Experimental Study And Numerical Simulation Of Falling Film Flow Pattern Between Tubes

Falling-film-type horizontal-tube technology has been widely applied to the desalination,chemical process, refrigeration, OTEC system, etc, because of its high heat transfercoefficient, low-cost devices, multilevel operation, and maintain control. During the processof horizontal-tube falling film, which was constrained from the solution properties, pipediameter, material, tube pitch, nozzle type, spray density and air velocity, the flow patterncould be influenced when the factors change. It resulted in the change of contact area betweenliquid and air. So it is imperative to research the flow pattern between tubes. It is of guidingsignificance in the practice that research result has an effect on developing heat and masstransfer model and experimental analysis.Falling-film-type horizontal-tube model has been established. The solution of lithiumbromide and water were selected as spray liquid. The flow pattern of tubes was simulated bythe Hydrokinetics calculating software called Fluent. The three critical value of flow patternin the droplet, the columnar and the sheet were obtained. Through debugging different flowrate to simulate, the minimum value which wet the whole tube wall was obtained. With thechange of pipe diameter, material, tube pitch and solution properties, etc, the change rule offlow pattern was obtained between tubes. Under the air flowing, the flow rule of solution wasanalyzed. The range of Re were obtained under different flow patterns, the maximum area ofvelocity and pressure. The minimum wetting flow rate was obtained, too.The experiment system was established, the solution properties, pipe diameter, material,tube pitch was filmed for visual analysis. The growth process of droplet was describedbetween tubes. There was a phenomenon of horizontal migration at the bottom of the tube.The range of Re was obtained at different flow pattern of tubes. The result of experiment wasconsistent well with the simulation result. The flow pattern can be transformed into one ormore levels of former with the increase of pipe diameter or tube pitch. When the material oftube was replaced, there was slip phenomena between tubes which lead to the tube wall not tobe wet next.