Effects of baffle configurations on heat transfer characteristics of nanofluids in a shell-and-tube heat exchanger: A numerical approach

Abstract

In the present study, four heat exchanger configurations of shell-side circular and hexagonal tube arrangements with segmental and staggered baffles are considered for the assessment of the heat-transfer performance on the shell side. A steady, pressure-based ANSYS Fluent 2020 R1 is used to implement the RNG k-ε turbulence model to develop a three-dimensional CFD model, which is based on a single-phase nanofluid approach. The relationship between the flow structure at the shell side, nanoparticle concentration, and heat transfer rate is taken into consideration while discussing the external forced convection phenomena around baffled tube bundles. Inlet temperature of the shell-side is 333 K and inlet temperature of the tube-side is 300 K, with various shell-side mass flow rates of 0.5–2.5 kg/s maintained. The Al₂O₃, CuO, TiO₂, and tri-hybrid nanofluids are investigated at volume fractions of 1–3% because Brownian diffusion and thermophoretic migration are assumed to be negligible. The thermal and flow characteristics are evaluated using temperature, pressure drop, friction factor, Nusselt number (Nu), and streamline contours. The findings demonstrate that the staggered baffles are more effective in mixing shell-side flow than the segmental baffles, and the hexagonal tube arrangement is more effective in wall sweeping and flow. The outlet temperature, heat transfer coefficient, Nusselt number, and flow fields are more uniform in the combination of hexagonal tubes with staggered baffles. While the friction factor stays almost constant with a tiny drop (0.66–0.76) for 1% CuO and 3% Al 2 O₃, demonstrating minor hydraulic variation among all nanofluids, the Nusselt number increases from 110-120 to 350–420 (max 420 for 1% of Al 2 O₃/hybrid nanofluids), indicating considerable convective heat transfer improvement.