基于热节点网络法的船用LNG梯级汽化器换热性能分析

Thermal Performance Analysis of Marine LNG Cascade Vaporizer Based on Thermal Network Method

将基于梯级汽化理论的LNG梯级汽化器作为研究对象,以热节点网络法为基础,利用一维数值模拟方法对其进行热力学分析并建立热阻分析模型,对该汽化器壳体中LNG、丙烷(PR)和海水3种工质的耦合换热特性进行研究。主要分析了LNG腔体和PR腔体内气液两相流动换热以及海水腔体内单相流动换热,比较不同LNG质量流量和不同海水质量流量分别对LNG侧及海水侧流动换热特性的影响。结果表明:在LNG侧质量流量为2.4 kg/s、2.8 kg/s、3.2 kg/s、3.6 kg/s和4.0 kg/s工况时,LNG侧出口温度分别为278 K、281.6 K、242 K、229.8 K和222.5 K,温度变化显著且呈先增大后减小的变化趋势;海水侧质量流量的增加使得LNG侧出口温度升高,但增幅并不明显;此外,随着LNG侧和海水侧质量流量增加,两侧流体流动压降均大幅增加。

Adapting one-dimensional mode, a thermal resistance model predicting the heat transfer performance occurring in the LNG cascade vaporizer based on the cascade vaporization theory is developed and used to analyze the coupled heat transfer characteristics of LNG, propane and seawater based on thermal network method. The two-phase flow in the LNG cavity and propane cavity including single-phase flow in seawater cavity are studied. The effects of different mass flow rates of LNG and seawater on the heat transfer characteristics of the LNG side and the seawater side are compared in the paper. The research results indicate that when the mass flow rate of LNG is 2.4 kg/s, 2.8 kg/s, 3.2 kg/s, 3.6 kg and4.0 kg/s, the outlet temperature of LNG is 278 K, 281.6 K, 242 K, 229.8 K and 222.5 K respectively. The temperature increases firstly and then decreases with obvious changes. The outlet temperature of LNG increases slightly with the increasing of mass flow rate of seawater. Meanwhile, the pressure drop of fluid on both sides increases greatly with the increasing of mass flow of LNG and seawater.