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首页> 外文期刊>Experimental Thermal and Fluid Science: International Journal of Experimental Heat Transfer, Thermodynamics, and Fluid Mechanics >Experimental study of the heat transfer characteristics of supercritical pressure R134a in a horizontal tube
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Experimental study of the heat transfer characteristics of supercritical pressure R134a in a horizontal tube

机译：水平管中超临界压力R134a传热特性的实验研究

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摘要

This study experimentally investigates the heat transfer characteristics of R134a at supercritical pressures in a 10.3 mm horizontal tube to provide basic heat transfer data and heat transfer correlation. The experiments cover wide parameter ranges of p = 1.02-1.2 p(c), G = 400-1500 kg/m(2)s, and q '' = 20-100 kW/m(2). The influences of the heat flux, the mass flux and the pressure on the wall temperature and heat transfer coefficient are analyzed. The results show that in a horizontal tube, the buoyancy effect due to density variations causes non-uniformity of the wall temperatures in the circumferential direction. The heat transfer deteriorates along the top surface at high q ''/G (heat flux to mass flux ratio), while the heat transfer along the bottom surface is enhanced at all operating conditions. The pressure mainly affects the heat transfer coefficient on the bottom surface at small q ''/G because of the c(p) variation with pressure. Nine heat transfer correlations are evaluated with the results showing that the Dittus-Boelter type correlations with property modifications have acceptable accuracy for the bottom surface but all of the correlations fail to predict the heat transfer coefficients on the top surface. A new correlation using a buoyancy parameter to include the buoyancy effect is then developed to predict the top surface temperatures and a DB type correlation with property modifications is used to predict the bottom surface temperatures. Results show that the new correlations agree well with the data.
机译：该研究通过在10.3mm水平管中实验在超临界压力下研究R134a的传热特性，以提供基本的传热数据和传热相关性。实验涵盖p = 1.02-1.2 p（c），g = 400-1500 kg / m（2）s和q''= 20-100 kW / m（2）的宽参数范围。分析了热通量，质量磁通量和压力对壁温和传热系数的影响。结果表明，在水平管中，由于密度变化引起的浮力效果导致围绕圆周方向的壁温度的不均匀性。热传递以高Q'/ g（热通量至质量磁通比）沿顶表面劣化，而沿底表面的热传递在所有操作条件下增强。由于C（P）的压力变化，压力主要影响小Q'/ g的底表面上的传热系数。评估九次传热相关性，结果表明，与性能修改的DTTUS-Boelter型相关性具有可接受的底表面的准确性，但所有相关性都不能预测顶表面上的传热系数。然后开发了使用浮力参数来包括浮力效果的新相关性以预测顶部表面温度，并且使用与性能修改的DB类型相关性来预测底表面温度。结果表明，新的相关性与数据很好。

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