Heat transfer coefficients in three phase fluidized beds
In order to obtain a semitheoretical correlation for the heat transfer coefficients in three phase fluidized beds, Deckwer's semitheoretical correlation for the heat transfer coefficients in the bubble column, which was derived from Higbie's surface renewal theory of interphase mass transfer with the concept of isotropic turbulence, has been extended to three phase fluidized beds with the modification of the energy dissipation rate. One of the desirable characteristics of three phase fluidized beds is the uniformity of temperature in the bed. The intense longitudinal and transverse turbulent mixing in a fluidized bed may induce the uniform fields of temperature and solids concentration. For highly exothermic reactions, the uniform temperature in the bed is essential to avoid the local hot spots. In order to control the uniform temperature of three phase fluidized beds, the addition or removal of heat in the bed is required and the information on heat transfer surface and the bed is essential to designing the heat exchanger. Recently, Chiu and Ziegler (1983) determined wall-to-bed heat transfer coefficients in three phase fluidized bed (5.08 cm ID) of glass beads and cylindrical gamma alumina particles which were fluidized by cocurrent flow of air and water. Their data were correlated in terms of the modified Colburn j factor. Kato et al. (1981) measured wall-to-bed heat transfer coefficients in three phase fluidized beds of 5.2 and 12.0 cm internal diameter. Four different sizes of glass beads (0.42-2.2 mm) were fluidized by air and aqueous carboxymethyl cellulose solutions. The coefficients increased with decrease in liquid viscosity and with increase in gas and liquid velocity.
- Research Organization:
- Department of Chemical Engineering Korea Advanced Institute of Science and Technology, Seoul
- OSTI ID:
- 6078937
- Journal Information:
- Int. J. Multiphase Flow; (United States), Vol. 11:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
FLUIDIZED BEDS
HEAT TRANSFER
MULTIPHASE FLOW
THERMODYNAMICS
ALUMINIUM OXIDES
BUBBLES
ENERGY TRANSFER
FLOW RATE
FLUIDIZATION
GLASS
HEAT EXCHANGERS
ISOTROPY
MASS TRANSFER
SURFACE PROPERTIES
TEMPERATURE CONTROL
TEMPERATURE DISTRIBUTION
TURBULENT FLOW
ALUMINIUM COMPOUNDS
CHALCOGENIDES
CONTROL
FLUID FLOW
OXIDES
OXYGEN COMPOUNDS
421000* - Engineering- Combustion Systems
420400 - Engineering- Heat Transfer & Fluid Flow