The industrial production and urban residents' lives have led to a large amount of wastewater and sludge

and the landfilling of sludge has caused severe ecological damage. To facilitate the large-scale disposal of municipal sludge

transform waste into valuable resources

and prepare low-carbon

low-cost thermal storage materials

an idea is innovatively proposed

in which the silicon carbide

boron nitride

and expanded graphite is added as thermal conductivity enhancers to enhance the thermal conductivity of sludge incineration ash/potassium nitrate composite phase change thermal storage materials(50% sludge incineration ash+50% potassium nitrate). The composite phase change thermal storage materials were prepared

and the effects of thermal conductivity enhancers on thermal performance of these materials were investigated. The results indicate that

the expanded graphite is not suitable as a thermal conductivity enhancer for sludge incineration ash/potassium nitrate composite phase change thermal storage materials. The addition of a thermal conductivity enhancer with a mass fraction of 2% is optimal for improving melting latent heat

with boron nitride performing better than silicon carbide. The samples with 2% boron nitride shows the most significant increase in thermal conductivity

rising by 65%

93%

117%

and 203% compared with samples SC3(without thermal conductivity enhancers) at temperatures of 100 ℃ to 400 ℃

respectively. After undergoing 1 000 cycles of heating/cooling

the samples with 2% boron nitride have a latent heat of 35.29 J/g and a thermal storage density of 292.1 J/g

while the samples with 2% silicon carbide have a latent heat of 40.90 J/g and a thermal storage density of 334.9 J/g. The heat transfer rates for the samples with 2% silicon carbide and 2% boron nitride are 0.16 ℃/s and 0.17 ℃/s

respectively. This preliminary evidence demonstrates the feasibility of using silicon carbide and boron nitride as thermal conductivity enhancers for sludge incineration ash/potassium nitrate composite phase change thermal storage materials.