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An investigation of the flow distribution through unglazed transpired-plate solar air heaters.

机译：通过无玻璃透明板式太阳能空气加热器的流量分布研究。

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摘要

Unglazed transpired-plate solar air heaters have proven effective in heating air on a once-through basis. However, the basic theory for these collectors has not evolved to the point where the flow distribution can be predicted. The purpose of this thesis is to characterize the flow distribution through the collector so that the underlying principles of the flow field can be established.; The maximum thermal energy gain for vertically oriented collectors occurs when the collector flow rate is established through buoyancy alone. At buoyancy driven flow rates, up to 45% of the heat transfer from the absorber to the air takes place in the collector's plenum. The effect of buoyancy on the inlet flow distribution is that near stagnation flow occurs at the top of the absorber, and relatively high inlet flow (suction) velocities at the bottom of the absorber. The absorber temperature will be high at near stagnation conditions. Reverse flow through the absorber will occur if the collector flow rate is fixed at a level below the collector's buoyancy driven flow rate, resulting in a thermal energy loss. Nonuniformity of the inlet flow distribution does not significantly reduce the absorber's heat transfer rate: as the suction velocity decreases, the air temperature rise increases. This relationship balances out the local heat transfer rate for the air passing through the absorber. For collectors experiencing nonuniform wind induced pressure distributions, the overall result is the same, but the collector flow rate must be increased to prevent reverse flow. A small plenum aspect ratio will reduce viscous and acceleration effects in the plenum, resulting in more uniform flow distributions. This strategy will reduce pumping head requirements, and the thermal efficiency will not be reduced by heat transfer from the plenum air stream to the absorber plate. (Abstract shortened by UMI.)
机译：经证明，无釉透明板式太阳能空气加热器可有效地一次加热空气。但是，这些收集器的基本理论尚未发展到可以预测流量分布的地步。本文的目的是表征流经集热器的流量分布，从而建立流场的基本原理。当仅通过浮力确定集热器流量时，就会发生垂直定向的集热器的最大热能增益。在浮力驱动的流速下，从吸收器到空气的热传递的多达45％发生在收集器的气室中。浮力对入口流量分布的影响是在吸收器的顶部出现了近停滞流，在吸收器的底部出现了相对较高的入口流速（吸力）。在接近停滞状态时，吸收器温度会很高。如果收集器的流量固定在低于收集器的浮力驱动流量的水平，则会发生通过吸收器的反向流动，从而导致热能损失。入口流量分布的不均匀不会显着降低吸收器的传热速率：随着吸气速度的降低，空气温度的升高会增加。这种关系平衡了通过吸收器的空气的局部传热率。对于遇到不均匀的风致压力分布的集热器，总体结果是相同的，但是必须提高集热器流速以防止逆流。较小的气室纵横比将减少气室中的粘性和加速作用，从而导致更均匀的流量分布。这种策略将减少对泵压头的需求，并且热效率不会因从增压空气流到吸收板的热传递而降低。 （摘要由UMI缩短。）

著录项

  • 作者

    Gunnewiek, Lowy H.;

  • 作者单位

    University of Waterloo (Canada).;

  • 授予单位 University of Waterloo (Canada).;
  • 学科 Engineering Mechanical.
  • 学位 M.A.Sc.
  • 年度 1994
  • 页码 145 p.
  • 总页数 145
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;
  • 关键词

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