Pulsating flow and magnetic field effects on the convective heat transfer of TiO2-water nanofluids in helically corrugated tube

Both passive heat transfer enhancement techniques; nanofluids, helically corrugated rib and active heat transfer enhancement techniques; pulsating flow, magnetic field on the convective heat transfer and flow characteristics in the helically corrugated tube are investigated. Experiments set up are designed and constructed to test by varying nanofluids mass flow rate of 0.01-0.10 kg/s, nanofluids concentrations of 0.25%, 0.50% by volume, and nanofluids pulsating flow frequency of 10, 15, 20 Hz and the helically corrugated rib with the depth and pitch of 1.25 mm, 6.35 mm, respectively. As comparing with the plain tube, the physical properties by using nanoparticles and disturbing at the thermal boundary zone of working fluid have significant effect on the enhancement of heat transfer. In addition, the disturbing of nanoparticles Brownian motion suspending in the based fluid by magnetic field and pulsating flow frequency have also significant increment of heat transfer. It can be seen that a combined heat transfer enhancement techniques are satisfy the practical applications to improve the thermal performance of thermal devices. (C) 2018 Elsevier Ltd. All rights reserved.