$V\%$	Volume percentage (-)
$wt\%$	Weight percentage (-)
$Re$	Reynolds number (-)
$Nu$	Nusselt number (-)
$ID$	Inner diameter (m)
$D$	Pipe diameter (m)
$x$	Critical length (m)
$h$	Heat transfer coefficient ($W/m^2.K$)
$T$	Temperature ($K)$
$c_p$	Specific heat ($J/kg.K$)
$\dot{m}$	Mass flow rate ($kg/s$)
$A$	Heat transfer area ($m^2$)
${\dot{Q}}_{absorbed}$	Rate of energy absorption ($W$)
$\dot{q}$	Heat flux ($W/m^2$)
Greek Symbols
$\varphi$	Nanoparticle Volume fraction (-)
$\rho$	Density ($kg/m^3$)
Subscripts
$nf$	Nanofluid
$oil$	Oil
$bf$	Base fluid
$p$	Particle
$in$	Inlet
$out$	Outlet