Effect of the curvature of the special-shaped tube on gas-liquid film distribution and condensation heat transfer characteristics

doi:10.11949/0438-1157.20201350

Abstract

Abstract:

Based on double film theory and boundary layer theory, mathematical models of gas and liquid film thickness and heat transfer coefficient of round tube, elliptical tube and drop tube are established. The model is verified based on the heat transfer coefficient of the round tube. The average deviation between the calculated result and the experimental value is about 6%, which basically meets the actual requirements of the project. Under the given conditions, distribution law of gas and liquid film thickness and heat transfer characteristics are obtained by calculating the heat transfer coefficient of each tube type under different curvature. The results show that: when the effective heat transfer area is the same, gas and liquid film thickness and heat transfer coefficient of the three types of tubes increase with the increase of curvature at a certain angle; when curvature is the same, the heat transfer coefficient of elliptical tube is the largest and that of circular tube is the smallest. At the same time, influence mechanism and separation mechanism of different tube shape and curvature on gas and liquid membrane discharge were analyzed. It provides some theoretical guidance for heat transfer enhancement.

Key words: condensation, mathematical simulation, curvature, special-shaped tube, non-condensable gas, membrane

摘要：

基于双膜理论及边界层理论，建立了圆管、椭圆管、滴形管的管外气、液膜厚度及传热系数的数学模型。以圆管传热系数为依据进行了模型验证，计算结果与实验值的平均偏差约为6%，基本符合工程实际要求。在给定条件下，通过对不同曲率下各管型管外传热系数的计算，得到了气、液膜厚度的分布规律及换热特性。结果表明：在有效换热面积相同时，三种管型的气、液膜厚度，传热系数在一定角度下，随曲率的增大而增大；当曲率相同时，椭圆管传热系数最大，圆管最小。同时，分析了不同管型及其曲率对气、液膜排泄的影响机理和分离机理。为强化换热提供一定理论指导。

关键词: 凝结, 数学模拟, 曲率, 异型管, 不凝结气体, 膜

CLC Number:

TK 172

LI Huijun, LI Dong, WANG Yeku, PENG Wenping. Effect of the curvature of the special-shaped tube on gas-liquid film distribution and condensation heat transfer characteristics[J]. CIESC Journal, 2021, 72(5): 2560-2569.

李慧君, 李东, 王业库, 彭文平. 异型管曲率对气液膜分布及凝结换热特性的影响[J]. 化工学报, 2021, 72(5): 2560-2569.

Figures/Tables 10

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分类依据	换热类型
凝结管型	圆管、椭圆管^[1-2]、等角螺旋曲线管和滴形管^[3]
凝结表面及其布置	凝结表面有平板、管内、管外；布置方式分为水平和竖直^[4]
介质流动方向	管外分为横掠和纵掠^[5]
管内两相流流动	单相流、分层流以及环状流
强化表面	低肋管、低翅片管、波槽管、螺纹管、微肋管^[6-10]
流动方式	自然对流、强迫对流和混合对流^[11]
流动状态	层流和紊流
混合气体组成成分	蒸汽-空气、烟气-蒸汽、制冷剂(制冷剂、人工制冷剂替代物和自然工质)^[12]-空气，一些地方还有三组分混合气体(蒸汽-空气-氦气)^[13]
凝结方式	膜状凝结、珠状凝结、均匀凝结^[14]

分类依据	换热类型
凝结管型	圆管、椭圆管^[1-2]、等角螺旋曲线管和滴形管^[3]
凝结表面及其布置	凝结表面有平板、管内、管外；布置方式分为水平和竖直^[4]
介质流动方向	管外分为横掠和纵掠^[5]
管内两相流流动	单相流、分层流以及环状流
强化表面	低肋管、低翅片管、波槽管、螺纹管、微肋管^[6-10]
流动方式	自然对流、强迫对流和混合对流^[11]
流动状态	层流和紊流
混合气体组成成分	蒸汽-空气、烟气-蒸汽、制冷剂(制冷剂、人工制冷剂替代物和自然工质)^[12]-空气，一些地方还有三组分混合气体(蒸汽-空气-氦气)^[13]
凝结方式	膜状凝结、珠状凝结、均匀凝结^[14]

参数	取值
主流流速U_∞/(m/s)	0.1~5.0
曲率e	0、0.2、0.4、0.6、0.8、0.9
主流温度T_b/K	373.0
空气质量分数W_nc,b/%	0.1~10
主流压力p/Pa	101325
管壁温度T_w/K	348.0~358.0
管径d/m	0.0254

参数	取值
主流流速U_∞/(m/s)	0.1~5.0
曲率e	0、0.2、0.4、0.6、0.8、0.9
主流温度T_b/K	373.0
空气质量分数W_nc,b/%	0.1~10
主流压力p/Pa	101325
管壁温度T_w/K	348.0~358.0
管径d/m	0.0254

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