Heat transfer enhancement using non-Newtonian nanofluids in a shell and helical coil heat exchanger

•Intensification of heat transfer due to use of non-Newtonian nanofluids in shell and helical coil has been investigated.•Aqueous CMC solution has been used as base fluid.•No detectable increase in stirring work was observed due to the addition of nanoparticles. The current investigation examines heat transfer using three different non-Newtonian nanofluids comprising of Fe2O3, Al2O3 and CuO nanoparticles in aqueous carboxymethyl cellulose (CMC) base fluid. The studies were carried out to determine enhancement in heat transfer compared to base fluid (aqueous CMC solution) in a shell and helical coil heat exchanger. Non-Newtonian nanofluids containing nanoparticles in the concentration range of 0.2–1.0wt% were prepared. Nanofluid and water were used on shell side and tube side respectively. The thermal analysis was carried out to determine overall heat transfer coefficient and shell-side Nusselt number, at different conditions such as flow rate of cold water (0.5–5lpm), shell side fluid (nanofluid) temperature (40–60°C) and stirrer speeds (500–1500rpm). The results show that the Nusselt number increases with increasing nanofluid concentration, shell side fluid temperature, Dean number (flow rate of coil-side water), and stirrer speeds. It was found that the CuO/CMC-based nanofluid showed better heat transfer than the other two types of fluid (Fe2O3 and Al2O3). The heat transfer performance of non-Newtonian nanofluids was significantly enhanced at higher nanofluid concentrations, shell-side temperatures, stirrer speeds and Dean numbers.