CHME 333 Workbook Handouts - Chapter 8

CHME 333 Workbook Handouts - Chapter 8 - CHME 333 Workbook...

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1 CHME 333 Workbook Chapter 8 – Internal Flows In Chapter 7 we considered external flows. In Chapter 8 we consider internal flows – where the boundary layer is constrained. The most common application is pipe or duct flow. The approach we will use in Chapter 8 is similar to what we used for external flow. However, several additional factors will need to be considered: Flow conditions o entrance region vs. fully developed flow o laminar vs. turbulent flow Pipe wall surface conditions o Constant surface temperature o Constant surface heat flux General energy balance for the fluid in the pipe The end-goal of this chapter is to prepare you for doing heat exchanger design and analysis calculations. Objectives – calculate convection coefficients for internal flow applications (mass and heat transfer) Review of pipe flow (Transport I) Thermal Consideration Correlations
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2 Internal Flow – boundary layers are constrained (pipe or duct flow) Review of Fluid Mechanics o Must distinguish between entrance and fully developed regions. o Assume laminar flow with uniform velocity profile at inlet of a circular tube. ± Velocity boundary layer develops on surface of tube and thickens with increasing x . ± Inviscid region of uniform velocity shrinks as boundary layer grows. ± Subsequent to boundary layer merger at the centerline, the velocity profile becomes parabolic and invariant with x - hydrodynamically fully developed ± How would the fully developed velocity profile differ for turbulent flow? o Entry Region – before fully developed flow ± µ ρ D u m D = Re where u m is the mean fluid velocity, and D is the diameter ± Laminar flow conditions: Re D 2300 Entry length D h fd D x Re 05 . 0
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This note was uploaded on 03/11/2011 for the course CHEME 333 taught by Professor Anthony during the Spring '11 term at UNL.

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CHME 333 Workbook Handouts - Chapter 8 - CHME 333 Workbook...

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