不同换热关联式在超临界R134a平均换热系数计算中的对比
首发时间:2015-11-26
摘要:着眼于有机工质跨临界循环/超临界循环应用,结合实验测量研究,对超临界压力下有机工质换热关联式的适用性进行了考察。以R134a为工质,在工质处于超临界压力状态和水冷边界条件下,实验测量了逆流式套管冷却器工质侧的平均换热系数。分别基于6个换热关联式计算得到了实验工况条件下的R134a侧平均换热系数计算值。对比各关联式下的计算值与实验测量结果发现,基于常物性的Dittus-Boelter关联式和Gnielinski关联式所得R134a侧平均换热系数计算值与实验测量结果分别符合在10%和15%以内;而基于加热边界条件的换热关联式以及CO2超临界换热关联式的计算结果,与实测结果偏差较大。研究还表明,各个换热关联式在工质处于液相区时所给出的R134a侧平均换热系数计算值与实验测量结果的偏差相对较小,而在工质处于伪临界状态区时偏差相对较大。
关键词: 工程热物理 超临界换热关联式 套管冷却器;R134a
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Comparation of several correlations in the calculation of average heat transfer coefficient of R134a at supercritical pressures
Abstract:The applicability of several correlations on the organic fluid at supercritical pressures were investigated, in the background of applications of transcritical and supercritical cycles . Taking R134a as the working fluid, the average heat transfer coefficients of the innei side of a contra-flow double tube heat exchanger were measured, The prediction precision of correlations which are based on constant physical property or local heat transfer respectively were discussed. Under the experimental conditions, the average heat transfer coefficients obtained from the experiment were compared with those from the mode calculations which were based on 6 different correlations respectively .It is found that the Dittus-Boelter and Gnielinski correlations which were based on constant physical properties, have the best prediction precision,with deviationsfrom no more than 10% and 15% respectively, while the other correlations based on heating boundary condition or CO2 have relatively poor prediction accuracy. All the correlations performed better in the liquid-like region than in the pseudo-critical region.
Keywords: engineering thermophysics;supercritical heat transfer;double tube heat R134a
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No.4662872111329214****
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