窄小通道内多组分低温液体流动沸腾传热特性和传质耦合机理

The flow boiling of Multi-components Cryogenic Liquids (MCL), which generally occurs during the cold releasing process in Liquefied Natural Gas (LNG) plants and terminals, has become a key problem to be solved imperatively in designing and optimizing of heat transfer devices with gas-liquid phase transition for LNG. In this proposal, visualizing experiments and numerical simulation will be conducted to investigate the heat and mass transfer of the flow boiling of MCL in mini-channels (ID: 1-3 mm). (1) Visualizing experiments will be done to investigate the flow patterns, heat transfer coefficients and pressure drop of flow boiling of Nitrogen/Methane /Ethane ternary cryogenic mixture in a mini-channel. The impacts of the mass flux, pressure, components of the mixture, the heat flux, the geometry of the channel on the flow pattern and the heat transfer coefficient of the flow boiling will be studied carefully. The flow pattern maps will be drawn and the transition criterions of the flow will be studied. We will fit a heat transfer correlation with high accuracy for the flow boiling of the MCL. (2) A coupled heat and mass transfer model for the nucleate flow boiling of the Nitrogen/Methane /Ethane mixture is to be established, and the model will be numerically simulated by FLUENT software. The object of the study is to illuminate the effects of the components of the mixture on the overall mass transfer coefficient and the heat transfer coefficient. The collaborative mechanisms of mass and heat transfer of MCL flow boiling will be explored. This proposal will have important scientific and practical significance due to the breakthrough of research on designing and optimizing theories of the compact heat transfer devices with gas-liquid phase transition for LNG.

液化天然气（LNG）生产和利用时普遍涉及的多组分低温液体（MCL）流动沸腾问题是LNG相变换热装置设计优化亟待解决的关键所在。本项目将对窄小通道(ID：1-3 mm)内MCL流动沸腾的传热传质问题开展可视化实验研究和数值模拟：(1)对氮/甲烷/乙烷低温混合液体在窄小通道内流动沸腾的流型、传热系数及压降特性进行可视化实验，揭示质量流量、热边界条件、操作压力、通道结构及组分成分变化与流型演变、传热系数及压降的关系，获得MCL流动沸腾的主要流型及转变条件、换热准则关联式；(2) 对氮/甲烷/乙烷低温混合液体的核态流动沸腾建立耦合传热传质数学模型，采用CFD软件进行数值模拟，研究不同组分成分下MCL核态流动沸腾的气/液相内及相际传质系数与沸腾传热系数，揭示相间传质效应对MCL沸腾传热的影响规律和耦合机理。本研究将为LNG相变换热装置设计优化提供基础理论和数据支持，具有重要的科学意义和工程应用价值。

液化天然气（LNG）是一种典型的多组分低温液体（MCL），其流动沸腾问题是LNG相变换热理论研究的重要内容，本项目对窄小通道内R600a/R290/R134a等制冷工质流动沸腾的传热传质问题开展了实验研究和数值模拟，旨在为LNG的流动沸腾特性研究提供理论支持，具体的工作有：(1) 按照项目研究方案和目标，开展了R290/R600a在水平管内的流动沸腾传热传质的数值模拟研究，并对细通道内气液两相Taylor流动的传质过程进行了数值模拟；（2）通过实验手段研究了内径为3mm窄小通道内R600a/R290/R134a的流动沸腾传热特性及阻力损失特性; (3)以LNG为实验工质，对其在内外强化换热管内的汽化沸腾换热过程进行了实验研究；（4）对高温超导与LNG联合远程输送的低温流动换热问题开展了理论研究，并提出了天然气液化的新系统及其改进方案。通过本项目研究，基本完成了研究目标，获得了在窄小通道内制冷剂流动沸腾的传热与阻力损失特性，并丰富了液化天然气的汽化及液化理论。本研究将为LNG相变换热装置设计优化提供基础理论和数据支持，并为天然气的液化系统提供理论指导，具有重要的科学意义和工程应用价值。