液化天然气在微通道内流动沸腾的气泡行为及蒸发薄液膜机理研究

The flow boiling heat transfer mechanism of liquefied natural gas (LNG) in microchannels is a key issue to be solved in the application of printed circuit heat exchanger (PCHE) to floating liquefied natural gas (FLNG) systems. The study of bubble behavior and bubble bottom evaporating thin film is an important theoretical basis for revealing the heat and mass transfer mechanism of flow boiling. This project is aimed at the gasification process of LNG in PCHE. The bubble behavior under micro-scale effects and the heat and mass transfer mechanism of evaporating thin film in the flow boiling process of zeotropic mixtures in microchannels are two key scientific problems. Visual experiments, numerical simulation and theoretical analysis will be applied. The mechanism of temperature slip and mass transfer resistance on bubble nucleation, growth, slip, detachment, limitation and elongation behavior will be studied. The micro-scale effect of bubble behavior will be clarified in the project. The morphology, heat and transfer characteristics of the evaporating thin film will be studied, the heat and mass transfer model of which will be established. The heat and mass transfer mechanism of LNG evaporating thin film will be revealed. The correlation mechanism between the bubble behavior and the heat and mass transfer mechanism of evaporating thin film will be explained. The research results play an important role in perfecting the theoretical system of LNG flow boiling heat transfer in microchannels, and provide a scientific basis for promoting the application of PCHE to the localization of FLNG.

液化天然气（LNG）在微通道内的流动沸腾换热机理是印刷电路板式换热器（PCHE）应用于浮式液化天然气（FLNG）系统亟待解决的关键问题，而气泡行为及气泡底层蒸发薄液膜的研究是揭示流动沸腾传热传质机理的重要理论基础。本项目拟针对LNG在PCHE内的气化过程，围绕非共沸混合工质在微通道内流动沸腾中微尺度效应作用下的气泡行为特性及蒸发薄液膜的传热传质机理两个关键科学问题，采用可视化实验、数值模拟及理论分析相结合的方法，研究温度滑移、传质阻力对气泡核化、生长、滑移、脱离、受限及拉长行为的影响机制，阐明气泡行为的微尺度效应；研究蒸发薄液膜的形态及换热特性，建立蒸发薄液膜传热传质模型，揭示LNG蒸发薄液膜的传热传质机理；阐明气泡行为与蒸发薄液膜传热传质机理之间的关联机制。研究成果对完善微通道内LNG流动沸腾换热理论体系具有重要作用，为推进PCHE应用于FLNG的国产化进程提供科学依据。

液化天然气（LNG）在微通道内的流动沸腾换热机理是印刷电路板式换热器（PCHE）应用于浮式液化天然气（FLNG）系统亟待解决的关键问题。针对烷烃混合冷剂在微通道内流动沸腾换热过程的能质输运机理开展研究是揭示FLNG用PCHE内流动换热特性的重要理论基础。本项目主要研究内容包括：（1）搭建了微通道流动沸腾换热和气液两相压降实验台，实验研究了R290、R600a及其不同组分配比混合物的沸腾换热和摩擦压降特性，探究了质量流速、干度、饱和温度、热流密度和组分对沸腾换热系数和两相摩擦压降的影响规律，揭示了温度滑移和传质阻力对非共沸混合工质流动沸腾换热的作用机理；（2）采用分子动力学模拟方法，针对甲烷、乙烷及其混合工质纳米液膜的沸腾换热特性开展研究。探究了纳米液膜在不同过热度下的沸腾现象，并与宏观池沸腾进行了对比，揭示了不同过热度引起的不同沸腾现象的机理。模拟了三种不同组分配比的甲烷/乙烷混合工质纳米液膜的膜态沸腾和核态沸腾的汽化现象，对不同沸腾过程中各组分分子汽化量与液膜中甲烷组分的变化特性进行分析。（3）针对超临界甲烷在翼型印刷电路板式换热器内的流动和换热性能开展了数值模拟，对翼型肋片类型和翼型肋片排布参数进行了结构优化，设计提出了翼型肋片非均匀分布形式，结果表明保持翼型肋片数量不变，在拟临界点附近布置更密的翼型肋片能够强化综合性能。本项目研究成果：在国内外核心刊物发表论文5篇，其中4篇被SCI收录、1篇被EI收录；培养在读硕士研究生5人。本项目研究成果对完善微通道内LNG流动沸腾换热理论体系具有重要作用，为推进PCHE应用于FLNG的国产化进程提供科学依据。