Study On Thermophysical Properties And Collector Performance Of Phase Change Nanofluids

With the increasing demand for energy,the environmental problems caused by fossil energy have become increasingly prominent.Solar energy is an inexhaustible clean energy,but its application is limited due to the intermittent use of solar energy.Phase change heat storage has a certain advantage in thermal energy storage.Phase change nanofluids prepared by using phase change fluid as the base liquid of nanofluids have excellent properties of high thermal conductivity and high heat storage,and have great potential in the application of solar thermal system.In this paper,the preparation methods and properties of phase change nanofluids are introduced,and the law of temperature rise of phase change nanofluids is explored.Firstly,phase change fluid was prepared by phase change emulsification.The effects of mass ratio of emulsifier moa-3pk to emulsifier s-185,mass ratio of paraffin to composite emulsifier and different emulsification time on particle size,viscosity and phase change cycle stability of phase change fluid were studied.Then,the particle size,viscosity,phase change cycle stability and thermophysical properties of phase change fluid with different content of paraffin were tested,and the influence of different content of paraffin on the performance of phase change fluid was analyzed.Comprehensive analysis shows that the composite emulsifier moa-3pk:s-185 with good performance is 1:2,the content of composite emulsifier and paraffin is 7:30,the emulsification time is 30 min or 40 min,and the paraffin content is 15wt%phase change fluid is selected as the base liquid of phase change nanofluid.Secondly,ZnO nanoparticles were added into the prepared phase change fluid to form phase change nanofluid.Adding dispersant can make ZnO nanoparticles disperse into phase change fluid to form stable phase change nanofluid.Therefore,the effects of different dispersants,different dispersants and different ZnO nanoparticles on the thermophysical properties of phase change nanofluid were investigated Stability and viscosity.In conclusion,the phase change nanofluids with 0.3 wt%CTAB and 0.2 wt%nanoparticles have the best performance.Based on the simulated total solar irradiance,temperature measurement point and relevant basic data,the influence of total solar irradiance,dispersant type,dispersant content and nanofluid content on the heat absorption and collection performance of phase change nanofluids was studied.With the increase of total solar irradiance,the maximum thermal efficiency of phase change nanofluids is 45.22%,corresponding to the total solar irradiance of 550 w/m~2,dispersant CTAB content of 0.3wt%,nanoparticle content of 0.2wt%,the phase change nanofluids have the best thermal performance.