Li Qihui, Yin Shuai, Wu Zide, Xu Xudong, Yan Kejin, Peng Hao
The paper proposes a rapid microfluidic fabrication method for encapsulated phase change materials （EPCMs）. C15/TMPTA EPCMs are prepared using an immersed co-flowing capillary microfluidic device with UV-curing, supplemented by thermally conductive modification of the shell material with silicon carbide. Characterization techniques including high-speed cameras, SEM, OM, FT-IR, XRD, DSC, TGA and LFA are utilized to investigate the generation of compound droplets and the properties of EPCMs. The results show that within the selected range of flow rate parameters, the generation process of compound droplets exhibits three phenomena： dripping, core leakage and jetting. Under dripping and jetting phenomena, stable compound droplets are formed. However, when the flow rate ratio （Qi/Qo） is larger than 1.5 and the total flow rate （Qtotal） is less than 160 µL/min, the core droplet will leak, resulting in the inability to generate the composite droplet normally. The sizes of core and compound droplets decrease with an increase in the outer phase capillary number （Cao）, while the frequency of compound droplet generation increases with Cao. Moreover, EPCMs prepared at Qi/Qo of 0.5, 1 and 1.5, with a Qtotal of 150 µL/min, exhibit a multi-core structure, high monodispersity （with a coefficient of variation （Cv） <4%） and controllable size, ranging from 1.32 to 1.55 mm in diameter. The addition of 2wt% nano silicon carbide for modification enhances the encapsulation efficiency of EPCMs （increased by 16.17%） and thermal cycling stability, with only a 1.19% decrease in enthalpy value after 25 thermal cycles.
