Abstract:
This work computationally explores the two-phase flow of nanofluids and their thermal energy
transport coefficients in 3D diamond-shaped cavities with square-shaped barriers having reducing
dimensions. Materials with two emissivity values, ε = 0.3 and 0.9, have been considered to investigate
the effect of the radiation thermal energy transport coefficient while the hot side is maintained
at 400 or 500 K. Two values of the Rayleigh number, Ra = 106 and 108, are used for the study. Cu
nanoparticles (NPs) with an average size of 25nm have been used at a concentration of 0.01–0.05%
in the base fluid. The temperature gradients and thermal energy transport coefficient characteristics
are enhanced by raising the volume concentration of nanoparticles, but the streamlines do not alter
substantially. By increasing Ra, the thermal energy transport coefficient rate is further augmented.
It is also found that increasing the Ra and volume concentration of NPs results in enhanced heat
transfer inside a cavity, while a change in the emissivity coefficient has no significant impact on the
thermal and flow characteristics of the nanofluid. For each case, there is an optimum NP volume
fraction for each model that leads to the highest Nusselt number.
