The continuous expansion of renewable energy installed capacity has propelled an increasingly urgent demand for deep peaking operations of coal-fired power units within the power system. However

the frequent and rapid load cycling operations of these units induce drastic alterations in the flow and heat transfer characteristics of the working fluid within water wall tubes. As a direct consequence

the risk of water wall overheating and bursting has escalated significantly. To tackle this critical issue

this study develops a one-dimensional dynamic model of the water wall. The research delves into the mechanism through which uneven water wall flow distribution affects the metal wall temperature during rapid load cycling processes. Additionally

maximum load cycling rates of the units under various metal material conditions are determined. Results clearly demonstrate that the wall temperature in the dry-out zone is remarkably higher compared to other sections of the water wall. For boilers equipped with a water wall made of 15CrMoG material

at 50% and 30% THA (turbine heat acceptance) operating conditions

the peak wall temperatures in the dry-out zone reach 419.5 and 389.5℃

respectively. When water wall temperature is factored in as a limiting parameter during load cycling operations

the maximum power ramp rate of the unit registers 1.0%Pe/min during the 30%~50% THA loading up process. When the water wall material is switched to 12Cr1MoVG

the unit’s maximum load cycling rate surges by 0.5%Pe/min

hitting 1.5%Pe/min. Further substitution with P91 material leads to an even more substantial increase of 1.5%Pe/min

with the maximum load cycling rate peaking at 2.5%Pe/min. By quantitatively assessing the risk of water wall overheating and bursting

this study lays a theoretical foundation for the peaking operation retrofit of coal fired power units.