Boundary layer integration method is applied to variable property turbulent flow in tube,and the shear stress distribution equation is derived.Based on this equation,a reasonable qualitative explanation can be made for the convective heat transfer behavior of supercritical pressure fluid.For the heat-transfer cases under heating conditions,and a thermal resistance coefficient of buoyancy is proposed to indicate the buoyancy effect due to the fluid density variation in radial direction,a thermal resistance coefficient of acceleration is proposed to indicate the acceleration effect due to the fluid density variation in axial direction.According to the boundary layer theory and the analogy between momentum and heat transfer,a new correlation equation has been developed to unify the calculation of turbulent convection heat transfer in tubes for incompressible and thermally compressible fluids.The proposed correlation is applied to predict the turbulent convective heat transfer coefficients in tubes for different supercritical fluids.The comparison between the calculated results and the experimental data shows that the correlation formula can accurately and reasonably predict the enhanced heat transfer and deteriorated heat transfer behavior under most heat transfer conditions,and its prediction accuracy is related to the calculation of friction resistance coefficient.
维普
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