Experimental examination of a boiler heat exchanger using nanofluids: Thermo-energetic and enviro-economic analysis

Single and hybrid nanofluids have been widely employed in different thermal systems, showing notable thermal advancements. The current work examines zinc oxide (ZnO) and hybrid multi-wall carbon nanotubes-zinc oxide (MWCNT-ZnO)-based nanofluids to maximize the thermal energy of boilers and assist sustainability. Energetic parameters, such as boiler efficiency and electric power consumption, are also quantified for proposed nanofluids compared to conventional water. Moreover, an enviro-economic analysis was presented to show the CO₂ emission minimization and electric energy cost savings on a daily basis. Experimental outcomes revealed that the MWCNT-ZnO hybrid nanofluid has increased the heat transfer rate, convective heat transfer coefficient, and Nu to about 4252 W, 1524 W/m²·K, and 226.19, when at 0.02 % and inlet temperature of 55.94 °C. However, minimum friction factor and pressure drop were reported for water compared to using ZnO and MWCNT-ZnO nanofluids. The hybrid nanofluid augmented boiler efficiency and electric power consumption by about 7 % and 43 %, respectively over water usage, indicating remarkable thermo-energetic progress. Moreover, the enviro-economic analysis results showed that using mono and hybrid nanofluids has decremented CO₂ emissions and saved energy costs by about 22 % and 30 % by employing ZnO and MWCNT-ZnO nanofluids, respectively.