| A gas-solid circulating fluidized bed heat-transfer apparatus is designed and built to enhance gas-phase heat transfer by combining the fluidized bed heat transfer and fouling prevention technology and gas-phase heat transfer process.Air and inert solid particles as working media.The effects of operating parameters such as the amount of added particles,air flow rate,heat flux and particle types on heat transfer performance and pressure drop of the gas-solid two-phase flow are systematically investigated by using resistance temperature detector and differential pressure sensor.Meanwhile,the corresponding cold-mold visualization research on the fluidization and distribution is also conducted for better understanding the heat transfer performance and pressure drop by using image measuring and dealing technology.Results show that different types of inert solid particles can obviously enhance heat transfer within the experimental range.The heat transfer enhancing factors reach up to 33.39%,56.06%,34.05%,15.87% and 23.08%,for GB1,GB2,GB3,POM and PP particles,respectively.The corresponding pressure drop ratios are 2.38%,2.84%,2.84%,0.90% and 4.48% respectively.The heat transfer enhancement factor fluctuates with the increase in the amount of added particles and air flow rate,but basically decreases with the increase in heat flux.The addition of inert solid particles basically increase the pressure drop,but the amplitude is small and no more than 11%.The pressure drop ratio fluctuates with the increase in the amount of added particles at low air flow rate,but increases with the amount of added particles 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 slightly influence on the pressure drop ratio.For particles with the same material,the pressure drop ratio fluctuates with the increase in particle diameter.The three-dimensional diagram is established to reflect the effect of the operating parameters on the heat transfer enhancing factors.The optimal operating parameters range can be obtained according to the three-dimensional diagram.Meanwhile,an empirical correlation is built to predict the convective heat transfer coefficient.The calculated values agree with the experimental results.The findings are helpful to advance the industrial application of gas-solid circulating fluidized bed heat exchanger. |
