为了提高气体冷却器内换热效率，对不同倾斜角下(-90°，-45°，0°，45°，90°)螺旋槽管内超临界CO2冷却对流换热特性进行了数值模拟，分析了各槽管内的湍动能和速度分布随倾斜角的变化趋势，并研究了不同螺旋角下倾斜角对换热特性的影响。结果表明:浮升力沿流动方向分量和垂直于流动方向分量对流动特性的影响并不相同;在类气区，流体速度对流动特性起主要作用，且换热系数随倾斜角的减小而增大；在类液区，流动特性的主要影响因素是速度梯度，此时换热系数随倾斜角的变化与类气区相反；螺旋角越大即螺旋程度越小，当流体倾斜向上流动时浮升力效应越为显著；当螺旋角为 0.70 rad时，最优倾斜角度为-45°，当螺旋角为0.94 rad时，最优倾斜角为45°。

The cooling convective heat transfer characteristics of supercritical carbon dioxide in spiral fluted tubes under various inclined angles of -90°,-45°,0°,45° and 90° were numerically simulated,in order to enhance the heat exchange efficiency of air cooler.The variation trends of the turbulent kinetic energy and the fluid velocity distribution in each fluted tube with the inclined angles were analyzed,and the influence of the inclined angle on the heat transfer characteristics under the different helix angles was studied.The results show that the components of the buoyancy force along the flow direction and perpendicular to the flow direction have different effects on the flow characteristics.In the gaslike region,the fluid velocity plays the main role on flow characteristics,and the heat transfer coefficient increases with the decrease of inclined angles.In the liquidlike region,the dominant impact factor of flow characteristics is the velocity gradient,and the variation of the heat transfer coefficient with the inclined angle is opposite to that in the gaslike region.The bigger the helix angle is,the smaller the helix degree is.The buoyancy effect will be more significant when the fluid inclines to flow upwards.The optimal inclined angle is -45° when the helix angle is 0.70 rad; The optimal inclined angle is 45° when the helix angle is 0.94 rad.

TK124

上海市动力工程多相流动与传热重点实验室（13DZ2260900）