INVESTIGATION OF THE INFLUENCE OF MECHANICAL-VIBRATIONAL SOUND ON HYDRODYNAMICS OF A FLUIDIZED BED

The main purpose of this paper is to investigate the concept of a heat treatment of a small amount of solid material with the maximum contact of the gas and solid material. The solution of this problem consists in passing the process in a fluidized bed. However, the key issue of this solution is the problem of entrainment of solid material. Among feasible ways of the fluid bed hydrodynamics creation is a sound waves transmission through a solid granular material. A visual study on the fluid bed hydrodynamics creation with sound waves was conducted. The estimation of the impact of the trajectory of the particles on the thermophysical properties of the fluidized system was determined. The exploitation of sound waves should increase the intensity of heat exchange inside and between the solid and gas phases. Reactor design scheme for pyrocarbon coatings creation was developed. This scheme implies a small amount of material to be treated. The results obtained can be subsequently applied in the process of developing new fluidized bed apparatus, when the usage of a gas or a liquid as a fluidizing agent is technically impossible (or insufficiently). The prospects for further research include homogenization of the agglomerate layer by means of sound waves. Bibl. 9, Fig. 4.

Experimental investigation of heat transfer in three phase fluidized bed cooling column

In this study, a three-phase (gas-liquid-solid) fluidized bed was used to study the heat transfer characteristics of the system. The system consisted of low density (290 kg/m3) spherical particles of the diameter of 2 cm in 0.25 m cylindrical column with the countercurrent flow of water and air. The experimental investigation and mathematical modeling of heat transfer between the hot air and the cooling water was carried out. The experiments were conducted for the variety of different fluid flow rates and inlet air temperatures, while the air flow rate was kept constant. Based on the obtained experimental results a new correlation for heat transfer in three-phase fluidized system was proposed. The mean percentage error between the experimental and the correlated values of the jHp obtained was 1.69%. The hydrodynamic parameters of the system were also calculated according to the available literature correlations.

Clustering, Jamming and Segregation in Cohesive Granular Materials

We present a series of experiments to investigate the stability, flow and segregation when liquid bridges or magnetic attraction forces between grains are present. Quantitative data is obtained by high speed and high resolution imaging. First, we measure the angle of repose of a granular pile formed by pouring wet grains in to a quasi-two dimensional silo and compare them to existing models. Second, we measure the size separation of bi-disperse grains as a function of size ratio and viscosity of the liquid. Finally, we introduce a vibro-fluidized system of magnetized particles to study the effect of cohesive forces and inelastic collisions on the formation of clusters and velocity distributions.

A Model of Heat Transfer in Fluidized Beds

An expression for estimating the heat transfer coefficient in a fluidized bed has been developed based on the surface renewal and penetration concept. The predicted heat transfer coefficients between walls and beds agree well with experimental results. The result of this analysis shows that, in general, the effect of thermal conductivity of particle on heat transfer is insignificant. The maximum possible Nusselt number for the gas fluidized system is determined theoretically as 13.5. This value appears to be reasonable in light of the majority of available experimental data.