【作者】 谢涛；

【导师】 邬田华；

【作者基本信息】 华中科技大学 ， 工程热物理， 2007， 硕士

【摘要】 混合对流中的浮升力存在某些令人惊奇的现象,前人为了理解和利用这种现象开展了大量相关的研究,目前对于含浮升力的管道流动,Launder Sharma低雷诺数k-ε湍流模型在数值计算上具有较好的适用性,这些构成了我们研究的前提,即在热力系统中经常遇到的流体在一个表面加热而另一个表面近似绝热的环形垂直通道的流动与换热。本研究将主要从数值计算方面进行。前期解决了如研究数值计算方法、选择湍流模型、确定计算步骤等问题。后期本研究从一通用于管流的FORTRAN程序入手,分析其主体框架,清除无用的语句,并在对此认识的基础上进行对适用于本研究模型的程序的编写。通过不断的修改调试,最后可以得到收敛的解。得到初步的解后,我们将参考类似的实验获得的若干数据与计算结果进行比较。通过参考的实验,我们选用的具体实验模型为:竖直环形管长5m,中间有3m长的一段实验段,环形管外壁绝热直径140mm,内壁实验段均匀加热直径76mm。另外,计算的范围是Re:1300~4000,加热功率:约7.5 kw。对于数据分析,将进行三种类型的比较。一是直观的参考实验数据的分析;二是无参考实验数据的多种数据比较;三是同条件下计算数据与若干参考实验数据的比较。通过比较可以发现目前程序的编制对于向上流动适用性差。单纯对于向下流动时,该程序在低雷诺数时能得到较精确的结果且能反映相关特性。因而该程序还不具有广泛的适用性。更多还原

【Abstract】 Many researches have been carried out about explaining and making use of the phenomenon astonishing researchers a lot, which comes out of buoyancy in mixed convection. Presently Launder Sharma low Reynolds number k-εturbulent model has been reported to describe the features of tube flow involving buoyancy perfectly well. Therefore it is available to do a further research about the heat transfer and flow in vertical annular passage that frequently seen as one surface is heated while the other adiabatic in various thermal systems.In this paper, research was mainly done through numerical computation. In the beginning, problems like choosing the exact computation method and turbulent model, determining the calculation procedures, were solved. Later, we started from a generalized FORTRAN program pointing to circular tube flow, then reserved the right sentences, and made a program which applied to our model. Through months of continuous modification and debugging time, converged solution can be obtained. Then, some of the referential experiment data were chosen to compare with those obtained from computation. And the simulated model was also determined from the referential experiment -- the vertical annular passage is 5 m long, including a test section 3 m long. The outer surface is considered adiabatic with a diameter of 140 mm while inner uniformly heated of 76 mm. In addition, calculation parameters were within the Reynolds number from 1300 to 4000 and a heating power 7.5 kw.Data analysis can be categorized into three types. One is direct referential experiment data analysis. Second is comparisons among data without those from experiment. The last is the comparison between computational data and some of the referential experiment data under the same conditions. Through comparisons, it can be concluded that the program currently is not still suitable to describe the features in a wide range, especially in upward flow, though it can reflect some features in downward flow in low Reynolds number quite well.更多还原