摘要随着环境与资源矛盾的日益突出和液化天然气（LNG）开采利用技术的不断发展， 天然气作为一种清洁能源逐渐进入公众视线，LNG 的存储和气化设备的也成为研究 热点。中间流体气化器（IFV）是一种带有中间传热介质的气化器，而作为 IFV 的气 化核心设备，IFV 冷凝器中的 LNG 气化过程直接影响气化器的整体换热效率和天然 气的输送效率。因此，针对 IFV 冷凝器中 LNG 的流动与传热过程分析显得尤为重要。84145

为了研究影响冷凝器内部 LNG 流动与传热过程的因素，得到冷凝器内 LNG 的流 动与传热过程的特征和规律，为冷凝器的优化设计提供理论依据。本文以 IFV 冷凝器 中的换热管为研究对象，使用甲烷代替 LNG 进行模拟研究，通过 fluent 软件对 IFV 冷凝器中的管程流体流动和传热过程进行数值模拟研究。在一定的设计参数下，研究 重力对流场细节和传热过程的影响；分别改变甲烷入口质量流量和管程操作压力研究 对流体物性、传热系数和出口温度等参数的影响。

结果表明，重力场对甲烷的流动和传热过程产生很大的影响，在研究过程中不能 忽略重力场的作用。甲烷在超临界状态下不利于对流换热，尤其是在低质量流量工况 下，换热管后半段会出现传热恶化现象。提高质量流量可以强化换热，有效改善传热 恶化现象，质量流量平均每提高 0。01kg/s，平均表面传热系数提高 13。56%，但这也提 高了总压损失，降低甲烷平均出口温度。增加管程操作压力使得平均表面传热系数降 低，但能小幅度提高甲烷出口温度，压力每提高 0。5MPa,出口平均温度提高 0。08K。

毕业论文关键词：LNG；数值模拟；IFV；超临界流体

ABSTRACT With the increasingly prominent contradiction between environment and resources and the continuous development of the technology of the exploitation and utilization of liquefied natural gas (LNG),natural gas as a clean energy gradually come into the public eyes,LNG’s storage and gasification equipment has also become a hot research topic。Intermediate Fluid Vaporizer (IFV) is a kind of vaporizer with intermediate heat transfer medium。However, when it is the core equipment of IFV gasification,the LNG gasification process in IFV condenser directly affects the overall heat transfer efficiency and the transmission efficiency of natural gas。Therefore, it is very important to analyze the flow and heat transfer process of LNG in the IFV condenser。

In order to study the factors that affect the flow and heat transfer process of LNG in the condenser, the characteristics and rules of the flow and heat transfer process of LNG in the condenser are obtained, which provides a theoretical basis for the optimal design of the condenser。In this paper, the heat transfer tube of IFV condenser is used as the research object。 The simulation is carried out by using methane instead of LNG。 The flow and heat transfer processes in the IFV condenser are simulated by fluent software。Under certain design parameters, study the influence of gravity on the details and heat transfer process of the convection field。Respectively change the inlet mass flow rate and pipe range operating pressure study on the influence of parameters such as fluid properties, heat transfer coefficient and outlet temperature of tube。

Results show that the gravity field has a great influence on the flow and heat transfer process of methane。The effect of gravity field can not be ignored in the research process。Methane is not conducive to convective heat transfer in supercritical state,especially under the condition of low mass flow,heat transfer deterioration phenomenon will appear in the next half of the heat exchange tube。Enhanced mass flow can enhance heat transfer,it can effectively improve the deterioration of heat transfer,the