Optimization Research On Resistance Reduction Of U-shaped And Z-shaped Elbows In Ventilation And Air-conditioning Water Supply Pipeline System

At present,the proportion of building energy consumption in my country is increasing day by day,and the energy consumption generated by heating,ventilation and air conditioning generally accounts for 40% to 50% of building energy consumption,and the energy consumption of fluid pipeline system accounts for HVAC.More than half of the system’s energy consumption.Therefore,it is of great practical significance to improve energy utilization efficiency and reduce system energy consumption by conducting research on drag reduction and consumption reduction of local resistance components in the system and exploring applicable drag reduction methods.Most of the existing research on local resistance components only focuses on a single90° elbow,tee,etc.,and it is believed that there will be no mutual influence between local resistance components.However,in specific engineering applications,due to the limitations of the actual building structure,pipe size and other facilities and equipment,there are usually situations where two local resistance members are very close to each other,and the local resistance between the members will be affected under certain conditions.The local drag coefficient will change accordingly.This study is a numerical simulation study on the flow field resistance characteristics of 90° elbows in U-shaped and Z-shaped connections.By changing the arc form of the elbow,adding guide vanes and grooved guide vanes,the suitable drag reduction design method of such elbows.This paper adopts the research method combining theoretical analysis and numerical simulation.First,using theoretical analysis,the flow field characteristics of the elbow are studied,the factors that affect the local resistance coefficient of the elbow are analyzed,the adjacent influence coefficient is calculated,and the relevant drag reduction mechanism and method are described;secondly,the specific use Numerical simulation research on the elbow was carried out by means of variable arc form drag reduction,adding guide vane drag reduction and guide vane groove drag reduction,obtained the optimized structure under different working conditions,calculated the local drag coefficient and the drag rate,and its drag reduction effect is verified by analyzing the changes of cloud images.The research shows that the drag reduction method of variable arc form is adopted for U-shaped and Z-shaped elbows,and the arc form with the best drag reduction effect is the retracted arc.The drag reduction rates of connecting elbows are 5.39% and 3.49%,respectively,and the drag reduction effect is average.When the drag reduction method of adding guide vanes is adopted,the type of guide vane with the best drag reduction effect is obtained,and the angle,placement and specific position of the guide vane are determined.In this form,U-shaped connection elbow and Z-shaped connection The best drag reduction ratios of elbows are 28.00% and 35.58%,respectively,and the drag reduction effect is good.When the guide vane grooved drag reduction method is used,the drag reduction rate is 11.70% under the condition of U-shaped connection and the length of the transition section is three times the pipe diameter.Under the condition of Ztype connection and the length of the transition section is three times the pipe diameter,the drag reduction rate is 24.79%.At the same time,by analyzing the pressure,velocity,and turbulent dissipation rate cloud diagrams of the optimized elbow drag reduction,it can be found that the elbow pressure distribution after drag reduction optimization is more uniform,the velocity at the elbow is reduced,and the overall turbulent flow energy consumption scatter rate is also reduced.In addition,this study also verified the applicability of the drag reduction effects of various guide vane types under different pipe diameters.This study compares and analyzes three drag reduction methods applied to U-shaped and Z-shaped elbows,which provides ideas for reducing drag and consumption of local components of the fluid piping system,and also provides a reference for the optimal design of green and energy-saving buildings.