HEAT TRANSFER ENHANCEMENT IN A HELICALLY CORRUGATED TUBE BY EMPLOYING W/EG BASED NON-NEWTONIAN HYBRID NANOFLUID UNDER TURBULENT CONDITIONS

In this study a numerical investigation is carried out for heat transfer and fluid flow analysis using ethylene glycol-based TiO2-SiO2 non-Newtonian hybrid nanofluid over a range of volume fractions from 0 to 5% inside a helically corrugated tube under turbulent flow conditions. The analysis is performed with different mixing ratios of TiO2 and SiO2 at different corrugation-height ratios (e/D-h = 0.05, 0.07, 0.09) and pitch ratios (p/D-h = 0.25, 0.30, 0.35). Numerical simulations have been conducted using ANSYS FLUENT 19.0 with a constant heat flux of 25 kW/m(2) maintained at the wall surface for a range of Reynolds numbers from 5000 to 30,000. The thermal-hydraulic performance factor exceeds unity in almost every tested combination. It increases by increasing the values of e/D-h and p/D-h and decreasing the concentration of TiO2 in the hybrid-nanoparticle mixing ratio. Thus employing hybrid nanofluids inside corrugated tubes is a worthwhile arrangement at a proper mixing ratio of TiO2 and SiO2.