Experimental and Numerical Analysis of Heat Transfer Enhancement Using Nanofluids in Circular Pipes

Abstract

This study investigated heat transfer enhancement in circular pipes using nanofluids through a combined experimental and numerical approach with the aim of improving the thermal performance of conventional heat transfer fluids. The motivation for the study arises from the limited thermal conductivity of traditional working fluids such as water, which constrains the efficiency of heat exchangers and piping systems used in industrial and energy applications. Aluminium oxide water based nanofluids were prepared using the two step method at volume fractions of 0.5 percent, 1.0 percent and 1.5 percent and tested under forced convection conditions in a uniformly heated circular pipe. Experimental measurements of inlet and outlet fluid temperatures, wall temperatures and pressure drop were obtained over a range of Reynolds numbers corresponding to turbulent flow regimes. Key performance parameters including the heat transfer coefficient, Nusselt number and friction factor were evaluated and compared with those of the base fluid. In parallel, a numerical model based on Computational Fluid Dynamics was developed using steady state incompressible flow assumptions and validated against experimental data and established correlations. The results indicate that the use of nanofluids leads to a significant enhancement in convective heat transfer, with the Nusselt number increasing with both nanoparticle concentration and Reynolds number, while also causing a moderate increase in friction factor due to higher viscosity. Numerical predictions showed close agreement with experimental results, with deviations generally below three percent, confirming the reliability of the simulation model. Performance evaluation revealed that a nanoparticle volume fraction of approximately 1.0 percent provides the best balance between heat transfer enhancement and hydraulic efficiency. The study concludes that nanofluids offer strong potential for improving heat transfer performance in circular pipe systems when optimal operating conditions are carefully selected.