常压加热炉辐射段耦合传热的数值模拟

Numerical Simulation of Coupled Heat Transfer in the Firebox of Atmospheric Heater

采用分区耦合的方法研究了某常压加热炉辐射段内的流动、燃烧和传热的全部工艺过程,并系统地分析了炉管表面温度和热强度分布。计算中,实现了燃烧器、炉膛、炉管整体几何结构的建模和网格划分,选用标准k-ε湍流模型、非预混燃烧模型和离散坐标辐射传热模型,将炉管黑度定为0.8,模拟得到了炉内的流场、温度场及炉管表面温度和热强度分布的详细信息。结果表明,底部燃烧器的高速射流在炉膛下部产生较大回流区,对炉膛下部烟气温度分布的均匀性至关重要;炉管管壁温度和热强度分布存在明显非均匀性,影响炉管使用寿命。炉膛温度及炉管管壁热强度模拟结果与常压炉测定数据和设计数据一致,证明了模拟计算的可行性和准确性,为常压炉的设计和优化提供理论参考。

The processes of fluid flow, combustion, heat transfer between the flue gas and tube without any simplification in the firebox of atmospheric heater were studied with the whole coupling method. The distribution of temperature and heat intensity in furnace tube was analyzed systematically. The geometrical model and the division of grid of the combustor, combustion chamber and furnace tube were generated. The standard κ-ε turbulent model, the non premixed combustion model and the discrete ordinate transfer radiation model were used to simulate the fluid flow, combustion, heat transfer in the furnace. The emissivity of the furnace tube was defined as 0.8 in the model. Detailed information about the flow field, temperature field, temperature and heat flux distribution in tube skin was obtained. Results showed that the high velocity of bottom combustors＇ jet flow resulted in large flue gas recirculation zone, which played an important role in the uniform temperature of flue gas in the bottom of the furnace. In addition, non-uniform distribution of temperature and heat flux existed in the furnace tube skin, which affected the service life of furnace tube. Compared with the measured and design date of the firebox temperature and the heat flux of tube skin, the simulation result was proved to be feasible and accurate. The successful simulation offered technical support to the design and improvement of atmospheric still.