﻿ 非对称型波纹通道流动与传热性能的数值模拟
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 哈尔滨工程大学学报  2020, Vol. 41 Issue (7): 998-1004  DOI: 10.11990/jheu.201811033 0

引用本文

HAN Huaizhi, YU Ruitian, LIAO Wenjun. Numerical simulation study on the flow and heat transfer characteristics of asymmetrical corrugated channels[J]. Journal of Harbin Engineering University, 2020, 41(7): 998-1004. DOI: 10.11990/jheu.201811033.

文章历史

1. 四川大学 化学工程学院, 四川 成都 610065;
2. 哈尔滨工程大学 动力与能源工程学院, 黑龙江 哈尔滨 150001

Numerical simulation study on the flow and heat transfer characteristics of asymmetrical corrugated channels
HAN Huaizhi 1, YU Ruitian 1, LIAO Wenjun 2
1. School of Chemical Engineering, Sichuan University, Chengdu 610065, China;
2. College of Power and Energy Engineering, Harbin Engineering University, Harbin 150001, China
Abstract: To explore the influence of corrugated channels' chamfer connection on the flow and heat transfer performance, in this study, numerical simulations are carried out on asymmetrical corrugated channels with large corrugated trough radius (rl) located upstream and downstream. Then, the numbers of average and local characteristics of the wall surface between the symmetrical and asymmetrical corrugated channels are compared under different Reynolds numbers. The results show that the average (Nu) and local Nusselt (Nux) numbers of the wall surface increase as the Reynolds number (Re) increases, and the growth rate of Nu of the symmetrical corrugated channel is greater than that of the asymmetrical corrugated channel. The average friction coefficient (f) and local friction coefficient (fx) of the wall surface decrease as Re increases, and f of the asymmetrical corrugated channel declines below that of the symmetrical one. The Nu of the asymmetrical corrugated channel is slightly smaller than that of the symmetrical corrugated channel, but itsf declines significantly. Comparing these two asymmetrical corrugated channels, when large corrugated trough radius (rl) is located upstream, the flow velocity and vortex scale are relatively small, the temperature boundary layer is slightly thicker, the conversion of the pressure gradient is relatively small, and the kinetic energy of turbulence is comparatively low, overall. Based on the aforementioned research, it is recommended that, in the heat exchanger design, rl is selected to locate downstream of the corrugated channel to increase the overall thermal performance.
Keywords: corrugated channel    plate heat exchanger    enhanced heat transfer    heat transfer mechanism    numerical simulation    asymmetrical    turbulent flow    flow characteristics

1 波纹通道流动与传热数值计算 1.1 物理模型及网格划分

1.2 数学模型

1) 流体为不可压缩牛顿流体；

2) 流体流动选择定常流动；

3) 忽略重力与浮升力的影响；

4) 忽略流体流动时的粘性耗散热效应；

5) 流体通道周边与外界无任何热质交换。

 $\frac{{\partial {u_i}}}{{\partial {x_i}}} + \frac{{\partial {u_j}}}{{\partial {x_j}}} = 0$ (1)

 $\frac{{\partial (\rho {u_i}{u_j})}}{{\partial {x_j}}} = - \frac{{\partial p}}{{\partial {x_i}}} + \mu \left( {\frac{{{\partial ^2}{u_i}}}{{\partial x_i^2}} + \frac{{{\partial ^2}{u_j}}}{{\partial x_j^2}}} \right) + \frac{\partial }{{\partial {x_j}}}( - \rho \overline {u_i^\prime u_j^\prime } )$ (2)

 $\frac{\partial }{{\partial {x_i}}}[{u_i}(\rho E + p)] = \frac{\partial }{{\partial {x_j}}}\left[ {\left( {k + \frac{{{c_p}{\mu _t}}}{{P{r_t}}}} \right)} \right]\frac{{\partial T}}{{\partial {x_j}}}$ (3)

 $\begin{array}{*{20}{l}} {\frac{\partial }{{\partial t}}(\rho k) + \frac{\partial }{{\partial x}}(\rho k{u_i}) = \frac{\partial }{{\partial y}}\left[ {\left( {\mu + \frac{{{\mu _t}}}{{{\sigma _k}}}} \right)\frac{{\partial k}}{{\partial y}}} \right] + }\\ {{\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {G_k} + {G_b} - \rho \varepsilon - {Y_M} + {S_k}} \end{array}$ (4)

 $\begin{array}{*{20}{l}} {{\kern 1pt} {\kern 1pt} \frac{\partial }{{\partial t}}(\rho \varepsilon ) + \frac{{\partial (\rho \varepsilon {u_j})}}{{\partial {x_j}}} = \frac{\partial }{{\partial y}}\left[ {\left( {\mu + \frac{{{\mu _t}}}{{{\sigma _\varepsilon }}}} \right)\frac{{\partial \varepsilon }}{{\partial y}}} \right] + }\\ {\rho {C_1}{S_\varepsilon } - \rho {C_2}\frac{{{\varepsilon ^2}}}{{k + \sqrt {v\varepsilon } }} + {C_{1\varepsilon }}\frac{\varepsilon }{k}{C_{3\varepsilon }}{G_b} + {S_\varepsilon }} \end{array}$ (5)

1) 雷诺数：

 ${Re = \frac{{uD\rho }}{\mu }}$ (6)

2) 努塞尔数：

 ${Nu = \frac{{hD}}{\lambda }}$ (7)

3) 传热系数：

 ${h = \frac{Q}{{\Delta {t_m}}}}$ (8)

4) 摩擦系数：

 ${f = \frac{{2\Delta pD}}{{L\rho {u^2}}}}$ (9)

1.3 数值求解条件设置

1) 本文主要目的是阐明波纹非对称结构对波纹通道流动与传热的影响，为简化条件，给定恒定的凹凸壁面温度Tw=360 K，且流体通道周边与外界不存在质与热的交换；

2) 边界条件设置速度入口，压力出口。流体进口速度根据雷诺数计算得到uin，且进口温度设置为300 K；

3) 壁面边界选择无滑移速度边界条件，其边界速度uw=0。

1.4 模型的验证 1.4.1 湍流模型验证

 $j = \frac{{Nu}}{{Re \cdot P{r^{\frac{1}{3}}}}}$ (10)

 Download: 图 4 湍流状态下换热因子与摩擦系数对比 Fig. 4 Comparison of heat transfer factor and friction coefficient
1.4.2 网格无关性验证

2 对称与非对称波纹通道性能对比 2.1 对称与非对称波纹通道壁表面特征数对比 2.1.1 平均壁表面特征数

 Download: 图 6 凹凸壁面Nu随Re变化曲线 Fig. 6 Variation of Nu along with various Re for concave and convex walls

 Download: 图 7 凹凸壁面f随Re变化曲线 Fig. 7 Variation of f along with various Re for concave and convex walls
2.1.2 局部壁表面特征数

 Download: 图 8 Re=6 000沿凹壁面Nux局部分布 Fig. 8 Local Nux of concave wall in Re=6 000

 Download: 图 9 Re=6 000沿凹壁面fx局部分布 Fig. 9 Local fx of concave wall in Re=6 000
2.2 对称与非对称波纹通道强化换热机理对比 2.2.1 波纹通道速度分布规律

 Download: 图 10 Re=6 000时速度矢量图 Fig. 10 Velocity field in Re=6 000
2.2.2 波纹通道温度分布规律

 Download: 图 11 Re=6 000时温度云图 Fig. 11 Temperature field in Re=6 000
2.2.3 波纹通道压力分布规律

2.2.4 波纹通道湍动能分布规律

 Download: 图 13 Re=6 000时湍动能云图 Fig. 13 Turbulent kinetic energyfield in Re=6 000

3 结论

1) 对称型与非对称型波纹通道Nu均随着Re的增加而增加，且对称型波纹通道Nu增长速率均大于非对称型波纹通道。对称型与非对称型波纹通道f均随着Re的增大而单调递减，且减缓速率越来越小。3种波纹通道的Nu差距不大，而大波谷半径位于来流侧非对称型通道的f整体最小，对称型通道最大。大波谷半径位于来流侧非对称型通道在换热能力损失较小的情况下大大减少了摩擦阻力，在换热器设计上建议选择大波谷半径位于来流侧通道以提高整体性能系数。

2) 从Nux局部分布规律可以看出，对称型与非对称型波纹通道凹壁面近入口存在一个极小值，近出口处存在一个极大值，而凸壁面分布规律与之相反。从fx局部分布规律可知，凹壁面上游区域和下游区域均出现极大值，并且下游区域的峰值更高。而凸壁面的极值则出现在上游区域。

3) 大波谷半径位于去流侧时拥有更高整体流速且涡旋范围较大，位于来流侧时流速较小且涡旋范围较小。整体来看，非对称型波纹通道温度边界层比对称型略厚，对于非对称型通道大波谷半径位于来流侧相比于位于去流侧略厚。对称型通道的压力梯度转换高于非对称型，对于非对称型通道大波谷位于去流侧明显大于来流侧。对称型波纹通道湍动能整体上大于非对称型，对于非对称型波纹通道大波谷位于去流侧要高于来流侧。

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