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Interactions Between Parallel Unevenly Heated Minichannels During Flow Boiling of R134A

机译：R134A流动沸腾过程中平行不均匀加热的小通道之间的相互作用

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摘要

Transient pressure drop of individual channels during flow boiling of R134a in four 0.54 mm square parallel minichannels was experimentally studied in this work. The design of the test section enabled the experimenter to control and to vary heat flux independently in each channel in the range from 3.82 to 18.66 kW/m~2 at five different overall flow rates from 86 to 430 kg/m~2-s. Flow rate fluctuation in parallel channels due to the formation of bubbles under the nonuniform heat flux conditions caused significant oscillations in local pressure drop. Statistical analysis indicated that the pressure drop signal was normally distributed when boiling was stable with no incoming flow disturbance. Pressure drop distribution was highly skewed and multimodal when significant evaporation rate at low mass fluxes led to rapid annular flow formation, reducing the free flow of incoming fluid. Cross-correlation analysis revealed a strong interaction between minichannels having the highest heat flux difference among the set of channels. The least heated channel was more sensitive to the fluctuations in other channels. Cross-correlation between the most heated channel and the adiabatic one was estimated to be 39% when the total flow rate was the lowest, 86 kg/m~2-s. The power of the relationship between channels dropped significantly as the flow rate increased. Less than 5% of data points could be considered cross-correlated at the highest flow rate of 430 kg/m~2-s. Increasing the two-phase pressure drop across each channel caused higher resistance to the incoming disturbances and led to less interchannel interaction. This study of the channels interaction in a system of parallel, nonuniformly heated minichannels can be used as a tool to identify and quantify instabilities and reversed flow conditions.
机译：在这项工作中，通过实验研究了在四个0.54 mm方形平行小通道中R134a流动沸腾过程中各个通道的瞬态压降。测试部分的设计使实验人员可以在三种不同的总流速从86到430 kg / m〜2-s的情况下，在3.82到18.66 kW / m〜2的范围内独立控制和改变每个通道中的热通量。在不均匀的热通量条件下，由于气泡的形成，平行通道中的流量波动引起局部​​压降的明显波动。统计分析表明，当沸腾稳定且没有输入流干扰时，压降信号呈正态分布。当低质量通量下的显着蒸发速率导致快速的环形流动形成时，压降分布高度偏斜并且是多峰的，从而减少了进入流体的自由流动。互相关分析显示，在一组通道中，具有最高热通量差的迷你通道之间存在强烈的相互作用。加热最少的通道对其他通道的波动更为敏感。当总流量最低（86 kg / m〜2-s）时，加热最强的通道与绝热通道之间的互相关估计为39％。随着流量的增加，通道之间关系的功率显着下降。在430 kg / m〜2-s的最高流速下，只有不到5％的数据点被认为是互相关的。跨每个通道的两相压降的增加导致对传入干扰的较高抵抗力，并导致较少的通道间交互作用。对平行，不均匀加热的微型通道系统中通道相互作用的研究可以用作识别和量化不稳定和逆流条件的工具。

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  • 来源
    《Heat Transfer Engineering》 |2016年第12期|921-937|共17页
  • 作者

    DOLAANA KHOVALYG; PREDRAG S. HRNJAK; ANTHONY M. JACOBI;

  • 作者单位

    Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 W. Green Street, Urbana, IL 61801, USA;

    Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA;

    Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
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  • 正文语种 eng
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