Air-water transient heat transfer in a bubble column

This work focuses on a direct contact heat transfer between water and air bubbles. A tube 0.2m in outer diameter and 1.4m high was filled with water. Low-humidity air was continuously dispersed into bubbles at the bottom of the tube. The water inside the tube could be heated initially or continuously during the experimental runs, using controllable electrical strip heaters. Temperature measurements were simultaneously performed at several locations inside the column. The results show that the water temperature was almost uniform due to perfect mixing induced by the bubbles movement. The column of water was not insulated, and the cooling by convection and radiation at the walls was accounted for. The heat-transfer rates between the water and the rising air bubbles were estimated for various modes encountered in the experimental study, and mathematically modeled. The model simulations for the batchwise cooled water compare well with the experimental results.