1. Thermodynamics Part II

2. Remaining Topics Mechanisms of Heat Transfer Thermodynamic Systems and Their Surrounding Thermal Processes Laws of Thermodynamics Heat Engines and Heat Pumps Carnot Engine Internal Combustion Engine Refrigerator and Airconditioner

3. MECHANISMS OF HEAT TRANSFER Conduction Convection Radiation

4. Conduction

6. Convection 1.The heat current due to convection is directly proportional to the surface area. 2.The viscosity of fluid slow natural convection near a stationary surface, giving a surface film that on a vertical surface typically has about the same insulating value as 1.3 cm of plywood. Forced convection decreases the thickness of the film.

7. Convection 3.The heat current due to convection is found to be approximately proportional to the 5/4 power of the temperature difference between the surface and the main body of fluid.

8. Convection

9. Radiation

12. Thermodynamic System In general, a thermodynamic system is any collection of objects that is convenient to regard as a unit, and that may have the potential to exchange energy with its surroundings.

13. Thermodynamic State A set of values of properties of a thermodynamic system that must be specified to reproduce the system The individual parameters are known as state variables, state parameters or thermodynamic variables. – ex. Temperature, pressure and volume

14. Thermodynamic Process Process that changes the state of a thermodynamic system. – Isobaric process – Isothermal Process – Isochoric/Isovolumetric Process – Adiabatic process

15. In summary… Thermodynamic system: able to exchange heat with its surroundings State variables: p, V, T,... describe the thermodynamic system Thermodynamic process: changes the state ( p, V, T,...) of the system

16. Thermodynamic Process Heat Q: can leave or enter system Work W: system can do work on its surroundings surroundings can do work on the system

17. thermodynamic system: can exchange heat with its surroundings state of system: (p, V, T,...) thermodynamic process: changes state of the system

18. Heat Q: can leave or enter system Q > 0: heat added to system Q < 0: heat removed from system

19. Work W: W > 0: system does work on its surroundings W < 0: surroundings does work on the system