EXPERIMENTAL INVESTIGATION OF FLOW AND CONVECTION HEAT TRANSFER OF SUPER-CRITICAL CARBON DIOXIDE IN A HORIZONTAL TUBE DURING COOLING

摘要

The frictional pressure drop and the heat transfer coefficients for carbon dioxide at super-critical pressures were measured in a horizontal small tube during cooling. The axially-averaged heat transfer coefficients reached to a maximum when the bulk temperature was near the pseudo-critical temperature. The local heat transfer coefficients were determined through a combination of experimental measurements and numerical simulations. The experiments were conducted at various CO_2 mass fluxes, inlet temperatures and system pressures. Petukhov's equation reasonably predicts the frictional pressure drop for the conditions in these experiments. The local convection heat transfer was greatly intensified when the wall temperature was near the pseudo-critical temperature and the bulk temperature was slightly higher than the pseudo-critical temperature.