Transient cooling wall temperatures of supercritical carbon dioxide boiler during load variation process

Efficient and flexible coal-fired supercritical carbon dioxide (sCO2) power plant is helpful to balance unstable renewable energies, available studies focus on transient sCO2 cycle analysis without coupling the sCO2 boiler heat source. Here, we explore thermal-hydraulic characteristics of sCO2 boiler during load variation process for a 300 MWe power plant. Modular boiler is applied to eliminate ultra-large pressure drop induced efficiency penalty, with analysis focused on two high heat flux modules of Part 1 and Part 2. The fluid-solid coupling model calculates spatiotemporal cooling wall temperatures by considering circumferential non-uniformity of furnace heat flux (ηq,c), using the accurate heat transfer coefficient correlation of sCO2 in tubes developed by our group. We demonstrate that during both load increase (50 %THA to 100 %THA) and decrease (100 %THA to 50 %THA) with load variation rates (LVRs) ranging from ±2 % to ±10 %Pe/min, the hot spot temperatures of cooling wall remain below the material temperature limit of 705 °C. In Part 1, hot spot temperature increases with LVR during load increase process, reaching 685.8 °C at 10 %Pe/min under ηq,c = 1.1. In Part 2, hot spot temperature remains constant at 698.2 °C across all LVRs under the same condition. However, temperature change rates increase with |LVR|, maintaining below the 5 K/min limit when LVR is smaller than (6.2–6.3) % Pe/min. We conclude important effect of the load variation rate on the temperature change rate of cooling walls, which dominates thermal stress of cooling walls.