Experimental evaluation of forced convective heat transfer of Fe3O4 ferrofluid in a horizontal u-shaped tube under variable magnetic field effect based on Taguchi approach

In this paper, the hydrodynamic and thermal behavior of a Fe3O4 ferrofluid flow was experimentally investigated inside a cupric u-shaped tube on a horizontal surface, under the effect of a variable magnetic field. The inlet flow regime was laminar and considered under the thermal boundary conditions of the tube with a uniform heat flux, which was affected by the variable magnetic field in some regions. The purpose of the study was to investigate the effect of parameters such as volume fraction of nanoparticles, Reynolds number of the flow, the radius of the curvature, and magnetic field frequency at three levels and four factors in the flow behavior in order to increase the convection heat transfer coefficient. The analyses were carried out separately for three regions of the tube, namely straight inlet section, tube curvature section, and straight outlet section following Taguchi method of experiment design and ANOVA. Results of ANOVA showed that changes in Reynolds number in the curvature of the tube had the greatest effect (82.88%) in increasing the convection heat transfer coefficient. However, this parameter affected straight sections of the inlet and outlet tube by 69.61% and 73.47%, respectively. In addition, the minimum influence on increasing convection heat transfer coefficient was observed with frequency parameter, which had its effect on a straight section of the inlet tube, curvature section of the tube, and straight section of the outlet tube by 1.48%, 0.66%, and 0.7%, respectively.