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Effects of geometry and fluid properties during condensation in minichannels: experiments and simulations

机译：小通道冷凝过程中几何形状和流体特性的影响：实验和模拟

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摘要

The present paper aims at investigating the condensation process inside minichannels, at low mass fluxes, where bigger discrepancies from conventional channels can be expected. At high mass flux, the condensation in minichannels is expected to be shear stress dominated. Therefore, models originally developed for conventional channels could still do a good job in predicting the heat transfer coefficient. When the mass flow rate decreases, the condensation process in minichannels starts to display differences with the same process in macro-channels. With the purpose of investigating condensation at these operating conditions, new experimental data are here reported and compared with data already published in the literature. In particular, heat transfer coefficients have been measured during R134a and R1234ze(E) condensation inside circular and square cross section minichannels at mass flux ranging between 65 and 200kg m(-2)s(-1). These new data are compared with those of R32, R717, R290, R152a to show the effect of channel shape and fluid properties and to assess the applicability of correlations developed for macroscale condensation. For this purpose, a new criterion based on the Weber number is presented to decide when the macroscale condensation correlation can be applied. The present experimental data are also compared against three-dimensional Volume of Fluid (VOF) simulations of condensation in minichannels with circular and square cross section. This comparison allows to get an insight into the process and evaluate the main heat transfer mechanisms.
机译：本文旨在研究低通量的微型通道内的冷凝过程，在这种情况下，与常规通道的差异可能更大。在高通量的情况下，预计微通道中的凝结主要是剪切应力。因此，最初为常规通道开发的模型仍然可以很好地预测传热系数。当质量流量降低时，微型通道中的冷凝过程开始显示出与宏通道中相同过程的差异。为了研究在这些操作条件下的冷凝，此处报告了新的实验数据，并将其与文献中已发布的数据进行了比较。特别是，在圆形和方形横截面微型通道内的R134a和R1234ze（E）冷凝期间，以65至200kg m（-2）s（-1）的质量通量测量了传热系数。将这些新数据与R32，R717，R290，R152a的数据进行比较，以显示通道形状和流体特性的影响，并评估为大型冷凝开发的相关性的适用性。为此，提出了基于韦伯数的新准则，以决定何时可以应用宏缩合相关性。本实验数据也与具有圆形和正方形横截面的微型通道中的冷凝的三维流体体积（VOF）模拟进行了比较。这种比较可以深入了解过程并评估主要的传热机制。

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  • 来源
    《Heat and mass transfer》 |2019年第1期|41-57|共17页
  • 作者

    Toninelli Paolo; Bortolin Stefano; Azzolin Marco; Del Col Davide;

  • 作者单位

    Univ Padua, Dipartimento Ingn Ind, Via Venezia 1, I-35131 Padua, Italy;

    Univ Padua, Dipartimento Ingn Ind, Via Venezia 1, I-35131 Padua, Italy;

    Univ Padua, Dipartimento Ingn Ind, Via Venezia 1, I-35131 Padua, Italy;

    Univ Padua, Dipartimento Ingn Ind, Via Venezia 1, I-35131 Padua, Italy;

  • 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
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