【作者】 林涛；

【导师】 焦文玲；

【作者基本信息】 哈尔滨工业大学 ， 土木工程， 2021， 硕士

【摘要】 液化天然气以热值高、易于储存输送的优势,通常被作为偏远城镇主气源的最佳选择。液化天然气需要在LNG场站中经过气化并达到一定温度以上,才可以通过城镇燃气管网输送至用户。因无需额外的能量消耗便可气化液态天然气,空温式气化器备受LNG场站的青睐。由于缺乏对空温式气化器气化机理的深入研究,LNG场站气化能力难以精确描述或定量优化,设计人员在进行场站气化系统选型及配置时缺乏参考依据,给LNG场站带来供气可靠性和经济性等诸多问题。本文以空温式气化器作为研究对象,建立并求解靠近本质运行的LNG空温式气化器整体传热模型,采用数值建模和调研测试相结合的方法,进行模型改进与AAV传热性能分析。在此基础上,联立空温式气化器和复热器的经济模型,提出双目标配置优化策略,构建空温式气化器配置优化模型,对于LNG空温式气化器设计选型指导及研究具有一定的参考价值。通过对空温式气化器结霜过程、空气侧传热特性的分析,运用能量守恒和质量守恒的原理,推导了结霜和非结霜工况下翅片管空气侧总换热系数方程,得到翅片管空气侧传热模型;在此基础上,探讨管内流动沸腾传热机理,选取热物性参数计算关联式,提出管内单相换热和两相换热的计算方法,最后构建动态的LNG空温式气化器整体理论传热模型并求解。通过实际调研及测试,对比实际运行数据和理论模型的计算结果,明确原理论模型的计算精度,并从传热机理和运行参数两个方面,分析挖掘理论模型计算产生误差的原因。在此基础上,对原理论模型进行相关参数的改进,从而得到精准性较高的整体传热理论模型。通过调研选取合理的设备模型,利用改进后的整体传热模型,探讨出口温度、管内流体各相长度以及传热系数随时间的变化关系,进而分析结构参数(翅片管几何形状和列数、翅片个数)和运行参数(环境温度和实际气化量)对空温式气化器传热性能的影响。在此基础上,以设备的运行条件作为依据,提出空温式气化器结构参数设计的建议。通过对空温式气化器和复热器常规配置的局限性分析,丰富空温式气化器配置原则;以投资费用和投资效益作为配置优化模型的优化目标,建立双目标优化模型,选取平方和加权法作为模型的优化方法,并以实际配置案例作为对比,得到富余系数在1.5～2.0时的配置方案经济性优于富余系数1.2～1.5的结论。更多还原

【Abstract】 With the advantages of high calorific value and easy storage and transportation,liquefied natural gas is usually regarded as the best choice for the main gas source in remote towns.Liquefied natural gas needs to be gasified in LNG station and reach a certain temperature before being transmitted to users through urban gas pipeline network.Air ambient vaporizers are favored by LNG stations,on account of gasifying liquid natural gas without additional energy consumption.Due to the lack of in-depth study on the gasification mechanism of air ambient vaporizers,it is difficult to accurately describe or quantitatively optimize the gasification capacity of LNG station.Designers lack reference basis in the selection and configuration of gasification system of LNG station,which brings many problems to the LNG station,such as the reliability and economy of gas supplying.In this paper,the air ambient vaporizer is taken as the research object,and the overall heat transfer model of LNG air ambient vaporizer close to the actual operation is established and solved.The method of combining numerical modeling with investigation and test is used to modify the model and analyze the heat transfer performance of air ambient vaporizer.On this basis,combining the economic model of air ambient vaporizer and reheater,the double-objective configuration optimization strategy is proposed,and the configuration optimization model of air ambient vaporizer is constructed,which has a certain reference value for the design and selection of air ambient vaporizer.Based on the analysis of the frosting process and heat transfer characteristics of the air side of the air ambient vaporizer,the total heat transfer coefficient equation of the air side of the finned tube under frosting and non-frosting conditions is derived by using the principles of energy conservation and mass conservation.And the heat transfer model of the air side of the finned tube is obtained.On this basis,the mechanism of flow boiling heat transfer in the tube is discussed,and the correlations of thermophysical parameters are selected.The calculation methods of single-phase heat transfer and two-phase heat transfer in the tube are proposed.Finally,the dynamic overall heat transfer model of LNG air ambient vaporizer is established and solved.Through the actual investigation and test,the actual operation data of the air ambient vaporizer are collected,and the actual operation data and the calculation results of the theoretical model are compared to clarify the accuracy of the original theoretical model calculation.From the two aspects of heat transfer mechanism and operation parameters,the reasons for the calculation error of the theoretical model are analyzed.On this basis,the relevant parameters of the original theoretical model are modified,so as to obtain the overall heat transfer theoretical model with high accuracy.Through the investigation and selection of reasonable equipment model,using the modified overall heat transfer model,the relationship between the outlet temperature,the length of each phase in the tube and the heat transfer coefficient with time is discussed,and then the influence of structural parameters(geometry and number of rows of finned tubes,number of fins)and operating parameters(ambient temperature and actual gasification volume)on the heat transfer performance of air ambient vaporizer is analyzed.On this basis,based on the operating conditions of the equipment,the suggestions for the design of the structural parameters of the air ambient vaporizer are put forward.By analyzing the limitation of conventional configuration of air ambient vaporizer and reheater,the configuration principle of air ambient vaporizer is enriched.The investment cost and investment benefit are taken as the optimization objectives of the configuration optimization model,and the double objective optimization model is established.The square sum weighted method is selected as the optimization method of the model,it is concluded that when the surplus coefficient is 1.5 ～ 2.0,the economic efficiency of the configuration scheme is better than that of the surplus coefficient 1.2 ～1.5.更多还原