论文总字数：25490字

摘 要

随着工业的迅速发展，两相热虹吸管在太阳能热利用、电子元器件冷却等领域应用较广，研究两相热虹吸管的传热机理对优化结构提高传热性能有重要的意义。可视化是研究两相热虹吸管流型变化的有效手段，透明材质可视化实验方法可以直接观测到两相流型及相变行为，在目前的研究中应用较多。本文研制了玻璃金属封接结构的全玻璃两相热虹吸管，考察了其不同操作参数下的两相流及传热特性。主要研究内容及结论如下：

搭建了全玻璃两相热虹吸管可视化实验平台，对不同充液高度下的两相流流型进行可视化实验研究。结果表明：两相热虹吸管随热流变化经历对流换热、间歇沸腾、过渡沸腾、核态沸腾四种沸腾机制，且两相流型取决于蒸发段相变行为。对流换热机制下，两相热虹吸管液池仅液池表面蒸发；间歇沸腾机制下，液池底部产生弹状气泡向上膨胀并携带大量工质上抛，然后在重力作用下，工质回落至蒸发段造成液池扰动；过渡沸腾机制下，充液高度50、90mm两相热虹吸管蒸发段生成弹状气泡，携带工质上升过程中工质回流，弹状气泡消失后生成环状液膜，而充液高度140mm两相热虹吸管在弹状气泡破裂后，液池内会产生大量的小汽泡；核态沸腾机制下，蒸发段持续沸腾，不断生成小气泡，扰动剧烈，液面上升。

对全玻璃两相热虹吸管传热性能进行实验研究，考察了冷却水温度、热流密度、加热高度、充液高度等操作参数对其传热性能的影响规律。结果表明：充液高度50mm时，沸腾传热系数与热流密度、加热高度及冷却水温度成正比，热阻与其成反比，冷凝传热系数均与冷却水温度、加热高度成正比。加热高度相同时，充液高度90mm的两相热虹吸管沸腾传热系数最大，热阻最小，传热性能最佳。加热高度与充液高度均为90mm时，两相热虹吸管沸腾传热系数最大；加热高度与充液高度均为140mm的两相热虹吸管冷凝传热系数最大，热阻最小。

关键词：两相热虹吸管，可视化，两相流，传热性能，相变

Abstract

With the rapid development of industry, two-phase thermosyphon is widely used in solar thermal utilization and electronic component cooling. It is important to study the heat transfer mechanism of two-phase thermosyphon to optimize the structure to improve heat transfer performance. Visualization is an effective means to study the flow pattern change of two-phase thermosyphon. The transparent material visualization experiment method can directly observe the two-phase flow pattern and phase transition behavior, which is widely used in the current research. In this paper, a full-glass two-phase thermosyphon with a glass-metal sealing structure was developed, and the two-phase flow and heat transfer characteristics under different operating parameters were investigated. The main research contents and conclusions are as follows:

A visualized experimental platform for all-glass two-phase thermosyphon was built, and the two-phase flow pattern under different filling heights was visualized experimentally. The results show that the two-phase thermosyphon undergoes four boiling mechanisms of convective heat transfer, intermittent boiling, transitional boiling and nuclear boiling with the change of heat flow, and the two-phase flow pattern depends on the phase transition behavior of the evaporation section. Under the convective heat transfer mechanism, the two-phase thermosyphon liquid pool only evaporates on the surface of the liquid pool; under the intermittent boiling mechanism, the bottom of the liquid pool generates elastic bubbles that expand upward and carry a large amount of working medium, and then under the action of gravity, the working medium falls back to The evaporation section causes the liquid pool to be disturbed; under the transitional boiling mechanism, the evaporating section of the two-phase thermosyphon with a liquid filling height of 50 and 90 mm generates elastic bubbles, and the working fluid returns during the rising of the working medium, and the annular liquid film is formed after the elastic bubbles disappear. The two-phase thermosyphon with a liquid filling height of 140mm will generate a large number of small bubbles in the liquid pool after the rupture of the elastic bubble. Under the nucleate boiling mechanism, the evaporation section continues to boil, and small bubbles are continuously generated, the disturbance is severe, and the liquid level rises.

The experimental study on the heat transfer performance of the all-glass two-phase thermosyphon was carried out. The effects of operating parameters such as cooling water temperature, heat flux density, heating height and filling height on the heat transfer performance were investigated. The results show that when the liquid filling height is 50mm, the boiling heat transfer coefficient is proportional to the heat flux density, heating height and cooling water temperature, and the thermal resistance is inversely proportional to it. The condensation heat transfer coefficient is proportional to the cooling water temperature and heating height. When the heating height is the same, the two-phase thermosyphon with a liquid filling height of 90 mm has the largest boiling heat transfer coefficient, the smallest thermal resistance and the best heat transfer performance. When the heating height and filling height are both 90mm, the two-phase thermosyphon has the largest boiling heat transfer coefficient; the two-phase thermosyphon with heating height and filling height of 140mm has the largest condensation heat transfer coefficient and the smallest thermal resistance.

Key words: Two-phase thermosyphon, visualization, two-phase flow, heat transfer performance, phase change

目录

摘 要 I

Abstract II

第一章 绪论 1

1.1 研究背景与意义 1

1.2 两相热虹吸管研究概述 1

1.3 两相热虹吸管传热技术研究现状 2

1.4 两相热虹吸管可视化研究进展 4

1.5 本文研究内容 6

第二章 全玻璃两相热虹吸管相变传热流型研究 7

2.1 可视化实验系统 7

2.1.1 全玻璃两相热虹吸管的研制 7

2.1.2 实验装置 7

2.1.3 实验条件 8

2.2 两相热虹吸管相变传热流型 9

2.2.1 充液高度50mm 9

2.2.2 充液高度90mm 11

2.2.3 充液高度140mm 13

2.3 蒸发段相变传热流型 15

2.3.1 对流换热 15

2.3.2 间歇沸腾 16

2.3.3 过渡沸腾 16

2.3.4 核态沸腾 18

2.4 两相热虹吸管冷凝现象 19

2.5 本章小结 20

第三章 全玻璃两相热虹吸管传热性能实验研究 21

3.1 实验系统 21

3.1.1 实验装置 21

3.1.2 实验条件 21

3.1.3 性能分析方法 22

3.1.4 均温性 22

3.2 充液高度50mm稳态传热性能 23

3.2.1 沸腾传热系数 23

3.2.2 冷凝传热系数 24

3.2.3 热阻 25

3.3 充液高度对传热性能的影响 26

3.3.1 加热高度相同充液高度不同 26

3.3.2 加热高度不同充液高度不同 27

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