Experimental investigation on the stability and heat transfer enhancement of modified mircoencapsulated phase change materials and latent functionally thermal fluids

•Introduce the thiol groups on the MEPCM surface, aiming to enhance the suspension stability of MEPCM in the base solution, which was not reported before.•The modified MEPCM showed a high encapsulation efficiency of 65.74% and can kept stable for 14 days. The LFTF with 2wt% modified MEPCM also appeared an heat transfer enhancement of 44%. All of these indicate the as-prepared capsules has a good comprehensive property for thermal application.•Proposed a novel method for growing nano-metals on MEPCM surface and successfully synthesized a layer of copper nanoparticles on the MEPCM, which has simple operation and less reagents usage. In this paper, the thiol-modified paraffin/silica microencapsulated phase change materials (MEPCM) was synthesized using tetraethoxysilane (TEOS) and (3-mercaptopropyl)-trimethoxysilane (MPTMS) by interfacial co-hydrolysis and co-polycondensation as the aim of improving the thermal stability and suspension stability. The effect of MPTMS was analyzed by SEM, TEM, FT-IR, DSC, TGA, the leakage test and gravity sedimentation test. The most satisfied sample (S3) showed a high thermal storage density of 125.82 J/g, along with an encapsulation efficiency of 65.74%. It also appeared excellent thermal stability after 1000 cycles with 94.11% latent enthalpy remained and kept 99.48% mass after heating at 80 °C more than 150 min. Beneficial from the hydrophobicity regulation by the thiol functional group, the MEPCM exhibited the good suspension stability for 14 days without any surfactant. The modified MEPCM was used to prepare latent functionally thermal fluids (LFTF), which presented 41% improvement of the heat transfer performance when 2wt% MEPCM was added. In addition, a layer of copper nanoparticles was successfully synthesized on the surface of MEPCM for the thermal conductivity enhancement. Therefore, the modified MEPCM provided a new sight on the interfacial modification of MEPCM and has a significant potential for new type thermal fluids.