三维矩形截面通道内不同流速下的过冷流动沸腾数值探究

To investigate the contribution of microlaycr cvaporation lo subcooled flow boiling, a numerical study is conducted based on a microlayer mathematical model suitable for flow boiling in Square tubes. In this study, the effects of fluid-solid conjugate heat transfcr and dynamic contact angles are considered, and the intcrfacc capturing mcthod (VOSET) is cmployed to capture interfaces. The focus is on the growth of a single attached bubblc on the wall during the process of subcooled flow boiling within a basic three-dimensional rectangular cross-section channel unit. The flow pattern evolution and wall superhcat dcgrcc changc during the growth and evolution of a single bubble in the channel under different flow velocity are discusscd, and the distribution of microlayer, evaporation capacity and heat transfer Performance arc quantitatively analyzed, which enhanecs the understanding and knowlcdgc of boiling heat transfer in microchannels, laying the foundaüon for research on flow boiling heat transfer in complete processes. The rcsults show that the initial bubble grows and slides along the wall under the influence of heating and flow, expanding in volumc until its diameter becomes comparable to the cross-sectional size of the channcl, then an extended bubble is formed, and it flows out of channel. The evaporation of the microlayer between the bubble and the wall contributes greatly to the bubble growth and heat transfer. Especially after the formation of an elongated bubble, the evaporation heat flux can aecount for ncarly 80% of the total, directly affecting the local wall superheat and convective heat transfer cocfficicnt. With the inercase of flow vclocity, the bubble grows faster, but their residence time in the channcl is shortened, thereby reducing the duration during which microlayer evaporation can play a significant rolc. On the whole, the average heat transfer coefficient decreases with the increase of inlet velocity.