Effect Of Flow Directions On The Circulating Fluidized Bed Evaporator Heat Transfer Performance

A circulating fluidized bed evaporator is designed and constructed to study the effect of flow directions,particle diameter and particle type on the heat transfer performance of three-phase circulating fluidized bed evaporator.And the effect of the amount of added particles(0.5%???2%),circulation flow rate(2.15 m~3/h?V?5.16 m~3/h)and heat flux(8 kW/m~2?q?16 kW/m~2)is also investigated.For the horizontal bed,particle distribution may be uneven in different vertical heights of the same cross section due to gravity;thus,the thermal performance of different vertical heights is also investigated.The results of the effect of flow directions on multiphase flow boiling heat transfer are shown as follows:The glass bead can improve the heat transfer coefficient and enhance the heat transfer.The heat transfer coefficient of the up-flow bed is the largest.At low heat flux,the heat transfer enhancing factor is obviously greater in the horizontal bed compared with the up-flow and down-flow beds.For all beds,the heat transfer enhancing factor generally increases with the circulation flow rate but decreases with the increase of heat flux.With the increase in the amount of added particles,the enhancing factors of the up-flow and down-flow beds increase,whereas that of the horizontal bed initially increases and then decreases.The results of the effect of particle diameter on multiphase flow boiling heat transfer are shown as follows:The four types of glass beads(GB)can enhance heat transfer.In most cases,the larger the particle size,the better the heat transfer enhancement.When the circulation flow rate is 2.15 m~3/h,the smaller the particle,the better the heat transfer enhancement in the up-flow bed.The results of the effect of particle type on multiphase flow boiling heat transfer are shown as follows:SiC,POM and GB can also enhance heat transfer.The thermal performance of SiC is the best,on the contrary,the thermal performance of POM is the worst.