A novel thermal efficiency analysis on the thermo-hydraulic performance of nanofluids in an improved heat exchange system under adjustable magnetic field

To improve the efficiency of heat exchanger systems for the purpose of reducing the size of the equipment and saving energy, the thermo-hydraulic performance of Fe3O4-water-arabic gum (AG) nanofluids in an improved heat exchange system is explored experimentally in this study. In the heat exchange system in these experiments, a corrugated tube is used instead of a smooth tube, a perforated turbulator is used instead of a smooth turbulator, and an adjustable magnetic field is applied. The effects of the magnetic flux density, nanoparticle mass fraction, arrangement of the magnetic field, shape of the turbulator, and Reynolds number on the thermal and hydraulic performance are analysed. In addition, a novel thermal efficiency index, R3, is proposed to analyse the comprehensive performance of each working condition. The experimental results reveal that a high nanoparticle mass fraction, high magnetic flux density, bilateral staggered magnetic field, and perforated turbulator can provide superior thermo-hydraulic performance. Further, nanofluids with a mass fraction of 0.5 wt% have the best thermo-hydraulic performance when using a bilateral staggered magnetic field and a perforated turbulator, and the thermal efficiency R3 reaches a peak when the Reynolds number is 7000.