Investigation on the thermal properties, heat transfer and flow performance of a highly self-dispersion TiO₂ nanofluid in a multiport mini channel

The present study experimentally investigated the single-phase convective heat transfer and pressure drop characteristics of a highly self-dispersion TiO₂ nanofluid inside a multiport mini channel with 1.22 mm hydraulic diameter. Nanofluids with volume concentrations of 0.5% and 1% were used. Thermal properties for the nanofluid were measured and compared with correlations. Results indicate that the adding of nanoparticles not only enlarges the thermal conductivity by 4.2% averagely but also significantly increases the viscosity by 14.9% for the 1% nanofluid. Besides the viscosity, the thermal conductivity and density can be predicted well by correlations. Compared with water flow, the nanofluid flow presents an earlier laminar-turbulent transition. Before the transition, the nanofluid has roughly the same performance but slightly smaller Nusselt numbers with water. After the transition, it shows better heat transfer performance and greater friction factors. Moreover, the thermal performance factor is greater than 1 for Reynolds number of 1500–2200 and the maximum of 1.57 occurs at the Reynolds of 1800. Outside this range, its value is close to 1 or even slightly smaller than 1. Finally, the exiting correlations for Nusselt number were evaluated. The present study provides a practical candidate and experimental data for the selection and design of nanofluid based heat exchanger.