Droplet distribution characteristics of dropwise condensation

doi:10.11949/0438-1157.20240552

Abstract

Abstract:

As a highly efficient form of heat transfer, steam condensation is effectively used in a wide range of applications in industrial fields such as petrochemical, thermal and nuclear power, desalination and thermal energy management, and has a wide range of application backgrounds. Among them, the study of droplet distribution characteristics is the key to analyze the droplet evolution and heat transfer process. In this paper, based on the evolution of droplet behavior such as nucleation, growth, shedding, etc., a mathematical model of the whole process of droplet condensation evolution and heat transfer is constructed, and the positional distribution law of the largest droplet and the number distribution law of droplets of different sizes in the process of evolution are summarized to show the characteristics of the distribution of droplets on the vertical and curved hydrophobic wall, which provides corresponding theoretical basis for the enhancement of heat transfer in condensation.

Key words: dropwise condensation, droplet distribution, maximum droplet, heat transfer, condensate, numerical simulation

摘要：

作为一种高效的传热形式，蒸汽冷凝有效应用于石油化工、火电核电、海水淡化及热能管理等工业领域，具有广泛的应用背景，其中研究液滴分布特性是分析液滴演变及传热过程的关键。基于成核、生长、脱落等液滴行为演变构建了滴状冷凝全过程演变及传热数学模型，总结演变进程中最大液滴的位置分布规律和不同尺寸液滴的数量分布规律，展示了竖直及弯曲疏水壁面上的液滴分布特性，为冷凝强化换热提供相应的理论依据。

关键词: 滴状冷凝, 液滴分布, 最大液滴, 传热, 凝结, 数值模拟

CLC Number:

TK 124

Liang ZHAO, Mengyan ZHANG, Zhenglong GUO, Yali GUO, Luyuan GONG, Shengqiang SHEN. Droplet distribution characteristics of dropwise condensation[J]. CIESC Journal, 2024, 75(12): 4490-4500.

赵亮, 张梦妍, 果正龙, 郭亚丽, 龚路远, 沈胜强. 滴状冷凝的液滴分布特性[J]. 化工学报, 2024, 75(12): 4490-4500.

Figures/Tables 13

Fig.1 Drop condensation on different hydrophobic wall surfaces

Fig.2 Schematic diagram of droplet merging judgment

Fig.3 Droplet shedding and cleaning diagram

Table 1 Basic parameters of simulation

冷凝工况及表面性质	数值
表面过冷度ΔT/K	1
水蒸气饱和温度T_sat/K	359.08
表面张力系数σ/(N·m^-1)	0.0616
冷凝水密度ρ/(kg·m^-3)	968
冷凝水潜热H_fg/(J·kg^-1)	2.293×10⁶
疏水涂层厚度δ/mm	0.01
水热导率k_w/(W·m^-1·K^-1)	0.6707
气液界面传热系数h_i/(W·m^-2·K^-1)	106
疏水膜热导率k_δ/(W·m^-1·K^-1)	1000

Fig.4 Comparison of droplet size distribution between numerical simulation and theoretical model

Fig.5 Comparison of maximum droplet size between numerical simulation and experiment

Fig.6 Comparison of droplet size and wall heat transfer in evolution process of dropwise condensation

Fig.7 Maximum droplet positional distribution during evolution of dropwise condensation with different condensation nuclei densities (a) and coordinate change (b)

Fig.8 Heat transfer effect of droplets and ideal number in simulation region with different sizes

Fig.9 Density comparison of sub-size droplets in evolution process of dropwise condensation with different condensation nuclei density

Fig.10 Density change of sub-size droplets during evolution of dropwise condensation

Fig.11 Spatial distribution, size change and heat transfer characteristics of the largest droplet during the evolution of dropwise condensation on different walls

Fig.12 Coordinate change of maximum droplet position during evolution of dropwise condensation on different walls

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