Nanoparticle Tio 2 Dispersed Composite Phase Change Material For Energy Storage In Air-conditioning

There is power shortage at peak period and surplus at low peak period in city while air-conditioning is one of the largest electrical equipments in the building. Then how to solve the effect of air-conditioning load on grid load will have great impacts. It may ease power shortage by cooling storage technology to shift peak at daytime to low peak at night to play an"electricity load peak shifting"role, which is practically significant. In the paper, we have mainly studied the preparation ofnano-composite phase change material (PCM), which is potential in air-conditioning by combining Tetra-n-butyl ammonium bromide solution with titanium dioxide (TiO₂) nanoparticles. The main work is as follows:1)Preparation and stability of nano-composite PCM Two-step method was adopted by mixing TiO2 nanoparticles and Tetra-n-butyl ammonium bromide solution, accompanied by stirring using magnetic mixer and ultrasonic dispersion, to get uniform and steady nano-composite PCM. Experimental studies have shown that mass fraction of TiO2, nanoparticle size and ultrasonic time exerted significant effect on dispersion stability of nano-composite PCM. And composite PCM dispersed TiO2 of 25nm at mass fraction of 0.05%, with ultrasonic time for 2h is the best choice in our research.2) Viscosity formula and measurements on viscosity coefficient of nano-composite PCMViscosity coefficient of nano-composite PCM with various concentration of TiO2 at different temperature was tested by Brookfield viscometer. The results demonstrated that TiO2 have significantly increased viscosity of matrix fluid with increase of concentration, especially viscosity increasing by 9% at 0.16%. However, there was a decrease in viscosity coefficient of nano-composite PCM with increase of temperature.3)Enhancement in heat transfer and measurements on thermal conductivity coefficient of nano-composite PCMThermal conductivity coefficient of composite PCM with different concentration of TiO2 was tested by transient plane thermal conductivity instrument. The results presented that thermal conductivity coefficient has significantly increased with the increase of concentration of TiO₂, especially increasing by about 30% at concentration of 0.16%. 4) Mechanism of nucleation and thermal analysis of nano-composite PCMWe made measurements on latent heat and phase change temperature using differential scanning calorimetry, whose latent heat was 166.724kJ/kg. It was found that TiO₂ hardly affected phase change temperature and latent heat. Also there was experiment on performance test and the results were characterized by temperature curves which showed that super-cooling can be reduced owing to the nanoparticle.Nano-compositePCM prepared in this article had better and more comprehensive performance on thermal conductivity and cooling storage capacity when compared with the matrix fluid.