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ME444 ENGINEERING PIPING SYSTEM DESIGN

ME444 ENGINEERING PIPING SYSTEM DESIGN. CHAPTER 4 : FLOW THEORY. CONTENTS. CHARACTERISTICS OF FLOW BASIC EQUATIONS PRESSURE DROP IN PIPE ENERGY BLANCE IN FLUID FLOW. 1. CHARACTERISTICS OF FLOW. WATER AT 20  C. Reynold’s Experiment.

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ME444 ENGINEERING PIPING SYSTEM DESIGN

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  1. ME444 ENGINEERING PIPING SYSTEM DESIGN CHAPTER 4 : FLOW THEORY

  2. CONTENTS • CHARACTERISTICS OF FLOW • BASIC EQUATIONS • PRESSURE DROP IN PIPE • ENERGY BLANCE IN FLUID FLOW

  3. 1. CHARACTERISTICS OF FLOW

  4. WATER AT 20C

  5. Reynold’s Experiment Osborne Reynolds (1842-1912) systematically study behavior of by injecting color in to a glass tube which has water flow at different speed

  6. Reynold’s Experiment

  7. Reynold’s Number Inertia effect Viscous effect Inertia effect leads to chaos  Turbulent Viscous effect holds the flow in order  Laminar

  8. Flow Patterns Laminar (Re < 2300) Turbulent (Re >10,000) Non-viscous

  9. Flow Patterns

  10. Re of flow in pipe Low velocity flow in a DN20 SCH40 pipe at 1.2 m/s (25 lpm) TURBULENT

  11. 2. BASIC EQUATIONS CONSERVATION OF MASS ENERGY EQUATION MOMENTUM EQUATION

  12. CONSERVATION OF MASS MASS FLOW IN = MASS FLOW OUT: INCOMPRESSIBLE FLOW:

  13. ENERGY EQUATION ENERGY IN FLUID IN JOULE / M3IS POTENTIAL ENERGY IN ELEVATION POTENTIAL ENERGY IN PRESSURE KINETIC ENERGY HEIGH UNIT IS MORE PREFERABLE  HEAD DIVIDE THE ABOVES WITH

  14. HEAD Total head = Static pressure head + Velocity head + Elevation ENERGY IS NOT CONSERVED

  15. GUAGE PRESSURE ATMOSPHERIC PRESSURE IS 1 ATM = 1.013 BAR = 10.33 m. WATER EVERYWHERE (AT SEA LEVEL) (1 BAR = 10.2 m. WATER) GAUGE PRESSURE IS MORE PREFERABLE IN LIQUID FLOW GAUGE PRESSURE IS MORE PREFERABLE IN LIQUID FLOW USUALLY CALLED m.WG., psig, barg

  16. MOMENTUM EQUATION

  17. LOSS MAJOR LOSS: LOSS IN PIPE MINOR LOSS: LOSS IN FITTINGS AND VALVES PA PB A B

  18. LOSS IN PIPE PRESSURE DROP IN PIPE IS A FUNCTION OF FLUID PROPERTIES (DENSITY AND VISCOSITY) ROUGHTNESS OF PIPE PIPE LENGTH PIPE INTERNAL DIAMETER FLOW VELOCITY FLOWRATE

  19. HEAD LOSS IN PIPE varies mainly with pipe size, pipe roughness and fluid viscosity

  20. DARCY-WEISSBACH EQUATION

  21. DARCY FRICTION FACTOR Detail Darcy friction factor is proposed by Lewis Ferry Moody(5 January 1880 – 21 February 1953)

  22. MOODY DIAGRAM

  23. Colebrook – White Equation Most accurate representation of Moody diagram in Turbulence region Implicit form, must be solved iteratively

  24. APPROXIMATION OF FRICTION FACTORIN TURBULENT REGIME

  25. APPROXIMATION OF FRICTION FACTORIN TURBULENT REGIME

  26. APPROXIMATION OF FRICTION FACTORIN TURBULENT REGIME

  27. Swamee - Jain Equation Swamee - Jain (1976)

  28. ROUGHNESS, e Drawn tube 0.0015 mm Commercial steel pipe 0.046 mm Cast iron 0.26 mm Concrete 0.3 – 3 mm ROUGHNESS INCREASES WITH TIME

  29. PRESSURE DROP CHART

  30. HAZEN-WILLIAMS EQUATION hf in meter per 1000 meters Q in cu.m./s D in meter C = roughness coefficient (100-140) NOT ACCURATE BUT IN CLOSED FORM = EASY TO USE.

  31. SMOOTH ROUGH ROUGHNESS COEFFICIENT, C GENERAL VALUE 100-140 PLASTIC 120-150 (130) COPPER 120-150 (130) STEEL 100-150 (100) STEEL 100-150 (100) 60 70 80 90 100 110 120 130 140 150 160

  32. Comparison of e and C

  33. Hazen vs. Darcy

  34. LOSS IN FITTINGS PRACTICALLY 25%-50% IS ADDED TO THE TOTAL PIPE LENGTH TO ACCOUNT FOR LOSS IN FITTINGS AND VALVES

  35. LOSS IN VALVES PRACTICALLY 25%-50% IS ADDED TO THE TOTAL PIPE LENGTH TO ACCOUNT FOR LOSS IN FITTINGS AND VALVES

  36. VALVE COEFFICIENT Kv QIN CU.M./HR DPIN BAR S.G. = SPECIFIC GRAVITY Kv = 0.86 x Cv

  37. EQUIVALENT LENGTH OF FITTINGS Another way to estimate loss in fittings and valves is to use equivalent length. http://machineryequipmentonline.com/hvac-machinery/pipes-pipe-fittings-and-piping-detailsvalves/

  38. EQUIVALENT LENGTH – L/D

  39. EQUIVALENT LENGTH – L/D https://neutrium.net/fluid_flow/pressure-loss-from-fittings-equivalent-length-method/

  40. EXAMPLE 4.1 5 m vertical pipe 15 m 15 m 25 m 15 m B DN100 50 m Compute friction loss in aDN100 SCH40 pipe carry water at 27C (n=0.862X10-6 m2/s) at the flowrate of 1000 LPM fromA toB. Both globe valves are fully open (Kv = 4) 1,000 LPM 15 m A 5 m vertical pipe

  41. EXAMPLE 4.1 (2) Pipe flow area: m2 Flowrate: LPM m3/s Velocity: m/s

  42. EXAMPLE 4.1 (3) (per 100m) m/100m

  43. EXAMPLE 4.1 (4) Loss in 90 degree bend K = 0.25x1.4 = 0.35 m/piece

  44. EXAMPLE 4.1 (4) Loss globe valve K = 4 m/valve Loss check valve K = 2  Half of globe valve m/valve

  45. EXAMPLE 4.1 (5)

  46. ENERGY GRADE LINE

  47. HYDRAULIC GRADE LINE z ENERGY LEVEL DISTANCE

  48. EXAMPLE 4.2 Draw static pressure line from point A to points B and C.

  49. EXAMPLE 4.2 Unknown pressure

  50. EXCEL SPREADSHEET

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