In this study, two types of pre-distributors (nonuniform-pores and dual-baffle)for the combined solids-liquid distributor in gas-liquid-solid circulating fluidized bed heat exchanger, were designed and the characteris...In this study, two types of pre-distributors (nonuniform-pores and dual-baffle)for the combined solids-liquid distributor in gas-liquid-solid circulating fluidized bed heat exchanger, were designed and the characteristics of particles distribution was compared. In the experiments, the sampling method was used to measure local solids flux and a U shape pipe was used to measure static pressure drop in the lower pipe box.The effects of different superficial liquid velocities and liquid viscosities on the parameters mentioned above were investigated.The degree of distribution of local solids flux in exchanger pipe was evaluated by the non-uniformity function.The results showed that the two types of pre-distributors were both suitable for gas-liquid-solid circulating fluidized bed heat exchanger at a lower static pressure drop in the lower pipe box.Compared with the nonuniform-pores pre-distributor, the dual-baffle pre-distributor showed better performance.展开更多
A hydrodynamic model of liquid-solid circulating fluidized bed is proposed to predict the slip velocity between fluid and solid particles and bed voidage by applying the theory of two-phase flow.The slip velocity can ...A hydrodynamic model of liquid-solid circulating fluidized bed is proposed to predict the slip velocity between fluid and solid particles and bed voidage by applying the theory of two-phase flow.The slip velocity can be represented by the following equation.u s =u-v=(1-ε)(ρ p -ρ f )g+F p -(1-ε)F f /εβ/εExperiments were carried out by using water and ceramic spheres,1.43 and 3.06 mm in mean diameter in a circulating fluidized bed of 31 mm diameter and 1700 mm height.The voidage was from 0.96 to 1,and the ratio between superficial liquid velocity and particle terminal velocity varied from 1.22 to 10.1 in the experiments.The fluid-particle interphase drag coefficient in the model was correlated from experimental data as followsd p βρ f =0.1881(1-ε) 1.0089 UU t -0.8043 d p D t -0.3228 The predicted values by the model proposed agreed with the experimental data well.In the meantime,the variation of slip velocity with superficial liquid velocity,bed voidage and particle diameter was discussed.The results showed that the model in the paper can well predict the hydrodynamics of liquid-solid two-phase flow in circuiating fluidized bed.The model is suitable for liquid-solid circulating fluidized bed under high flow rate and low concentration and can be also used on each tube in liquid-solid circulating fluidized bed heat exchanger.展开更多
文摘In this study, two types of pre-distributors (nonuniform-pores and dual-baffle)for the combined solids-liquid distributor in gas-liquid-solid circulating fluidized bed heat exchanger, were designed and the characteristics of particles distribution was compared. In the experiments, the sampling method was used to measure local solids flux and a U shape pipe was used to measure static pressure drop in the lower pipe box.The effects of different superficial liquid velocities and liquid viscosities on the parameters mentioned above were investigated.The degree of distribution of local solids flux in exchanger pipe was evaluated by the non-uniformity function.The results showed that the two types of pre-distributors were both suitable for gas-liquid-solid circulating fluidized bed heat exchanger at a lower static pressure drop in the lower pipe box.Compared with the nonuniform-pores pre-distributor, the dual-baffle pre-distributor showed better performance.
文摘A hydrodynamic model of liquid-solid circulating fluidized bed is proposed to predict the slip velocity between fluid and solid particles and bed voidage by applying the theory of two-phase flow.The slip velocity can be represented by the following equation.u s =u-v=(1-ε)(ρ p -ρ f )g+F p -(1-ε)F f /εβ/εExperiments were carried out by using water and ceramic spheres,1.43 and 3.06 mm in mean diameter in a circulating fluidized bed of 31 mm diameter and 1700 mm height.The voidage was from 0.96 to 1,and the ratio between superficial liquid velocity and particle terminal velocity varied from 1.22 to 10.1 in the experiments.The fluid-particle interphase drag coefficient in the model was correlated from experimental data as followsd p βρ f =0.1881(1-ε) 1.0089 UU t -0.8043 d p D t -0.3228 The predicted values by the model proposed agreed with the experimental data well.In the meantime,the variation of slip velocity with superficial liquid velocity,bed voidage and particle diameter was discussed.The results showed that the model in the paper can well predict the hydrodynamics of liquid-solid two-phase flow in circuiating fluidized bed.The model is suitable for liquid-solid circulating fluidized bed under high flow rate and low concentration and can be also used on each tube in liquid-solid circulating fluidized bed heat exchanger.
