Dynamics of gas-fluidized beds

Abstract

Governing equations for the motion of gas-fluidized beds are derived within the framework of the theory of interacting continua. Steady-state solutions for two simple cases (incompressible fluid, isothermal ideal gas) are outlined in detail. The stability of these steady-state solutions is examined by conventional linear hydrodynamic stability analysis. Finally, some numerical results illustrating the effects of various physical parameters are presented.

A Linear Stability Analysis of a Homogeneous Fluidized Bed

“…Such disturbances, usually arise close to the distributor region of real fluidized beds, are the origin of bubbles and clusters that appear in the upper region of the bed, changing completely the dynamics of the system [10,11]. The stable condition for this analysis is the uniform state of fluidization, one of the simplest solutions of the governing equations, [2,3,4]: u = u 0 e 3 , v = 0, φ = φ 0 and p = p 0 (z), where p 0 (z) is the hydrostatic pressure. Small disturbances are imposed to the system in terms of non-dimensional quantities:…”

“…In real beds, disturbances can be found in the distributor and lead to the formation of bubbles of fluid. Garg & Pritchett [4] introduced a particle pressure term and found that fluidized beds can be stable in some conditions. There are few correlations for describing effects of particle pressure and particle viscosity in fluidized beds (e.g.…”

Particle pressures in fluidized beds. Final report

“…Thus, this two-bubble injection situation simulates a freely bubbling bed and explains that the difference in particle pressure generation between a single and a fieely bubbling bed is due to the presence of other bubbles. Garg & Pritchet (1975), Batchelor (1988)) that an elasticity of the particle phase can stabilize the bed. Jzckson (1985) argues that the large value required of the elasticity ccdd not be generated by particle fluctuationr.…”

Разрешимость Системы Уравнений Одномерного Движения Теплопроводной Двухфазной Смеси

“…Данная начально-краевая задача описывает одномерное движение между непро-ницаемыми теплоизолированными стенками двухфазной смеси, состоящей из твер-дых частиц и газа [1]. Здесь ρ 0 i , v i -соответственно истинная плотность и скорость i-й фазы (i = 1 -твердые частицы, i = 2 -газ), s -объемная концентрация твердых частиц, θ -абсолютная температура смеси, p 1 -эффективное давление твердых ча-стиц, p 2 -внутреннее давление газа, g -плотность массовых сил, c 1 = const > 0 -теплоемкость при постоянном объеме первой фазы; кроме того, µ(s) -вязкость пер-вой фазы, B(s) -коэффициент взаимодействия фаз, χ(s) -коэффициент теплопро-водности смеси, p c (s) -разность давлений (заданные функции).…”