Overview
This research numerically investigates the dynamics of vapor bubble trains in microchannel flow boiling. The study specifically focuses on the interactions within bubble trains, a common occurrence in practical microchannel flow boiling applications, contrasting with previous work that predominantly examined isolated bubbles.
Research Context
Microchannel flow boiling is identified as a promising technique for thermal management in micro-devices. Effective application of this technique relies on understanding the dynamics of bubbles formed during the boiling process. Existing research efforts have primarily concentrated on single, isolated bubbles. However, in actual microchannel flow boiling scenarios, bubbles frequently form and move as trains, necessitating an understanding of their interactive dynamics for practical utility.
Approach
The study employed a numerical investigation approach to analyze vapor bubble trains within microchannel flow boiling. A flow-focusing technique was adopted to generate monodispersed bubbles upstream of the microchannel. Variables manipulated in the numerical model included the initial vapor-liquid volume ratio, the heat flux on the channel wall, and the latent heat of the working fluid.
Findings
- Effect of Initial Vapor-Liquid Volume Ratio: As the initial vapor-liquid volume ratio increased, the bubble frequency was observed to increase. Concurrently, the growth rate of the bubbles decreased, which was attributed to a reduction in individual bubble size.
- Effect of Heat Flux and Latent Heat: Increasing the heat flux applied to the channel wall or reducing the latent heat of the working fluid resulted in an increased growth rate of the bubble train. This enhancement in growth rate was linked to an increased vaporization rate.
- Bubble Expansion and Movement: The vaporization of the fluid occurring in the upstream sections of the microchannel led to bubble expansion. This expansion, in turn, caused an acceleration of the bubble movement in the downstream sections.
- Thermal Fluctuations: The periodic passage of bubbles through the microchannel caused fluctuations in both the wall temperature and the Nusselt number.