Abstract:

Under surging conditions in the sea, the phase change and flow characteristics of two-phase fluids in plate-fin heat exchanger channels will change, which will affect the heat exchanger performance. In order to clarify the surging impact mechanism, a model for heat transfer characteristics of liquefied natural gas flow boiling in channel of plate-fin heat exchanger under surging conditions was established. Firstly, the mechanism of heat transfer and mass transfer of two-phase flow in the channels was analyzed, and the numerical model to simulate the flow and heat transfer under steady conditions was established; secondly, a model for reflecting the surging acceleration was added in the numerical model, which realizes the simulation of heat transfer charactersitics under surging conditions; the proposed model was verified based on the experimental data under onshore conditions. Based on the proposed model, the effects of vapor quality, frequency and amplitude of surging on heat transfer characteristics were analyzed. The results show that, the heat transfer coefficient increases with the increasing surging amplitude, while it decreases with the increasing surging frequency; as vapor quality increases, the influence of surging on heat transfer gradually changes from deterioration to enhancement; as vapor quality is within 0.2-0.8, the surging impact factor for the heat transfer coefficient is within 87.9%-110.0%. The effect of surging on time-average heat transfer coefficient changes with different conditions, representing a maximum deterioration of 5.0% and a maximum enhanceent of 2.0%.

摘要：

海上纵荡工况下，板翅式换热器通道内两相流体相变流动特性会发生变化，从而影响换热器性能。为了明确纵荡对换热特性的影响机理，建立了纵荡工况下板翅式换热器通道内两相流动沸腾换热性能预测模型。首先对板翅式换热器内流型变化和传热传质机理进行分析，建立了陆基非晃荡工况下的流动与传热过程的数值模型；然后将纵荡加速度模型嵌入模型中，从而实现晃荡工况下换热特性的模拟；通过陆基工况下的实验数据对模型进行了验证。基于建立的模型，分析了不同干度下纵荡幅度和纵荡频率对传热性能的影响。结果显示：纵荡幅度增大，传热系数增大；纵荡频率提高，传热系数降低；随着干度的增大，纵荡对换热的影响逐渐由恶化变为加强；在0.2～0.8干度之间，纵荡对传热系数的影响因子范围为87.9%～110.0%；晃荡对传热系数时均值影响随工况不同而变化，最大恶化5.0%，最大强化2.0%。