This paper carries out an experimental investigation on R455A, a low GWP (148) non azeotropic mixture, to determine its performance in terms of flow boiling heat transfer coefficient and pressure drop in a smooth circular horizontal stainless-steel tube, with an internal diameter of 6 mm. The effect of the operating parameters, such as mass flux (from 300 to 500 kg‧m⁻²‧s⁻¹), bubble saturation temperature (from 10 to 40 °C), heat flux (from 5 to 40 kW‧m⁻²) and vapor quality (between 0 and 1) is analyzed. Results show an increase of the heat transfer coefficient with mass and heat flux, while it decreases with saturation temperature. On the other hand, pressure drop increases with mass flux, and decreases with bubble saturation temperature. An assessment of several predictive methods from literature is finally conducted. Two-phase heat transfer methods based on an exclusive convective contribution can predict quite well the experimental results, while all other methods improve their statistics once a glide-related modification on the nucleate boiling contribution is assumed. The fictional pressure gradient results are well fitted with the separated flow model of Müller Steinhagen and Heck and with the Cicchitti two-phase viscosity expression considering a homogeneous flow approach.

本文对低GWP（148）非共沸混合物R455A进行了实验研究，以确定其在光滑圆形水平不锈钢管中的沸腾传热系数和压降方面的性能。 6毫米 操作参数，诸如质量流量的（300〜500kg‧m效果^-2 ‧s ^-1），气泡饱和温度（从10到40℃），热通量（从5到40kW‧m ^{- 2}）并分析蒸气质量（介于0和1之间）。结果表明，传热系数随质量和热通量的增加而增加，而随饱和温度的降低而减小。另一方面，压降随着质量通量而增加，并且随着气泡饱和温度而降低。最后对文献中的几种预测方法进行了评估。基于唯一对流贡献的两相传热方法可以很好地预测实验结果，而所有其他方法都可以改善其统计数据，前提是假设与滑行有关的对核沸腾贡献的修正。虚构的压力梯度结果与MüllerSteinhagen和Heck的分离流动模型以及考虑均相流动方法的Cicchitti两相粘度表达式非常吻合。