Experimental investigation of thermal performance of a sample of solar water heater vacuum tube modified with the help of nanofluids

Today, energy plays an important role in the economic growth of human societies. Among the types of energy consumed by humans, solar energy can be considered the most abundant. Therefore, over the years, various types of solar water heating systems have been developed and used. Considering the remarkable capabilities of nanofluids in improving heat transfer processes and increasing the thermal efficiency of heating systems, the use of nanoparticles as a substitute for conventional fluids in various heating systems, especially solar energy systems, as well as the effect of widely used nanofluids So much attention has been paid to increasing the thermal efficiency of the solar vacuum tube collector. In this research, the most important component, namely the efficiency of solar water heaters and also the heat transfer process using three types of nanofluid (with mass percentage 1%), has been investigated. All tests were performed in accordance with the relevant standards (ISO-9806), on sunny days. The highest increase in heat transfer of nanofluids and also the thermal efficiency of the system is related to noon (religious noon), among which, the highest efficiency is related to aluminum oxide nanofluid (AL2O3 nanofluid), with a 3.46% increase compared to the base fluid (Oil fluid) is. The thermal efficiency of the system with titanium oxide nanofluid (TiO2 nanofluid) and carbon oxide nanofluid (C nanofluid) as well as the base fluid (oil fluid) show 2.54%, 2.12% and 1.6%, respectively. Due to the increase in heat capacity of the nanofluids used, the heat capacity can be considered an important factor in increasing the efficiency of vacuum tube solar water heaters.