Research On Optical Properties And Solar Absorption Properties Of Nanoparticle-Containing Paraffin

Paraffin containing nanoparticles is a new engineering material which optimizes the optical and thermal properties of paraffin by adding nanoparticles.It has broad application prospects in improving the light absorption properties of glass envelope with paraffin.In this paper,paraffin nanofluids were prepared by two-step method,and their transmission spectra were measured by spectrophotometer.The influencing factors were analyzed by controlling variable method,and the optical properties of paraffin were obtained by inversion calculation based on spectral characteristics.Considering the absorption and scattering of paraffin particles,an optical model was established to analyze the optical properties of paraffin with nanoparticles.Finally,the paraffin with nanoparticles was used as an index to evaluate the optical properties of paraffin,and the photothermal conversion efficiency was calculated.The main research contents are as follows:1.The Two-step preparation of paraffin nanofluid was selected.After considering the influence of dispersant,the amount of dispersant?ratio 1:0.75?was added to prepare paraffin nanofluids with SiO₂,Al₂O₃,TiO_2,ZnO and CuO.Moreover,the optical error was eliminated by differential dual-beam spectroscopy.2.Based on the prepared paraffin nanofluid,the spectral characteristics of paraffin nanofluids were measured and analyzed.The influence factors and the relationship between of the spectral properties were analyzed by adjusting the particle parameters?material type,particle concentration,particle size?and the enviroment parameters?system temperature,opitical path?.The results show that the spectral properties of paraffin nanofluid are changed by the doping of nanoparticles in the spectrum from 250 to 900nm.The absorbance of paraffin nanofluid with different materials is different.In the range of saturated concentration?100 ppm?,the transmittance decreases with the increase of concentration.The transmittance of paraffin nanofluid increases slightly with the decrease of particle size and the increase of temperature,and decreases with the increase of optical path.Then,based on the measured paraffin spectral data,a thickness inversion model was introduced to calculate the paraffin optical physical parameters.3.In view of the complex optical properties caused by particle addition,the internal optical transmission mechanism of paraffin containing nanoparticles was analyzed.First,the Rayleigh scattering approximation model was used to describe the optical properties of paraffin system.The results show that the optical properties obtained by Rayleigh model can not accurately predict the optical behavior of paraffin nanofluids with TiO₂,CuO,ZnO in the ultraviolet region.The Mie scattering model was optimized by combining Monte Carlo model.The extinction coefficient,scattering coefficient and absorptive efficiency of paraffin containing nanoparticles are obtained.The effect of particle parameters on light absorption and scattering was analyzed.The results show that TiO₂ and CuO have better absorptive efficiency,and the proportion of scattering is small.The extinction coefficient of paraffin nanofluid increases linearly with the particle concentration and the larger the particle size,the stronger the scattering effect.4.The thermal properties of paraffin containing nanoparticles were measured.The results show that the paraffin nanofluid has a wireless relationship with its thermal conductivity.An experimental platform for measuring the temperature variation of paraffin nanofluid was built under indoor and outdoor with different environment.The results show that CuO,Al₂O₃ and TiO₂ nanoparticles can increase the heating,cooling rate of paraffin and the equilibrium temperature in the form of increasing thermal conductivity and absorbency.Within the concentration of 5-15 ppm,the paraffin absorbency and transmittance can be satisfied at the same time,and the increase of particle size will improve the absorption effect of paraffin.Finally,the photothermal conversion efficiency of paraffin containing nanoparticles was calculated based on the temperature-dependent data.The results of this research can provide theoretical reference and data support for the future development and application of glass envelope with paraffin.