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CHS220804 MEKANIKAFLUIDA (S1 Reguler) CHS220803E MEKANIKAFLUIDA (S1 Ekstensi) Departemen Teknik Kimia FT-UI Pengajar : Ir. SUKIRNO M.Eng/Ir. Diyan S.

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Presentation on theme: "CHS220804 MEKANIKAFLUIDA (S1 Reguler) CHS220803E MEKANIKAFLUIDA (S1 Ekstensi) Departemen Teknik Kimia FT-UI Pengajar : Ir. SUKIRNO M.Eng/Ir. Diyan S."— Presentation transcript:

1 CHS MEKANIKAFLUIDA (S1 Reguler) CHS220803E MEKANIKAFLUIDA (S1 Ekstensi) Departemen Teknik Kimia FT-UI Pengajar : Ir. SUKIRNO M.Eng/Ir. Diyan S M.Eng

2 Periode 2009-2010 Lectures : Senin 19:00-21:30 K-204
Selasa 10:00-12:30 K-106 Kamis 10:00-12:30 K-210 Sbl Mid Test Pak Sukirno Stl Mid Test Pak Diyan S Tutorials : Asisten

3 Assessment Pak Kirno 50% 25% : MidTest (2 jam)
10% : Kuis selama kelas/tutorial 15% : Tugas

4 Books Noel de Nevers Fluid Mechanics for Chemical Engineer, Second Ed.
Coulson & Richardson Chemical Engineering, Vol 1, 5e (1996) Butterworth-Heinemann

GARIS BESAR KULIAH PENDAHULUAN Mengenal aplikasi Mekanika Fluida, Fluida dan propertiesnya FLUIDA STATIK Pressure, Pascal’s Principle,Gravity and fluid pressure, Measurement of pressure, Archimedes’ Principle FLUIDA MENGALIR (FLUID FLOW) Persamaan dasar: Pers. Kontinuitas (Neraca massa) Pers. Bernoulli (Neraca Energi) dan aplikasiBernoulli pada flowmeter (orificemeter, venturimeter), alat transfer fluida (pompa) KEHILANGAN FRIKSI (FRICTION LOSS) DALAM PIPA Faktor friksi, diagram Moody, Perhitungan friksi pada pipa sudden contraction/expansion fitting, APLIKASI NERACA MOMENTUM UNTUK PERHITUNGAN GAYA PADA PIPA Neraca momentum, perhitungan gaya pada belokan ALIRAN GAS KECEPATAN TINGGI, SATU DIMENSI Kecepatan suara, Aliran stedi fritionless, nozzle choking, aliran dengan friksi dan pemanasan, nozzle-difusser INTERAKSI FLUIDA DAN PADATAN Lapisan batas dan Gaya seret (drag force), Friksi fluida dalam media berpori, Pers. Blake-Kozeny, Ergun Darcy, Fluidisasi, Filtrasi, Internal and external flows Air, sea-water – oil & gas – fresh water, mud, hydraulic oil Drilling, pumping, extraction, power generation, effluent disposal, fire systems, sanitation

6 Fluid Mechanics Definition Engineering applications
The study of liquids and gasses at rest (statics) and in motion (dynamics) Engineering applications Oil /process fluid in pipelines Pumps, filters, rivers, etc Groundwater movement Blood in capillaries

7 Industrial application …
Home : water, heating, appliances – fridge, washing / dish-washer machines Car: engine cooling + car heater, fuel, oil, hydraulics, external aerodynamics Aeroplane: fuel, hydraulics, air-conditioning, cabin pressurization, oxygen, sanitation, external aerodynamics, gas turbines

Storage Pipe system Valves Flow Measurement Pump Process/Resistance

HYDRAULICS : the flow of water in rivers, pipes, canals, pump, turbines HYDROLOGY : the flow of water in the ground RESERVOIR MECHANICS : the flow of oil, gas and water in petroleum reservoir AERODYNAMICS : the flow of air around aeroplanes, rocket projectils METEOROLOGY : the flow of the atmosfeer PARTICLE DYNAMICS : the flow of fluid around particles (dust settling, slurry, pneumatic transfort, fluidized be, air pollutant particles) MULTIPLEPHASE FLOW oil well, carburetirs, fuel injector, combustion chamber, sprays. COMBINATION OF FLUID FLOW with chemical reaction in combustion chamber, with mass transfer di distillation or drying VISCOUS DOMINATED FLOW; lubrication, injection molding, wire coating, volcanoes, continental drift


11 What is a Fluid? … a substance which deforms continuously under the action of shearing forces however small. … unable to retain any unsupported shape; it takes up the shape of any enclosing container. ... we assume it behaves as a continuum

12 Liquids and gasses – What’s the difference?
Expands Liquid Free Surface Liquids: Close packed, strong cohesive forces, retains volume, has free surface Gasses: Widely spaced, weak cohesive forces, free to expand Almost incompressible Relatively easy to compress

13 Common Fluids Liquids: Gasses: Borderline:
water, oil, mercury, gasoline, alcohol Gasses: air, helium, hydrogen, steam Borderline: jelly, asphalt, lead, toothpaste, paint, pitch

14 Density The density of a fluid is defined as its mass per unit volume. It is denoted by the Greek symbol, . kg  water= 998 kgm-3 m  = V air =1.2kgm-3 kgm-3 m3 If the density is constant (most liquids), the flow is incompressible. If the density varies significantly (eg some gas flows), the flow is compressible. (Although gases are easy to compress, the flow may be treated as incompressible if there are no large pressure fluctuations)

15 Density Mass per unit volume (e.g., @ 20 oC, 1 atm)
Water rwater = 1000 kg/m3 Mercury rHg = 13,500 kg/m3 Air rair = 1.22 kg/m3 Densities of gasses increase with pressure Densities of liquids are nearly constant (incompressible) for constant temperature Specific volume = 1/density 950 960 970 980 990 1000 50 100 Temperature (C) Density (kg/m3)

16 Specific Weight Weight per unit volume (e.g., @ 20 oC, 1 atm)
gwater = (998 kg/m3)(9.807 m2/s) = 9790 N/m3 [= 62.4 lbf/ft3] gair = (1.205 kg/m3)(9.807 m2/s) = 11.8 N/m3 [= lbf/ft3]

17 Specific Gravity Ratio of fluid density to density at STP
20 oC, 1 atm) Water SGwater = 1 Mercury SGHg = 13.6 Air SGair = 1

18 States of Matter “a fluid, such as water or air, deforms continuously when acted on by shearing stresses of any magnitude.” - Munson, Young, Okiishi Solid Shear Stress t Fluid

19 Fluid Deformation between Parallel Plates
Side view Force F causes the top plate to have velocity U. Distance between plates (b) What other parameters control how much force is required to get a desired velocity? Area of plates (A) Viscosity!

20 Tangential force per unit area Rate of deformation
Shear Stress F v b Tangential force per unit area Rate of deformation change in velocity with repect to distance rate of shear

21 Dynamic and Kinematic Viscosity
Area A Friction force F vb b v z Absolute Viscosity Kinematic Viscosity Shear stess (dyne/cm2 ) Shear strain rate (s-1) Dyne-s/cm2=Poise N-s/m2=103 cP

22 Fluid classification by response to shear stress

23 Fluid Viscosity Examples of highly viscous fluids
______________________ Fundamental mechanisms Gases - transfer of molecular momentum Viscosity __________ as temperature increases. Viscosity __________ as pressure increases. Liquids - cohesion and momentum transfer Viscosity decreases as temperature increases. Relatively independent of pressure (incompressible) molasses, tar, 20w-50 oil increases increases _______

24 Role of Viscosity Statics Flows zero
Fluids at rest have no relative motion between layers of fluid and thus du/dy = 0 Therefore the shear stress is _____ and is independent of the fluid viscosity Flows Fluid viscosity is very important when the fluid is moving zero

25 Perfect Gas Law Note deviation from the text! PV = nRT R is the universal gas constant T is in Kelvin Use absolute pressure for P and absolute temperature for T

26 Bulk Modulus of Elasticity
Relates the change in volume to a change in pressure changes in density at high pressure pressure waves _________ ______ __________ 2.00 2.05 2.10 2.15 2.20 2.25 2.30 2.35 20 40 60 80 100 Temperature (C) Bulk Modulus of elasticity (GPa) sound Water water hammer speed of sound

27 Vapor Pressure 101 kPa liquid
1000 2000 3000 4000 5000 6000 7000 8000 10 20 30 40 Temperature (C) Vapor pressure (Pa) liquid What is vapor pressure of water at 100°C? 101 kPa Connection forward to cavitation!

28 Surface Tension Pressure increase in a spherical droplet DppR2 2pRs
0.050 0.055 0.060 0.065 0.070 0.075 0.080 20 40 60 80 100 Temperature (C) Surface tension (N/m) Pressure increase in a spherical droplet DppR2 2pRs Surface molecules DppR2 = 2pRs

29 Example: Surface Tension
Estimate the difference in pressure (in Pa) between the inside and outside of a bubble of air in 20ºC water. The air bubble is 0.3 mm in diameter. s = N/m R = 0.15 x 10-3 m Statics! What is the difference between pressure in a water droplet and in an air bubble?

30 Bagaimana mengukur viskositas ?

ASTM D445 P = Pressure difference across capiller R = Radius of capiller L = Length od capiller V = Volume fluida  = Viscosity

(Poiseuille Eq.) 1 V x z cP = fluid density X cSt 2


34 Example: Measure the viscosity of water
Outer cylinder Thin layer of water Inner cylinder The inner cylinder is 10 cm in diameter and rotates at 10 rpm. The fluid layer is 2 mm thick and 10 cm high. The power required to turn the inner cylinder is 50x10-6 watts. What is the dynamic viscosity of the fluid?

35 Solution Scheme Restate the goal
Identify the given parameters and represent the parameters using symbols Outline your solution including the equations describing the physical constraints and any simplifying assumptions Solve for the unknown symbolically Substitute numerical values with units and do the arithmetic Check your units! Check the reasonableness of your answer olution

36 Outline the solution Restate the goal
Identify the given parameters and represent the parameters using symbols Outline your solution including the equations describing the physical constraints and any simplifying assumptions

37 Viscosity Measurement: Solution
Outer cylinder Thin layer of water Inner cylinder wr 2prh Fwr r = 5 cm t = 2 mm h = 10 cm P = 50 x 10-6 W 10 rpm


39 Dimensions & Units Tujuan : mereview satuan untuk menghilangkan kebingunan konversi satuan SI dan Engineering

40 Dimensions and Units The dimensions have to be the same for each term in an equation Dimensions of mechanics are length time mass force temperature L T M MLT-2

41 Dimensions and Units Quantity Symbol Dimensions
Density r ML-3 Specific Weight g ML-2T-2 Dynamic viscosity m ML-1T-1 Kinematic viscosity  L2T-1 Surface tension  MT-2 Bulk mod of elasticity E ML-1T-2 These are _______ properties! fluid 4 How many independent properties? _____

42 Units Unit: Particular dimension kg, m, s, oK (Systeme International)
slug, ft, s, oR (British Gravitational) lbm, ft, s, oR (something else)

43 What’s a SLUG?! Unit of mass in the BG system (~ 14.59 kg, ~32.17 lbm)
1 lbf will accelerate a slug 1ft/s2 32.17 lb/14.59 kg = 2.2 lbm/kg

44 Secondary Units Force N = kg-m/s2 (Newton)
lbf = slug-ft/s2 (pound force) = 32.2 lbm-ft/s2 Work (Force through a distance) J = N-m (Joule) ft-lbf (foot pound) Energy (Work per time) W = J/s (Watt) ft-lbf/s (foot pound per sec) hp 550 ft-lb/s (horsepower)

Fisika Engineering W = mg W = mg /gc. (g: gravitational acceleration).

46 Conversion of Units

47 MEKANIKA FLUIDA Tujuan Pengajaran
Memahami fenomena/konsepnya dan mampu mengaplikasikan PERSAMAAN DASAR fluida statik maupun fluida mengalir, untuk mendapatkan solusi persoalan praktis, yang sering dijumpai dalam enjinering terutama yang berkaitan dengan operasi teknik kimia seperti transportasi fluida, pengontakkan fluida-padatan, pemisahan fluida padatan. PERSAMAAN DASAR MEKANIKA FLUIDA H. Newton F= m.a H. Kekekalan Massa H. Kekekalan Energi (H.Termodinamika 1) H. Termodinamika 2

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