管内空气流动对大口径厚壁P92管道局部焊后热处理温度场的影响

使用Ansys CFX软件建立了P92管道与管内空气的共轭传热模型,并进行了试验验证.使用该模型计算了不同管内空气流速时,局部焊后热处理的温度场分布.结果表明,管内空气流动对恒温后管道外壁温度影响较小,但会显著降低内壁温度,并增加内、外壁的轴向温度梯度.随着管内空气流速的增加,焊缝中心内外壁温差和轴向温度梯度近似线性增加,空气流速每增加1 m/s,内外壁温差将增大约5.0℃,内、外壁轴向温度梯度分别增加约0.03和0.02.对热处理温度要求很高的P92管道,局部焊后热处理时应限制管道内空气流动,或在选取热处理参数时考虑空气流速的影响.

Influence of internal air flow on temperature field of large diameter and thick wall P92 pipe during local PWHT

A conjugate heat transfer model is proposed based on the Ansys CFX code. The established model which has been verified by experiment is used to simulate the temperature distributions of P92 pipe during PWHT in the case of air flow in pipe with different velocities. The results show that the velocity of air flow in pipe has little influence on the temperature distributions of the outer wall, especially on the weld metal region, but its increase significantly reduces the temperature on inner wall of pipe and rises temperature gradient along the axial direction of pipe. The temperature difference between the inner and outer wall, as well as the axial temperature gradient increases linearly with the increase of the air flow velocity. For each 1m/s increase of the velocity of air flow in pipe, the temperature difference between inner and outer wall will increase by 5.0℃, and the axial temperature gradients on inner and outer wall of pipe increase 0.03 and 0.02, respectively. Meanwhile, the soak band width on inner wall will also be reduced obviously. Due to the influence on the temperature field of pipe during local PWHT of P92 steel, the air flow in pipe should be suppressed, otherwise, it is necessary to increase the width of heating zone.