CHEN 304 1st Edition Lecture 9Outline of Last Lecture I. Rotational Motion and Angular MomentumOutline of Current Lecture I. Fluid Friction in PipesII. NomenclatureIII. Laminar and Turbulent FlowIV. Laminar Flow Shear StressV. Laminar Flow Velocity ProfileCurrent LectureChapter 3Fluid Friction in Pipes- In chemical engineering process operations fluids are typically conveyed through pipelineso Oil industryo Ethane productiono Waste treatmento Pharmaceutical- In pipelines viscous action causes friction and a dissipation of useful work in heat- Pump or fluid falling under gravity can be used to overcome such frictiono It is essential to be able to estimate frictional losses to design pumps and elevated pipelines- The terms pipe, duct, and conduit are usually interchangeably for flow sectionsNomenclature- Flow sections of circular cross section are referred to as pipeso Especially for liquids- Flow sections of noncircular cross section are referred to as ductso Especially for gases- Small diameter pipes are usually referred to as tubesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Duct is used for gases because it is easier and cheaper to manufactureLaminar and Turbulent Flows- Laminar flow is characterized by smooth streamlines and highly ordered motion- Turbulent flow is characterized by velocity fluctuations and highly disordered motion- The transition from laminar to turbulent flow does not occur suddenlyo It occurs over some region in which the flow fluctuates between laminar and turbulent flows before it becomes fully turbulent- Under what conditions do we observe laminar or turbulent flow?o The transition from laminar to turbulent flow depends on the geometry, surface roughness, flow velocity, surface temperature, and type of fluid among other thingso Reynolds number is used as main criteria The ratio of inertial forces to viscous forces in the fluidℜ=ρ umDμ- The fluid velocity in a pipe changes from zero at the surface because of the no-slip condition to a maximum at the pipe center- In fluid flow it is convenient to work with mean velocity which remains constant in incompressible flow when the cross-sectional area of the pipe is constant- Laminar flowo Re ≤ 2000- Transitional flowo 2000 ≤ Re ≤ 4000- Turbulent flowo Re ≥ 4000Laminar Flow Shear StressdPdx=−2 τwRLaminar Flow Velocity Profileu(r)=−R24