Effect of particle diameter of porous media on flow and heat transfer in a mixing tee

Numerical simulations have been carried out to investigate flow and heat transfer in a mixing tee filled with periodic sintered copper spheres. Three particle diameter cases of 28 mm, 14 mm and 7 mm with the array of 4 × 4, 8 × 8 and 16 × 16 at the same porosity of 0.3 have been calculated using large-eddy simulations and the Smagorinsky–Lilly sub-grid scale model. With the particle diameter decreasing, the mixture scale of hot and cold fluid tends to decrease in the mixing tee; the pressure drop of fluid flow through porous media increases. When the particle diameter ratios are 4:2:1 and the specific surface ratios are 1:2:4, the pressure drop ratios are 1:2:4; the thermal mixing in porous media is weakened because the temperature fluctuation decreases and the stratification of hot and cold fluids is observed.

► Three particle diameter cases of 28 mm, 14 mm and 7 mm were simulated by LES.
► With the diameter decreasing, mixing scale tends to decrease in the mixing tee.
► With the diameter decreasing, thermal mixing is weakened.
► With the diameter decreasing, the thermal stratification is obvious.
► When the particle diameter ratio is 4:2:1, pressure drop ratio is 1:2:4.