Friction Factor and Heat Transfer Enhancement of Hybrid Nanofluids in a Heated Circular Tube

This work investigates the potential of hybrid nanoparticles suspended in pure water to enhance the thermal performance of heat exchangers at minimal weight fractions. A hybrid nanofluid consisting of 50% ZnO and 50% Al 2 O 3 nanoparticles dispersed in pure water at weight fractions of 0.1%, 0.3%, and 0.5% was prepared. An experimental rig, featuring a straight horizontal tube with a constant wall heat flux, was equipped with eight thermocouples positioned at the inlet, outlet, and along the tube's surface. The study focuses on the impact of the hybrid nanofluid on the friction factors and heat transfer coefficients within a Reynolds number range of 5000 to 20000. Observations indicate that the Nusselt number escalates with an increase in the Reynolds number through the horizontal tube, while the friction factor exhibits a converse relationship. The peak Nusselt number and friction factor were observed at a 5% mass fraction of the hybrid nanofluid. Specifically, enhancements in the Nusselt number were recorded at 9%, 11.8%, and 16.7% for the weight fractions of 0.1%, 0.3%, and 0.5% respectively. Additionally, the deviation in the friction factor was noted at 2.3%, 3.6%, and 4.1% in comparison to pure water. This study thus provides critical insights into the role of hybrid nanofluids in optimizing heat transfer in heat exchangers.