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首页> 外文期刊>International Journal of Heat and Mass Transfer >Experimental comparison of the heat transfer of supercritical R134a in a micro-fin tube and a smooth tube
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Experimental comparison of the heat transfer of supercritical R134a in a micro-fin tube and a smooth tube

机译：超临界R134a在微翅片管和光滑管中传热的实验比较

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摘要

Measured heat transfer rates of supercritical R134a were compared for flows in a horizontal micro-fin tube and in a smooth tube for mass fluxes from 100 to 700 kg m(-2) s(-1), heat fluxes from 10 to 70 kW m(-2), and pressures from 4.26 to 5 MPa. The results showed that the micro-fin tube wall temperatures had smaller changes as the heat flux was increased than on the smooth tube. The heat transfer coefficients along the top of the smooth tube are reduced more by the buoyancy effect than in the micro-fin tube. Then, the results were used to evaluate four buoyancy criteria for horizontal flows for both the smooth tube and micro-fin tube with the Gr(b)/Re-b(2.0) (rho(b)/rho(w)) x/d criterion found to give the best prediction accuracy for both types of tubes. The threshold for die onset of the buoyancy effect in the smooth tube was around 100 but was around 2000 in the micro-fin tube, which indicates that the effect of buoyancy is greatly reduced in the micro-fin tube. Comparisons of the measured heat transfer coefficients for all 5520 experimental data points showed that the heat transfer coefficient in the micro-fin tube was 1.68 times that in the smooth tube on the top and 1.59 times that in the smooth tube on the bottom. (C) 2018 Elsevier Ltd. All rights reserved.
机译：比较了在水平微翅片管和光滑管中测量的超临界R134a的传热速率，其质量通量为100至700 kg m（-2）s（-1），热通量为10至70 kW m （-2），压力为4.26至5 MPa。结果表明，与热管相比，随着热通量的增加，微翅片管壁温度的变化较小。与微型翅片管相比，通过浮力作用，沿光滑管顶部的传热系数降低得更多。然后，将结果用于用Gr（b）/ Re-b（2.0）（rho（b）/ rho（w））x /评估光滑管和微翅片管水平流动的四个浮力标准。 d标准被发现可以为两种类型的管提供最佳的预测精度。光滑管中的浮力作用的模具开始的阈值在100左右，而在微翅片管中是大约2000，这表明在微翅片管中浮力的作用大大降低。比较所有5520个实验数据点的测得的传热系数，结果表明，微翅片管的传热系数是顶部光滑管的1.68倍，底部光滑管的1.59倍。 （C）2018 Elsevier Ltd.保留所有权利。

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