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1、Local resistance on the pipeline and total energy loss of the pipeline systemPrinciples of Chemical Engineering-CDUTLocal resistance on the pipelineBecause the fluid flow through elbow,tee,valve,and experience sudden expansion,sudden reduction of the pipe and complex mivwments,and there are many inf
2、luencing factors,it is difficult to accurately calculate the flow resistance of this part.Except for a few kinds of theoretical analysis,it generally needs to be determined by actual test.Generally,two approximate calculation methods are local resistance coefficient method and equivalent length meth
3、od.（1）Local resistance coefficient methodLocal energy loss can be written as:22fuh 1The is called the local resistance coefficient.Principles of Chemical Engineering-CDUTLocal resistance on the pipeline图1Principles of Chemical Engineering-CDUTLocal resistance on the pipelineTable 1NameLocal resistan
4、ce coefficientNameLocal resistance coefficientelbow，45degrees0.35standard valveelbow，90degrees0.75full open6.0tee1semi-open9.5Return Bends 1.5angle-type valve，full open2.0pipe joint0.04non-return valveunion0.04ball type70.0gate valvewobble plate type2.0full open0.17water meter,disc-type7.0semi-open4
5、.5Principles of Chemical Engineering-CDUTLocal resistance on the pipeline23（2）Equivalent length methodAccording to the computation formula of friction resistance of straight pipe【2】：The formula of local resistance expressed by equivalent length can be written as：Principles of Chemical Engineering-CDUTFigure223Principles of Chemical Engineering-CDUTThe total energy loss of the pipeline system4The total resistance loss of the fluid flowing through the pipeline system can be expressed as the sum of all straight pipe resistance and all local resistance on the pipeline,namely: