Analysis at cell scale of porosity effect on forced convection with nanofluids in porous structures with Kelvin cells

Abstract

In this paper a numerical investigation in metal porous structures with Kelvin cell model is carried out on water/Al2O3 nanofluids using the single-phase model. The employed foams are characterized by a fixed value of cells per inch (CPI) equal to 10 for porosity ɛ equal to 0.85, 0.90, 0.92, 0.95, 0.97. For porosity of 0.95 structures at 5, 20 and 40 CPI are also analyzed. Three different values of Al2O3 nanoparticle volume concentrations ϕ, equal to 0, 2 and 4% are used. Results are showed and discussed in terms of pressure drop and temperature profiles, velocity and temperature fields. Correlations for the evaluation of permeability K and drag coefficient CF and their values are also shown. Furthermore, dimensionless entropy generation as function of Reynolds number has been evaluated.The results reveal that both the pressure and the temperature have a periodic trend with oscillations that vary both for the geometric aspects and for the properties of the fluids used. The velocity and temperature fields then serve to understand the dynamic and thermal characteristics: the highest velocities are recorded at lower porosities and at the contact zones from between two cells, as well as the highest temperature differences between outlet and inlet sections. The correlations with which permeability and drag coefficient are obtained reveal that they depend only on the foam used and not on the fluid considered. Finally, the trend of the dimensionless entropy generation as a function of the Reynolds number is decreasing and reducing with increasing porosity.

Keywords

• Open metal foams
• Nanofluids
• Forced convection
• Kelvin cells
• Entropy generation analysis