Effects of novel hybrid nanofluid (TiO2–Cu/EG) and geometrical parameters of triangular rib mounted in a duct on heat transfer and flow characteristics

Abstract

Heat transfer and flow characteristics have been numerically analyzed by using four different fluids [pure ethylene glycol (EG), TiO2/EG and Cu/EG nanofluids and 50%:50% TiO2–Cu/EG hybrid nanofluid] and changing the position, length and height of a triangular rib placed in a two-dimensional duct under forced convection and turbulent flow conditions using RNG k-epsilon turbulence model. While forming the hybrid nanofluid, all nanoparticles are added at 50–50%. A constant heat flux of 500 W m−2 is applied to the bottom wall of the duct. The Reynolds number is considered in the range of 50,000 and 100,000. Two different nanoparticle volume fractions, 1.0% and 4.0%, are used. The parameters of the rib are dimensionlized, and three different rib positions (X/H = 1, 3 and 5), lengths (S/H = 0.5, 1 and 1.5) and heights (h/H = 0.1, 0.2 and 0.3) are used. Governing equations are determined with the finite volume method. In the study, analysis of Nusselt number, Darcy friction factor (f), PEC number and velocity streamlines is performed in detail. Generally, heat transfer performance increases with increasing Reynolds number and nanoparticle volume fraction, but the increase in nanoparticle volume fraction also increases the Darcy friction factor. TiO2–Cu/EG hybrid nanofluid having the 4.0% nanoparticle volume fraction is the best heat transfer fluid. When using TiO2–Cu/EG hybrid nanofluid, the increase in the PEC number varies between 8 and 30% in the smooth duct. From the results obtained by using hybrid nanofluid in the duct with the triangular rib, it is understood that the rate of heat transfer enhances with increasing dimensionless rib position, length and height. But the most effective parameter of these is change in the rib height. The most suitable fluid for the study is TiO2–Cu/EG hybrid nanofluid with 4.0% nanoparticle volume fraction, and the most favorable rib parameters are rib height of h/H = 0.3, rib length of S/H = 1.5 and rib position of X/H = 5.