摘要超临界流体在很多领域有着广泛的应用，如超临界二氧化碳用于空调的跨临界制冷循环和热泵循环，超临界水用于火力发电和核反应堆冷却系统等。超临界压力下管内流动摩擦压降的确定对于这类系统和设备的设计、分析和仿真极其重要。超临界流体的流型与传统的单相流有点类似，没有相变发生，在拟临界点区附近热物性会发生急剧变化，传统的单相摩擦因子关联式已经不能满足超临界压力下管内流动的摩擦压降计算要求。因此，研究获得较高预测精度的摩擦因子关系式对超临界流体技术的应用具有十分重要的意义。目前针对超临界压力下管内流动的实验研究还不充分，缺少较普遍认可的预测关系式。86827

本文收集了390组超临界流体摩擦阻力实验数据，其中有263组数据由R410A在超临界压力下被冷却时获得，45组数据由R404A在超临界压力下被冷却时获得，64组数据由CO2在超临界压力下被冷却时获得，18组数据由R22在超临界压力下被加热获得。利用实验数据对现有9个预测关联式进行分析评价，并基于实验数据利用最小二乘法拟合得到新预测关联式。经验证，新关联式的预测精度更高、适用范围更广。同时，利用MATLAB GUI开发超临界压力下管内流动摩擦压降的计算软件，实现用户输入工况条件，软件能按照相应的预测关联式计算出压力降。

毕业论文关键词： 超临界；压降；摩擦因子

Abstract Supercritical fluid has been used in many industrial fields。 For example, supercritical carbon dioxide (CO2) is used for transcritical cycles of air conditioning and heat pump systems。 Supercritical water is used for fossil-fired power plants and nuclear reactor cooling systems。 The determination of the in-tube friction pressure drop under supercritical pressure is important to the design, analysis and simulation of of systems and apparatus mentioned above。 The flow pattern of supercritical fluid is somewhat similar to the conventional single-phase flow, and no phase transition occurs。 The thermophysical properties of fluids vary dramatically near the pseudo-critical point。 Thus the friction pressure drop of supercritical fluids cannot be fairly predicted with conventional single-phase friction factor correlations。 Therefore, the study of friction pressure drop for supercritical fluids is necessary。 Experimental investigations of pressure drop to supercritical fluid is insufficient。 There is no a correlation commonly believed。   

This paper has collected 390 experimental data of the pressure drop from the available literature, including 263 data of R410A and 45data of R404A under supercritical cooling, 64 data of supercritical CO2 cooling, and 18 data of supercritical R22 heating。The same bank of experimental data is used for the evaluation of 9 available supercritical friction factor correlations。 A new friction factor correlation for supercritical tube flow is proposed using least square method based on 633 experimental data points。 It is proved that the new correlation has higher prediction precision and a wider range of application。 Besides, MATLAB GUI, an interface development tool, is used to develop software which can be used to study the pressure drop of supercritical fluid。 The software can calculate the pressure drop according to the corresponding correlations, after the user inputting the conditions。 

Keywords: Supercritical pressure; pressure drop; friction factor

目 录

第一章 绪论 1

1。1 研究背景 1

1。2 超临界流体及其应用 3

1。2。1 超临界二氧化碳 3

1。2。2 超临界水