Abstract
With the aim of improving the usefulness of a solar system in energy-saving, the thermal behavior of the domestic hot water system was investigated. The energy/continuity equations were developed to investigate the transient analysis of a solar hot water system in three climatic regions in Saudi Arabia (Najran, Jeddah and Riyadh). By using a water-filled solar system, the energy consumption of the boiler reduced by 12478, 13,289 and 13,896 kWhyear in Najran, Riyadh and Jeddah, respectively. With the addition of WO3, CeO2, Al2O3, Fe3O4, CuO and MWCNT nanoparticles, although the thermal conductivity increases (positive effect), but at the same time, the parameter of density × specific heat may be reduced (negative effect), hence using nanoparticles maybe not useful. In this study, it was found that increasing the conductivity has a greater effect and therefore for all nanoparticles, the collector heat gain increased. The best results were related to the collector equipped with MWCNT, so that this collector had more energy-saving than the water-based one by 9963 (for Najran), 10,000 (for Riyadh) and 10,379 kWh/year (for Jeddah).