沸腾是一类伴随有大量气泡生成和气液两相流动的高效相变传热过程，在地面常重力环境热能、核动力、化工等诸多工业过程及空间微重力环境热控、低温流体管理及载人航天环控生保技术等中都有着重要的应用价值或潜力。气液两相介质密度的巨大差异，导致地面常重力环境浮力往往主导着沸腾传热特征。微重力环境中，浮力效应被抑制甚至是完全消失，沸腾现象中气泡动力学行为、气液两相流动与传热特性将与地面常重力环境下截然不同。对微重力沸腾传热特性的研究不足，极大地制约了沸腾现象在航天工程领域的应用。鉴于空间技术与载荷均需在地面研发与测试，空间任务全寿命周期往往经历着不同的重力（或加速度）环境。因此，需要把重力作为可控变量，研究不同重力条件下的沸腾现象，揭示重力对沸腾传热特性的影响机制及其正确表述，支撑航天科技研发需求。另一方面，微重力环境抑制浮力效应，可以扩大气泡生长的时间尺度和空间尺度，有利于更好地观察沸腾过程中的气泡动力学行为和细观流动特征，深入理解沸腾传热机理，具有重要的学术意义。本文基于实践十号返回式科学实验卫星微重力池沸腾实验及中国空间站变重力沸腾实验，对池沸腾传热特性与气泡动力学行为中的重力效应开展系统研究。主要内容和结论如下：

（1）基于SJ-10单气泡沸腾实验装置正交双CCD观测系统特征，开发了基于双目视觉算法的图像分析软件，对空间微重力环境单气泡沸腾实验模式下气泡生长过程进行了定量分析。基于加热面局部温度测点数据，分析了微重力单气泡生长过程中底部温度和热流密度的演化特征，讨论了液体过冷度、基板加热功率对单气泡动力学特性及传热特性的影响。

（2）提出了基于遗传算法的加热固壁热传导反问题求解算法，完善了沸腾传热瞬态热流密度的计算方法，提高了热流密度反演计算的精度。对地面常重力和空间微重力条件下的常规沸腾模式实验数据分析，获得了不同重力条件下池沸腾传热曲线，据此讨论了重力水平、液体过冷度等因素对核态池沸腾传热性能的影响。结果表明，在所采用的平板加热面情形里，微重力条件下在较低热流密度下即可进入核态池沸腾，同时在远小于地面临界热流密度时就会偏离核态沸腾转向过渡沸腾甚至膜态沸腾；常、微重力条件下核态沸腾传热曲线近似落在同一条趋势线上，为揭示传热特性中的重力作用机制提供了新的数据。

（3）对有限尺度加热面上微重力膜态沸腾传热与气相形态的演化特征进行了详细分析，探究了微重力膜态沸腾现象中覆盖加热面的截球状的大蒸汽团内部蒸汽流动特性，针对性地提出了截球状气团蒸发-冷凝传热传质模型，即通过底部的蒸发及顶部与过冷液体接触的气液界面冷凝来维持传热传质，同时，表面张力梯度驱动了气液界面及邻近流体内的Marangoni对流，强化了膜态沸腾对流传热传质的效率。实验数据分析和理论探索揭示了微重力膜态沸腾传热机理，以及液体过冷度、壁面过热度等对微重力膜态沸腾传热的影响。

（4）完成了中国空间站问天实验舱变重力科学实验柜首批两项科学实验项目之一的变重力沸腾实验装置的研制工作，重点开展了温度、压力传感器的标定及实验工质FC-72除气充装和地面科学匹配试验与地面常重力科学实验数据分析等。此外，参与了空间站实验数据的实时分析与判读，对已获得的若干重力水平下的实验数据进行了初步分析，特别是0.38g（火星重力）、0.16g（月球重力）、0.10g及0.063g（低重力）下长时间、稳定的常规池沸腾实验数据，探究了沸腾传热过程中的重力效应，为整个项目后续任务执行奠定了坚实基础，将支撑空间实验目标的顺利实现。

The boiling phenomenon is accompanied by the generation of a large number of bubbles and the flow of gas-liquid two-phase medium, which has a high heat transfer efficiency. Boiling heat transfer is widely used in many industrial processes such as environmental heat energy, nuclear power, and chemical industry. In addition, it has great potential in thermal control, cryogenic fluid management, manned spaceflight environmental control and life protection technology in microgravity environment. The difference in the density of the gas-liquid two-phase medium leads to the fact that the buoyancy dominates the characteristics of boiling heat transfer in normal gravity. However, in microgravity, the buoyancy effect is suppressed or even completely elimineted, causing bubble behavior, two-phase flow and heat transfer characteristics completely different from those in terrestrial environment. Insufficient research on the heat transfer characteristics of microgravity boiling has greatly restricted the application of boiling in aerospace engineering. Both space technology and apparatus need to be developed and tested on the ground, the entire life cycle of space missions often experiences different gravity (or acceleration) environments. Therefore, in order to reveal the mechanism of gravity effort on boiling heat transfer and to correctly express the gravity effect, it is necessary to take gravity as a controllable variable and study boiling phenomena under different gravity. This will support the development of aerospace technology. On the other hand, the microgravity environment can weaken and suppress the buoyancy effect, and can expand the time scale and space scale of bubble growth, which is conducive to better observation of bubble dynamics and mesoscopic flow characteristics during the boiling process and heat transfer mechanism. Therefore, it is of great academic significance to better understand the mechanism of boiling. Based on the microgravity pool boiling experiment carried out by the SJ-10 returnable scientific experiment satellite and the variable gravity boiling (vgBoiling) experiment carried out by the Chinese Space Station (CSS), this paper conducts a systematic study on the gravity effect on the heat transfer and bubble dynamics in pool boiling.
(1) Based on the orthogonal dual CCD observation system of the SJ-10 experiment, this paper develops the image analysis software based on binocular vision algorithm, and obtained the kinetic characteristics of the bubble growth process in the microgravity under single-bubble boiling experiment mode. Based on the local temperature measurement data of the heating surface, the evolution characteristics of the temperature and heat flux during the microgravity single bubble growth process are analyzed, and the effects of liquid subcooling and heating power on the bubble dynamic and heat transfer characteristics of the single bubble are discussed. The results of image and scientific data analysis, including the evolution of the bubble shape and the local heat transfer at the bottom of the growing bubble during the growth of a single bubble under microgravity conditions, not only revealed the mesoscopic mechanism for maintaining the heat transfer performance of boiling in microgravity, but also provides verifiable measured data for the further development of the boiling bubble model.
(2) A genetic algorithm-based solution algorithm for the inverse problem of heat conduction in solid walls is proposed, which improves the calculation method of transient heat flux in boiling heat transfer and improves the accuracy of heat flux inversion calculation. Based on the analysis of boiling experiment of normal gravity on the ground and microgravity in space, the heat transfer curves of pool boiling under normal gravity and microgravity are obtained, and the influence of factors such as gravity and liquid subcooling on the heat transfer of nucleate pool boiling is discussed. The results show that in the case of the flat heating surface, boiling in microgravity occurs at a lower heat flux and wall superheat than ground experiment. Under the condition of far less than the critical heat flux on the ground, it will deviate from nucleate boiling and turn to transition boiling or even film boiling. The heat transfer curves of nucleate boiling under normal and microgravity conditions approximately fall on the same trend line, which provides new data for revealing the mechanism of gravity effects on heat transfer characteristics.
(3) The evolution characteristics of heat transfer and patterns of gas phase of microgravity film boiling on a finite-scale heating surface are analyzed in detail, and the steam flow characteristics inside the large steam bubble covering the heating surface in the microgravity film boiling phenomenon are explored. The evaporation-condensation heat and mass transfer model of the steam bubble is specifically proposed, that is, the heat and mass transfer is maintained by evaporation at the bottom and condensation at the gas-liquid interface at the top contacting the subcooled liquid. At the same time, the surface tension gradient drives the Marangoni convection at the gas-liquid interface and adjacent fluids, enhancing the efficiency of convective heat and mass transfer in film boiling. Experimental data analysis and theoretical exploration revealed the heat transfer mechanism of microgravity film boiling and the effects of liquid subcooling and wall superheat on microgravity film boiling heat transfer.
(4) This paper completed the development of the vgBoiling experimental device, which is one of the first two scientific experimental projects of the Varying Gravity Rack in the Wentian Lab Module of the CSS, focusing on the calibration of temperature and pressure sensors, the degassing and filling of working fluid FC-72, the ground scientific matching test and the data analysis of ground normal gravity scientific experiments. In addition, this paper participated in the real-time analysis and interpretation of the experimental data of vgBoiling experiment in orbit, and conducted a preliminary analysis of the data obtained under several gravity levels. Long-term and stable normal pool boiling experiment data at 0.38g (Mars gravity), 0.16g (lunar gravity), 0.10g and 0.063g (low gravity) are obtained, helps explore the gravity effect on boiling, which has laid a solid foundation for the the follow-up tasks of the entire project and will support the realization of vgBoiling experiment goals.