Numerical simulation on flow boiling characteristics in sinusoidal channels of airborne micro heat exchanger

Abstract

With the miniaturization of airborne system, heat dissipation has become a critical issue. Since sinusoidal channel can enhance flow disturbance, it has a stronger heat exchange capacity than that of straight channel. However, flow boiling characteristics in sinusoidal channel are more complex. Here, numerical simulations of flow boiling in sinusoidal and straight microchannels are conducted based on the VOF model with the inner diameter of 1 mm, mass flux of 500 kg/m2 s and heat flux of 50 kW/m2. The effects of channel structure and hypergravity are obtained. The simulation results indicate that bubble evolution in sinusoidal channel is more complex than that in straight channel, and bubbles are more likely to coalesce, deform and break. Vortices appear in sinusoidal channel and disrupt the near-wall boundary layer. Bubble evolution combined with vortices affect the flow boiling performances. For straight channel, dryout is less likely to occur, while for sinusoidal channel, it is more likely due to more drastic flow changes. Furthermore, the transition of flow patterns is faster under hypergravity. For sinusoidal channel, flow patterns transform earlier into slug and circular flows.