Heat transfer characteristics and boiling heat transfer performance of novel Ag/ZnO hybrid nanofluid using free surface jet impingement

ABSTRACT

An experimental study has been performed to analyze the heat transfer characteristics by impinging a hybrid nanofluid jet on horizontal-heated test surface. The Ag/ZnO nanoparticles are synthesized and dispersed in DI water Φ = 0.02% to 0.1% by volume. A set of experiments were performed to calculate heat transfer coefficient and boiling performance at varying Reynolds numbers ranging from 1769 to 8273 and different ratios of H/D. The experimental analysis reveals that there is 88.53% and 87.17% improvement in the heat transfer coefficient and boiling performance for Ag/ZnO hybrid nanofluid when it is compared with water at H/D = 3.5.

KEYWORDS:

• Jet impingement
• heat transfer
• boiling heat transfer
• hybrid nanofluid

List of symbols

d	=	diameter of test disc (m)
D	=	diameter of a jet (m)
Dh	=	hydraulic diameter (m)
h	=	heat transfer coefficient (W.m−2.K−1)
H	=	distance between jet to disc surface (m)
k	=	thermal conductivity (W.m−1.K−1)
q	=	heat flux (W.m−2)
T	=	temperature (K)
V	=	flow velocity (m.s−1)
Re Reynolds number ($\left(\rho VD/\mu \right)$	=
Nu	=	Nusselt number $\left(hD/k\right)$
Pr	=	Prandtl number $\left(\mu C_p/k\right)$
µ	=	viscosity (Pa.s)
Φ	=	volume concentration (%)
m	=	mass (kg)
ρ	=	density (kg m−3)

Subscript

bf base fluid (deionized water)	=
np	=	nanoparticles
nf	=	nanofluid