New achievements in Fe3O4 nanofluid fully developed forced convection heat transfer under the effect of a magnetic field: an experimental study

The fully developed forced convection of Fe3O4 nanofluid inside a copper tube is empirically investigated under the effect of a magnetic field. All the investigations are performed under a laminar flow regime (670?Re?1700) and thermal boundary conditions of the tube with uniform thermal flux. The tube is under the effect of a magnetic field at certain points. The aim is to study the effect of various parameters, namely the use of nanofluid, the volume percent of nanoparticles, the Reynolds number of the flow, the constant magnetic field, and the alternating magnetic field with various frequencies in terms of flow behavior. To validate the experiment set-up, distilled water is utilized as the working fluid. The results are compared with Shah’s equation, and acceptable agreement is achieved. The results suggest that due to complex convectional flows that developed in the fluid as a result of the Fe3O4 nanoparticles–magnetic field interaction, the increased alternating frequency of the magnetic field and the increased volume fraction lead to an increase in the heat transfer to a maximum value of 4.62. As the Reynolds number increases, the rate of the said increase is reduced and reaches 0.29. At a constant Reynolds number, the increased frequency of the alternating magnetic field results in an increased local heat transfer coefficient. However, this increase is unproportional to the increase in frequency. At high frequencies, increased frequency leads to a slight increase in the heat transfer coefficient.