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在亚临界、近临界及超临界压力区,对600MW超临界W火焰锅炉水冷壁中垂直上升低质量流速优化内螺纹管的传热特性进行了试验研究,得到了不同运行工况下内螺纹管的壁温分布,分析了压力、外壁热流密度、质量流速对传热特性的影响。结果表明:低质量流速优化内螺纹管具有良好的传热特性,能够有效避免膜态沸腾;在亚临界压力区,压力与热流密度的增大以及质量流速的减小,均会导致干涸提前发生和干涸后的壁温飞升值增大。与亚临界压力区相比,内螺纹管在近临界压力区的传热特性变差,随着压力的增大,管壁温度显著升高,发生传热恶化时的临界干度减小。在超临界压力区,内螺纹管在拟临界点附近出现了传热强化;压力越接近临界压力,传热强化越明显;压力与热流密度的增大以及质量流速的减小均会导致壁温增大。
In sub-critical, near-critical and supercritical pressure zones, the heat transfer characteristics of a vertically-rising, low-mass flow rate optimized internally threaded tube in a water wall of a 600MW supercritical W flame boiler were studied. Of the wall temperature distribution, the pressure, the heat flux density, the mass flow rate on the heat transfer characteristics. The results show that the low-mass flow rate optimized internally threaded tube has good heat transfer characteristics and can effectively avoid membrane boiling. In the subcritical pressure region, the increase of pressure and heat flux density and the decrease of mass flow rate will lead to early dry-out And dried up the wall temperature soaring value increases. Compared with the subcritical pressure zone, the heat transfer characteristics of the internally threaded tube in the near critical pressure region deteriorate. With the increase of the pressure, the temperature of the tube wall increases significantly, and the critical dryness decreases when the heat transfer deteriorates. In the supercritical pressure zone, the heat transfer enhancement occurs in the internally threaded pipe near the pseudo-critical point. The closer the pressure is to the critical pressure, the more obvious the heat transfer enhancement. The increase of the pressure and the heat flux density and the decrease of the mass flow rate will cause the wall temperature Increase.