Abstract:

A phase change emulsions is termed as a latent heat functional thermal fluid, which can not only maintain the fluidity of a conventional heat transfer fluid, but also have the latent heat storage capacity of phase change material. It is believed that the phase change slurry enables to enhance the heat transfer rate of a conventional heat transfer fluid, expanding the potential application fields and improving energy utilization efficiency. Two organic phase change materials were selected to prepare multi-melting point phase change emulsion, and its heat transfer was enhanced. Morphology, physical and chemical properties and thermophysical properties of phase change slurry were analyzed in detail. The results indicate that the obtained phase change slurry are milky white colloidal system at room temperature with average particle size range of 129.3—204.4 nm and excellent fluidity and stability. Multi-phase change temperatures appear in the phase change process, and the latent heat is in the range of 27.49—34.54 J/kg. Moreover, the solid specific heat and liquid specific heat range from 2.98 to 3.83 J/(g·K), and from 2.26 to 2.93 J/(g·K). Thermal conductivity of phase change slurry is between 0.42 and 0.47 W/(m·K), and 0.5%(mass) nano-Si₃N₄ can increase the thermal conductivity of slurry by 6.0%—13.5%. The enhanced phase change slurry can be used as an excellent heat exchange working medium in the field of cooling.

Key words: phase change slurry, multiple-phase change temperature, thermal properties, thermal stability, heat transfer enhancement

摘要：

相变乳液是一种潜热型功能热流体，既能保持常规传热流体的流动性，还具有相变材料的潜热蓄热能力，可以强化流体传热速率拓展其应用潜力。选用两种有机相变材料并制备多熔点相变乳液，并对其传热进行强化。实验结果表明，所制备相变乳液常温下为平均粒径为129.3~204.4 nm的乳白色胶体体系，具有优良的流动性及稳定性。相变过程出现多个相变控温点，相变潜热为27.49~34.54 J/kg。另外，固态比热容为2.98~3.83 J/(g·K)，液态比热容为2.26~2.93 J/(g·K)。相变乳液的热导率为0.42~0.47 W/(m·K)，0.5%（质量分数）的纳米Si₃N₄可以将乳液热导率提高6.0%~13.5%。导热强化后的相变乳液可以作为优良的换热工质应用于降温领域。

关键词: 相变乳液, 多熔点, 热物性能, 热稳定性, 强化传热