Augmentation of pool boiling performance using Ag/ZnO hybrid nanofluid over EDM assisted robust heater surface modification

Abstract

Recently, miniaturization has been scaled up tremendously to improve the compactness and aesthetics of devices. Such changes require adequate thermal management for efficient and flawless operation. Pool boiling in such scenarios is preferred as it offers significant amounts of latent heat for transferring thermal energy. The current research looks at augmentations offered using Ag/ZnO hybrid nanofluid concentrations of 0.02%, 0.06%, and 0.1% over heater surfaces modified through electro discharge machining (EDM). The modified surfaces had average surface roughness (Ra) values ranging from 2.96 µm to 8.53 µm for EDMed surfaces (E1, E2, and E3). Amongst all experimental trials, the one with a 0.1% concentration of Ag/ZnO hybrid nanofluid over surface E3 exhibited the highest critical heat flux (CHF) of 225.68 W/cm2 and a heat transfer coefficient (HTC) of 151.63 kW/m2 °C, which are respectively 80.43% and 252.98% greater than the control surface (CS)-DI water combination with a Ra value of 1.61 µm used for comparison. Overall, increased nucleation sites owing to EDM machining and decreased surface contact angle owing to nanoparticle deposition attributed to an augmented pool boiling performance.