Abstract This study experimentally investigated the boiling flow patterns, local heat transfer coefficients, and pressure drops of R32/lubricant oil mixtures flowing inside a horizontal multiport extruded tube having rectangular minichannels. The experiments were carried out in a mass flux range of 50–400 kg m−2 s−1, heat flux range of 5–40 kW m−2, and oil circulation up to 3.7 wt% at an evaporation temperature of 15 °C. The boiling flow patterns were visualized by using a setup that consisted of horizontal multiple square minichannels, each with a hydraulic diameter of 1.0 mm. The heat transfer coefficients of the R32/oil mixtures were lower compared with those of pure R32 and decreased with increasing oil concentration at lower heat fluxes, while they were higher for conditions of higher heat flux and low vapor quality. In addition, the heat transfer coefficients of the mixtures significantly decreased at a lower mass flux and in a higher vapor quality region. The frictional pressure drops of the R32/oil mixtures was higher compared with that of pure R32 and increased with increasing mass flux, vapor quality, and oil concentration. The effect of oil concentration on the pressure drop was significant at the higher vapor quality region. Furthermore, the pressure drops increased with increasing heat flux for lower to middle vapor quality, in contrast to pure refrigerants.

中文翻译：

---

润滑油对多端口管内 R32 沸腾传热和流动模式的影响

摘要 本研究通过实验研究了在具有矩形微通道的水平多端口挤压管内流动的 R32/润滑油混合物的沸腾流动模式、局部传热系数和压降。实验在 50-400 kg m-2 s-1 的质量通量范围、5-40 kW m-2 的热通量范围和高达 3.7 wt% 的油循环中进行，蒸发温度为 15 °C . 沸腾流动模式通过使用由水平多个方形微型通道组成的装置进行可视化，每个微型通道的水力直径为 1.0 毫米。与纯 R32 相比，R32/油混合物的传热系数较低，并且在较低的热通量下随着油浓度的增加而降低，而在较高的热通量和低蒸汽质量的条件下它们较高。此外，在较低的质量通量和较高的蒸汽质量区域中，混合物的传热系数显着降低。与纯 R32 相比，R32/油混合物的摩擦压降更高，并且随着质量通量、蒸汽质量和油浓度的增加而增加。在较高的蒸汽质量区域，油浓度对压降的影响是显着的。此外，与纯制冷剂相比，对于中低蒸汽质量，压降随着热通量的增加而增加。在较高的蒸汽质量区域，油浓度对压降的影响是显着的。此外，与纯制冷剂相比，对于中低蒸汽质量，压降随着热通量的增加而增加。在较高的蒸汽质量区域，油浓度对压降的影响是显着的。此外，与纯制冷剂相比，对于中低蒸汽质量，压降随着热通量的增加而增加。