Due to the importance of the boiling phenomena and the need of studying the bubble nucleation in different conditions, a series of experiments have been performed in the present study to investigate a Fe3O4 magnetic nanofluid subcooled flow boiling phenomenon inside an annulus. The test section is made of outer glass and inner stainless-steel tubes. The effect of three important parameters, including mass flux, inlet subcooling temperature, and pressure on the bubble lift-off diameter and frequency in the absence and presence of a magnetic field caused by quadrupole magnets, have been considered. The experiments were visualized by using a superzoom camera to study the bubble behaviors on the heating surface. The obtained results show that increasing the mass flux, subcooling temperature, and pressure contributes to decreasing bubble lift-off diameter both in the absence and presence of the magnetic field during the flow boiling. The bubble lift-off diameter decreases by applying the magnetic field, and the bubbles lift from the surface faster. Moreover, the bubble lift-off frequency showed stochastic behavior such as dependence on heat transfer surface, bubble nucleation site properties, and fluid velocity. The obtained results show that the bubble lift-off frequency decrease with increasing the fluid mass flux.
