On interaction between a bubble with evaporation and heated pillar block in microchannel

Abstract

As demand for managing high heat flux in specialized applications grows, flow boiling in microchannels has received escalating attention for its high efficiency and cost-effectiveness. The complex interaction between an evaporating bubble and a heated pillar in a microchannel is governed by a confluence of transport mechanisms, including bubble morphology, fluid convection, heat transfer, and phase change phenomena. This study develops a three-dimensional mathematical model, employing the saturated-interface-volume approach to simulate the complex interaction process effectively. The results indicate that the liquid film thickness between the bubble and the heated surface is the primary factor affecting heat transfer. A reduction in the Reynolds number as well as an increase in the initial bubble diameter lead to a decrease in the liquid film thickness and an increase in the temperature gradient within the thin liquid film, which enhance both the evaporation rate and heat transfer efficiency. The temperature of the surrounding fluid is also decreased. The bubble passage disrupts the flow structure, particularly impacting the boundary layer and vortex structure. These perturbations in temperature and flow structure constitute a secondary factor influencing heat transfer. The efficiency of heat transfer varies significantly across different surfaces; surfaces with a larger thin liquid film region exhibit the most significant improvement, followed by the downstream surface where the flow and temperature fields are most affected. This study advances the fundamental comprehension of the complex interaction between an evaporating bubble and a heated pillar in a microchannel, integrating a detailed analysis of the relevant transport mechanisms.