MEPCM涂层微小通道内HFE-7100的流动沸腾传热特性研究

Study on flow boiling heat transfer characteristics of HFE-7100 in microchannels coated with microencapsulated phase change material (MEPCM)

中文关键词: 微小通道，流动沸腾，HFE-7100，相变微胶囊，表面涂层

英文关键词: Microchannel, flow boiling, HFE-7100, microencapsulated phase change material, surface coating

中文摘要:

      随着电子器件不断向微型化发展，散热问题日趋严峻，微通道流动沸腾冷却技术因其在高效热管理中的巨大潜力而受到广泛关注。为进一步提升氟化液的流动沸腾传热性能，本研究在水力直径为1.5 mm的矩形平行微小通道内，制备了芯材为正十八烷（C18）和@64号石蜡的相变微胶囊涂层，探究相变微胶囊对通道流动沸腾传热性能的影响。实验以HFE-7100为工质，在入口温度51℃、质量流率225~300 kg?m-2?s-1和热流密度为25.5~191.6 kW?m-2的条件下开展。实验结果表明，光滑通道和涂层通道的传热系数在分别在热流密度为40.1~174.6 kW?m-2和40.1~143.1 kW?m-2时，随热流密度的升高而增大，光滑通道中主要以核态沸腾为主，传热系数与质量流率相关性较弱。相比之下，涂层通道的传热系数与质量流率的相关性增强，并且在热流密度为40.1~174.6 kW?m-2时传热系数显著提高。芯材为C18的相变微胶囊涂层通道的沸腾传热性能最高提升了49.7%，而芯材为@64号石蜡的相变微胶囊涂层通道因相变潜热效应，传热性能进一步提升，最高提升了68.6%。通过可视化实验观察，发现相变微胶囊涂层的多孔结构促进了气泡生成，增加了汽化核心密度，从而提高了气泡频率。此外，相变潜热的作用进一步促进了气泡产生和传热效率的提高。两相流的压降随着热流密度的增大而增加。涂层通道的压降在热流密度为67.3 kW?m-2时比光滑通道最大增加了28.32%，但随着热流密度的增加，两者之间的差距逐渐缩小。本研究结果表明相变微胶囊能够有效提升微小通道流动沸腾的传热性能，并为高效热管理系统的设计提供了新的思路。

英文摘要:

      Miniaturization of electronic devices demands a better heat dissipation technology, and the flow boiling in microchannels has attracted widespread attention due to its significant potential for efficient thermal management. To further enhance the flow boiling heat transfer performance of fluorinated liquids, flow boiling was studied experimentally in rectangular parallel microchannels coated with microencapsulated phase change material of n-octadecane (C18) and paraffin wax @64. Using HFE-7100 as the working fluid, the experiments were conducted with inlet temperatures of 51°C, mass fluxes ranging from 225 to 300 kg?m-2?s-1 and heat flux densities ranging from 25.5 to 191.6 kW?m-2. The experimental results indicated that the heat transfer coefficients in both smooth and coated channels increase with the heat flux density in the ranges of 40.1~174.6 kW?m-2 (smooth channels) and 40.1~143.1 kW?m-2 (coated channels). In the smooth channels, nucleate boiling dominates in the investigated working conditions and thus the heat transfer coefficient shows weak correlation with mass flux. In contrast, in the coated channel, the heat transfer coefficient has a stronger correlation with mass flux and increases significantly in the heat flux density range of 40.1~ 174.6 kW?m-2. The boiling heat transfer coefficient in the microchannels coated with microencapsulated phase change material with C18 improved by up to 49.7%, while the channels coated with paraffin wax @64 showed an even greater improvement of 68.6% due to the latent heat. Visualization results revealed that the porous structure of the microchannels coated with microencapsulated phase change material promotes bubble generation and enhances the bubble frequency. Additionally, the latent heat effect further promotes bubble formation and improves heat transfer efficiency. The two-phase flow pressure drop increases with the heat fluxes. At heat flux of 67.3 kW?m-2, the pressure drop in the coated channel increased by a maximum of 28.32% compared to the smooth channel. However, as the heat flux increases, the difference between the two channels gradually decreases. The results of this study indicate that microencapsulated phase change material can effectively enhance the flow boiling heat transfer performance in microchannels and provide new insights for the design of efficient thermal management systems.