Experimental study on thermo-hydraulic performances of TiO2-H2O nanofluids in a horizontal elliptical tube

Stable TiO2-water nanofluids are prepared by a two-step method, and the morphologies of nanoparticles and the stability of nanofluids are investigated. The heat transfer and flow characteristics of nanofluids flowing through a horizontal circular tube and a horizontal elliptical tube are experimentally investigated. The effects of nanoparticle mass fractions (φ = 0.1 wt%, φ = 0.3 wt%, φ = 0.5 wt%) and Reynolds numbers ( Re = 5000 - 15 , 275 ) on the Nusselt number and flow frictional resistance coefficient are discussed. In addition, computational formulas for heat transfer and flow performances are put forward based on the experimental data using the polynomial fit technique. Also, thermo-hydraulic comprehensive performances of nanofluids in the horizontal circular tube and the horizontal elliptical tube are studied.