Book contents
- Frontmatter
- Contents
- Contributors
- Preface
- Common nomenclature
- 1 Introduction
- 2 Initiation of spouting
- 3 Empirical and analytical hydrodynamics
- 4 Computational fluid dynamic modeling of spouted beds
- 5 Conical spouted beds
- 6 Hydrodynamics of spout-fluid beds
- 7 Spouted and spout-fluid beds with draft tubes
- 8 Particle mixing and segregation
- 9 Heat and mass transfer
- 10 Powder–particle spouted beds
- 11 Drying of particulate solids
- 12 Drying of solutions, slurries, and pastes
- 13 Granulation and particle coating
- 14 The Wurster coater
- 15 Gasification, pyrolysis, and combustion
- 16 Spouted bed electrochemical reactors
- 17 Scaleup, slot-rectangular, and multiple spouting
- 18 Mechanical spouting
- 19 Catalytic reactors and their modeling
- 20 Liquid and liquid–gas spouting of solids
- Index
- References
9 - Heat and mass transfer
Published online by Cambridge University Press: 04 February 2011
- Frontmatter
- Contents
- Contributors
- Preface
- Common nomenclature
- 1 Introduction
- 2 Initiation of spouting
- 3 Empirical and analytical hydrodynamics
- 4 Computational fluid dynamic modeling of spouted beds
- 5 Conical spouted beds
- 6 Hydrodynamics of spout-fluid beds
- 7 Spouted and spout-fluid beds with draft tubes
- 8 Particle mixing and segregation
- 9 Heat and mass transfer
- 10 Powder–particle spouted beds
- 11 Drying of particulate solids
- 12 Drying of solutions, slurries, and pastes
- 13 Granulation and particle coating
- 14 The Wurster coater
- 15 Gasification, pyrolysis, and combustion
- 16 Spouted bed electrochemical reactors
- 17 Scaleup, slot-rectangular, and multiple spouting
- 18 Mechanical spouting
- 19 Catalytic reactors and their modeling
- 20 Liquid and liquid–gas spouting of solids
- Index
- References
Summary
Introduction
A great number of processes carried out in spouted beds require the application of different modes of heat and/or mass transfer. We may distinguish among the following modes:
Heat transfer, mass transfer, simultaneous heat and mass transfer – between fluid and particles,
Heat transfer between wall and bed, and
Heat transfer between submerged object and bed.
For each mode, transfer mechanisms are examined; then experimental findings and, in some cases, theoretical studies are discussed.
Between fluid and particles
Transfer mechanisms and models
Quite often, the basic assumption for analysis of heat or mass exchanged between fluid and particles is that heat is transferred to the particles under conditions of external control, neglecting heat transmission within the particles. For heat transfer in the absence of mass transfer, this is justified when the particle heat transfer Biot number is sufficiently small (e.g., <0.1) and the corresponding Fourier number exceeds 0.22. For simultaneous heat and mass transfer, such as when the particles are well wetted at the surface, the average temperature at the particle surfaces is substantially uniform, and external control again prevails.
Assuming plug flow conditions through the bed, the axial fluid temperature distribution can be described by a dimensionless function. Because the spouted bed consists of two distinct regions, with the average gas velocity in the spout being one or two orders of magnitude greater than that in the annulus, the decline of gas temperature in these two zones is quite different; it is slight in the spout and considerable in the annular zone.
- Type
- Chapter
- Information
- Spouted and Spout-Fluid BedsFundamentals and Applications, pp. 161 - 174Publisher: Cambridge University PressPrint publication year: 2010