Đang chuẩn bị liên kết để tải về tài liệu:
Ebook Principles of heat transfer (7th edition): Part 2

(BQ) Part 2 book "Principles of heat transfer" has contents: Forced convection inside tubes and ducts, forced convection over exterior surfaces, heat exchangers, heat transfer by radiation, heat transfer with phase change. | 67706_06_ch06_p350-419.qxd 5/14/10 12:44 PM Page 350 CHAPTER 6 Forced Convection Inside Tubes and Ducts Typical tube bundle of multiple circular tubes and cutaway section of a mini shell-and-tube heat exchanger. Source: Courtesy of Exergy, LLC. Concepts and Analyses to Be Learned The process of transferring heat by convection when the fluid flow is driven by an applied pressure gradient is referred to as forced convection. When this flow is confined in a tube or a duct of any arbitrary geometrical cross section, the growth and development of boundary layers are also confined. In such flows, the hydraulic diameter of the duct, rather than its length, is the characteristic length for scaling the boundary layer as well as for dimensionless representation of flow-friction loss and the heat transfer coefficient. Convective heat transfer inside tubes and ducts is encountered in numerous applications where heat exchangers, made up of circular tubes as well as a variety of noncircular cross-sectional geometries, are employed. A study of this chapter will teach you: • How to express the dimensionless form of the heat transfer coefficient in a duct, and its dependence on flow properties and tube geometry. • How to mathematically model forced-convection heat transfer in a long circular tube for laminar fluid flow. • How to determine the heat transfer coefficient in ducts of different geometries from different theoretical and/or empirical correlations in both laminar and turbulent flows. • How to model and employ the analogy between heat and momentum transfer in turbulent flow. • How to evaluate heat transfer coefficients in some examples where enhancement techniques, such as coiled tubes, finned tubes, and twisted-tape inserts, are employed. Copyright 2011 Cengage Learning, Inc. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. 67706_06_ch06_p350-419.qxd 6.1 5/14/10 12:44 PM Page 351 Introduction Heating and cooling of fluids .