Lesson 7 Review of fundamentals: Heat and Mass transfer

This heat transfer text provides a comprehensive treatment of the fundamental aspects of conduction, convection, and radiation. Emphasis is placed on careful and complete theoretical developments, and numerous solved example problems and design problems are included to illustrate practical applications of fundamental principles. The appendices provide properties of materials, tables of mathematical functions, author index, and subject index. (LCL)

* The author dedicates this chapter to little Senaan Asil Aziz whose sparkling smile "makes my day." 161 CONDUCTION HEAT TRANSFER

This second part of Fundamental Principles of Heat Transfer deals primarily with the applications of convection and radiation. Emphasis is again placed on careful and complete theoretical developments.

Thermal energy is that of rotation of atoms and molecules around their proper rotation axes. The temperature of a substance is the mean energy of its molecules’ rotation, while its indicator is their rotation frequencies around their own axes. Atoms and molecules of a substanse distance themselves due to ethereal or elonic whirls (electromagnetic fields) created by means of their rotation around their proper axes. The said elonic whirls contre-balance the forces of Fatio that try to attract molecules together. Besides, these elonic whirls function as transferers of rotation from a molecule to its neighboring molecule, and such transfer of rotation represents the process of thermoconduction. In crystallic solids, e.g. metals, thermoconduction priority directions lie along sides of crystals’ lattices. Solids with molecules non-organized in crystals’ lattices such as thermoinsulators, liquids and especially gases, are much less thermoconductive than metals, which can be explained by greater intermolecular distances that diminishe the ethereal tranfer effectivness.

International Journal of Heat and Mass Transfer, 1994

Composite(s) or layered material(s)/anisotropic media Papers addressing heat contact in composite construction, thermal expansion issues, thermal cracks, multi-layered models, influences due to various heat loads and boundary effects, thermal calculations in composite wall(s) and anisotropic media, effective thermal conductivity approximations, multilayered media, graphite fiber/polymer matrix composites, transverse thermal diffusivity evaluations, thermal resistance in multi-layer composites appear in refs. [18A-39A]. Injluence of laser/pulse heat and thermal propagation The effect(s) due to sudden laser impact on materials, pulse heat loading situations and thermal shock(s) are addressed in this subcategory. Of mention are also publications involving thermal wave propagation problems under the influence of a hyperbolic heat conduction mode. Tbe papers in this subcategory are identified in refs. [40A-53A]. Conduction in arbitrary geometries and complex configurations In this subcategory, papers dealing with simplified models for homogeneous cylinders, temperature distribution in journal bearings and spherical ridges and troughs in a plane are addressed. These are identified in refs. [54A-56A]. Models/methods and approaches and numerical studies This subcategory continues to attract a wide range of interest in the development of accurate models, and modeling/analysis approaches including numerical studies for a variety of physical situations involving heat transfer due to conduction. Finite difference, finite element, boundary element methods and the like have been employed for a wide range of research investigations. These appear in refs. [57A-8lA]. Thermo-mechanical problems The influence of temperature effects on materials and components in particular, thermal-stresses and thermally induced stress waves are addressed in this subcategory. Both linear and nonlinear thermal-stress issues are addressed including theoretical/numerical and experimental studies. These papers are identified in refs. [82A-145A]. Inverse heat conduction Inverse heat conduction aspects including development of methods, substitution of multi-dimensional problems, prediction under the influence of heat sources and various types of boundary conditions, regularized solutions, explicitly sometimes, numerical approximations and simulations appear in refs. [146A-148A]. Miscellaneous conduction studies Various types of miscellaneous heat conduction problems have been studied in literature and appear in refs. [149A-178A]. Special applications Specialized applications involving heat conduction via theoretical, numerical/approximate method sand/or experimental investigations are addressed in refs. [179A-209A]. Electronic packaging Various theoretical, experimental and numerical studies dealing with thermal heat transfer characteristics, influence of heat sources, contact issues, prediction of temperature field and the like in microelectronic packaging appear in refs. [210A-232A]. BOUNDARY LAYERS AND EXTERNAL FLOWS The research on boundary layer and external flows during 1992 has been categorized as follows: flows influenced externally, flows with special geometrir Heat transfer-a review of 1992 literature 1287 effects, compressible and high-speed flows, analysis and modeling techniques, unsteady flow effects, films and interfacial effects, flows with special fluid types, and conjugate heat transfer situations. Unsteady eflects External effects Several papers documented the effects of an imposed streamwise pressure gradient [lB, 3B, lOB, IJB-lSB]. Some included the effects of acceleration on the stabiiity of the boundary layer indicating conditions of transition and reiaminarization. One addressed the effect of agitation. Other effects discussed were variations of the thermal boundary condition, raising of the external (free stream) disturbance level, imposition of longitudinal vortex arrays, and application of sonic disturbances [2B, 4B-9B, llB, 12B] Heat transfer-a review of 1992 literature 1289 periodically perturbed flow and heat transfer due to electrohydrodynamical forcing was treated in refrigerant 113. Transient flow was examined in the presence of twisted oval tubes and for time-varying temperature field in a thick-walled pipe [88C-97C]. Multi-phase jlow in ducts Multi-phase flow in ducts was examined in over a wide range of physical situations. Solid-gas two-phase flow was considered in the following studies: submicron particle flow in a cooled laminar tube considering convection, diffusion, and thermophoresis; gas-particle flow of nonisothermal turbulent swirling flow was studied in a cylindrical channel; and mixtures of combustible and non-combustible particles in gas were studied. Gas (typically air) and liquid flow was examined in the presence of wave motion; the interfacial heat transfer was investigated. A new correlation was presented for the air-water flow in horizontal rectangular channels. Air-water flow was also treated in the stratified arrangement found in certain rod bundles. Polydisperse aerosols in cooled laminar flow was studied theoretically and experimentally. Three-phase flow of water (ice-steamliquid) was examined and compared to single-phase flow. A three-phase system of air-water-sand was also studied in the presence of a tube bundle [98C-109C]. Non-Newtonian jlow in ducts Non-Newtonian fluid flow in ducts was a particularly active research area during the year. Power law tluids in concentric annular ducts were examined, where both the heat transfer and pressure drop were considered. Viscous dissipation effects on heat transfer to power law fluids was studied in arbitrary duct cross sections. Non-Newtonian flow was investigated in a variety of geometries including: axisymmetric sudden expansion (with applications to extruston processes and capillary rheometry); flow in a rectangular duct (viscoelastic, inelastic, and polymerizable fluids were considered); Couette flow in an annuli with moving outer cylinder (power law fluids); and viscoelastic fluid flow in a screw-wall channel. A second law analysis of non-Newtonian forced convection was also presented [l lOC-12OC]. Miscellaneous duct jlow A handful of studies did not fit well into the categories highlighted above. These investigations included cryogenic applications (e.g. liquid helium), high-speed gas flows, and fluidized bed channel flow [121C-128C].