E xtended surfaces, in the forms of longitudinal or radial fins or spines are ubiquitous in applications where the need exists to enhance heat transfer between a surface and an adjacent fluid. Applications range from very large scale, as with tubes in heat exchangers, to the very small, as is the case for the temperature control of electronic components.
At the fundamental level, the analysis of heat transfer from finned surfaces involves solving second-order differential equations in a variety of coordinate systems. The subject of extended surface heat transfer is one where analytical methods have been very successful in providing design information for a variety of geometries, some of which are very complex. As both primary and extended surfaces involve convective exchange as a boundary condition, the convective heat transfer coefficient h, which appears as a parameter in the solution, must be evaluated using standard analysis or empirical correlations.
This coefficient can be modeled, most simply, as a constant, in which the governing second-order differential equation is linear. When the more realistic definition of has a function of temperature is employed, the problem becomes nonlinear and is considerably more difficult to solve. This nonlinearty is exaggerated when the solid–fluid interface encounters a phase change in the form of evaporation or condensation. The subject of convective heat transfer is included as a separate chapter in this work, and this chapter provides some direction in evaluating the coefficient h. Two later chapters are devoted entirely to the areas of boiling and condensation. Arather extensive treatise on the subject of extended surface heat transfer is a book by Donald Q. Kern and Allan D. Kraus published in 1972. One might have thought this subject area sufficiently mature that only modest developments, probably of an incremental nature, would occur in the ensuing 28 years following its publication. The reality is that considerable additional work has been done and that the field is much in need of a contemporary treatment which includes both the fundamental material addressed earlier and the substantial additional contributions that have been made during the interim. Indicative of the advances made is the fact that the 1972 work of Kern and Kraus contained about 150 references to the technical literature, most applicable to the design of heat exchangers. The present work represents about a tenfold increase over the number of fundamental citations listed in 1972. When examining the table of contents, the reader will observe that several additional subjects are included in the present work. The first eight chapters treat the fundamentals of extended surface analysis, including the implications of the Murray–Gardner assumptions, the analysis of single fins, and analysis and optimization of finned arrays. Subsequently, application areas considered include finned passages, heat exchangers of various configurations, radiation effects, optimum designs, heat transfer with change of phase, and augmentation. Three of the later chapters treat twodimensional effects, time-dependent and periodic heat transfer. A common feature of this book is the extensive employment of example problems to illustrate the use of expressions derived and/or discussed in the text.
Penerbit : Wiley-Interscience
Total Halaman : 1120
Tahun Terbit : 2001-01-22
ISBN-10 / ASIN : 0471395501
ISBN-13 / EAN : 9780471395508
Jenis File : PDF
Ukuran File :8,19 MB
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