Hydrodynamics and heat transfer investigation of air-water dispersed flow

A review of current research activities in air-water dispersed flow hydrodynamics and heat transfer at the Department of Mechanical Engineering, University of Sarajevo, is given. Droplet deposition was investigated in vertical upward air-water dispersed flow. Results are presented for different gas Reynolds numbers, ranging from 4x10(4) to 9.5x10(4). Different liquid concentrations and mean droplet sizes were used. It is shown that the deposition coefficient decreases with increasing droplet concentration at the inlet of the test section. A method for relating droplet deposition coefficient in terms of droplet concentration based on droplet sticking ratio (probability of sticking) analysis is proposed. It is found by data analyses that droplet sticking ratio on a liquid wall film in the test section is low, ranging from 10 to 30 %. Also, a concise description of the experiment on two-phase dispersed heat transfer is given. Wall temperature distributions have been measured in post-dryout region of air-water dispersed flow in the uniformly heated stainless steel test section. The pressure is near atmospheric, the wall heat flux ranges from 5 to 30 kW/m(2). The analysis utilises the proposed deposition theory for computing the deposition flux of droplets on to the wall.