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

摘要

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 < Re < 2124) and constant heat flux was applied externally on the pipe surface. It is aimed to study effect of different parameters such as Reynolds number, volume concentration of nanoparticle (0 <= phi <= 0.05), constant magnetic field (B = 0.3 T), alternating magnetic field with different wave types (sinus, square and triangle) and different frequencies (2, 5 and 15 Hz) of alternating magnetic field on the convective heat transfer. Experimental results showed that the constant magnetic field offers 13% convective heat transfer enhancement compared to the absence of a magnetic field. On the other hand, the alternating magnetic field increases the convective heat transfer in the pipe up to 35%. Furthermore, lower frequencies of the alternating magnetic field have been more effective in convective heat transfer enhancement. Square wave type alternating magnetic field steps forward in the aspect of convective heat transfer enhancement rate among the other wave types. The alternating magnetic field applications look promising in the future for increasing energy efficiency, and it can also be implemented in heat exchangers, solar collectors, emergency heat removal systems in nuclear power plants.