肋密度对齿状翅片管外冷凝换热和流动的影响

doi:10.11949/0438-1157.20230603

摘要/Abstract

摘要：

采用数值和实验相结合的方法研究了齿状翅片管周围的冷凝流动和传热特性。利用经过验证的计算模型，分析了齿状翅片管在周向和轴向上的膜流动特性和冷凝传热系数，提供了有关高性能管中冷凝过程的信息。结果表明，齿状翅片管的周向和轴向薄膜厚度随着肋密度的增加而增加。对齿状翅片管特殊的传热结构进行了研究，发现复杂的传热结构导致表面张力的变化，从而改变了液膜的分布。齿状翅片管的局部冷凝传热系数对液膜分布非常敏感。得到了与最大总传热系数相对应的最佳肋密度，表明齿状翅片管的强化传热机理是传热面积和液膜厚度的共同作用。

关键词: 齿状翅片管, 肋密度, 冷凝传热, 数值模拟, VOF

Abstract:

The condensing flow and heat-transfer characteristics around dentate-fin tubes were investigated using numerical and experimental methods. Using the examined computational model, the film flow characteristics and condensing heat-transfer coefficient of the dentate-fin tubes in the circumferential and axial directions were analyzed. Comprehensive information regarding the condensation process in high-performance tubes was provided. The results showed that the circumferential and axial film thicknesses of the dentate-fin tubes increased with increasing fin density. The liquid film distribution of dentate-fin tubes with a low fin density was relatively uniform, and condensate drainage was easy. The special heat-transfer structure of dentate-fin tubes was examined, and it was found that the complex heat-transfer structure led to variations in the surface tension, which changes the liquid-film distribution. The local condensing heat-transfer coefficient of the dentate-fin tubes was very sensitive to the liquid-film distribution. The optimal fin density corresponding to the maximum total heat-transfer coefficient was obtained, indicating that the enhanced heat transfer mechanism of dentate-fin tubes is the combined effect of heat transfer area and liquid film thickness.

Key words: dentate-fin tube, fin density, condensing heat transfer, numerical simulations, volume of fluid method

中图分类号:

TB 657.5

李猛, 陶乐仁, 黄理浩, 金程. 肋密度对齿状翅片管外冷凝换热和流动的影响[J]. 化工学报, 2023, 74(10): 4087-4096.

Meng LI, Leren TAO, Lihao HUANG, Cheng JIN. Effect of fin density on condensing heat transfer and flow outside dentate-fin tubes[J]. CIESC Journal, 2023, 74(10): 4087-4096.

图/表 15

图1 实验系统流程图1—液压隔膜泵;2—前端过热板式换热器;3—后端过冷板式换热器;4—实验测试部分;5—膨胀电磁阀;6—板式换热器;7—脉冲阻尼器;8—质量流量计;9—电加热器;10—蓄水池;11—恒温水箱;12—膨胀箱;13—电磁流量计;14—水泵;15—阀;16—差压传感器;17—液体反射镜;18—压力传感器;19—温度传感器

Fig.1 Schematic diagram of the experimental apparatus

图2 (a) 齿状翅片管的几何参数；(b) 齿状翅片管细节示意图

Fig.2 (a) Geometric parameters of dentate-fin tubes; (b) Detail drawing of dentate-fin tubes

表1 管道的具体结构参数

Table 1 Specifications of the tubes

管道名称	外径/mm	翅片间距/mm	肋密度/ fpi	周向齿数/个	管道长度/mm
光管	15.88	—	—	—	40.00
TLC-1	15.88	0.45	32	50	2.55
TLC-2	15.88	0.35	36	50	2.10
TLC-3	15.88	0.25	42	50	1.65
TLC-4	15.88	0.15	51	50	1.35

图3 模拟区域的部分网格

Fig.3 A partial mesh of the simulation area

图4 网格独立性验证

Fig.4 Verification of independence of grids

图5 光滑管外冷凝传热系数实验结果、模拟结果和Nusselt理论值的对比

Fig.5 Comparison of experimental results， numerical results and Nusselt analytical solution of condensing heat transfer coefficient outside the plain tube

图6 齿状翅片管外传热系数模拟值与实验值的对比

Fig.6 Comparison of numerical results and experimental results of condensing heat transfer coefficient outside dentate-fin tubes

图7 水平齿状翅片管外冷凝的模拟过程

Fig.7 Simulation progression of condensation outside a horizontal dentate-fin tube

图8 水平齿状翅片管外冷凝的实验结果

Fig.8 Experimental results of condensation outside a horizontal dentate-fin tube

图9 冷凝液平均温度随时间的变化

Fig.9 Change of average temperature of the condensate at different time

图10 周向翅片尖端截面上液体体积分数的轮廓线

Fig.10 The contours of liquid volume fraction in the circumferential section of the fin tip

图11 局部冷凝传热系数和薄膜厚度的周向分布

Fig.11 Local condensing heat transfer coefficient and film thickness distribution at the circumferential section of the fin tip

图12 轴向翅片尖端截面上液体体积分数的轮廓线

Fig.12 The contours of the liquid volume fraction in the axial section of the fin tip

图13 局部冷凝传热系数和薄膜厚度的轴向分布

Fig.13 Local condensing heat transfer coefficient and film thickness distribution at the axial section of the fin tip

图14 平均冷凝传热系数随温差的变化

Fig.14 Variation of overall condensing heat transfer coefficient with temperature difference

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