The water-cooled wall is the main heating part of the boiler, consisting of several rows of steel pipes distributed around the boiler furnace. Its interior consists of flowing water or steam, while the outside receives heat from the flames of the boiler furnace. Mainly absorbing the radiation heat from high-temperature combustion products in the furnace, the working fluid undergoes upward movement and evaporates upon heating.
The full name is "water-cooled wall tube", formerly known as "water-cooled wall" or "riser tube". Usually vertically laid on the inner wall of the furnace wall, it is mainly used as the heating surface of the boiler to absorb the radiation heat emitted by the flames and high-temperature flue gas inside the furnace. It is the main type of evaporation heating surface in various modern boilers and also a basic component in the boiler water circulation circuit. Due to its dual function of cooling and protecting the furnace wall.
When the water-cooled wall was initially designed, its purpose was not to heat, but to cool the furnace and prevent it from being damaged by high temperatures. Later, due to its excellent heat exchange function, it gradually replaced the steam drum as the main heating part of the boiler. The evaporation heating surface is laid on the inner wall of the boiler furnace and composed of many parallel pipes. The function of water-cooled walls is to absorb the radiation heat from high-temperature flames or flue gas in the furnace, generate steam or hot water inside the pipes, and reduce the temperature of the furnace wall to protect it. In large capacity boilers, the flame temperature inside the furnace is very high, and the intensity of thermal radiation is significant. 40-50% or even more of the heat in the boiler is absorbed by the water-cooled wall. Except for a few small capacity boilers, modern water tube boilers use water-cooled walls as the main evaporative heating surface in the boiler.