Effect of ZnO nanofluids on thermo-hydraulic characteristic of flow in a heated duct

ABSTRACT

Utilizing nanofluids in place of traditional fluids is an innovative technique to boost heat exchange capability, as conventional fluids are ineffectual due to their limited thermal conductivity. In this study, nanofluids containing zinc oxide are produced at concentrations ranging from 0% to 1.5% by volume. Nanofluids are evaluated for zeta potential and particle size using a particle analyzer based on dynamic light scattering (DLS) and electrophoretic light scattering (ELS). The particle distribution curve for 0.2% concentration peaks at approximately 102 nm, but for 1.5% it moves to 185 nm, demonstrating that agglomeration increases at greater concentrations. All of the produced nanofluids are stable and exhibit zeta potentials greater than 30 mV. The stable nanofluids are characterized for viscosity and thermal conductivity as a function of concentration and temperature. The thermal conductivity of nanofluid is observed to increase with concentration and temperature, whereas the viscosity increases with concentration but decreases with temperature. A maximum increase of 12.1% in thermal conductivity and 30% increase in viscosity are found at 1.5% concentration. By passing it through a heated rectangular duct, the heat transfer characteristics of a ZnO nanofluids are determined numerically. The Nusselt number and entropy generation rate are examined at various temperatures and concentrations. Nusselt number is observed to rise with concentration with a maximum of 9.2% augmentation at 60${\hspace{0.17em}}^{\circ }C$ for 1.5% concentration whereas the rate of entropy generation decreases with concentration. In addition, the thermal performance index of the flow is found to rise with concentration from 0.956 at 0.2% concentration to 0.991 at 1.5% concentration.

KEYWORDS:

• Thermal conductivity
• Zinc oxide (ZnO)
• nanofluid
• viscosity
• thermal characteristics
• heated duct

Disclosure statement

No potential conflict of interest was reported by the author(s).

Nomenclature

P	=	Pressure (Pa)
$\rho$	=	Density (kg/m3)
Cp	=	Specific Heat Capacity (J/kg.K)
T	=	Temperature (K)
$\mu$	=	Dynamic Viscosity (Pa.s)
$\varphi$	=	Volume fraction
$\nu$	=	Kinematic viscosity (m2/s)
u, v	=	X and Y-velocity(m/s)