Preparation And Heat Transfer Performance Of Phase Change Material For Heat Storage

Phase change heat storage technology is paid more attentions with the development of energy consumption and environment protect.Organic phase change materials have broad application in the fields of solar energy utilization,building energy conservation,heat energy recovery,aerospace because of their non-corrosive properties,no phase separation and no subcooling.Nano-Fe₂O₃/stearic/acid-octadecyl composite phase change materials with high thermal conductivity are prepared to overcome the low thermal conductivity of organic phase change materials using the method of two-step.The dispersion stability of nanocomposite thermal storage phase change material is studied from ultrasonic time and quality of dispersant and nanomaterial.SDBS has the best dispersion effect.The mass ratio of SDBS to nano-Fe₂O₃ is 2:1.The optimum addition amount of nano-Fe₂O₃ is 0.4%.The optimal ultrasonic time is 80min.The phase transition temperature and the latent heat of phase change decreases,but the thermal conductivity increased by 34.3%.After 300thermal cycles,the phase transition temperature fluctuation of the nanocomposite phase change material is 0.41?and the phase change latent heat variation range is 4.0%.The thermal stability of nanocomposite phase change material is good.The performance of charging and discharging of stearic/acid-octadecyl composite phase change materials and nano-Fe₂O₃/stearic/acid-octadecyl composite phase change materials is tested by the charging/discharging test bench.The temperature trends of the binary organic and nanocomposite phase change materials are the same during the heat storage process.No phase transition occurs at the same time at all measuring points.There is no obvious platform in the phase change process.Natural convection is the dominant way of heat transfer during heat charge.The phase change platform of binary organic and nanocomposite phase change materials is obvious during the discharge process.Heat conduction is the leading role during the heat discharge.The times of heat charge is less than the times of heat discharge.Natural convection accelerates heat transfer.The addition of ferumoxytol reduces the charge/discharge time of the composite phase change material.The charging and discharging process of nano composite phase change material was numerically simulated by FLUENT software.In the initial stage of melting,there are few liquid phase change materials,almost no natural convection,and heat transfer is mainly heat conduction.With the progress of melting,natural convection is strengthened,and the heat transfer mode is mainly changed from heat conduction to natural convection.The liquid phase change material is reduced,and the influence of natural convection is weak during the solidification process.The heat transfer is mainly changed from short convection to long heat conduction.The simulated phenomenon is consistent with the temperature variation in the experiment.