Описание
xviii Preface
in a consistent manner; therefore, the instructor can use classroom time to emphasize some key concepts, to give other examples, and to solve example problems.
By addressing engineering heat transfer problems, along with the fundamentals, the
book will show students – by the time they have worked through it – how to analyze
and solve many practical heat transfer problems.
Transfer of heat occurs by mechanisms of conduction, convection, and radiation.
The transfer of heat may cause, or may be the result of, the energy storage or energy
conversion processes. Examples of such processes are sensible or phase change
heat storage (i.e., a physical- or chemical-bond energy and work done or energy
converted, including mechanical and electromagnetic energy). In many heat transfer
problems, more than one phase (solid, liquid, gas) is present, leading to single- or
multiphase media. In multiphase media, depending on where the source of heat is
located, these phases may or may not be in local thermal equilibrium (i.e., have the
same local temperature). Because of vast variations in geometry and in the initial
and bounding-surface conditions of the medium, no general solution to the energy
equation is available and, therefore, specific cases must be considered separately.
Here, around a central theme of the heat flux vector and its spatial and temporal
variations caused by the volumetric storage and conversion of energy, the intra- and
intermedium heat transfers are examined. The heat flux vector, along with the three
mechanisms, can be tracked through the heat transfer media. This allows visualization of heat transfer with the aim of enhanced innovative ideas. This visualization
is made progressively more complete by addressing the heat transfer mechanisms,
the phases present, the volumetric energy storage and conversion, and the role of
geometric, initial, and bounding surface conditions. Thermal circuit models are used
and some heat-transfer-based devices are also presented throughout the text.
This book is divided into eight chapters. Chapter 1 gives a general introduction
to the analysis of thermal systems, the heat flux vector (and the contributions from
various mechanisms), and the integral-volume energy conservation equation. The
concept of heat flux vector tracking is emphasized to help with the visualization
of heat transfer. This chapter is intended as a descriptive guide and addresses the
basic concepts and applications (compared to the following chapters, which are more
quantitative). The energy equation is posed with the heat flux vector as the focus
(i.e., playing the central role).
Chapter 2 discusses spatial temperature nonuniformity and the need for
differential-, integral-, combined differential- and integral-, and the finite-smalllength forms of the energy conservation equation, various forms of which are used
in succeeding chapters. Energy and work conversion mechanisms and their relations
and the bounding-surface thermal conditions are also discussed. After a general,
broad, and unified introduction, various heat transfer mechanisms and their respective roles in heat transfer problems are discussed in more detail in the chapters that
follow.
Chapter 3 covers steady-state and transient conduction heat transfer. This allows
for the examination of the spatial and temporal variation of temperature and heat
flow rate within a heat transfer medium or through multimedia composites. The
Детали
- Год издания
- 2011
- Format