Hydrothermal behavior of hybrid magnetite nanofluid flowing in a pipe under bi-directional magnetic field with different wave types

Abstract

• Convection of Fe 3 O 4 /water nanofluid flow experimentally investigated. • Constant and alternating magnetic field effects are considered. • Sinus, square, and triangle waves were used for alternating magnetic field wave type. • Square wave is the best option to obtain higher Nusselt numbers for Fe 3 O 4 /water nanofluid flow. • Lower frequencies offer better enhancement. This experiment setup has been developed to elucidate the effect of different wave types (sinusoidal, triangle, square) of bi-directional magnetic field on hydrothermal characteristics of hybrid magnetite nanofluid flowing through a tube. The bi-directional magnetic field is not a novel method among active methods of heat transfer enhancements, yet the effects of different wave types have not been researched so far. In this study, the effects of different wave types of alternating magnetic fields with various frequencies ( f ) (2, 5, and 15 Hz) on flow and heat transfer characteristics of Fe 3 O 4 -Cu/Water hybrid magnetic nanofluid flow have been investigated experimentally. The major findings have been discussed for different combinations of hybrid magnetite nanofluid, types of waves, values of Reynolds number ( Re ), and f . The hydrothermal characteristics and their effects on usability in the industry with high efficiency have been established in terms of average Nusselt number ( Nu ), average friction factor (f), and Performance Evaluation Criteria ( PEC ). It is concluded that the use of triangle wave type with f = 15 Hz with 2% Fe 3 O 4 /water shows the highest enhancement in f by 500% compared to distilled water ( DW ) at Re = 994 while the use of square wave type with f = 5 Hz using the same Re and nanofluid presents the highest increase in Nu by 15.3% compared with DW. Above all, the triangular wave type is determined as an optimum wave type for f = 15 Hz while the sinus and square wave types are realized as optimum ones for f = 5 Hz .