Thermal-hydraulic behavior of lotus like structured rGO-ZnO composite dispersed hybrid nanofluid in mini channel heat sink

Abstract

An experimental investigation in mini channel heat sink has been performed to assess the thermal-hydraulic behavior of composite dispersed hybrid nanofluid. Reduced graphene oxide-Zinc oxide (rGO-ZnO) nanocomposite particles have been synthesized and dispersed in water to prepare hybrid nanofluid with 0.01% volume concentration. Effects of different Reynolds number (50–600), volumetric flow rate (0.1–0.5 lpm), heat flux (33.33–66.67 W/cm2), channel aspect ratio (2.5–5; corresponding hydraulic diameter: 1.14–1.33 mm) on heat transfer, pressure drop and their relative performance characteristics are examined in details. Reduction in channel aspect ratio from 5 to 2.5 (hydraulic diameter from 1.33 to 1.11 mm) enhances the convective heat transfer coefficient by 47.2% at a flow rate of 0.5 lpm. The heat transfer coefficient significantly increases by about 17.41%, with rise in heat flux from 33.33 W/cm2 to 66.67 W/cm2. The effect of heat flux on the friction factor is not significant throughout the Reynolds number range. Performance evaluation criteria has a decreasing-increasing-decreasing trend with flow rate for all channel aspect ratios and heat fluxes. An optimal flow rate has been observed for the figure of merit at all the combinations of heat flux and channel aspect ratio. The figure of merit has a maximum value of 1.39 for a channel aspect ratio of 3.75 (i.e., hydraulic diameter of 1.26 mm) and heat flux of 66.67 W/cm2.