Droplet Deposition and Heat Transfer Simulations of Turbulent Air-Water Dispersed Flow in a Vertical Tube

抄録

A theoretical study of the droplet deposition and heat transfer of a vertically heated tube cooled internally by a turbulent air-water dispersed flow has been performed. In the analysis of the droplet deposition on the wall, an equation for the dimensionless droplet deposition velocity k_d/u* is proposed, and the calculated results show good agreement with experimental data measured by many authors. In the heat transfer analysis, a model is proposed taking into account the presence of an initial liquid film on the wall that flows uniformly until the dryout point. The calculations of wall temperature distribution and heat transfer enhancement are performed and compared with experimental values measured by other authors, and a satisfactory agreement is obtained. The heat transfer enhancement is found to be caused mainly by the evaporation of the liquid film on the wall, which is quite different from the case of a single-component mist flow. It is assumed that in an actual case, the liquid film on the wall breaks down nonuniformly before the dryout point, depending on the wall heat flux and the liquid film flow rate.