Heat Transfer Materials Storage, Transport, and Transformation Part I: Physics

1. A Short Course by Reza Toossi, Ph.D., P.E. California State University, Long Beach Heat Transfer MaterialsStorage, Transport, and TransformationPart I: Physics

2. Outline • Atomic and Molecular Bonds • Energy Carriers • Specific Heat • Thermal Conductivity • Discussions

3. History • Aristotle (384 BC–323 BC) • Antoine Lavoisier (1743-1794) • John Dalton (1766 - 1844) • Benjamin Thompson (Count Rumford) (1753-1814) • Robert Mayer (1814-1878) • William Thompson (Lord Kelvin) (1824-1907) • Gustav Boltzmann (1844-1906) • James Maxwell (1831–1879) • Max Planck (1858 –1947) • Neil Bohr (1855–1962) • Wolfgang Pauli (1900–1958) • Erwin Schrodinger (1887–1961) • Enrico Fermi (1901–1954)

4. Heat Transfer Medium • Gases • Vapors, ideal gases, and plasmas • Liquids • Organics • Inorganics • Metals and Nonmetals • Solids • Conductors (metals) • Insulators (nonmetals) • Semiconductors • Composites • Layered and non-layered • Liquid-gas (aerosol spray) • Liquid-Liquid (emulsion) • Solid-solid (wood, resin-filled fiberglass) • Solid-gas (coal, membrane) • Solid-liquid-gas (nucleate boiling on a solid surface)

5. Thermochemical and Thermophysical Properties

6. Microscopic Heat Transfer

7. Microscopic Energy Carriers • Particles • Waves • Quasi-Particles • Phonon • Acoustic • Optical • Photon • Electron (and Hole)

8. Strong and Weak Bonds • Strong Bonds • Ionic • Covalent • Metallic • Weak Bonds (~kcal/mole) • Van der Waals • Hydrogen • Electrostatic (ionic)

9. Strong (Primary) Bonds • Ionic (metal to nonmetal) NaCl • Covalent (nonmetal to nonmetal) Diamond, organic matters • Metallic bonding (metal to metal) Silver

10. Weak (Secondary) Bonds • Hydrogen Forces (H2O, NH3) • Van der Waals • Dipole-Dipole Forces (HCl-HCl) • London Dispersion Forces (Xe-Xe) • Ion-Dipole Forces

11. Bond Strength

12. Bonding Between Neutral Atoms • Attractive force @ large distances (van der Waals) • Repulsive force @ short distances (Pauli repulsion) • Models • Quantum mechanical (Dipole-dipole and London forces) • Classical (LJ) • V is the energy potential •  Is the equilibrium distance • is the energy of interaction (depth of the potential well) • r is the distance of separation

13. Cohesion and Adhesion • Cohesion: Intermolecular attraction between molecules of the same kind or phase (viscosity in fluid) • Adhesion: Intermolecular attraction between molecules of different kind or phase (water wetting of a glass, oil droplets in a hot skillet)

14. Transport Phenomena • Conduction • Macroscale (> 1 mm, Fourier’s Law ) • Microscale (1-100 μm, Thermalization) • Nanoscale (1-100 nm, Non-equilibrium) • Surface Tension • Macroscale • Microscale

15. Continuum Approach • Continuity • Species • Momentum (Navier-Stokes) • Energy

16. Continuum Flow Limitations • Continuum regime (Kn< 0.01) • Slip flow regime (0.01 < Kn< 0.1) • Transition regime (0.1 < Kn< 3) • Free molecular flow regime (Kn> 3) Knudsen Number:

17. Statistical Approach • Boltzmann Transport Equation

18. Nanoscale Considerations • Nonequilibrium Phenomenon • Ultra small dimensions • Ultrafast processes • Different conduction equations for electrons and the lattice • Nucleation

19. Laser Irradiation

20. Example: Laser Processing of Material Melting of Gold Films • Short-pulsed laser melting of thin films involves two non-equilibrium processes. • (1) Deposition of laser energy • (2) Energy transfer between electrons and lattice • (3) Melting One –Step Model Two –Step Model Electron: Lattice: Kuo, L.S., and Qui, T.Q., 1996, “Microscale Energy Transfer During Picosecond Laser Melting of Metal Films,” ASME HTD-Vol. 323, Vol. 1, pp.149-157.

21. Results (Gold film with L = 1000 nm, tp=20 ps)

22. Specific Heat of Various Substances

23. Heat Storage • Specific Heat Capacities: Cp and Cv • Gases • Translational • Rotational • Vibrational • Electronic • Solids (metals, dielectrics, and semiconductors) • Lattice vibration (phonons) • Free electrons • Liquids • Near critical point (behaves like a gas) • Away from critical point (behaves like a solid)

24. Modes of Energy Storage (H2)

25. Cp 0 to ∞

26. Specific Heat of Selected gases at 300 K Cp for Gases

27. Cp for solids • Einstein (Classic) Model • cv= 3 k (per molecule), 3R (per mole) • Debye Model • cv increases until TD

28. Cp for liquids

29. Cp for Water

30. Thermal Conductivity • Thermal Conductivity (k) • Gases • Solids • Metals (Drude classical theory) • Nonmetals (Debye model) • Semiconductors • Liquids • Composites • Effective conductivity

31. Contributions from Heat Carriers

32. Equilibrium vs. Transport

33. Mechanism of Heat Conduction in Gases

34. Mechanism of Heat Conduction in Solids • Roles of the conduction electrons and the thermal lattice vibration are significant • Conduction electrons (Drude Model) • Lattice (phonons) vibration (Callaway Model) • Amorphous (non-periodic) • Crystalline (Periodic)

35. k = km+ ke + kp • Molecular • For an ideal monatomic gas • For an ideal polyatomic gas • Electronic • Contribution to thermal conductivity • Contribution to electrical conductivity • Phonons

36. Metals, Nonmetals, and Semiconductors • Metals • Excellent heat conductor • Excellent electrical conductor • Nonmetals • Poor heat conductor • Poor electrical conductor • Semiconductors • Fair heat conductor • Good electrical conductor

37. Thermal Conductivities of Solids

38. Thermal Materials:From Ideal Insulators to Perfect Conductors

39. Thermal Conductivity of Liquids

40. Thermal Conductivity of Composites

41. Part V- Q/A For additional questions, Please email rtoossi@csulb.edu.

42. Further Readings • Lee, J., Sears, F. W, and Turcotte, D. L., “Statistical Thermodynamics,” Addison-Wesley, 1963. • Tien, C. L., and Lienhard, J. H., “Statistical Thermodynamics,” Holt, Rinehart and Winston, 1971. • Kaviany, M., “Principal of Heat Transfer,” Wiley, 2002. • Atkins, P. W., “Molecular Quantum Mechanics,” Clarendon Press, 1970. • Siegal, R., and Howell, J. R., “Thermal Radiation Heat Transfer,” Hemisphere Publishing Corporation, 3rd Ed., 1992