This paper presents the results of an experimental investigation on pressure drop characteristics for R134a and R134a-lubricant mixtures in multiport flat tubes (MPFT). An experimental facility has been set up, carefully validated and used to determine the pressure drop value in the two-phase flow regime inside extruded MPFT with hydraulic diameters from 0.91 mm to 0.53 mm with either triangular or rectangular channel cross sections with and without an axial fin structure. Based on the investigation published in Knipper et al. (2019), the operating parameters have been varied within a broad range to ensure a high degree of reliability and comparability to pressure drop correlations. In addition, the nominal oil content has been varied between 0 and 7% by weight. A good agreement of the pressure drop data with several correlations can again be confirmed for most of the flat tubes. With respect to the urgent need for reliable correlations regarding low liquid only Reynolds numbers $\left(R{e}_{lo}=800-5000\right)$, the authors present an approach based on the Cavallini et al. (2006) correlation that is also considering the surface roughness of the tube. For both, pure R134a and R134a-PAG-oil-mixtures, a good agreement with the newly determined data can be achieved and, thus, an enlarged range of applicability can be stated.

本文介绍了对多口扁管（MPFT）中R134a和R134a润滑剂混合物的压降特性进行实验研究的结果。已经建立了一个实验设施，经过仔细验证，并用于确定水力直径为0.91 mm至0.53 mm的，具有三角形或矩形通道横截面（带或不带轴向）的MPFT内两相流态中的压降值鳍结构。根据发表在Knipper等人的调查。（2019），操作参数已在很大范围内变化，以确保高度的可靠性和压降相关性的可比性。另外，名义油含量在0至7重量％之间变化。对于大多数扁平管，可以再次确认压降数据具有多种相关性。关于迫切需要仅低流动性的雷诺数的可靠相关性$（\mathrm{[R}{Ë}_{升Ø}=800-5000）$，作者提出了一种基于Cavallini等人的方法。（2006年）的相关性也考虑了管的表面粗糙度。对于纯R134a和R134a-PAG油混合物，都可以与新确定的数据很好地吻合，因此可以扩大适用范围。