A designed wall roughness approach to improve turbulent heat transfer to supercritical CO2 flowing in horizontal tubes

Supercritical flow through a horizontal pipe leads to non-uniform peripheral wall temperature distribution even when the heat flux is kept constant and uniform. This attributed lower transfer coefficient at top section where denser fluid tends sink. Hence, obtain uniform temperature, designed roughness devised. Uniform sand-grain employed only partly cover half of wall. Numerical simulations were conducted using SST k−ω turbulence model. The simulation results indicate that our proposed design can lead more over periphery compared with smooth pipe. An extreme case was also considered inner completely covered elements. While augmentation observed for this case, excess pressure drop prohibitively higher roughness.