Thermal efficiency of flat plate thermosyphon solar water heater with nanofluids

Background:Many techniques are used to improve the thermal efficiency offlat plate solar collectors. Theprevious studies showed the high potentials of nanofluids for thermal efficiency improvement offlat platesolar collectors. Methods:In this study, a numerical simulation is carried out to investigate the thermal efficiency of theflatplate thermosyphon solar water heater with different nanofluids. The water-aluminum oxide, water-copperoxide, water-copper, and water-titanium oxide nanofluids are used. The effects of different parameters, suchas the volume fraction of nanoparticles, volumetricflow rate, solar radiation intensity, ambient temperature,and inlet temperature of water on the efficiency, useful energy, and mean temperature of absorber of thesolar collector are investigated. Findings:The results indicated that among the various nanoparticles, the addition of copper nanoparticles,followed by copper oxide, results in the greatest improvement in the efficiency and useful energy. The effi-ciency and useful energy increase with increasing the volumetricflow rate and volume fraction of nanopar-ticles. As the volume fraction of nanoparticles increases, the mean temperature of absorber decreases. As theambient temperature increases from 20 degrees C to 40 degrees C, the efficiency increases by 5.5%. As the inlet temperatureof water increases from 30 degrees C to 55 degrees C, the efficiency decreases by 15%. The efficiency decreases with increas-ing the solar radiation intensity. (c) 2021 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved