Numerical Simulation Of Heat And Mass Transfer Of Water And Air Outside The Horizontal Tube

The numerical simulation is made for the heat and mass transfer ofwater and count current air outside the single horizontal tube to investigatethe influence of air volume and spray amount on the water film thickness,film temperature, air temperature, and air humidity, and to provide thevaluable reference for the sake of laboratory experiment and industrialapplying.The physical model of wind-water currents and mathematical model ofheat-mass transfer was established. And numerical simulation model andmethod was selected for FLUENT simulation. The study attempt to obtainwater film distribution outside the horizontal tube under the situation ofwater-wind current. By the simulation of the water-wind current outside thehorizontal tube under different spraying volume and wind speed, thewater-wing threshold was gotten. The heat transfer model was added in thesimulation, and the thickness of liquid film outside the tube was accuratelyread on good working conditions. Water film temperature and airtemperature changing with distance against wall y and annular angle outsidethe horizontal tube was analyzed by taking water film thickness as the twophase interface of gas and liquid. What’s more, the variation of water filmsurface temperature and air temperature of y=5mm was studied on differentconditions.Considering the mass transfer outside the horizontal tube, a UDFprogram was written to be add into the VOF simulation model. Thesimulation result shows that the film shape is good and humidity ratio in theair was obviously changed, which agrees with practical situation. In addition,the distribution of air humidity ratio and temperature field outside the tubebetween mass transfer and no-mass transfer was studied and analyzed.In the same annular angle, and in a certain distance against wall, thetemperature distributed in radial direction with mass transfer is lower thanthe temperature distributed in radial direction without mass transfer; whenthe annular angle is smaller, the temperature distributions in radial directionoutside the tube tend to be the same whether mass transfer or not. As theannular angle decreases from large to small near the water film, both the airtemperature with mass transfer and that without mass transfer all appears thetrend of falling; in the place apart from the water film, the air temperaturewith mass transfer and that without mass transfer verifies in the same trend: as the annular angle decreases from large, the temperature falls first, andthen goes up, and drops finally.When annular angle is in the range of15o~90o, the film thickness withmass transfer approximately equals that without mass transfer; as the angleis in the range of90o~165o, the film thickness with mass transfer is thin, andcontrast to that, the thickness without mass transfer is thick.