| An analytical investigation is carried out on near supercritical turbulent forced convection in pipes. The primary objective is to utilize a unified theoretical model, together with available experimental data, to identify and determine the physical mechanisms involved in the heat transfer deterioration anomaly of the near supercritical phenomena.; A finite-difference scheme is used to solve the boundary layer-parabolic type of hydrodynamic and energy equations. A "rate equation" for determining the turbulent viscosity is added to the governing equations, which takes into account the effects of turbulence convection, turbulence diffusion, and turbulence generation and decay due to mean shear, small eddy dissipation, buoyancy and pressure straining. Logarithmic-law equations for the wall region of the pipe are utilized as the forcing function of boundary conditions for the mean and turbulent field calculations.; The theory, procedures, and computer program are successfully tested in several limiting cases such as the thermal laminar flow in the entrance region in a tube, the turbulent flow in the entrance region in a pipe, and in fully developed turbulent flow with heat transfer in tubes. Subsequently, they are applied to the near-supercritical case dealing with turbulent upward flow of supercritical carbon dioxide through a vertical heated tube and using experimental data of other researchers relative to the formation of temperature peaks at the wall.; The results of this study, presented in the form of tables and plots, are used to give a physical explanation of the occurrence of the deterioration of heat transfer for the above mentioned case.; The theory is a tool that potentially can be used to predict the behaviors of near-supercritical heat transfer under a variety of flow, thermal, and geometric conditions. It could also be used to design high flux heat transfer equipment operating in the thermodynamic near supercritical regime. |
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