Determination of operational flow regime and heat transfer performance optimization of mono and hybrid nanofluids using FOM and sensitivity analysis

Abstract

Nanofluids are considered as the most suitable replacement for conventional coolants due to their augmented thermal properties. The current study focuses on the operational suitability of different nanofluids (45 nanofluids) and estimates their heat transfer performance through Figure of merit (FOM) analysis. To perform an FOM-based ranking of these nanofluids, the heat transfer coefficient, friction factor, and pumping power of several nanofluids were also calculated. The effect of varying the volumetric concentration (0.01–1 vol%) on the pumping power, heat transfer coefficient, and thermo-physical characteristics of several nanofluids was examined. Different process and design parameters like pressure drop, flow velocity, mass flow rate, internal channel diameter, fluid temperature gradient, and wall temperature of the system were varied to check their effect on heat transfer coefficient, friction factor, and pumping power. Based on the FOM analysis, the authors determined that the majority of the nanofluids (26 nanofluids) investigated can be used in both laminar and turbulent flow regimes. The heat transfer coefficient decreases with increasing nanoparticle concentration. Therefore, it is essential to keep the concentration at an optimum level to attain the desired heat transfer performance. Among various key findings from the study, authors reported that the friction factor and pumping power of the nanofluid increases when the pressure drops and the channel’s internal diameter increases, while with increasing flow velocity, the friction factor and pumping power decrease. The authors also suggest that the pressure drop should be limited to 1–1.003 bar, the flow velocity should be greater than 1.4–1.5 m/s and the internal diameter should be 0.02 m to maintain the friction factor below 0.1. The aforementioned parameters are crucial when optimizing the heat transfer performance of a cooling system using nanofluid as a coolant.