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EAT 104- Asas Proses Kejuruteraan Kimia / Fundamental of Chemical Engineering Processes

EAT 104- Asas Proses Kejuruteraan Kimia / Fundamental of Chemical Engineering Processes. Chapter 2. Processes and Process Variables. Density. Temperature. Processes and Process Variables. Flow rate. Pressure. Chemical composition. Moles & molecular weight.

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EAT 104- Asas Proses Kejuruteraan Kimia / Fundamental of Chemical Engineering Processes

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  1. EAT 104- Asas Proses Kejuruteraan Kimia / Fundamental of Chemical Engineering Processes Chapter 2 Processes and Process Variables

  2. Density Temperature Processes and Process Variables Flow rate Pressure Chemical composition Moles & molecular weight Part per million (ppm) & part per billion (ppb) Mass & mole fractions Concentration Average molecular weight

  3. Process Process Unit Input/Feed Output/Product • Process Any operation that cause a physical or chemical change in a substance. • Can consist of several process unit. • Chemical/bioprocess engineering is responsible to design and operate the process. • Formulation of process flow sheet/layout running day-to-day process • Specification of individual process unit • Associated operating variables

  4. Density & Specific VOLUME • Density () • Mass per unit volume of the substance • Unit g/cm3; kg/m3; lbm/ft3 • Specific Volume • Volume occupied by a unit mass of the substances • Inverse of density • Unit cm3/g; m3/kg; ft3/lbm Densities of pure solids and liquids are essentially independent of pressure and vary relatively slightly with temperature.

  5. EXERCISE • The density of CCl4 is 1.595 g/cm3; what is • Mass of 20 cm3 of CCl4 • Volume of 6.20 lbm of CCl4 Solution: a) b)

  6. Specific Gravity • Specific Gravity (SG) • Ratio of the density () of the substance to the density of a reference (ref) substance at a specific condition: • SG = /ref • The reference most commonly used for solids and liquids is water at 4˚C: ref@H2O(l) (4˚C) = 1.000 g/cm3 = 1000 kg/m3 = 62.43 lbm/ft3

  7. Specific Gravity • Specific Gravity (SG) • SG is dimensionless. • means that the specific gravity of a substance at 20˚C with reference to water at 4˚C is 0.6

  8. Specific Gravity • To get the density of a substance, multiply the SG value to the value of reference density. TEST YOURSELF • If the specific gravity of a liquid is 2.00, find its density in the following units: • g/cm3 • kg/m3 • lbm/ft3 • Solution: • 2.00 g/cm3 • 2.00 x 103 kg/m3 • 124.86 lbm/ft3

  9. EXERCISE • A liquid has a SG of 0.50. Find • Density in g/cm3 • Density in lbm/ft3 • Mass of 3 cm3 of this liquid • Volume occupied by 18 g of this liquid

  10. SOLUTION • Density in g/cm3 • Density in lbm/ft3 • Mass of 3 cm3 of this liquid • Volume occupied by 18 g of this liquid

  11. Question • The density of carbon tetrachloride is 1.595 g/cm3: the mass of 20.0 cm3 CCl4 is therefore: • The volume of 6.20 lbm of CCl4 is: • What are the units of specific gravity ? • A liquid has a specific gravity of 0.50. What is the density in g/cm3? What is its specific volume in cm3/g? What is the density in lbm/ft3? What is the mass of 3.0 cm3 of this liquid? What volume is occupied by 18 g? • ρwater =1 g/cm3 = 1 g/ml = 1 kg/litre = 1000 kg/m3 = 1 tonne/m3 = 62.4 lbm /ft3 = 8.34 lb/gallon.

  12. Question • The specific gravity of mercury at 200C is 13.546, find the density of mercury inlbm /ft3 and calculate the volume in ft3 occupied by 215 kg of mercury • Answer: density of mercury: 845.7 lbm /ft3 • Volume : 0.56 ft3 • The mass flow rate of n-hexane ( ρ =0.659 g/cm3) in a pipe is 6.59 g/s. What is the volumetric flow rate of the hexane? • Answer: 10 cm3/s • The volumetric flow rate of CCl4( ρ =1.595 g/cm3) in a pipe is 100.0 cm3/min. What is the mass flow rate of the CCl4 • Answer: 159.5 g/min

  13. FLOW RATE • Flow rate The rate at which a material is transported through a process line • Can be expressed as : • mass flow rate, (mass/time) • volumetric flow rate, (volume/time) • The density of a fluid can be used to convert a known volumetric flow rate of a process stream to the mass flow rate of that stream or vice versa. The mass flow rates of process streams must be known for many process calculations, but it is frequently more convenient to measure volumetric flow rates than mass flow rate. Therefore, the density is used to convert volume flow rate to mass flow rate.

  14. FLOWmeter • Flow meter Device mounted in a process line that provides a • continuous reading of the flow rate in the line. • Two commonly used flow meter: a) Rotameter b) Orifice meter

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