海洋条件下印刷电路板式换热器多通道内超临界液化天然气瞬态分配特性分析

印刷电路板式换热器（PCHE）是海上LNG浮式储存和再气化装置的核心部件。在海洋条件下，其内部微细多通道间的流量分配特性复杂多变，易急剧恶化，严重影响气化效率和运行安全。本文通过UDF分别引入晃荡导致的周期性变化的附加惯性力及LNG物性计算关联式，构建适用于PCHE内超临界LNG流动与传热的三维非稳态模型，并开展了数值研究。结果表明，相比于初始稳态条件，晃荡过程中PCHE各通道内超临界LNG的流量及温度等参数随之发生周期性的震荡，而且工质分配的均匀性明显恶化，各通道间流量、温度分布的相对标准偏差均显著高于初始稳态值，本文算例中最高甚至达到初始稳态值的3倍以上；晃荡振幅及晃荡频率越大，PCHE各通道间工质的流量分配及温度分布越不均匀；相比于在垂直于通道内工质流动方向上施加晃荡作用力，当在工质流动方向上施加晃荡作用力时，晃荡作用引发的工质分配恶化现象明显较为微弱，通道内参数的震荡幅度明显降低。

Analysis on the Transient Flow Distribution Characteristics of Supercritical LNG in Printed Circuit Heat Exchanger under Sloshing Conditions

Printed circuit heat exchanger (PCHE) is the core component of LNG floating storage and regasification unit (FSRU) at offshore conditions. The flow distribution among the small mini-channels becomes more complex and changeable, and it is prone to rapid deterioration under sloshing conditions. This seriously affects seriously affects the regasification efficiency and operational safety of FSRU. In this regard, a three-dimensional mathematical model suitable for analyzing flow and heat transfer of supercritical LNG in PCHE under sloshing conditions is constructed, introducing the additional periodic inertial force caused by sloshing and calculation correlation of LNG multi-component physical properties through UDF. Then the related numerical research is carried out and the following conclusions are obtained. The flow rate and temperature of supercritical LNG in each channel of PCHE periodically oscillate, and the uniformity of the working fluid distribution is obviously deteriorated when inducing the sloshing condition. The relative standard deviations of the flow rate and temperature distribution among channels during the sloshing process are significantly higher than that at the initial steady value, and the max value even reaches more than 3 times the initial steady state value. The larger the sloshing amplitude and the sloshing frequency, the more uneven the flow distribution and temperature distribution among channels of PCHE. When the sloshing is applied in the flow direction of the channel, the deterioration of the flow distribution caused by the sloshing effect is obviously weaker, and the oscillation amplitude of the parameters in the channel is obviously reduced, compared to the situation when the sloshing is applied in the direction vertical to flow direction of the channel.