【作者】 陈欢；

【导师】 胡亚才； 洪荣华； 俞自涛；

【作者基本信息】 浙江大学 ， 工程热物理， 2013， 硕士

【摘要】 槽式太阳能热利用技术是当前研究的热点,通过该技术产生120～200℃的中高温蒸汽可以在工业中广泛应用。槽式技术通过抛物柱面反射镜将太阳光聚焦到集热管的外壁上,加热集热管内工质。在系统正常工作时,集热管正对反射镜面部分温度较高,背面温度较低,一直处于管壁局部受热的状态。要提高系统光热转换效率和系统运行稳定性,对局部加热条件下集热系统的流动传热特性进行研究具有重要意义。本文设计并搭建了自然循环槽式太阳能蒸汽发生系统模拟实验台,集热管热流密度3.7-7.5kW/m2,排汽压力0.15～0.35MPa。本文根据分离型热管特点重新定义了热管充液率,从集热管加热方式(全管加热,底部加热,顶部加热)、集热管加热温度(500℃,550℃),热管充液率(60%,120%)三个方面对稳定排汽阶段,热管回路的温度分布特征和变化规律进行了实验研究。随着排汽压力和加热温度的提高,热管回路整体温度上升;热管充液率增大,冷凝水入口端蒸汽逆流和上升管液体回流作用增强,热管回路温度出现周期性波动。以0.2MPa稳定排汽工况为例,得到以下结论：(1)热管60%充液率,500℃加热温度下：底部加热方式相比全管加热方式集热管平均传热系数(hj)升高了13.20%,系统热阻(Rpipe)下降了11.41%；顶部加热方式相比全管加热方式hj升高了7.98%,Rpipe下降了8.49%。(2)热管60%充液率,随着加热温度由500℃增加到550℃：全管加热方式hj升高了13.53%,Rpipe降低了12.27%；底部加热方式hj升高了15.25%,Rpipe降低了14.37%；顶部加热方式hj升高了18.54%,Rpipe降低了15.42%。(3)500℃加热温度,随着热管充液率由60%增加到120%：全管加热方式hj升高了25.80%,Rpipe降低了17.74%；底部加热方式hj升高了20.40%,Rpipe降低了14.82%；顶部加热方式hj升高了32.64%,Rpipe降低了18.58%。在本文定温加热工况下,蒸发段水平布置的分离型热管,底部加热方式集热管平均传热系数较高,热管热阻较低,系统的自然循环传热特性较好。更多还原

【Abstract】 Trough solar thermal technology is a hotspot of current research,120-200℃medium-high temperature steam produced by this technology can be widely used in industry. Trough system use parabolic mirror to focus sunlight to the outer wall of the collector tube, heat working fluid within the collector tube. The wall of collector tube will be in the state of partially heating when system working properly, the portion face the mirror has higher temperature than the back of the collector tube. In order to improve the photo thermal conversion efficiency and operational stability of the system, it is very important to make a deeply study of the flow and heat transfer characteristics of the collector system in local heating state.A natural circulation separated heat pipe steam generating system applied to the trough solar collector was designed, with the heat flux of collector tube varies from3.7kW/m2to7.5kW/m2, and the exhaust steam pressure varies from0.15MPa to0.35MPa. According to characteristics of our separate type heat pipe, we re-definition the filling ratio of heat pipe, and study the features and variation of the temperature distribution of the heat pipe loop experimentally, from aspects of heating way of the collector tube (whole heating, bottom heating, top heating), heating temperature of the collector tube (500℃,550℃), and the filling ratio of heat pipe (60%,120%) at stable exhausting stage.The overall temperature of the heat pipe circuit increased, with the improving of the pressure of the exhaust steam and heating temperature. With the filling ratio of the heat pipe increases, countercurrent vapor at the inlet of condensing water and liquid reflux of the rising pipe enhanced, the cyclical fluctuations of temperature of the circuit of the heat pipe occurs. We get following conclusions under the0.2MPa stable steam exhausting conditions:(1) Under60%filling ratio,500℃heating temperature:The average heat transfer coefficient of the collector tube (hj) of the bottom heating method increased13.20%, and the system thermal resistance (Rpipe) decreased11.41%while compare to that of whole heating method; the hj of the top heating method increased7.98%, and the Rpipe decreased8.49%while compared to that of whole heating method.(2) Under60%filling ratio, when heating temperature varies from500℃to550℃:the hj increased13.53%, and the Rpipe decreased12.27%under whole heating method; the hj increased15.25%, and the Rpipe decreased14.37%under bottom heating method; and the hj increased18.54%, and the Rpipe decreased15.42%under top heating method.(3) Under500℃heating temperature, when filling ratio varies from60%to120%:the hj increased25.80%, and the Rpipe decreased17.74%under whole heating method; the hj increased20.40%, and the Rpipe decreased14.82%under bottom heating method; and the hj increased32.64%, and the Rpipe decreased18.58%under top heating method.Under the constant temperature heating conditions of this paper, the collector tube under bottom heating method has a higher hj, lower Rpipe, and better natural circulation heat transfer characteristics of the separate type heat pipe system, while the evaporator section is placed horizontally.更多还原