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Experimental investigation of the two-phase local heat transfer coefficients for condensation of R134a in a micro-structured plate heat exchanger
Heat and Mass Transfer ( IF 1.7 ) Pub Date : 2021-06-05 , DOI: 10.1007/s00231-021-03091-0
Ru Wang , Tingyan Sun , Anja-Elsa Polzin , Stephan Kabelac

Plate heat exchangers are widely used for two-phase heat transfer in the industrial applications, and recently more attention has been paid to the plate heat exchangers with enhanced surface due to their better heat transfer performance. In this paper, the local condensation heat transfer coefficients are studied using R134a in a micro-structured plate heat exchanger. In order to obtain a more accurate prediction model, a series of measurements are conducted under various operating conditions. The mass flux of R134a varied from 47 kg/m2s to 77 kg/m2s, the saturation pressure in the condenser ranged from 6.32 bar to 8.95 bar, and the value of the heat flux was between 13 kW/m2 and 22 kW/m2. The local two-phase Nusselt number increases with the increase of the mass flux. As the saturation pressure increases, the local two-phase Nusselt number increase at the beginning of the condensation and decrease at the end of the condensation. However, the effect of heat flux on local heat transfer is irregular, due to the interaction of these parameters in the experiment. Comparing with the unstructured plate heat exchanger, R134a condenses faster at the beginning of the process in the micro-sturctured plate heat exchanger, and the local heat transfer performs better when the vapor quality is lower. Combing with the phenomenon that the overall heat flux in micro-structured plate is larger under the same working conditions, it shows that the overall heat transfer of the micro-structured plate is improved, but the local heat transfer uprades only at lower vapor qualities. A new correlation is developed, it predicts all the experimental data within the root mean square error 10%, and a new correlation for the waterside is suggested as well.



中文翻译:

R134a在微结构板式换热器中冷凝两相局部传热系数的实验研究

板式换热器在工业应用中广泛用于两相传热,近来由于具有更好的传热性能,增强表面的板式换热器受到越来越多的关注。在本文中,在微结构板式换热器中使用 R134a 研究了局部冷凝传热系数。为了获得更准确的预测模型,在各种运行条件下进行了一系列的测量。R134a 的质量通量在 47 kg/m 2 s 到 77 kg/m 2 s 之间变化,冷凝器中的饱和压力范围从 6.32 bar 到 8.95 bar,热通量值在 13 kW/m 2和22 千瓦/米2. 局部两相努塞尔数随着质量通量的增加而增加。随着饱和压力的增加,局部两相努塞尔数在冷凝开始时增加,在冷凝结束时减小。然而,由于实验中这些参数的相互作用,热通量对局部传热的影响是不规则的。与非结构化板式换热器相比,R134a在微结构板式换热器过程开始时冷凝速度更快,蒸汽质量较低时局部传热效果更好。结合相同工况下微结构板整体热通量较大的现象,表明微结构板整体传热得到改善,但局部传热仅在较低的蒸汽质量下才会提高。开发了一种新的相关性,它预测所有实验数据均在 10% 的均方根误差内,并且还建议了水边的新相关性。

更新日期:2021-06-05
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