱动的颗粒流横掠圆管和不同椭圆度（e=1.0,1.5,2.0,2.5）的滴形管下的流动与换热情况，分析了滴形管的椭圆度对停滞区大小、管周受力以及有效传热系数的影响，并与圆管进行了对比。主要结论如下：滴形管的停滞区和空区均小于圆管，随着椭圆度增大，管顶部颗粒流速增加，流动性变好；滴形管受颗粒流的法向力和切向力均小于圆管，在椭圆度大于1.0后，增加椭圆度，两力不再减小；滴形管的有效传热系数小于圆管，且随着椭圆度增大，有效传热系数降低。

关键词: 颗粒过程, 颗粒流传热, 离散单元法, 滴形管, 数值研究, 移动床

Abstract:

Gravity-driven granular flowing across inverted drop-shaped tubes is investigated, with the aim to enhance flow and heat transfer performance and avoid particle stagnant. The discrete element method was used to simulate the flow and heat transfer of a gravity-driven particle flow across a circular tube and a drop-shaped tube with different ellipticities (e= 1.0, 1.5, 2.0, 2.5) was analyzed.t The effect of ellipticity on the size of the stagnation zone, the normal and tangential force on the pipe, and the effective heat transfer coefficient was compared with the circular tube. The main conclusions are as follows: compared with circular tube, granular flow drop-shaped tubes perform better in flow and stagnation avoidance. The stagnation area and the void area of the drop-shaped tube are smaller than the circular tube. As the ellipticity increases, the particle flow velocity at the top of the tube increases, and the flow upward the tube becomes better. The drop-shaped tube is subjected to the normal force and the tangential force of the granular flow and both are smaller than the circular tube. After the ellipticity is more than 1.0, the ellipticity is increased, and the two forces are no longer reduced. The effective heat transfer coefficient of the drop-shaped tube is smaller than that of the circular tube, and the effective heat transfer coefficient decreases as the ellipticity increases.

Key words: particle process, granular flow heat transfer, discrete element method, drop-shaped tube, numerical investigation, moving bed

中图分类号:

TQ 025.2

谈周妥,郭志罡,杨剑,王秋旺. 重力驱动颗粒流横掠倒置滴形管管外流动传热特性的数值研究[J]. 化工学报, 2019, 70(S2): 94-100.

Zhoutuo TAN,Zhigang GUO,Jian YANG,Qiuwang WANG. Numerical investigation on flow and heat transfer performance of gravity-driven granular flowing across inverted drop-shaped tube[J]. CIESC Journal, 2019, 70(S2): 94-100.

图/表 15

图1 颗粒绕圆管流动示意图

Fig.1 Granular flow around circular tube

图2 几何模型

Fig.2 Geometry model

表1 滴形管的几何参数

Table 1 Geometry parameters of drop-shaped tube

e	a/mm	b/mm
0(圆管)	10	10
1.0	11.02816	7.79809
1.5	11.65153	6.463104
2.0	12.13529	5.427069
2.5	12.13529	4.642921

图3 滴形管几何参数

Fig.3 Geometrical parameters of drop-shaped tube

图4 模型验证

Fig.4 Model validation

表2 几何模型参数

Table 2 Geometry parameters

H ₁/mm	H ₂ /mm	H ₃ /mm	L/mm	T _wall/K	k _t/(W?m^-1?K^-1)
40	10	160	10	287	15.0

表3 颗粒物性参数

Table 3 Physical properties of particles

d _p/mm	ρ/(kg·m^-3)	c_p /(J?kg^-1·K^-1)	k _p/(W?m^-1·K^-1)
0.2	2600	1600	2.5

表4 边界条件

Table 4 Boundary conditions

u _m/(mm·s^-1)	T _in/K	T _wall/K	其余壁面
5	1000	287	绝热

图5 圆管与椭圆管下的颗粒速度分布

Fig.5 Velocity distribution of circular tube and drop-shaped tube

图6 统计区域的选取

Fig.6 Selection of statistical regions

图7 不同椭圆度下的颗粒平均速度

Fig.7 Average particle velocity in various ellipticities

图8 不同椭圆度下有效传热系数

Fig.8 Heat transfer coefficient in different ellipticities

图9 不同椭圆度下平均接触数

Fig.9 Average contact number in different ellipticities

图10 不同椭圆度下的切向力

Fig.10 Tangential force in different elliptcities

图11 不同椭圆度下的法向力

Fig.11 Normal force in different elliptcities

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