[Objective] Particle deposition within the tubes of supercritical boiler heat exchangers is one of the key factors affecting the unit’s ability to operate across a wide range of loads. Clarifying the initial nucleation and deposition behavior of particles within the tubes is crucial for improving the stability of the unit’s wide load range operation. This paper aims to conduct relevant experimental and simulation studies by using a supercritical water tube deposition test system. 

[Methods] The experiments monitored changes in the outer wall temperature in realtime during the process and examined samples from the experimental section after offline removal to observe the deposition behavior of particles and the microscopic morphology. By sectioning the experimental samples, the microstructure of the particle deposition layer on the inner tube wall was examined, and particle samples collected via high-pressure filters were analyzed to determine particle composition, particle size, and other characteristics. The simulations focused on the influence of particle oxidation and nucleation on the distribution of deposits. First, experimental data were used to select an appropriate turbulence model. A particle nucleation model based on classical nucleation theory was established and combined with the Euler-Lagrange method. A random walk model was incorporated to improve the accuracy of wall surface predictions. The axial deposition distribution of particles was simulated, and the effects of particle nucleation and roughness factors on the patterns o f particle deposition were analyzed. 

[Results] The results indicate that the particles are primarily micron -sized spherical Fe₃O₄ clusters with a median cluster diameter of 5.832 μm, and the thickness of the deposition layer tends toward a dynamic equilibrium over time; A comparison of the simulation results with experimental data from multiple centers revealed that the constructed ionic oxidation nucleation model demonstrates good applicability; the influence of particle nucleation on deposition distribution is related to multiple factors, specifically: in the subcritical region, where fluid density and viscosity are high, fluid flow is the primary factor affecting particle deposition, while in the supercritical 2 region, the larger the particle size and the higher the nucleation temperature, the smaller the influence of the fluid on the particles; the impact of increasing wall roughness on particle deposition exhibits self-limiting behavior; when the average wall roughness exceeds five times the particle diameter, changes in roughness have no significant impact on the particle deposition distribution; within the supercritical region, the influence of roughness on particle deposition is relatively small. 

[Conclusion] This study is of great significance for elucidating the initial nucleation and deposition behavior of particles within supercritical heat exchanger tubes and for improving the wide -load peaking stability of power generation units.