Avaliação do desempenho de coletores solares utilizando nanofluidos de grafeno em água destilada

Abstract

This work experimentally approaches the use of graphene nanofluids in distilled water in flat plate solar collectors. The evaluated nanofluids were produced in volumetric concentrations of 5 ppm, 10 ppm and 20 ppm. An experimental bench was built and instrumented with three solar collectors for heating water operating under the conditions: traditional flat plate collector, collector without absorber plate and using nanofluid as an absorption medium, and collector with absorber plate and using nanofluid. The tests were carried out in three stages, evaluating each concentration to sun exposure for 5 consecutive days. The results showed higher outlet temperatures and temperature variation in the joint action condition absorber plate and nanofluid, ensuring an increase in temperature variation of up to 8.44% compared to the traditional collector. For this collector, using the nanofluid at a concentration of 5 ppm, the highest efficiency was verified, with a maximum of 45.10%, the other concentrations did not prove to be advantageous in relation to the traditional collector. The condition using only the nanofluid did not show gains in relation to the traditional collector, thus indicating that removing the absorber plate to replace it with the nanofluid was not viable. Considering the stability assessment, its decrease was identified with increasing concentration, obtaining in this study the 20 ppm nanofluid with the worst stability, by visual inspection, noting the greater formation and deposition of nanoparticle agglomerates, in addition to the absorbance results showing reduction of up to 96.32% after exposure to solar radiation, compared to the initial sample.