Comparison of bi-directional multi-wave alternating magnetic field effect on ferromagnetic nanofluid flow in a circular pipe under laminar flow conditions

•Convection of Fe3O4/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 Fe3O4/water nanofluid flow.•Lower frequencies offer better enhancement. Nanofluids have been attracting huge attention because of their heat transfer enhancement capabilities. Furthermore, magnetic field effect has been being researched recently. By reason of further heat transfer enhancement potential, constant and alternating magnetic fields have been utilized in the present work. Forced convection heat transfer of Fe3O4/water nanofluid flow in a straight pipe under constant and alternating magnetic field effect has been investigated experimentally. Experiments were performed under laminar flow regime (1122