低温预冷换热规律及表面改性影响研究

调研了低温管路预冷及两相换热的研究现状,阐述了低温预冷瞬态换热特性;介绍了金属表面改性对预冷规律的影响,仿真了低导热涂层管的预冷换热规律。研究发现:液氮预冷主要由膜态沸腾支配,且预冷耗时较长;液氢预冷未见膜态沸腾,预冷耗时更短。促进膜态沸腾向过渡沸腾的更早转化有利于预冷加速,且转化温度迁移可通过内壁表面结构改性实现,可采用的方法包括表面纳米微结构、低导热涂层、增加微肋结构等,讨论了结构改性对换热规律及预冷效率的影响。

Research on Heat Transfer Characteristics in Cryogenic Precooling Process and Surface Modification Influence on Precooling Efficiency

Research status of cryogenic precooling and associated two-phase heat transfer are reviewed,and the transient heat transfer characteristics during pipeline precooling are analyzed.Influence of metal surface modification on precooling effect is introduced,and also a simulation study is performed to reveal the heat transfer characteristics in a low thermal conductivity precooling process.It is found that liquid nitrogen precooling process is dominated by film boiling,and the total precooling time is long.Comparatively,no film boiling is observed in liquid hydrogen precooling process,and the precooling time is shorter.Besides,earlier transformation from film boiling to transition boiling is beneficial to fast precooling.This transformation could be realized though three methods including creating nano-microstructure at the wall inner surface,applying a low thermal conductivity coating,and increasing micro-fin structure inside the pipeline.The influence of structure modification on heat transfer and precooling efficiency are also discussed.