竖直三维内肋管管内变压器油自然对流换热特性

Natural convective heat transfer characteristics of thansformer oil in the vertical 3-D internal finned tube

利用田口法对具有不同肋结构参数的竖直三维内肋管管内变压器油自然对流换热特性进行了实验研究,获得了肋高、肋宽、轴向间距和周向间距等肋结构参数对管内自然对流换热性能的影响规律,提出了肋结构参数最佳组合。结果表明:变压器顶层油温从40变化至100℃,肋高和肋宽对换热性能的影响占比基本不变,周向间距的影响占比逐渐减小,轴向间距的影响占比逐渐增大;相比光管,三维内肋管的自然对流强化换热性能随顶层油温的增大而增加,变压器油自然对流Nu最大约为光管的1.75倍。拟合了竖直三维内肋管管内变压器油自然对流换热计算关联式,其与实验数据的最大偏差为±16%。

The natural-convection heat transfer characteristics of transformer oil inside the three-dimensional(3-D)internally finned tubes were experimental investigated by using Taguchi method.The effects of fin structural parameters(fin height,fin width,axial fin pitch and circumferential fin pitch)on the performance of transformer oil nature-convection heat transfer in 3-D internally finned tubes were presented,and the optimum combination of fin structural parameters was put forward.The results show that when the top oil temperature of transformer varied from 40 to 100℃,the influence of fin height and fin width on the heat transfer performance was barely changed,however the influence of circumferential fin pitch decreased gradually,and the influence of axial fin pitch increased gradually.Compared with that of smooth tube,the nature-convection heat transfer augmentation of 3-D internally finned tube was increasingly apparent with the increasing of top oil temperature of transformer,and the maximum Nusselt(Nu)number was approximately 1.75 times bigger than that of smooth tube in the scope of experiments.Finally,the empirical correlation of transformer oil nature-convection heat transfer was proposed for vertical 3-D internally finned tube,the predicted values of Nu number in agreement with the experimental values within the error of±16%.