Heat transfer in co‐current vertical two‐phase flow

Abstract

AbstractHeat transfer in co‐current two‐phase upflow and downflow of air–water has been investigated in a 25.8 mm electrically heated vertical pipe at 172.3 kPa for water mass velocities of 54 to 172 kg/m2s and gas flow rates of 0 to 1.322 × 10−2 m3/s. It was found that although the injection of air in the liquid flow increased the two‐phase heat transfer coefficients significantly for both systems, upflow coefficients were generally higher than those for downflow for the same liquid flow rate. This could have important implications in the design of some chemical reactors and heat engineering processes. Changes in heat transfer rates were found to occur at the flow pattern transition boundaries. Two‐phase heat transfer coefficients were well correlated by an expression based on dimensional analysis for both upflow and downflow.