Experimental investigation of uniform and non-uniform magnetic fields on minichannel heat transfer using ferrofluid and non-ferrofluid

This study experimentally investigates the effects of uniform, non-uniform, and zero magnetic fields on heat transfer performance in ferrofluids (Fe 2 O 3 /water) and non-ferrofluids (SiO 2 /water) within a minichannel. For ferrofluids, the application of magnetic fields led to a reduction in heat transfer; however, this decline was less pronounced under non-uniform fields. Microscopic observations revealed that non-uniform magnetic fields, in conjunction with shear forces and inertial effects, induced the transformation of clusters of particles into compact, rounded aggregates. This restructuring facilitated rapid particle redistribution, which periodically disrupted both thermal and hydrodynamic boundary layers. The resulting disturbances enhanced fluid mixing and improved heat exchange between the channel wall and the working fluid, thereby mitigating the reduction in heat transfer observed under uniform magnetic fields. In contrast, the non-ferrofluid suspensions exhibited no measurable sensitivity to the applied magnetic fields, consistent with their negligible magnetic susceptibility.