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ChemE 260 Foundation of Thermodynamics

ChemE 260 Foundation of Thermodynamics. Dr. William Baratuci Senior Lecturer Chemical Engineering Department University of Washington TCD 1: All CB 1: ALL. March 29, 2005. Classical Thermodynamics. Large Groups of Molecules – Continuum Scale The Laws of Thermodynamics

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ChemE 260 Foundation of Thermodynamics

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  1. ChemE 260 Foundation of Thermodynamics Dr. William Baratuci Senior Lecturer Chemical Engineering Department University of Washington TCD 1: AllCB 1: ALL March 29, 2005

  2. Classical Thermodynamics • Large Groups of Molecules – Continuum Scale • The Laws of Thermodynamics • 1st Law: Energy can neither be created nor destroyed. It can only change form. • 2nd Law: Energy in the form of heat only flows spontaneously from regions of higher temperature to regions of lower temperature. • Forms of Energy • Gravitational Potential : • Kinetic : • Internal: • Heat • Work Baratuci ChemE 260 March 29, 2005

  3. Dimensions & Units • Dimensions: Mass, Length, Time • Units: m, ft, kg, lbm, J, Btu • Force • IS a fundamental unit in the AE System • Is NOT a fundamental unit in the SI System • Newton’s 2nd Law of Motion: • SI: • AE: • Conversion Factors • Online: “The Foot Rule” website • http://www.FootRule.com Baratuci ChemE 260 March 29, 2005

  4. Terminology or Nomenclature • System: The material or volume that we are studying • Systems have boundaries • Closed Systems: Mass does not cross the boundary • Open Systems: Mass does cross the boundary • Properties • Intensive vs. Extensive Properties • Extensive properties depend on the size of the system, intensive properties do not. • Molar Properties: per mole. Molar volume: • Specific Properties: per kg or per lbm. Specific volume: • States • The condition of a piece of matter or system as determined by its intensive properties. • If ANY intensive property is different, then the system is in a different state. Baratuci ChemE 260 March 29, 2005

  5. More Nomenclature • Process • A change in the state of a system • Process Path • The series of states that a system moves through on its way from the initial state to the final state. • Special Types of Processes • Isobaric – constant pressure • Isothermal - constant temperature • Isochoric - constant volume • Cycles • Special process paths in which the initial state is the same as the final state • Thermodynamic cycles are a key topic in this course Baratuci ChemE 260 March 29, 2005

  6. Equilibrium • A system is in equilibrium when no unbalanced potentials or driving forces exist within the system boundary. • Thermal: no temperature driving forces • Chemical: no chemical driving forces • Phase: no mass transfer driving forces • Mechanical: no unbalanced mechanical forces • Quasi-Equilibrium Processes • A process during which the system only deviates from equilibrium by an infinitessimal amount. • Every state along the process path is very nearly an equilibrium state. Baratuci ChemE 260 March 29, 2005

  7. Pressure, Volume & Temperature • Volume: • SI: L, m3, mL=cm3 • AE: ft3 • Pressure: acts in all directions  to all surfaces • SI: Pa, kPa, MPa, bar, atm • AE: psia • Absolute, Gage and Vacuum Pressures Baratuci ChemE 260 March 29, 2005

  8. Manometers • Barometer Eqn: • Manometer Eqn: • DifferentialManometer Eqn: Baratuci ChemE 260 March 29, 2005

  9. Temperature • Thermometers and Thermocouples • Temperature conversions are straightforward • T (oC) = T(K) and T (oF) = T(oR) • Ideal Gas Thermometry • Must be calibrated • Tedious, but extremely accurate • IG T-scale is identical to the Kelvin Scale ! Baratuci ChemE 260 March 29, 2005

  10. Next Class • Problem Solving Session • Ch 1 • Homework #1, due Friday 4/1 ! Baratuci ChemE 260 March 29, 2005

  11. Example #1 • Force Required to Accelerate a Rocket • Calculate the force necesssary to accelerate a 20,000 lbm rocket vertically upward at a rate of 100 ft/s2. • Ans.: Ftotal = 82,200 lbf Baratuci ChemE 260 March 29, 2005

  12. Example #2 • Relationships between Different Types of Pressures • Complete the following table if Patm = 100 kPa and Hg = 13.6 H2O . Baratuci ChemE 260 March 29, 2005

  13. Example #2 - Answers • Relationships between Different Types of Pressures • Complete the following table if Patm = 100 kPa and Hg = 13.6 H2O . Baratuci ChemE 260 March 29, 2005

  14. Example #3 • A horizontal 2 m diameter man-hole is located in the bottom of a water tank as shown here. Determine the extra upward force, F, that a man or machine must exert on the man-hole cover to just barely lift it. • Ans.: F = 154 kN Baratuci ChemE 260 March 29, 2005

  15. Example #4 • Gravity is given as a function of altitude by g = 9.81 - 3.32 x 10-6 h (m/s2), where h is the altitude above sea level. An airplane is traveling at 900 km/h at an elevation of 10 km. If its weight at sea level is 40 kN, determine: • Its kinetic energy • Its potential energy relative to sea level • Ans.: Ekin = 127 MJ • Ans.: Ekin = 399 MJ Baratuci ChemE 260 March 29, 2005

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