Flow And Resistance Characteristics Of Fluid Equalizing Distributors And Optimization For Resistance Reduction

In the fields of energy,chemical industry,environment,and construction,etc.,fluid equalizing distributors are often used to realize fluid transmission and distribution on demand.As a flow distribution hub,it plays a role of connecting upstream and downstream pipe fittings in the fluid transmission and distribution systems.However,due to unreasonable design,processing,installation,operation,and other factors,the internal pressure distribution of the fluid equalizing distributor is unbalanced,which often leads to flow cannot be distributed “on-demand” or the flow resistance loss increases.It will not only cause energy consumption increasement and system performance decline,the resulting safety and production problems also cannot be ignored.Therefore,uniform flow distribution and resistance reduction optimization are the key issues to improve the performance of the fluid transmission and distribution systems.As common components in fluid transmission and distribution systems,fluid equalizing distributors,such as dividing/combining manifolds and plenum chambers,are large in quantity,and are widely used in practical engineering.They are all located at the source of power equipment.There are many similarities in terms of flow pattern and action mechanism.This research takes the dividing/combining manifolds and plenum chambers as the objects,and the uniform flow distribution and low-resistance optimization design were conducted through the combination of theoretical analysis,experimental testing,and CFD modelling.The flow distribution and resistance characteristics of the fluid distribution system were analyzed.The high flow resistance area of the system was precisely located based on the energy dissipation function,and the targeted resistance reduction optimization was carried out.Finally,an optimization design method aiming for low-flow resistance and uniformly distributed flow field was proposed.The specific research contents are as follows:(1)The flow distribution characteristics and mass flux distribution rule were studied with the dividing/combining manifold systems with parallel pipe arrays(D/CMS-PPA),which is commonly used in practical engineering.An orthogonal experiment design was applied to determine the influence degree and trend of the design parameters on system performance,including the inlet Reynolds number,crosssectional area ratio of inlet/outlet pipe,pipe pitch,height of convex head,and branch pipe number.The non-uniformity coefficient(Ф)and total pressure drop(ΔPj)was adopted as test indicators.The results show that the inlet/outlet area ratio(AR)has the most significant impact on the flow distribution of system,and the AR should be minimized for design.In addition,the entropy method was used to determine the weight of each index,and the multi-attribute evaluation of “flow uniformity-resistance characteristics” was carried out to provide theoretical guidance for the scientific comparison and selection of flow field optimization schemes.(2)The energy dissipation function was proposed to characterize the resistance distribution of flow field,so as to achieve “precise positioning” of the high flow resistance area of the system.Based on the analysis of the fluid energy dissipation function,the mixing of vortex was suppressed through the optimization of sidewall.After comparing a variety of resistance reduction optimization methods,a low-flow resistance guide vane inserted into the header of manifold combined with the optimization of sidewall curve was proposed.The recommended value for the optimized dimensionless structure parameters of the DMS-PPA was obtained by stepwise optimization,and the optimization method is extended to the general situation of different inlet Reynolds number,branch pipe number and manifold specifications.The resistance reduction rate can reach more than 30%,and the energy-saving effect is remarkable.(3)Taking the commonly used “one in and one out” type plenum chamber with parallel inlet/outlet axes in ventilation and air-conditioning engineering as the object,the interior airflow movement and resistance distribution characteristics were studied.The key factors influencing the structural design of the plenum chamber were determined by orthogonal experiments,and the structural parameters were optimized based on the analysis of jet diffusion characteristics.By analogy with free jet expansion,the degree of airflow restriction in the chamber was judged,and the recommended value for the optimal design of the chamber length was finally obtained.Additionally,the influence of the inlet flow boundary on the flow and resistance distribution characteristics of the plenum chamber system was analyzed,and the flow pattern was verified through the flow field visualization experiment.It was also proposed to add an orifice inside the chamber to further improve flow uniformity,and its applicability in the multiple-path plenum chambers was verified.(4)Based on the above research,through the flow characteristics analysis and resistance reduction optimization of the fluid equalizing distributors,the optimization design principle and method aiming for a low-flow resistance and uniformly distributed flow field are summarized.Besides,the design and calculation steps of the DMS-PPA and plenum chamber are proposed and applied to practical engineering cases.The applicability and rationality of the structural optimization design method is verified,which provide theoretical support and technical guidance for the design of the same type of fluid equalizing distributors.