The Advanced Chemical Engineering Thermodynamics The second law of thermodynamics

1. The Advanced Chemical Engineering ThermodynamicsThe second law of thermodynamics Q&A_-5- 10/13/2005(5) Ji-Sheng Chang

2. Heat and work • The heat and work in first law of thermodynamics • The heat and work in second law of thermodynamics • The quality of the heat and work

3. Statements of second law • The second law of thermodynamics by written language statements • No apparatus can operate in such a way that its only effect is to convert heat absorbed by a system completely into work done by the system • No process is possible which consists solely in the transfer of the heat from one temperature level to a higher one

4. Statements of second law • The second law of thermodynamics by written language statements • It is impossible by cyclic process to convert the heat absorbed by a system completely into work done by the system

5. Machines • The heat engines and refrigerator • Heat engine • Using the heat to generate the work • Refrigerator • Using the work to transfer the heat from a lower temperature space to a higher temperature space

6. Cyclic process • A cyclic process – heat engine • Pumping water to boiler • Heating water in boiler • Drafting the work from water by turbine • Cooling water that has exhaust from the turbine • The working fluids • water

7. TH QH W QC TC Heat engine • The efficiency of the heat engine

8. PE P Reversible process • The work of expansion • Case 1, PE = 0 • Case 2, PE = PEatm = 1.0 bar • Case 3, PE = P

9. P PE PE P P V1V2 V Reversible process • The work of expansion V1 V2

10. Th, Qh W W Tc, Qc Carnot’s engine • The Carnot cycle • Reversible adiabatic process • Th to Tc , input work • Reversible isothermal process • Adsorbed heat at Th • Reversible adiabatic process • Tc to Th , output work • Reversible isothermal process • Release heat at Tc

11. Carnot’s theorem • The efficiency of the Carnot’s engine • For two given heat reservoirs no engine can have a thermal efficiency higher than that of a Carnot engine • An Engine /Refrigeratorcombination

12. Carnot’s theorem • The Carnot’s theorem • If engine E has the greater of η then • The sole result of the operation is transfer of heat from temperature Tc to the higher temperature Th • This is in violation of the statement 2 of the second law

13. Temperature • What’s the temperature? • The zeroth law of thermodynamics • The temperature scales • The Celsius temperature scales • The ideal gas temperature scales • The thermodynamic temperature scales

14. Thermodynamic temperature scales • Deriving

15. Cyclic process • The Carnot’s engine • Carnot’s equation；ideal-gas temperature scales • Adiabatic compression • Isothermal expansion • Adiabatic expansion • Isothermalcompression

16. Definition • The definition of the entropy • A states function properties

17. Entropy • The second law of thermodynamics by mathematical statements. • ΔStotal ≧ 0

18. Entropy • The third law of thermodynamics. • The absolute entropy • Calculated the absolute entropy from classical thermodynamics; properties as • Heat capacity • Heat of phase changes