Two series of flow boiling experiments have been conducted onboard the International Space Station (ISS) as a part of the TPF (Two-Phase Flow) experiment promoted by JAXA during July 2017–March 2018, February 2019–July 2019. Microgravity data on two-phase flow and heat transfer in flow boiling of n-Perfluorohexane (FC-72) have been obtained by a copper heated test tube and a transparent glass heated tube in a wide experimental range of mass velocity, liquid subcooling, vapor quality and heat flux. Furthermore, detailed two-phase flow behaviors have been observed by using high frame rate camera in the unheated observation section. In order to elucidate the accurate influence of gravity on flow boiling, it is essential to compare the heat transfer data and two-phase flow behaviors obtained under normal (terrestrial) gravity and microgravity environments at the same flow and heating conditions. However, both experiments cannot be performed by using the same experimental apparatus and under the same thermal environmental conditions. In addition, the heat loss cannot be negligible due to the forced avionics air flow inside the experimental apparatus in ISS. Therefore, exact evaluation of the fluid conditions at the inlet of the heated test tube requires the heat loss model with high-accuracy. In the present paper, the heat loss models for evaluating the degree of liquid subcooling at the inlet of the heated test tube and net heat flux from the heated tube to test fluid has been developed by using the results of preliminary heat loss experiments conducted onboard ISS. The correction of the degree of liquid subcooling by the proposed heat loss models is not negligible for the accurate analysis of gravity effects. The accuracy of the heat loss models has been verified through the evaluation of heat transfer coefficients for single-phase turbulent forced convection obtained from the heating experiments onboard ISS.

作为JAXA在2017年7月至2018年3月，2019年2月至2019年7月进行的TPF（两相流）实验的一部分，国际空间站（ISS）上进行了两个系列的沸腾实验。n沸腾过程中的相流和传热通过全铜加热试管和透明玻璃加热管在质量速度，液体过冷，蒸气质量和热通量的广泛实验范围内获得了全氟己烷（FC-72）。此外，通过在未加热的观察区域中使用高帧频相机观察到了详细的两相流动行为。为了阐明重力对流动沸腾的精确影响，必须比较传热数据和在相同流动和加热条件下在正常（地面）重力和微重力环境下获得的两相流动特性。但是，两个实验不能使用相同的实验设备和相同的热环境条件进行。此外，由于ISS实验装置内部强制的航空电子气流，因此热量损失不可忽略。因此，要对加热后的试管入口处的流体状况进行准确评估，就需要高精度的热损失模型。在本文中，通过使用在ISS上进行的初步热损失实验的结果，建立了用于评估受热试管入口处的液体过冷程度和从受热管到测试流体的净热通量的热损失模型。 。通过所提出的热损失模型对液体过冷度的校正对于重力效应的精确分析是不可忽略的。