A new theory of the instability of a uniform fluidized bed

摘要: The form of the momentum equation for one-dimensional (vertical) unsteady mean motion solid particles in a fluidized bed or sedimenting dispersion is established from physical arguments. In case that slightly non-uniform this contains two dependent variables, local particle velocity V and concentration ϕ, several statistical parameters uniform bed. All these are functions ϕ with clear meanings, important ones measurable. It novel feature it explicit contributions to bulk modulus elasticity configuration, one arising transfer by fluctuations effective repulsive force exerted between random motion. This latter contribution, which proves be more two, related gradient diffusivity particles, key quantity new theory.The conservation sufficient determine behaviour small disturbance sinusoidal variation vertical direction. Particle inertia forces such propagating wavy may promote amplitude growth, whereas diffusion tends suppress it, instability occurs when Froude number exceeds critical value. Rough estimates relevant allow criterion put approximate numerical both gas-fluidized beds (for flow Reynolds at marginal stability small) liquid-fluidized spherical well above unity), although information about particular needed. predictions theory appear qualitative accord available observational data on gas- beds.