Experimental Investigation of Convection Heat Transfer in High Pressure and High Temperature Gas Flows

Abstract

This work focuses on an experimental investigation of convection heat transfer to a gas in a vertical tube under strongly heated conditions at high temperatures and pressures up to 943 K and 65 bar. A unique test facility for convection heat transfer experiments has been constructed, and used to obtain experimental data useful for better understanding and validation of numerical simulation models. This test facility consists of a single flow channel in a 2.7 m long, 0.11 m diameter graphite column with four 2.3 kW heaters placed symmetrically around the 16.8 mm diameter flow channel. Upward flow convection experiments with air and nitrogen were conducted for inlet Reynolds numbers from 1300 to 60,000, thus covering laminar, transition, and fully turbulent flow regimes. Experiments were performed at different flow rates (3.8 × 10−4 to 1.5 × 10−2 kg/s) and heater power up to 6 kW. Importantly, the data analysis considered the thermophysical properties of the gas and graphite changing with temperature and pressure. Nusselt number results are further compared to existing correlations. The effect of pressure and heater power on degraded heat transfer is examined. The analyses of the experimental data showed significant reductions in Reynolds number of up to 50% and Nusselt numbers of up to 90% between the gas inlet and outlet.