Experimental Study On Paraffin-based Composite Phase Change Materials And Application In Heat Pump System

In this thesis, a new composite cool and heat storage material is studied for air-source and solar energy heat pump. The method which theory analysis and numerical simulation are combined with experiment is used in research on the paraffin wax based composite phase change materials. Paraffin base carbon nanotube composite materials(PW-CNTs) and paraffin base of nano aluminum composite material(PW-NAl) have been prepared with various mass fractions. The thermal properties include phase transition temperature, latent heat of phase change, thermal conductivity and thermal stability during the phase change process are investigated. The phase change property was characterized using differential scanning calorimeter(DSC), the thermal conductivity was measured by using transient hot wire method. We can estimate the thermal stability of the materials in thermal cycle conditions. The experimental results have been shown that PW-0.1CNTs have good stability as cool storage material,via concentrated nitric acid modified, ultrasound concussion and using surfactants SDBS. Thermal conductivity of PW-0.1CNTs is 0.487W/(m·K)(solid) and 0.262W/(m·K)(liquid), increased by 21.1% and 29.1% compared with the pure paraffin. Phase transition temperature of PW-0.5NAl is 5~8℃, latent heat of phase change is 155.3~161.6k J/kg, thermal conductivity is 0.513W/(m·K)(solid) and 0.277W/(m·K)(liquid), so it can be widely used as cool storage materials. Thermal conductivity of PW-0.5CNTs and PW-0.5NAl were 0.341 W/(m·K)(solid) and 0.359 W/(m K)(solid) as heat storage material, compared with the pure paraffin increased by 26.1% and 32.2%, the change of the phase change temperature and phase change enthalpy is small.The melting and solidification process of the heat exchanger of air-source and solar energy heat pump are simulated, compared to pure paraffin waxs, the time of the phase change materials charge and discharge process is reduced.