Heat-transfer Performance And Pressure Drop In A Gas-solid Circulating Fluidized Bed Spiral-plate Heat Exchanger

A gas–solid circulating fluidized bed spiral-plate heat-exchange apparatus is designed and built by combining fluidized bed heat transfer and antiscaling technology with spiral-plate heat exchanger in the present paper.Air is used as the cold fluid,and thermostatic water is used as the hot fluid.Glass bead(GB)and polyformaldehyde(POM)particles are selected as the inert solid particles.The influences of the amount of added particles(0.5%-2%),air flow rate(80-125 m~3/h),and particle types are also systematically discussed to investigate the heat-transfer performance and pressure drop in the spiral-plate heat exchanger.To analyze the variation of heat-transfer performance and pressure drop,the influences of operation parameters on the fluidization and distribution of solid particles in the spiral-plate heat exchanger are investigated by visualization experiment.Results show that particle addition improves the heat-transfer performance and pressure of the spiral-plate heat exchanger.The maximum heat-transfer enhancing factor is 29.8%when GB2 particles are added atε=1%and V_g=80 m~3/h,and the corresponding pressure-drop ratio is 30.7%.In general,except for POM2 particle,the enhancing factor initially increases and then decreases with increased amount of added particles.For POM2 particle,the enhancing factor increases with increased amount of added particles.However,the variation trend of the enhancing factor with air flow rate depends on the operation parameters.The difference of enhancing factor among particle types decreases with increased air flow rate.The pressure-drop ratio increases with increased amount of added particles.For particles with low sedimentation velocity,the pressure-drop ratio decreases with increased air flow rate.For particles with high sedimentation velocity,the pressure-drop ratio increases with increased air flow rate.The pressure-drop ratio for GB or POM decreases with increased dimension or sedimentation velocity of the particles at a low air flow rate but fluctuates or increases at a high air flow rate.The pressure-drop ratio for POM is generally less than that for GB particles under a similar sedimentation velocity.According to the experimental results,three-dimensional diagrams are established to display the variation ranges of the enhancing factor and pressure-drop ratio under different operating parameters.The empirical correlations of the enhancing factor and pressure-drop ratio of are constructed.The research results are helpful to the industrial extension and application of gas-solid circulating fluidized bed spiral-plate heat exchanger.