In the purification treatment of printing and dyeing wastewater, the addition of nanoparticles can promote energy absorption and regulate evaporation processes through spectral property modulation. To clarify the influences of nanoparticle structure and material on the regulation of spectral properties, nanoparticle models with standard sphere, rough sphere and double-layer core-shell structure are established in this paper. The materials of nanoparticles are silver and silicon, respectively. The scattering and absorption properties in the wavelength band of 200nm-2000nm are calculated by the FDTD method and analyzed. The results show that the surface roughness of nanoparticle has little effect on spectral properties, and the variation of the particle diameter has a larger effect on the scattering factor. Comparing with the single-component nanoparticle, the core-shell structure composing two materials has better ability to regulate the spectral properties.
Aiming at solving the problem integrating the low-grade heat recovery from waste water and the high-temperature hot water demand for the printing and dyeing industry, the single-stage heat pump model and cascade heat pump system model are built and analysed. Two refrigerants, including R134a and R152a, are selected separately as the working fluids of single-stage heat pump. Meanwhile, these refrigerants are used in the cascade heat pump for two joint systems. For different heat pump systems, the performance parameters are calculated and compared through the simulation of thermodynamic process, with the help of EES and MATLAB. The results show that COP of cascade heat pump is generally greater than that of single-stage heat pump system, for various evaporation temperature and condensation temperature. For the heating power and exergy, the performance of the cascade heat pump is between the single-stage heat pumps with corresponding different refrigerants chosen. Considering the compression process of heat pump system, the compression ratio in the single-stage heat pump cycle is far greater than that of the corresponding cascade heat pump. In order to ensure the practicability and safety of the system, the performance of the cascade heat pump is better.
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