QQ客服 官方微博 反馈留言

题名	周向非均匀受热圆管内充分发展段的对流换热研究; 周向非均匀受热圆管内充分发展段的对流换热研究
作者	1常春,电工研究所
学位类别	博士
答辩日期	2008-05-28
授予单位	中国科学院电工研究所
导师	1王志峰,电工研究所
关键词	太阳能热发电 换热器 熔融盐 变物性 对流换热 solar power plant heat exchanger molten salt variable properties convective heat transfer
其他题名	周向非均匀受热圆管内充分发展段的对流换热研究
中文摘要	周向非均匀热流边界条件下的圆管内对流换热问题，在换热设备中广泛存在，如聚光式太阳能热发电系统的吸热器和常规火电站、核电站使用的大型锅炉等。周向非均匀受热，常常导致换热设备面临工质过热，材料烧蚀、蠕变，结构疲劳破坏等一系列问题，熔融盐等换热工质的物性随温度发生变化使得上述问题愈加复杂。到目前为止，工程技术领域对解决该问题还缺乏便捷准确的方法。 本文即围绕熔融盐工质在太阳能高温热发电系统中运用时遇到的热流非均匀和工质变物性的核心问题，采用理论分析、实验测试与数值计算的方法展开研究，提出了在周向非均匀热边界条件下，常物性和变物性的流体工质在圆管内层流和湍流状态下的对流换热规律。其中，利用解析法求解了层流状态下，周向非均匀受热时圆管内对流换热规律。得到了换热管内壁面与流体之间的局部换热温差的表达式及局部的计算表达式。研究结果显示，在加热量相同的情况下，换热管周向非均匀受热时的最大局部换热温差是周向均匀受热时的3.54倍，显示了周向非均匀热流对换热管温度分布的重大影响。通过设计和搭建实验台，用实验方法分析了周向非均匀热流边界条件下，换热管壁面温度分布特点，并与周向均匀热流边界条件下的温度分布做了对比分析，显示出了巨大差异。用数值模拟的方法分析总结了该种特殊热流边界条件下的湍流换热规律，提出了湍流状态下，换热管内壁面与流体之间的局部换热温差的表达式及局部努塞尔特数的计算表达式，并与4个工况下的实验测量结果做了对比验证，相对误差小于8%。最后，考虑熔融盐物性变化因素影响，通过物性修正，提出了针对熔融盐工质在周向非均匀受热圆管内对流换热的局部换热温差的表达式及局部努塞尔特数的计算表达式。并在特定工况下，对修正公式与经典公式计算结果进行了对比分析。结果显示，本文公式在解决周向非均匀热流边界条件下的圆管内对流换热问题时，具有更强的针对性和更好的适应能力。 Convective heat transfer in circular tubes with non-uniform circumferential heat flux is widely existed in heat exchangers, for example, receivers of the concentrated solar thermal power plant, boilers of the coal power plant and boilers of the nuclear power plant. Heat transfer in a circular tube with non-uniform heat flux around its circumference is not as good as that with uniform heat flux, because of its insufficient heat exchange. Overheating, melting ablation, fatigue, thermal stress and corrosion are very likely to happen under such conditions, and the variation of thermal properties of heat transfer fluid such as molten salt makes the analysis of heat transfer more complex and difficult to get the solution. This dissertation is focusing on the analysis of heat transfer in circular tubes with non-uniform circumferential heat flux, and presents the solution by experimental, analytical and numerical researches. By analytical research, we got the local temperature difference between inner wall surface temperature of the tube and the fluid mean temperature in fully developed laminar flow; we also obtained the local equation at the same time. The results obtained shows that be heated with same energy input, the maximum temperature difference of non-uniform heat flux is 3.54 times than that of uniform heat flux. We compared the experimental results with the classical Dittus-Boelter formula and show that the formula produced by Dittus-Boelter can not be directly applied to solve the heat transfer in circular with non-uniform circumferential heat flux. By numerical heat transfer analysis, we also got the solution of local temperature difference and local Nu for heat transfer of fully developed turbulent flow in a circular tube under the same boundary condition. Compared with the experimental results, the relative error between numerical solution and experimental result is no larger than 8%. By comparison the results under several operating conditions, we show that the solution obtained here can also be applied to the molten salt with varying thermal properties by appending a modified coefficient.
语种	中文
公开日期	2010-10-18
页码	133
分类号	TM1
内容类型	学位论文
源URL	[http://ir.iee.ac.cn/handle/311042/6700]
专题	电工研究所_其他部门_其他部门_博士学位论文
推荐引用方式 GB/T 7714	1常春,电工研究所. 周向非均匀受热圆管内充分发展段的对流换热研究, 周向非均匀受热圆管内充分发展段的对流换热研究[D]. 中国科学院电工研究所. 2008.

个性服务

查看访问统计

相关权益政策

暂无数据

收藏/分享

除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。