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Using Direct Simulation Monte Carlo With Improved Boundary Conditions for Heat and Mass Transfer in Microchannel

机译：使用直接模拟蒙特卡洛和改进的边界条件进行微通道传热和传质

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摘要

Micro-electromechanical systems and nano-electromechanical systems have attracted a great deal of attention in recent years. The flow and heat transfer behaviors of microma-chines for separation applications are usually different from that of macro counterparts. In this paper, heat and mass transfer characteristics of rarefied nitrogen gas flows in microchannels are investigated using direct simulation Monte Carlo with improved pressure boundary conditions. The influence of aspect ratio and wall temperature on mass flowrate and wall heat flux in microchannels are studied parametrically. In order to examine the aspect ratio effect on heat and mass transfer behaviors, the wall temperature is set constant at 350 K and the aspect ratio of the microchannel varies from 5 to 20. The results show that as the aspect ratio increases, the velocity of the flow decreases, so does the mass flowrate. In a small aspect ratio channel, the heat transfer occurs throughout the microchannel; as the aspect ratio of the microchannel increases, the region of thermal equilibrium extends. To investigate the effects of wall temperature (T_w) on the mass flowrate and wall heat flux in a microchannel, the temperature of the incoming gas flow (T_(in)) is set constant at 300 K and the wall temperature varies from 200 K to 800 K while the aspect ratio is remained unchanged. Results show that majority of the wall heat flux stays within the channel entrance region and drops to nearly zero at the halfway in the channel. When T_w T_(in), the molecular number density of the flow drops rapidly near the inlet and the temperature of the gas flow increases along the channel. As T_w increases, the flow becomes more rarefied, the mass flowrate decreases, and the resistance at the entrance region increases. Furthermore, when T_w>T_(in), a sudden jump of heat transfer flux and temperature are observed at the exit region of the channel.
机译：近年来，微机电系统和纳米机电系统引起了极大的关注。用于分离应用的微通道的流动和传热行为通常与宏观对应物不同。本文采用改进的压力边界条件直接模拟蒙特卡洛方法研究了微通道中稀有氮气流的传热和传质特性。通过参数研究了长宽比和壁温对微通道中质量流量和壁热通量的影响。为了检查纵横比对传热和传质行为的影响，将壁温设置为恒定的350 K，微通道的纵横比设置为5到20。结果显示，随着纵横比的增加，速度会增加。流量减少，质量流量也减少。在小长宽比的通道中，传热发生在整个微通道中。随着微通道的长宽比增加，热平衡区域扩大。为了研究壁温（T_w）对微通道中质量流量和壁热通量的影响，将进入气流的温度（T_（in））设置为恒定于300 K，壁温从200 K变为800 K，而宽高比保持不变。结果表明，大部分壁热通量停留在通道入口区域内，并在通道的中途降至近零。当T_w ＜T_（in）时，在压力驱动条件和压力连续性的限制下，流的分子密度在进入区域短暂增加之后沿着流向降低。当T_w> T_（in）时，气流的分子密度在入口附近迅速下降，气流的温度沿通道增加。随着T_w的增加，流量变得越来越稀少，质量流量减少，并且入口区域的阻力增加。此外，当T_w> T_（in）时，在通道的出口区域观察到传热通量和温度的突然跳跃。

著录项

  • 来源
    《Journal of Heat Transfer》 |2010年第4期|p.041008.1-041008.9|共9页
  • 作者

    J. Yang; J. J. Ye; J. Y. Zheng; I. Wong; C. K. Lam; P. Xu; R. X. Chen; Z. H. Zhu;

  • 作者单位

    P. Tang Institute of Chemical Engineering Process and Machinery, Zhejiang University, Hangzhou 310027, China;

    P. Tang Institute of Chemical Engineering Process and Machinery, Zhejiang University, Hangzhou 310027, China;

    P. Tang Institute of Chemical Engineering Process and Machinery, Zhejiang University, Hangzhou 310027, China;

    Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, Los Angeles, CA 90095;

    Department of Mechanical Engineering, University of California, Berkeley, Berkeley, CA 94704;

    School of Aeronautics and Astronautics, Zhejang University, Hangzhou 310027, China;

    Zhejang Chengxin Pharm&Chem Equipment Co. Ltd., Taizhou 318012, China;

    Zhejang Chengxin Pharm&Chem Equipment Co. Ltd., Taizhou 318012, China;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    direct simulation Monte Carlo; heat flux; mass flowrate; microfluidics; pressure boundary conditions;

    机译：直接模拟蒙特卡洛;热通量质量流率;微流体压力边界条件;

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