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Natural convection heat transfer from enclosed helical coils.

机译:来自封闭螺旋线圈的自然对流换热。

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摘要

Experiments were conducted to investigate natural convection heat transfer from enclosed helical coils in a vertical orientation. Coils ranging in mean diameter from 26.8 to 88.7 mm were tested in combinations of two, three and four coils, and as single coils enclosed in a shell of 100 mm inner diameter. A model was developed to determine the distribution of the forced convection flow rate in the tubes. A dimensional analysis was also carried out to determine the dimensionless parameters that are relevant to the natural convection heat transfer on the shell side of the enclosure. Heated propylene glycol was pumped inside the coils, while water circulated naturally on the shell-side of the heat exchanger. Validation tests were conducted using a straight tube of the same diameter as that used for the coils in the same shell diameter. Eleven configurations, including single foils, were tested at power settings between 200 W and 3000 W, and tube-side flow rates between 0.010 and 0.035 kg/s.The measured flow rate distribution and pressure drop were in good agreement with the theoretical predictions. The Nusselt number for the shell-side heat transfer, based on the hydraulic diameter of the enclosure, was found to depend on a modified Rayleigh number and the dimensionless flow space, which is a function of the shell-to-coil diameter ratio. The Nusselt number is also a function of the number of coils and the flow number, when the latter is less than unity. The function for the experimental Nusselt number was in general agreement with that predicted by the dimensional analysis. Correlations are presented covering the range of modified Rayleigh number, flow number and flow space of interest for the coils tested. A general correlation covering all flow numbers, and flow space less than 1.5 is NuFor any configuration of coils and their enclosure, an equivalent annulus exists, which is obtained by using an equivalent diameter of the coil(s) as the diameter of the imaginary inner solid cylinder. The resulting annular space is the flow space and the dimensionless form is the dimensionless flow space S
机译:进行实验以研究垂直方向上封闭螺旋线圈的自然对流传热。测试了两个,三个和四个线圈组合的平均直径范围为26.8至88.7 mm的线圈,并且将单个线圈封装在内径为100 mm的外壳中。开发了一个模型来确定管道中强制对流流速的分布。还进行了尺寸分析,以确定与外壳壳侧自然对流传热相关的无因次参数。将加热的丙二醇泵入盘管内部,同时水在热交换器的壳侧自然循环。验证测试使用的是直管,该直管的直径与壳直径相同的线圈的直径相同。在200 W至3000 W的功率设置和0.010至0.035 kg / s的管侧流速下测试了包括单箔在内的11种配置,测得的流速分布和压降与理论预测相吻合。发现基于壳体的水力直径的壳侧传热的努塞尔数取决于修改后的瑞利数和无因次流动空间,该空间是壳与线圈直径比的函数。当后者小于一时,努塞尔数也是线圈数和流量的函数。实验努塞尔数的函数与尺寸分析预测的函数基本一致。提出的相关性涵盖了所测试线圈的修改的瑞利数,流动数和感兴趣的流动空间的范围。涵盖所有流数且流空间小于1.5的一般相关系数为Nu对于线圈和其外壳的任何配置,都存在等效环,这是通过将线圈的等效直径用作虚构内径来获得的实心圆柱体。最终的环形空间是流动空间,无量纲形式是无量纲流动空间S

著录项

  • 作者

    Ajele, Oladele Josiah.;

  • 作者单位

    Technical University of Nova Scotia (Canada).;

  • 授予单位 Technical University of Nova Scotia (Canada).;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 1995
  • 页码 287 p.
  • 总页数 287
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 耳科学、耳疾病;
  • 关键词

  • 入库时间 2022-08-17 11:49:41

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