喷射器制冷系统的分析与设计

发布时间：2018-03-27 10:30

本文选题：喷射器　切入点：制冷系统　出处：《华中科技大学》2014年硕士论文

【摘要】：化石燃料在现代社会发展中的大量使用造成了一系列的能源和环境问题，为了实现社会的可持续发展，人们将研究的焦点转向清洁与可再生能源。在喷射器制冷循环中，太阳能、工业废热能等低品质热源取代了高品质的机械能，在一定程度上提高了能源利用效率并改善了环境问题。然而喷射器制冷循环的核心-喷射器的效率制约了其大规模的应用，因此提高喷射器效率，合理设计喷射器成为喷射器制冷循环研究的焦点。本文研究中将发动机尾气作为高温热源，利用发动机尾气为喷射器制冷循环提供能量。首先对喷射器最优工况点进行研究，在此基础上提出喷射器关键截面优化设计的数学模型同时利用VB编程进行实现，通过与已知实验结果进行对比对本数学模型的准确性进行验证，接着对喷射器的运行特性以及影响其性能的设计参数进行研究。热交换器、冷凝器和蒸发器作为喷射器制冷系统中的关键部件也是喷射器制冷系统性能的重要影响因素，对其的研究包括热交换器中的温差以及工作流体出口过热度，冷凝温度以及冷凝器出口过冷度，蒸发温度以及蒸发器出口过热度对制冷系统性能的影响，最终得出在给定工况下的最优系统设计参数。在对制冷工质比较的基础上选择R134a为本设计采用的工质，并通过上述设计模型对喷射器关键截面进行设计，喷射器的轴向尺寸利用CFD分析进行研究设计，，对喷嘴出口位置的研究结果表明在大约1Dmix的距离时喷射器有更好的性能。接着提出喷射器性能分析模型对非设计工况点效率进行计算，最后对喷射器在选择运行工况范围内的失效行为提出解决措施。
[Abstract]:The extensive use of fossil fuels in the development of modern society has caused a series of energy and environmental problems. In order to realize the sustainable development of society, the focus of research has been shifted to clean and renewable energy. Low quality heat sources, such as solar energy and industrial waste heat, have replaced high quality mechanical energy. To some extent, it improves energy efficiency and environmental problems. However, the efficiency of ejector, which is the core of the ejector refrigeration cycle, restricts its large-scale application, thus increasing the efficiency of ejector. Reasonable design of ejector has become the focus of research on ejector refrigeration cycle. In this paper, engine exhaust gas is used as high temperature heat source, and engine exhaust gas is used to provide energy for ejector refrigeration cycle. On this basis, the mathematical model of the optimal design of the key section of the ejector is proposed, and the accuracy of the mathematical model is verified by comparing the experimental results with the known experimental results. Then the operating characteristics of the ejector and the design parameters affecting its performance are studied. Heat exchangers, condensers and evaporators are the key components of the ejector refrigeration system, which are also the important factors affecting the performance of the ejector refrigeration system. The effects of temperature difference in heat exchanger and superheat of working fluid outlet, condensation temperature and outlet undercooling degree of condenser, evaporation temperature and outlet superheat of evaporator on the performance of refrigeration system are studied. Finally, the optimal system design parameters under given working conditions are obtained. Based on the comparison of refrigerants, R134a is chosen as the working medium in this design, and the key sections of the ejector are designed through the above design model. The axial dimensions of the ejector are studied and designed by CFD analysis. The results of the study on the nozzle exit position show that the ejector has better performance at a distance of about 1Dmix. Then, the performance analysis model of the ejector is proposed to calculate the off-design working point efficiency. Finally, the measures to solve the failure behavior of the ejector in the range of selected operating conditions are put forward.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB657

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