One of the most important issues in design of water tube boilers is the prediction of the critical heat flux and the corresponding critical quality of the steam and vice versa. This phenomenon directly affects growth rate of oxide/deposit layers, rising water wall tubes temperature, and consequently tubes burnout. In the present work, the critical situations in a furnace of a subcritical drum boiler were investigated. It was shown that by moving to higher altitudes of the investigated furnace, its water wall tubes were more sensitive to heat flux distribution, which consequently increased the possibility of dryness phenomenon and failure of the tubes. Besides, this study demonstrated that in the event of a disturbance in the fluid flow inside the tubes, all the length of water wall tube are at serious risk of burning and overheating. Microstructural evolutions, existence of thick deposits, and frequent failures at higher the altitudes confirmed the semi-analytical results.

水管锅炉设计中最重要的问题之一是预测临界热通量和相应的蒸汽临界质量，反之亦然。这种现象直接影响氧化物/沉积层的生长速度、水冷壁管温度的升高，进而影响管子的烧坏。在目前的工作中，研究了亚临界汽包锅炉炉膛中的临界情况。结果表明，随着被调查炉向更高的高度移动，其水冷壁管对热通量分布更敏感，从而增加了管子干燥现象和故障的可能性。此外，这项研究表明，如果管内流体流动发生扰动，水冷壁管的所有长度都存在严重的燃烧和过热风险。