Heat transfer mechanisms in bubbly Rayleigh-Benard convection

TL;DR

This study investigates how vapor bubbles influence heat transfer in Rayleigh-Benard convection near boiling conditions, revealing that bubble effects depend on the Jacob number and can either stabilize or destabilize the flow, affecting heat transfer efficiency.

Contribution

The paper introduces a numerical simulation framework for bubbly Rayleigh-Benard convection that accounts for bubble growth, evaporation, and condensation, highlighting the role of the Jacob number in flow stability.

Findings

Small Jacob number stabilizes flow by heat absorption and release.

Increasing Jacob number destabilizes flow and enhances heat transfer.

Bubble dynamics significantly impact convection behavior.

Abstract

The heat transfer mechanism in Rayleigh-Benard convection in a liquid with a mean temperature close to its boiling point is studied through numerical simulations with point-like vapor bubbles, which are allowed to grow or shrink through evaporation and condensation and which act back on the flow both thermally and mechanically. It is shown that the effect of the bubbles is strongly dependent on the ratio of the sensible heat to the latent heat as embodied in the Jacob number Ja. For very small Ja the bubbles stabilize the flow by absorbing heat in the warmer regions and releasing it in the colder regions. With an increase in Ja, the added buoyancy due to the bubble growth destabilizes the flow with respect to single-phase convection and considerably increases the Nusselt number.