The low thermal conductivity of phase-change materials(PCMs)limits the heat transfer efficiency of phase-change energy storage systems.The problem of the low thermal conductivity of paraffin was addressed by preparing a series of nano-carbon-based composite PCMs(CPCMs)with different nano-carbon mass concentrations using a two-step method using paraffin as the substrate material and carboxylated multi-walled carbon nanotubes(MWCNT)and carbon nano-onions(CNOs)as high-thermal-conductivity media.The effects of adding the two nano-materials on the phase transition temperature,latent heat of fusion,thermal conductivity,and kinematic viscosity of CPCMs were investigated.It was found that adding nano-carbon materials had a negligible effect on the phase transition temperature,and the maximum temperature deviation was 1.811 ℃.However,the latent heat of fusion decreased with the increasing mass concentration of nanoparticles.The maximum reduction in the latent heat of fusion was 16.4％,with a mass CNO fraction of 4％.The increasing nano-carbon concentration increased the thermal conductivity and the kinematic viscosity of liquid CPCMs.The thermal conductivity of 4％CNO-PCM in liquid and solid state was 0.3167 W/(m·K)and 0.8322 W/(m·K),respectively,with the most significant increase in thermal conductivity of 80.7％and 195.9％,respectively.Compared with MWCNT,using CNOs was more conducive to enhancing the PCM thermal conductivity.This study provides an experimental basis for developing composite paraffin PCMs with high thermal conductivity and a reference for selecting CPCMs for different demands.
关键词
相变储能/石蜡/纳米洋葱碳/多壁碳纳米管/导热系数/相变潜热/运动黏度
Key words
phase change energy storage/paraffin/CNOs/MWCNT/thermal conductivity/latent heat of fusion/kinematic viscosity
维普
万方数据