This is the second report on the development of heat loss model for flow boiling experiments conducted onboard International Space Station (ISS). In the first paper (Inoue et al. 2021), a heat loss model was developed for subcooled flow boiling experiments, a single-phase liquid at the inlet of heated test tube was discussed. In the present report, a heat loss model is developed for saturated flow boiling experiments, where two-phase liquid and vapor mixture flows to the inlet of heated test tube. The accurate evaluation of vapor quality is essential for the exact investigation of gravity effects on flow boiling. Since long straight test tube could not be introduced due to the strict dimensional restriction of experimental setup in the ISS experiments, a high-power serpentine-type preheater is employed for adjusting vapor quality at the inlet of heated test tube. Therefore, in addition to the heat loss model for subcooled flow boiling developed in the first report, where the temperature of subcooled liquid is measured directly behind the preheater, an additional heat loss model for the sections including the preheater and the downstream piping is needed. A new heat loss model is developed based on the heat transfer data obtained in the preliminary heat loss experiments with liquid single-phase flow and in the liquid-vapor two-phase flow where power is supplied only to the preheater. For the ISS experiments, the amount of heat loss is quite large due to the existence of the avionics air flowing inside the experimental setup. Decrease of vapor quality due to the heat loss increases as the mass velocity decreases and it reaches a difference of predicting quality as much as 0.53 in an extreme example for low mass velocity of 50 kg/(m²·s). Developed heat loss model can estimate vapor quality at the inlet of heated test tube with sufficient accuracy for investigating detailed flow boiling characteristics under microgravity conditions.

这是关于在国际空间站 (ISS) 上进行的流动沸腾实验的热损失模型开发的第二份报告。在第一篇论文（Inoue 等人，2021 年）中，为过冷流沸腾实验开发了热损失模型，讨论了加热试管入口处的单相液体。在本报告中，为饱和流动沸腾实验开发了热损失模型，其中两相液体和蒸汽混合物流向加热试管的入口。蒸汽质量的准确评估对于精确研究重力对流动沸腾的影响至关重要。由于国际空间站实验中实验装置的尺寸限制严格，无法引入长直试管，加热试管入口采用大功率蛇形预热器调节蒸汽质量。因此，除了第一份报告中开发的过冷流动沸腾的热损失模型（其中过​​冷液体的温度直接在预热器后面测量）之外，还需要一个额外的热损失模型，用于包括预热器和下游管道在内的部分。基于在液体单相流和仅向预热器供电的液气两相流的初步热损失实验中获得的传热数据，开发了一种新的热损失模型。对于国际空间站实验，由于实验装置内部流动的航空电子空气的存在，热损失量相当大。² ·s)。开发的热损失模型可以以足够的精度估计加热试管入口处的蒸汽质量，以研究微重力条件下的详细流动沸腾特性。