Hysteresis and packing in gas-fluidized beds
نویسندگان
چکیده
The packing fraction and the pressure drop across gas-fluidized beds of granular media exhibit hysteresis as the gas-flow rate is cycled up and down across the fluidization transition. Presumably this is due to contact forces and transfer of stress to the surrounding walls, and hence should vary nontrivially with the aspect ratio of the sample. Here we present systematic measurements of the variation of hysteresis with particle size and aspect ratio of the sample. Remarkably, the hysteresis scales in a trivial way with these parameters, showing no evidence of long-range effects of the wall. Our measurements also show that the packing fraction becomes 0. 590+/-0.004, independent of particle size and container shape, when the fluidizing flow of gas flow is slowly removed.
منابع مشابه
Effect of Bed Diameter on the Hydrodynamics of Gas-Solid Fluidized Beds
Effect of scale on the hydrodynamics of gas-solid fluidized beds was investigated in two fluidized beds of 152 mm and 78 mm in diameter. Air at room temperature was used as the fluidizing gas in the bed of sand particles. The Radioactive Particle Tracking (RPT) technique was employed to obtain the instantaneous positions of the particles at every 20 ms of the experiments. These data were u...
متن کاملDetermination of Cluster Hydrodynamics in Bubbling Fluidized Beds by the EMMS Approach
The local solid flow structure of gas-solid bubbling fluidized bed was investigated to identify and characterize the particle clusters. Extensive mathematical calculations were carried out using the energy-minimization multi-scale (EMMS) approach for evaluating cluster properties including the velocity, the size and the void fraction of clusters in the dense phase of the bed. The results showed...
متن کاملCFD-DEM Investigation on van der Waals Force in Gas-Solid Bubbling Fluidized Beds
Effect of interparticle force on the hydrodynamics of gas-solid fluidized beds was investigated using the combined method of computational fluid dynamics and discrete element method (CFD-DEM). The cohesive force between particles was considered to follow the van der Waals equation form. The model was validated by experimental results from literature in terms of bed voidage distribution and Eule...
متن کاملEvaluation of Eulerian Two-Fluid Numerical Method for the Simulation of Heat Transfer in Fluidized Beds
Accurate modeling of fluidization and heat transfer phenomena in gas-solid fluidized beds is not solely dependent on the particular selected numerical model and involved algorithms. In fact, choosing the right model for each specific operating condition, the correct implementation of each model, and the right choice of parameters and boundary conditions, determine the accuracy of the results i...
متن کاملSegregation Behaviour of Particles in Gas Solid Fluidized Beds at Elevated Pressure
A comprehensive mathematical model based on the discrete particle model and computational fluid dynamics was utilized to investigate mixing and segregation of particles in fluidized beds at high pressure. To quantify the extent of mixing in the bed, the Lacey mixing index was used. Simulations were carried out with different mass fractions of small particles at various pressures ranging from 1 ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics
دوره 62 3 Pt B شماره
صفحات -
تاریخ انتشار 2000