Conjoint effect of nanofluids and baffles on a heat exchanger thermal performance: Numerical approach

Abstract

Nanofluids have gained attention in recent years as a practical solution for enhancing thermal
system performance. However, conjoint enhancement methods, such as fins and baffles, have shown further
improvement in overall efficiency of systems. This paper explores the advancements of heat characteristics of a circular heat exchanger pipe with conical geometry baffles employing three nanofluid types, namely oxide (Al2O3), metallic (Fe), and carbon (Gr) based water. The baffled pipe was examined for varying nanofluid concentrations, represented by the volume fraction of nanoparticles in water (0.5%, 1%, and 1.5%) and exposed to a constant surface heat flux in turbulent flow conditions. The impact of various Reynolds numbers (Re), ranging from 5000 to 25000, on the thermal characteristics of the baffled heat exchanger pipe is studied. The numerical findings showed that employing nanofluids as an alternative working fluid to water has improved thermal properties considerably. Moreover, nanoparticles have increased the Nu of nanofluids compared to the usage of water. Significant improvements in the heat transfer coefficient were observed for all three nanofluids at a Reynolds number (Re) of 25000 and a nanoparticle concentration of 1.5%, compared to water. The Al2O3 -water nanofluid showed the most notable enhancement, with a 4.5% increase in the heat transfer coefficient. This improvement is due to the superior thermal conductivity of Al2O3 nanoparticles and their ability to induce localized turbulence within the fluid. Meanwhile, the Fe-water nanofluid demonstrated a 3.1% enhancement due to its metallic properties promoting better thermal energy transfer than the base fluid. Lastly, the Grwater nanofluid achieved a 1.4% increase, which, while lower than the other two, still indicates that carbon-based nanoparticles can provide a measurable boost in thermal performance under turbulent conditions