Influence of Particle Size Distribution on the Optical Properties of Fine-Dispersed Suspensions

Nanofluids have great potential for solar energy harvesting due to their suitable optical and thermophysical properties. One of the promising applications of nanofluids is utilization in solar collectors with the direct absorption of light (DASC). The design of a DASC requires detailed knowledge of the optical properties of nanofluids, which can be significantly affected by the particle size distribution. The paper presents the method to take into account the particle size distribution when calculating nanofluid extinction spectra. To validate the proposed model, the particle size distribution and spectral absorbance were measured for aqueous suspension with multi-walled graphite nanotubes; the minimum size of primary nanoparticles was 49 nm. The proposed model is compared with experiments demonstrating the concentration averaged and maximum discrepancies of 6.6% and 32.2% against 12.6% and 77.7% for a model assuming a monosized suspension.