AN EXPERIMENTAL INVESTIGATION OF FORCED CONVECTIVE HEAT TRANSFER FROM SUPERCRITICAL CARBON DIOXIDE IN HORIZONTAL MINI/MICRO CHANNELS

摘要

We report an experimental investigation of forced convective heat transfer from supercritical carbon dioxide flowing in horizontal mini/micro circular tubes cooled at a constant temperature. Six stainless steel circular tubes having inside-diameters of 0.5 mm, 0.7 mm, 1.1 mm, 1.4 mm, 1.55mm, and 2.16 mm were tested. Measurements were carried out for the pressures of carbon dioxide ranging from 72 to 120 bar and the temperature ranging from 20 to 110°C. It is found that the heat transfer performance deteriorated when the tube diameter was reduced. The experimental results also indicate that the existing correlations developed in the previous studies for large tubes deviate significantly from the experimental data for the present min/micro tubes. Based on the experimental data, a correlation was developed for the axially-averaged Nusselt number in terms of appropriate dimensionless parameters for forced convection of supercritical carbon dioxide in horizontal mini/micro tubes cooled at a constant temperature.