Nanofluid in a Minichannel: Multiphase

Multiphase CFD Simulation of Nanofluid inside a Minichannel, ANSYS Fluent

Description

This project simulates heat transfer inside a minichannel using Al₂O₃ nanoparticles suspended in water, employing the Mixture multiphase model to capture the two-phase behavior — with water acting as the carrier phase and Al₂O₃ nanoparticles as the dispersed secondary phase.

The geometry consists of 9 parallel minichannels, each 30 mm long with a 3×1 mm cross-sectional area, designed in SpaceClaim and meshed in ANSYS Meshing using hexahedral elements, totaling 2,850,000 cells.

Methodology

Given the low Reynolds number characteristic of minichannel flow, the flow regime was treated as laminar. A heat flux of 53 kW/m² was applied at the bottom surface, with all other walls treated as adiabatic. The Mixture multiphase model captures the nanofluid behavior throughout, with the mixture entering the channels at 30°C, functioning as the coolant for the applied heat load.

Conclusion

Post-processed contours reveal the resulting thermal and flow behavior throughout the channel array, with the nanoparticle volume fraction set to 1%. The nanoparticles serve to enhance the working fluid's thermal conductivity, thereby improving overall heat transfer performance compared to the base fluid alone.

The mixture exits the channels at 33.6°C, having entered at 30°C — corresponding to a heat gain of 82.2 J. From this, the convective heat transfer coefficient was calculated as:

h = Q / [A × (Tw − Tb)] = 82.2 / [0.00216 × 4.94] = 7703 W/m²·K

This result confirms the nanofluid's effectiveness in enhancing convective heat transfer within the compact minichannel geometry, demonstrating the practical benefit of nanoparticle addition for high-heat-flux cooling applications.