Bubble Lift-Off Diameter and Frequency in Ferrofluid Subcooled Flow Boiling

Abstract

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 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 liftoff 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 liftoff diameter both in the absence and presence of the magnetic field during the flow boiling. The bubble liftoff diameter decreases by applying the magnetic field, and the bubbles lift from the surface faster. Moreover, the bubble liftoff 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 liftoff frequency decrease with increasing the fluid mass flux.