Research on the along-path absorption characteristics of distinctive nanofluids with different radiative features during the process of photothermal conversion

Abstract

Accurately predicting the distinctive absorption characteristics along the transfer path for the radiative transfer process analysis inside the multiple type nanofluids is vital for the study of photothermal utilization capacities of nanofluids. In this work, the photothermal conversion capacities of water-based nanofluids composed of multi nanoparticles (including Ag, TiN and TiO₂) with different scattering and absorption characteristics are analyzed. Firstly, a coupled numerical calculation model integrating the FEM and the MCRT method is presented, and then the absorption characteristics of radiative energy transfer along the path are predicted by proposed numerical model. Additionally, the photothermal conversion performance of various nanofluids with different distinctive nanoparticles are compared. Meanwhile, different nanofluids are also prepared for the photothermal conversion experiment, which verifies the accuracy of the proposed numerical model. After analyzing the solar-weighted absorption fractions of nanofluids with different radiative properties at different absorption depths, it is found that when the volume fractions of nanoparticles increase, the radiative energy absorbed by the nanofluids will decrease at the saturated absorption condition. This effect becomes more pronounced for the nanofluids with stronger scattering characteristics. When the volume fraction increases from 0.01 % to 0.5 %, the solar-weighted absorption fraction of the TiO₂ nanofluid with a diameter of 100 nm decreases from 0.44 to 0.25. After simulating the photothermal conversion of the nanofluids composed of three material nanoparticles, it is found that the photothermal conversion efficiencies of nanofluids are simultaneously related to the total amount of absorbed radiative energy and its distribution characteristic along the transfer path.