微重力气液两相流动与池沸腾传热
doi: 10.6052/1000-0992-2010-4-J2010-067
TWO-PHASE FLOW AND POOL BOILING HEAT TRANSFER INMICROGRAVITY
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摘要: 综述了近年来中国科学院微重力重点实验室(国家微重力实验室)完成的一系列微重力气液两相流动与池沸腾传热方面的地基实验、飞行实验和理论研究等方面获得的主要成果.在微重力气液两相流动方面,提出了半理论Weber数模型用于预测微重力条件下气液两相弹--环状流转换,并采用Monte Carlo方法,针对气泡初始尺寸对泡--弹状流转换的影响进行数值研究.通过俄罗斯``和平号''空间站与IL--76失重飞机实验,获得了微重力下的气液两相流型图,与此同时在地面利用小尺度毛细管模型模拟了微重力气液两相流动特征.实验测量了微重力气液两相流压降,并基于微重力流动特性建立了一个泡状流压降关联模型.在微重力池沸腾传热方面, 利用我国返回式卫星完成了两次空间实验,其中,第22颗返回式卫星搭载铂丝表面R113池沸腾实验采用控制温度的稳态加热方式,而实践8号育种卫星搭载平面FC--72池沸腾实验则采用控制加热电压的准稳态加热方式.同时, 还进行了地面常重力和落塔短时微重力条件下的对比实验研究.观察到丝状加热表面微重力时轻微的传热强化现象,而平板加热表面微重力核态池沸腾低热流时传热强化、高热流时传热恶化.微重力实验中观察到气泡脱落前存在横向运动现象,据此分析了气泡行为与传热之间关系,并提出了一个预测丝状加热表面气泡脱落直径的半理论模型.旨在对相关领域的进一步发展和空间两相流系统的应用提供数据及理论支持.
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关键词:
- 微重力, 两相流, 流型,池沸腾, 传热
Abstract: Researches ontwo-phase flow and pool boiling heat transfer in microgravity,which included ground-based tests, flight experiments, andtheoretical analyses, were conducted in the National MicrogravityLaboratory/CAS. A semi-theoretical Weber number model was proposedto predict the slug-to-annular flow transition of two-phasegas-liquid flows in microgravity, while the influence of theinitial bubble size on the bubble-to-slug flow transition wasinvestigated numerically using the Monte Carlo method. Two-phaseflow pattern maps in microgravity were obtained in the experimentsboth aboard the Russian space station Mir and aboard IL-76 reducedgravity airplane. Mini-scale modeling was also used to simulatethe behavior of microgravity two-phase flow on the ground.Pressure drops of two-phase flow in microgravity were alsomeasured experimentally and correlated successfully based on itscharacteristics. Two space experiments on pool boiling phenomenain microgravity were performed aboard the Chinese recoverablesatellites. Steady pool boiling of R113 on a thin wire with atemperature-controlled heating method was studied aboard RS-22,while quasi-steady pool boiling of FC-72 on a plate was studiedaboard SJ-8. Ground-based experiments were also performed both innormal gravity and in short-term microgravity in the drop towerBeijing. Only slight enhancement of heat transfer was observed inthe wire case, while enhancement in low heat flux anddeterioration in high heat flux were observed in the plate case.Lateral motions of vapor bubbles were observed before theirdeparture in microgravity. The relationship between bubblebehavior and heat transfer on plate was analyzed. Asemi-theoretical model was also proposed for predicting the bubbledeparture diameter during pool boiling on wires. The resultsobtained here are intended to become a powerful aid for furtherinvestigation in the present discipline and development oftwo-phase systems for space applications.
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