3/6/2012
1
Today’s Agenda 3-6-12
1. Determine if internal (pipe) flow is laminar or
turbulent.
2. Calculate entrance length for fully developed flow.
3. Calculate losses (major and minor) as input to energy
equation.
Internal Flow
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Determining Laminar and Turbulent Flow in Pipes and Calculating Entrance Length and Losses, Study notes of Fluid Mechanics
Information on how to determine if internal pipe flow is laminar or turbulent, calculate entrance length for fully developed flow, and calculate major and minor losses as input to the energy equation. It includes examples and problem-solving exercises.
Typology: Study notes
2011/2012
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1. 2.3. (^) Determine if internal (pipe) flow is laminar orturbulent. Calculate entrance length for fully developed flow.Calculate losses (major and minor) as input to energyequation.^ Today’s Agenda 3-6- Internal Flow
Laminar vs. Turbulent Flow
Carbon dioxide at 20°C and 550 kPa (abs) flows in a pipe at a mass flow rate of0.004 kg/s. Determine the maximum diameter allowed if the flow is to be turbulent. Example problem: laminar vs. turbulent flow
Fully Developed Flow Fully Developed Flow
Is the flow laminar or turbulent? Laminar28% Turbulent68% I don’t^ know4%
Air flows through a rectangular galvanized iron duct (0.30 x 0.15 m) at 0.1 mA. LaminarB. TurbulentC. I don’t know ρair = 1.23 kg/m 3 μair = 1.79 x 10 -5 N·s/m 2 3 /s.
Is the entrance length larger for laminar or turbulent flow?
A. LaminarB. Turbulent Laminar73% Turbulent27%
Major losses: from friction
For a smooth walled pipe (Prandtl, 1935) f (^121) (^) Re (^2) f .d 0 log(Re0.0399 4000 Turbulent friction factor d 0.0309 f 1021 ) 4 0 0.0180. (^8105) 0.0116 (^106) 0.0081 (^107) 0.0059 108
Data show a dependence of f on pipe roughness Accounting for pipe wallroughness (Colebrook, 1938) f^1 21 2. 0 log( 3. D 7 (Nikuradse 1933) Re^2. d^51 f 12 )
r = sand grain sizek = pipe diameter The Moody Chart
Is the friction factor larger for laminar or turbulent flow?
Is the friction factor larger for laminar or turbulent flow? Air flows through a rectangular galvanized iron duct (0.30 x 0.15 m) at 0.1 m^ A. LaminarB. Turbulent ρair = 1.23 kg/m 3 μair = 1.79 x 10^ Laminar26% -5 N·s/m 2^ Turbulent74% 3 /s.
The Moody Chart Laminar vs. Turbulent Flow
Minor losses: from geometry and components