The Experimental Investigation For Enhancing The Thermal Storage Performance Of Paraffin With Nanoparticles

Octadecane is selected as the phase change materials of solar chimney power plant system with vertical heat collector to ensure the continuous operation of the syetem. But its thermal conductivity is poor, so a method of adding Al, Cu or nanoparticles is used to strengthen the thermal conductivity of octadecane.The nano composite phase change materials (NC-PCMs) are prepared by combining chemical dispersants and ultrasonic oscillation, with Al, Cu or nanoparticles mass fraction of0.2%,0.5%,1%,2%,3%,4%and5%. The methods of the gravity sedimentation and granularity analysis are both adopted to analyze the dispersion stability of nanoparticles in NC-PCMs. The results show that:Al nanoparticles; Fe2O3nanoparticles disperse worst in octadecane.The phase change latent heat, phase change temperature and phase change time of phase change materials are measuered by differential scanning calorimetry (DSC) instrument. The experimental results show that:with the increase of the the mass fraction of nanoparticles, the phase change latent heat of NC-PCMs decreases gradually, but decreases slightly; the phase change of temperature of NC-PCMs have small change; the phase change time decreases first and then increases; the time needed for phase change is shortest when the mass fraction of nanoparticles is3%. The phase change latent heat and temperature of NC-PCMs which experience many thermal cyclings both change slightly, which indicates that NC-PCMs have stable and reliable thermal performance.The thermal conductivity of NC-PCMs is measured with the method of transient thermal probe. The results show that:the thermal conductivity of NC-PCMs increase with the increase of the mass fraction of nanoparticles, but the increasing trend slows down or even decreases with the continue increase of nanoparticles which is over certain content; the thermal conductivity of NC-PCMs which contain3%Al nanoparticles is the highest, and the maximum of thermal conductivity is0.533W/(m·K) in phase change process. In addition, the thermal conductivity of NC-PCMs change slightly with the increase of thermal cyclings, which indicates that NC-PCMs have a better thermal cycling stability.Add nanoparticles to strengthen the heat conduction performance of octadecane and gain more ideal results. It is significant for the investigation of phase change energy-storage materials.