Research Based On Resistance Characteristics Of Ventilation Air-conditioning Ducts Under The Condition Of Adjacent And Drag Reduction Method

With the development of the society and technology,people spend more and more time working and studying in buildings.People have a higher demand on building environment.In order to meet the demand,great changes have taken place in the technologies of buildings and its accessory equipments.More and more air-conditioning systems are required in buildings.With this trend,building energy consumption is higher and higher,among it the proportion of the ventilation duct spending is up to 15%～30%.Fittings are common seen in the duct system of buildings.The previous researches always investigate the case of single fitting.But if fittings are close enough,they will have a influence on each other.In this research,coupling fittings are the research objects.The flow regime will be studied,and the rules will be summarized.With experimental data,the trends of the velocity changes and pressure changes of the system under different ventilation velocities can be concluded.The data also can provide numerical calculation as reference and check the correctness of the models.Using the computational fluid dynamics(CFD),this research summarized the trends of the centerline velocity and average pressure of cross-section.Getting the local resistance according to the definition.By changing the different factors of the system,getting the influence of factors on the flow regime.Under the condition of coupling bends,reducing the local resistance by means of adding pipes between bends,optimizing the arc of bends and pipes,setting flow deflector in the bends.Different kinds of drag reduction method have different effect.Adding pipes can reduce the resistance 17%at most.Changing the shell of the bends also can save 6%of the resistance under the U-shape connection,with _sL=3D and9.8%under the S-shape connection with _sL=7D.With the method of setting flow deflector,the resistance can be reducing up to 28%.