Thermal efficiency of flat plate thermosyphon solar water heater with nanofluids

Abstract

BackgroundMany techniques are used to improve the thermal efficiency of flat plate solar collectors. The previous studies showed the high potentials of nanofluids for thermal efficiency improvement of flat plate solar collectors. MethodsIn this study, a numerical simulation is carried out to investigate the thermal efficiency of the flat plate thermosyphon solar water heater with different nanofluids. The water-aluminum oxide, water-copper oxide, water-copper, and water-titanium oxide nanofluids are used. The effects of different parameters, such as the volume fraction of nanoparticles, volumetric flow rate, solar radiation intensity, ambient temperature, and inlet temperature of water on the efficiency, useful energy, and mean temperature of absorber of the solar collector are investigated. FindingsThe 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 efficiency and useful energy increase with increasing the volumetric flow rate and volume fraction of nanoparticles. As the volume fraction of nanoparticles increases, the mean temperature of absorber decreases. As the ambient temperature increases from 20 °C to 40 °C, the efficiency increases by 5.5%. As the inlet temperature of water increases from 30 °C to 55 °C, the efficiency decreases by 15%. The efficiency decreases with increasing the solar radiation intensity.