Numerical investigation of heat transfer in the near-critical point applications

Abstract

In recent years, employing CO2 in supercritical Brayton cycle in industry is under research and development due to its enormous advantages specifically high thermal efficiency of cycle at operating condition with relative lower turbine inlet temperature compared to other cycles. Uncommon behavior in fluid properties near the critical point can cause uncertain numerical simulation, which should be investigated through optimizing design parameters such as flow characteristics and boundary layer behavior. In present study, a large horizontal heated pipe at different experimental conditions such as mass flow rates, heat fluxes and boundary conditions have been studied. The numerical simulation has been examined with different turbulence models and the best approach based on comparing CFD and given experimental results was selected. The trend of friction factor coefficient in heated pipe investigated and compared to other well-known friction factor correlations. Results showed that part of selected friction factor correlations have the best match with CFD results and some of them cannot be applied.