超级开架式气化器相变传热的数值模拟研究

发布时间：2018-03-01 02:37

本文关键词： Super ORV 相变传热数值模拟优化　出处：《华南理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着能源危机和环境问题日益严峻,液化天然气(Liquefied Natural Gas,简称LNG)作为一种清洁高热值能源备受关注,天然气工业的发展已成为改善能源结构、推动低碳经济发展的重要力量。在实际应用中,液化天然气需要气化并加热到常温才能使用,因而LNG气化器成为天然气工业中必不可少的核心设备。目前,我国用于基本负荷型LNG接收站的开架式气化器设备主要依赖国外进口。LNG产业快速发展与LNG接受终端再气化技术受限的矛盾越来越突出,对超级开架式气化器(Super Open Rack Vaporizer,简称Super ORV)的国产化提出了强烈的要求。本论文分析了前人关于Super ORV的研究状况,并设计了一种与新型开架式内螺旋气化器配套的气化内管,对其传热传质特性进行了研究。本论文首先根据不同的混合规则对液化天然气(LNG)和气态天然气(NG)热物性进行计算。通过计算得到了LNG泡点温度随压力的变化曲线图以及LNG和NG密度、定压比热容、导热系数、动力粘度随温度的变化曲线图。分析了Super ORV的传热过程:预热过程、气化过程、加热过程。并对每一个过程的传热计算进行了总结。建立了Super ORV气化段的物理模型和数值模型。其中,数值模型包括:Mixture多相流模型、湍流模型、相变模型以及自定义相变传热传质函数(UDF)。应用FLUENT流体力学软件模拟了两种气化管的流动和传热特性,分析了两种气化管速度场、温度场和截面含气率分布情况。结果表明:螺旋气化管截面有显著垂直于主流方向的二次流;入口速度0.91m/s时,螺旋管出口气相含量比光滑管高6.1%;入口速度在0.91 m/s增加到1.63 m/s的流量范围内,传热强化综合性能评价因子η皆大于1,螺纹管传热强化效果明显;随着LNG入口流速的增大传热综合性能评价因子η也增大。用正交试验方法对螺纹气化管进行结构优化。根据正交实验结果,对壁面平均换热系数的影响因素排序为:小径、螺纹肋宽度、螺距;对管程压降的影响因素排序为小径、螺距、螺纹肋宽度。螺纹气化管最优结构方案为:螺旋气化管的小径为8 mm、螺旋肋宽度为55°、螺距为120 mm。最后,确定数值模拟的验证方法,即通过借助前人实验研究数据,在相同的工况下进行数值模拟,结果表明:模拟值与实验值误差在合理范围内。本论文的研究成果不但为Super ORV的开发提供理论依据,同时为其性能研究与优化提供一种合理的研究方法与思路。
[Abstract]:With the increasingly severe energy crisis and environmental problems, LNG (liquefied Natural Gas) as a clean and high calorific energy source has attracted much attention, and the development of natural gas industry has become the improvement of energy structure. In practice, liquefied natural gas needs to be gasified and heated to normal temperature before it can be used, so LNG gasifier has become an essential core equipment in the natural gas industry. The contradiction between the rapid development of imported LNG industry and the limitation of LNG receiving terminal regasification technology is becoming more and more prominent in China, which is mainly used in the open-shelf gasifier equipment for the basic load type LNG receiving station. A strong requirement for the localization of Super Open Rack Vaporizer (Super ORV) for super open-shelf gasifier is put forward. In this paper, the research status of Super ORV is analyzed, and a new type of gasification inner tube is designed to match the new open-shelf internal spiral gasifier. The characteristics of heat and mass transfer are studied in this paper. Firstly, the thermal properties of liquefied natural gas (LNG) and gaseous natural gas (NGG) are calculated according to different mixing rules. The curves of LNG bubble temperature with pressure are obtained by calculation. Graphs and LNG and NG densities, The curves of specific heat capacity, thermal conductivity and dynamic viscosity with temperature at constant pressure are analyzed. The heat transfer process of Super ORV is analyzed: preheating process, gasification process, The heat transfer calculation of each process is summarized. The physical model and numerical model of Super ORV gasification section are established. Phase change model and self-defined phase change heat and mass transfer function are used to simulate the flow and heat transfer characteristics of two kinds of gasification tubes by using FLUENT fluid dynamics software, and the velocity fields of two kinds of gasification tubes are analyzed. The distribution of temperature field and gas content in the section. The results show that there is a significant secondary flow perpendicular to the main stream in the section of the spiral gasification tube, and the inlet velocity is 0.91m / s. The gas phase content at the outlet of the spiral tube is 6.1 higher than that of the smooth tube, and the inlet velocity increases from 0.91 m / s to 1.63 m / s, the evaluation factor 畏 of heat transfer enhancement is all greater than 1, and the heat transfer enhancement effect of the threaded tube is obvious. With the increase of inlet velocity of LNG, the heat transfer evaluation factor 畏 also increases. The structure of threaded gasification tube is optimized by orthogonal test. According to the results of orthogonal experiment, the influence factors of wall average heat transfer coefficient are ranked as small diameter. Thread rib width, pitch, pressure drop of pipe are ranked as small diameter, pitch, thread rib width. The optimum structure scheme of screw gasification pipe is: diameter of helical gasification pipe is 8 mm, width of helical rib is 55 掳, pitch is 120 mm. The verification method of numerical simulation is determined, that is, by means of previous experimental research data, numerical simulation is carried out under the same working conditions. The results show that the error between the simulated value and the experimental value is within a reasonable range. The research results of this paper not only provide a theoretical basis for the development of Super ORV, but also provide a reasonable research method and train of thought for its performance research and optimization.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE96;TK124

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