Heat transfer enhancement in a heated copper tube using the electromagnetic vibration method for nanofluids as working fluid: An experimental study

This study proposes a novel active method, the electromagnetic vibration method, to augment heat transfer in a heated copper tube. To that end, a stretched wire turbulator with a designed vibrational frequency is installed in the middle of a tube. The water, Al2O3-water, and CuO-water with different volume fraction(ϕ) ranging 1% to 2% is employed as working fluids. The tests are conducted for various mass flow rates, and the results are compared. The findings revealed that the vibrating wire turbulator could significantly affect the heat transfer rate. The results showed that the oscillator vibration has a double effect on the heat transfer rate of nanofluids. The results showed that at the mass flow rate of 0.47 L/min, in the best case, CuO-water nanofluid alone increases the average heat transfer coefficient by 21.1%, while using vibrating wire turbulator, this value can be increased up to 150.7%. Also, the results show the fact that by increasing (ϕ), and inserting vibrating wire turbulator simultaneously for CuO-water nanofluid, thermal enhancement factor can be increased from 1.09 to 1.91. To this end, it can be said that the vibrating wire turbulator magnified the heat transfer rate in the all studied nanofluids. Finally, the sedimentation time of the nanoparticles for the case with/without the vibrating wire turbulator is compared. Samples observation shows a notable delay in deposition of nanofluids by employing vibrating wire turbulator.