三角形微通道中环状冷凝过程的数值模拟

Numerical simulation for annular condensation flow in triangular microchannels

建立了三角形微通道中环状冷凝的一维稳态模型,给出了等边三角形微通道中环状冷凝过程的液相毛细半径沿轴向的变化曲线.计算发现,在等边三角形微通道中,气液界面毛细半径先沿程急剧增加,然后趋向平缓,最后再急剧上升,且毛细半径的平缓段占据了绝大部分冷凝段总长度.在接触角和通道热流密度较小或者通道水力直径和入口蒸气压力较大时,冷凝段长度较长.在冷凝过程中,流速和液相压力沿程变化剧烈.该模型较好地解释了三角形微通道环状冷凝机理,并能用于估算冷凝过程的部分参数,为进一步推导更完善的微通道冷凝模型奠定了基础.

A one dimensional steady condensation model for annular flow in triangular microchannels was developed. The curvature radius distribution of the condensate stream along the channel was calculated. It is found that the curvature radius of the liquid phase increases rapidly at the beginning. When the condensation process developes along the microchannels, the radius increase turns to be more slowly. At the end of condensation range the radius increases rapidly again. The smooth radius distribution takes place in the most part of the total condensation length. The total condensation length is determined by the contact angle, the hydraulic diameter of the channel, the steam pressure and the heat flux. A smaller contact angle and heat flux or a larger hydraulic diameter and steam pressure cause a longer condensation length. The change of the pressure in the liquid phase and the velocities along the channel is remarkable. This one dimensional steady model provides a better understanding of the mechanisms of condensation in triangular microchannels.