LNG空温式气化器传热问题的研究进展

空温式气化器在运行过程中的传热恶化问题有可能会带来灾难性的后果,是液化天然气再气化过程中必须要重视和解决的难题。为此,在全面回顾和总结空温式气化器传热问题研究成果及现状的基础上,重点阐述了管内流动沸腾传热特点及其传热系数关联式的发展,分析了管外结霜过程及其对空温式气化器换热性能的影响,对当前气化器研究所面临的问题进行了梳理和总结,并对进一步解决传热恶化问题的研究方向进行了展望。研究结果表明:①以甲烷为主的多组分烷烃混合有机物的管内流动沸腾是未来的研究难点;②对于LNG竖直管内的流动沸腾试验还需要开展更加深入的研究,除了热流密度、干度、质量流量以外,还应包括入口压力、管径、管长以及内壁面粗糙度的影响;③管外结霜是造成气化器传热恶化的主要原因;④完善低温表面抑霜技术是改善气化器传热恶化的重点,对于空温式气化器设计、制造以及运行均具有普遍的理论指导意义;⑤疏水材料的抑霜除霜剂比亲水材料的抑霜除霜剂更加适用于空温式气化器。结论认为,该研究成果有助于破解空温式气化器传热恶化难题。

Research progress on the heat transfer of ambient air LNG vaporizers

The heat transfer deterioration of an ambient air vaporizer in the process of its operation may bright about disastrous consequences, so this difficulty shall be concerned and solved in the process of LNG regasification. After reviewing and summarizing the research achievements and status of the heat transfer problems in ambient air vaporizers, this paper mainly illustrated the characteristics of the flow boiling heat transfer inside the tube and the development of its heat transfer coefficient relation. Then, the frosting process outside the tube and its effect on the heat exchange performance of an ambient air vaporizer were analyzed. Finally, the current problems in the research of vaporizers were analyzed and summarized, and the research direction for further solution of heat transfer deterioration was prospected. And the following research results are obtained. First, the flow boiling of the organic mixture of multi-component alkane dominated by methane inside the tube is the research difficulty in the future. Second, the experiments on the flow boiling inside the LNG vertical tube shall be researched further. And besides heat flow density, dryness fraction and mass flow rate, the effects of inlet pressure, tube diameter, tube length and inner wall roughness shall be investigated. Third, frosting outside the tube is the main reason for a vaporizer's heat transfer deterioration. Fourth, improving the low-temperature surface anti-frosting technology is the key point to solve heat transfer deterioration, and it is of universal significance in theoretically guiding the design, manufacturing and operation of ambient air vaporizers. Fifth, compared with the frost restraining and removing agent with hydrophilic material, the one with hydrophobic material is more suitable for an ambient air vaporizer. In conclusion, the research results are conducive to solving the heat transfer deterioration of ambient air vaporizers.