Heat transfer characteristics of supercritical CO2 with high mass flux in vertical tube
Based on the flow heat transfer experimental data,the ability of different turbulence models to predict heat transfer on supercritical CO2(S-CO2)was evaluated and selected,and the SST k-ω turbulence model was confirmed as the optimal model.The effects of inlet temperature,heat flux,mass flux,buoyancy and flow acceleration on the convective heat transfer characteristics of S-CO2 were analyzed in a vertical heating tube with an inner diameter of 10mm.The results showed that Bu<10-5,Bu*<5.6×10-7 and Kv<3×10-6 were not satisfied in some working conditions,indicating the effects of buoyance and flow acceleration could not explain the heat transfer characteristic at high mass flux.Based on the supercritical boiling theory,the S-CO2 boiling heat transfer model in vertical heating tube was established,and the deterioration of S-CO2 heat transfer was described.The detailed distribution of S-CO2 thermophysical properties and turbulence in the radial direction showed that the supercritical heat transfer was greatly affected by the thickness of the pseudo-gas film,the thermal properties of the quasi-gas film and the turbulent kinetic energy in the near-wall region.The heat transfer mechanism of S-CO2 at high mass flux was explained successfully.By introducing the supercritical boiling number,a heat transfer correlation formula for high quality flow rate was proposed.
supercritical CO2high mass fluxheat transfercorrectionnumerical calculation
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