换热器中氢扩散及消氢温度场数值模拟研究

Numerical Simulation for Temperature Field in Heat Exchanger under Hydrogen Diffusion and Hydrogen Elimination Conditions

为探究换热器修复中焊前热处理消氢效果,以换热器为研究对象,采用有限元方法对氢扩散过程和焊前加热过程进行数值模拟。结果表明:换热器中氢浓度分布呈现由换热管内壁到外壁、管板上端面到下端面非线性下降的规律。换热管受到双重扩散的影响,纵向上内外壁氢浓度差逐渐增大。靠近管板上端面区域氢浓度值高且下降缓慢。换热器温度场在管板厚度方向上呈递减趋势,在管板上端面截面处中心区域内,换热管温度高于管板温度,而换热管和管板的温度高于边缘的温度。当加热毯工作温度为350℃,加热换热器5880s后,管板上端面高温区域温度为252.7℃,管板厚度9mm处温度为250.8℃,满足修复换热器焊前消氢处理的加热工艺要求。

To determine the hydrogen elimination effect using pre-welding heat treatment in repair of heat exchanger,the numerical simulation of hydrogen diffusion and pre-welding heating procedure were performed by using finite element analysis.It was shown from the results that the distribution of hydrogen in heat exchanger appears less concentrated from inside to outside;at the upper zone approaching tubesheet,hydrogen concentration is high and decrease slowly;the temperature in the tubesheet reduces along thickness;at upper surface and near the center of the tubesheet,the temperature of the heat transfer tubes is higher than that of the tubesheet,and the temperatures of both tubes and tubesheet at central area are higher than that at the edge.When the heat exchanger is heated to 350°C and for 5880 seconds,the temperatures of the tubesheet at the upper surface reaches 252.7°C and at 9 mm from the upper surface reaches 250.8°C,from which the heating process required for pre-welding hydrogen elimination treatment can be met in repair of heat exchanger.