Accurate measurement of the boundary heat transfer characteristics of supercritical CO2 flow-through a channel is crucial for the safe design and operation of advanced supercritical CO2 cycle systems.The research is based on an improved non-contact phase-shifting laser interference system to explore the evolution trend of the boundary thermal flow field of supercritical CO2 in a rectangular cross-section channel under turbulent conditions.A phase-shift technique is utilized to analyze the transient variations in density and temperature fields following the sudden localized heat addition applied in the bottom boundary.These quantitative data are used to estimate the local criterion numbers for supercritical boundary heat transfer under different heat flux(q=14057,5500,2014 W/m2).The results indicate that the rapid density reduction(1.8 kg/m3)occurs in a localized boundary transfer process.The buoyancy force induces the turbulent mixing from the boundary to the bulk flow region,eventually reaching equilibrium.Relatively dramatic and rapid shifts in temperature and density gradients occurs under high heat flux conditions,emphasizing the fast generation and transport of thermal boundary layers.
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