The flow boiling heat transfer characteristics of NH₃/H₂O mixture in a 2D single horizontal microchannel (0.4 mm width × 6 mm length) were investigated by Computational Fluid Dynamics (CFD) method. The multiphase VOF model and modified phase change Lee method were adopted to address the non-isothermal phase change process of the flowing zeotropic NH₃/H₂O mixture, while the variations of the binary mixture thermophysical properties were also taken into account. The effects of mass flux (46~552 kg/(m²∙K)), inlet NH₃ concentration (0-35% by mole) and heating wall temperature (20.5~70 ${}^{\circ }\mathrm{C}$) on the overall and local flow boiling heat transfer performance have been comparatively evaluated under constant heating wall temperatures. According to the numerical results, the heat dissipation rate of NH₃/H₂O mixture flow boiling could reach up to 1.41 MW/m² at a mass flux of 552 kg/(m²∙s), which was 2.05 times of water single-phase flow cooling under a same constant heating wall temperature of 50 ${}^{\circ }\mathrm{C}$. It was also revealed that, for NH₃/H₂O mixture flow boiling in the microchannel, there was a threshold of inlet NH₃ concentration to maintain a certain level of heat dissipation rate at a given mass flow rate and further increasing the inlet NH₃ concentration would no longer benefit the heat dissipation process. Furthermore, there were no local dry-outs found throughout the whole microchannel length under all the simulation conditions in this study, which could be attributed to the unique flow boiling behaviors of zeotropic NH₃/H₂O mixture. Therefore, it should be noticed that NH₃/H₂O mixture, under certain conditions, could be a good alternative coolant for preventing local dry-outs and maintaining a certain functional temperature of electronic components.

通过计算流体动力学（CFD）方法研究了二维单水平微通道（0.4 mm宽×6 mm长）中NH ₃ / H ₂ O混合物的沸腾传热特性。采用多相VOF模型和改进的相变Lee方法解决了流动性共沸NH ₃ / H ₂ O混合物的非等温相变过程，同时还考虑了二元混合物热物理性质的变化。质量通量（46〜552 kg /（m ² ∙K）），入口NH ₃浓度（0-35％摩尔）和加热壁温度（20.5〜70）的影响${}^{\circ }\mathrm{C}$）在加热壁温度恒定的情况下，对整体和局部流动沸腾传热性能进行了比较评估。根据数值结果，NH ₃ / H ₂ O混合流沸腾的散热速率在552 kg /（m ² ∙s）的质量通量下可以达到1.41 MW / m ²，是水的2.05倍在相同的恒定加热壁温为50的条件下进行单相流冷却${}^{\circ }\mathrm{C}$。还揭示出，对于在微通道中沸腾的NH ₃ / H ₂ O混合物流，存在入口NH ₃浓度的阈值，以在给定质量流量下保持一定的散热率水平并进一步增加入口NH ₃浓度将不再有益于散热过程。此外，在本研究中的所有模拟条件下，在整个微通道长度上均未发现局部变干，这可归因于共沸NH ₃ / H ₂ O混合物的独特沸腾行为。因此，应注意NH ₃ / H ₂在某些条件下，O混合物可能是防止局部变干并保持电子组件的某些功能温度的良好替代冷却剂。