套管式换热器注气强化传热数值模拟

为研究注气技术强化换热的效果，采用混合模型建立了立式套管式换热器的数学模型，对不同流动状态下的注气强化换热过程进行数值模拟，基于努塞尔数对强化换热性能进行评价，比较了不同流动状态下注气速度对换热器的速度场、温度场和压降的影响。结果表明，注入气泡能够促进流场产生垂直于壁面方向的运动，提高努塞尔数并降低压降，改善了换热器的换热性能；层流时强化换热效果最好，努塞尔数最大提升102%；过渡流和湍流状态下，气泡流速大小对努塞尔数和压降变化无明显影响。

Numerical Simulation of Enhanced Heat Transfer by Air Injection in Double-Pipe Heat Exchanger

To study the effect of air injection technology on enhancing heat transfer， a mathematical model of a vertical double-pipe heat exchanger was established using mixture model. The process of heat transfer with air injection under different flow conditions was numerically simulated. The enhanced heat transfer performance was evaluated based on the Nusselt number. The effects of air injection speed on the velocity field， temperature field and pressure drop of the heat exchanger under different flow conditions were compared. The results show that the injection of bubbles can promote the movement of the flow field perpendicular to the wall， increase the Nusselt number and reduce the pressure drop. As a result， heat transfer performance of the heat exchanger can be improved.In the condition of laminar flow，the heat transfer performance will be enhanced utmostly， and the Nusselt number will be increased maximally to 102%. In the condition of transitional and turbulent flow， the bubble velocity has no significant effect on the Nusselt number and pressure drop changes.