Abstract:

By combination of infrared thermal imaging technique and high-speed visualization method, the surface temperature distribution of condenser in a pulsating heat pipe (PHP) and operating state of working fluid inside the PHP are obtained and the relationship between them and heat transfer performance of the PHP is analyzed. The results indicate that the working fluid sequentially exhibits three quasi-steady operation modes with the increasing heat load viz. small pulsation in single pipe, large pulsation among different pipes and unidirectional circulation. In addition, in the condenser the dominated flow patterns are dispersed bubbles and vapor plugs, and the proportion of the dispersed bubbles decreases with increasing heat load. The difference in strength of heat and fluid flow in the PHP leads to the different characteristics of temperature distribution in the condenser, implying that the infrared thermal image of condenser is an important evidence to the evaluation of working fluid operation and heat transfer performance of the PHP.

Key words: pulsating heat pipe, operation states, infrared thermal imaging, gas-liquid flow, heat transfer

摘要：

基于红外热成像技术和高速可视化观测手段,得到了不同热负荷下脉动热管冷凝段表面的温度分布和管内工质的运行状态,分析了两者与热管传热性能间的内在联系。研究表明:随着热负荷的升高,工质准稳定运行状态依次呈现单管小幅脉动、管间大幅脉动和整管单向循环3种模式;冷凝段内主要出现泡状流和塞状流两种流型且离散气泡所占的份额逐渐减小;不同运行模式下工质能质输运强度的差异导致脉动热管冷凝段壁温分布各具特征;冷凝段表面的红外热图像可成为辨识管内工质运行状态和判断热管传热性能优劣的重要依据。

关键词: 脉动热管, 运行状态, 红外热成像, 气液两相流, 传热