The Research On Mass Transfer Outside Horizontal Tubes By Falling Film

Evaporative cooling is a method that directly getting cold energy from nature. Which don't use CFCs, no environmental pollute. It is a high efficiency energy saving method. The COP is 2.5-5 times than normal mechanical refrigeration. Therefore it can save more air condition energy. So it can be widely used in air condition systems. Especially in dry areas, it can replace normal air condition systems. In moisture area, it can be used by some technical improvement.In recent years, there are many research shows that evaporative cooling is advantage in energy saving, environment protect and economic, especially use as a cooling supply system in high temperature and dry areas. Although there are many research on evaporate cooler recently, the theory research of heat and mass transfer is not much. So it is limited in equipment improvement and applications. As we all know the evaporate heat and mass transfer is combined with water in tubes, water outside tubes and air outside tubes. Every factors change of it can affect the heat and mass transfer. The research on heat and mass transfer theory play an important role in evaporate cooling. It provide theory gist to consummate evaporate thermodynamic, improvement choosing equipment. Aim to save energy, reduce environment pollution, enhance work efficiency.The prediction of heat and mass transfer coefficient and flow course can be got from calculation and experiment. The analytical solution is hard to get because of the complex heat and mass transfer process. The most reliable data of a physical process can get from experiment. But in most situations, experiment limit by existing conditions and accuracy. This topic put attention to computer simulation and experimental calculation. Through researching on operating and structural parameters aim to improve performance. collaborative consider the affect of spray water, air state parameters and so on.By combining computer simulation with experiment, this topic gets the results as: (1) According to actual operation conditions simulate the experimental device inside velocity field, temperature field, relative humidity and droplet trajectory. The velocity field figure can provide basis of experiment. The temperature field figure shows the temperature of the air inside device. It shows that the air close to the tubes is higher than other place. The heat transfer is severe. The relative humidity figure shows the relative humidity above first tube is higher than other place. It explains the intense mass transfer above first tube. The droplet trajectory figure shows the real situation of drop down.(2) Convective mass transfer coefficient enhance with the spray water flow. But it increase slowly when the spray water flow is high. Tubes can also affect the coefficient significantly. Oval tubes are better than round tubes. Wind flow which can not be ignored also affects the coefficient, but weaken than the two above. The coefficient enhance with the Cooling water flow first increase and than decrease. The critical point is close to small flow side. Analysis variance by orthogonal test and F test. The order of the primary and secondary factors is water pray flow, tubes, air flow and cooling water flow.