The Heat Transfer Characteristics Between Immersed Horizontal Tubes And A Vibrated Fluidized Bed

The vibrated fluidized bed(VFB) has been used widely in the chemical industry, metallurgy and food industry for drying particle material. Developing the new drying technology and equipment for the producing process has economical significance. The heat transfer characteristics in an aerated VFB of titanium concentrate was investigated to provide the scientific bases for the drying of titanium concentrate with high drying efficiency and low dissipation of energy.The heat transfer coefficients between immersed horizontal tubes and a VFB under different operating conditions were measured by using a computer data collection system. The factors that affect the heat transfer process were analyzed. The experimental results show that moderate vibration can enhance the heat transfer between immersed horizontal tubes and a VFB. Violent vibration can enhance the heat transfer under low gas velocities and undermine it under high gas velocities. Within the experimental range of gas velocity and vibration intensity, the heat transfer coefficients of fine titanium concentrate increase with increasing gas velocity, and the coefficients of coarse titanium concentrate decrease when gas velocity increases. The effect of frequency of vibration on heat transfer coefficients under different amplitudes of vibration is nonuniform. Under the amplitude of vibration 2mm, the heat transfer coefficients of fine titanium concentrate increase with increasing frequency of vibration,and the coefficients of coarse titanium concentrate decrease with increasing frequecy ofvibration. In general, the heat transfer coefficients of fine titanium concentrate go up at first and then decline when amplitude of vibration increases continuously. Under low gas velocities, the way of variation of the heat transfer coefficients of coarse titanium concentrate with amplitude of vibration is the same as fine titanium concentrate. Higher amplitudes of vibration results in lower heat transfer coefficients of coarse titanium concentrate under high gas velocities. The moisture content of particles has important effect on the heat transfer coefficients of titanium concentrate. The heat transfer coefficients of dry titanium concentrate exceed that of wet titanium concentrate notably. The heat transfer coefficients between immersed horizontal tubes and a VFB increase evidently when particle size decreases.A mathematical model was developed based on unstable heat transfer theory. A formula for calculating the heat transfer coefficients was also obtained by regressing experimental data,which can predicted the heat transfer coefficients within deviation of + 1 l%.The formula can satisfied the precision requirement in project design.