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

Classical Thermodynamics Large Groups of Molecules – Continuum Scale The Laws of Thermodynamics –1 st Law: Energy can neither be created nor destroyed. It can only change form. –2 nd 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

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

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 lb m.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

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

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

Pressure, Volume & Temperature Volume: –SI: L, m 3, mL=cm 3 –AE: ft 3 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

Manometers Barometer Eqn: Manometer Eqn: Differential Manometer Eqn: Baratuci ChemE 260 March 29, 2005

Temperature Thermometers and Thermocouples Temperature conversions are straightforward  T ( o C) =  T(K) and  T ( o F) =  T( o R) 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

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

Example #1 Force Required to Accelerate a Rocket –Calculate the force necesssary to accelerate a 20,000 lb m rocket vertically upward at a rate of 100 ft/s 2. –Ans.: F total = 82,200 lb f Baratuci ChemE 260 March 29, 2005

Example #2 Relationships between Different Types of Pressures –Complete the following table if P atm = 100 kPa and  Hg = 13.6  H2O. Baratuci ChemE 260 March 29, 2005 P gage (kPa) a.)5 b.)150 c.)30 d.)30

Example #2 - Answers Relationships between Different Types of Pressures –Complete the following table if P atm = 100 kPa and  Hg = 13.6  H2O. Baratuci ChemE 260 March 29, 2005 P gage (kPa) a.) b.) c.) d.)

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

Example #4 Gravity is given as a function of altitude by g = x h (m/s 2 ), 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.: E kin = 127 MJ Ans.: E kin = 399 MJ Baratuci ChemE 260 March 29, 2005