气-固循环流化床换热器的传热性能与压降

Heat Transfer Performance and Pressure Drop of a Gas-solid Circulating Fluidized Bed Heat Exchanger

为强化气相换热,将流化床换热防垢节能技术和气相换热过程相结合,设计并构建了一套气-固循环流化床换热装置。以空气和玻璃珠颗粒作为工质,利用热电阻和差压传感器,系统地考察了颗粒加入量、空气流量和热通量等操作参数对于其传热性能和压降的影响。研究结果表明,玻璃珠颗粒的加入可以明显地强化气相的传热。实验范围内,最大的传热增强因子为33.4%,所对应的操作参数为ε=1.5%,Vg=19.78 m3·h^(-1)和q=1 kW·m^(-2),相应的压降比率不超过2.5%。传热增强因子随颗粒加入量和空气流量的增加呈现出波动的趋势。空气流量较低时,传热增强因子随着热通量的增加而增大;随着空气流量的增加,热通量对传热增强因子的影响减小。构建了操作参数对传热性能和压降影响的三维图,以利于选择适宜的操作参数范围。研究结果有利于流化床换热防垢节能技术在气相换热过程中的应用。

A gas-solid circulating fluidized bed heat-exchange apparatus is designed and built to enhance heat transfer by combining the fluidized bed heat transfer and fouling prevention technology with gasphase heat-exchange process. Air and glass bead particles are selected as the working media. The effect of operating parameters,such as the amount of added particles,air flow rate and heat flux,on the heat transfer performance and pressure drop are investigated by using resistance temperature detectors and differential pressure transmitter. Results show that the addition of the glass beads can significantly enhance heat transfer. The heat transfer enhancement factor reaches 33. 4% at ε=1. 5%,Vg= 19. 78 m3·h^(-1) and q= 1 kW·m^(-2),and the corresponding pressure drop ratio does not exceed 2. 4%. The heat transfer enhancing factor fluctuates with the increase in the amount of added particles and air flow rate. At low air flow rate,the enhancing factor increases with the increase in heat flux. With the increase in air flow rate,the effects of heat flux on the enhancing factor decreases. With the increase in the amount of added particles,the pressure drop ratio fluctuates at low air flow rate,but increases at high air flow rate. The pressure drop ratio fluctuates with the increase in air flow rate,depending on the amount of added particles and heat flux. Heat flux has a little effect on the pressure drop ratio. The three-dimensional diagrams are established to show the effect of the operating parameters on the heat transfer performance and pressure drop. These findings are beneficial to the industrial application of the fluidized bed heat transfer and fouling prevention technology in the gas-phase heat-exchange process.