Thermal Performance Of Modified Paraffin Phase Change Heat Storage Materials

Paraffin is a chemically stable, latent heat, no cooling and phase separation as organic phase change heat storage materials. In some extent, the application of paraffin thermal storage at high temperature was restricted because of the low phase transition temperature and poor thermal conductivity; The modified paraffin can be used as solar thermal energy storage material on wood drying, it can reduce fossil energy used in the process of wood drying based on improving phase transition temperature and thermal conductivity through paraffin modified. And it has important theoretical significance and practical value for the energy saving. The stearic acid, palmitic acid, aluminum ammonium sulfate, sodium acetate inorganichydrated salt, high thermal conductivity and particle size of small micron-sized metal powder and nano metal powder were selected as the additive to the modified paraffin. A series of modified paraffin wax phase change heat storage material samples were made with different mass ratio. The differential scanning calorimetry (DSC), data acquisition system (M400) and other instruments were used on several thermal properties of the modified paraffin test. The results showed that:(1) The reservoir/heat release rate, the phase transition latent heat and thermal conductivity of modified paraffin wax phase change thermal storage materials were improved;(2) The thermal conductivity, latent heat and the storage/heat release rate of1%nano-graphite modified paraffin were significantly improved and the phase transition temperature slightly improved;(3) Through the changing of aluminum tube diameter, wind speed and air temperature, the results indicated that:①when the aluminum tube diameter unchanged, the wind speed was less than3m/s, the impact of air temperature on the actual measurement of heat transfer coefficient effect was very little, the difference value was about1W/(m2·℃);②The heat transfer coefficient and heat release rate was improving with the increase of wind speed in the same diameter, temperature conditions and the heat release rate can reach to95.3%;③The heat transfer coefficient was decreasing and the heat release rate was increasing with the increase of pipe diameter in the same circular wind speed、air temperature.④The optimum condition for the nanographite modified paraffin wax phase change thermal storage materials was that:30mm pipe diameter,3m/s wind speed and90℃air temperature.