Evaluating the heat transfer characteristics of hybrid nanofluid flow in circular ducts with constant heat flux

Researchers have recently been interested in introducing solid nanoparticles into thermal systems in order to improve their thermal performance as a nanofluid. Researchers have investigated nanoparticle types, sizes, and concentrations using theoretical, numerical, and experimental approaches. In the present study, a hybrid nanofluid was utilized in two concentrations, namely (0.5% ZnO+0.5% SiO2-distilled water) and (1% ZnO+1% SiO2-distilled water), in a 45o inclined heated pipe at a constant heat flux of 12000 W/m2 and a range of 4000 to 12000 for the Re number.Initially, the performance of the test apparatus was evaluated using distilled water in the same conditions as the hybrid nanofluids experiment, and its results were compared to an empirical relation to ensure accurate results. The experimentation results indicated that the nanofluids significantly improved heat transfer coefficients when nanoparticle concentration increased in hybrid fluids. This indicates that increasing nanoparticle concentrations can substantially improve heat transfer coefficients. Using hybrid nanofluids with a concentration of (0.5 and 1)% increases the heat transfer coefficient by 1.2 and 1.4 times compared to distilled water.