The particle collision behavior and heat transfer performance are investigated to reveal the heat transfer enhancement and fouling prevention mechanism in a Na_(2)SO_(4) circulating fluidized bed evaporator.The partic...The particle collision behavior and heat transfer performance are investigated to reveal the heat transfer enhancement and fouling prevention mechanism in a Na_(2)SO_(4) circulating fluidized bed evaporator.The particle collision signals are analyzed with standard deviation by varying the amount of added particles ε(1%–3%),circulation flow velocity u(0.37–1.78 m·s^(-1)),and heat flux q(7.29–12.14 kW·m^(-2)).The results show that the enhancement factor reach up to 14.6%by adding polytetrafluoroethylene particles at ε=3%,u=1.78 m·s^(-1),and q=7.29 kW·m^(-2).Both the standard deviation of the particle collision signal and enhancement factor increase with the increase in the amount of added particles.The standard deviation increases with the increase in circulation flow velocity;however,the enhancement factor initially decreases and then increases.The standard deviation slightly decreases with the increase in heat flux at low circulation flow velocity,but initially increases and then decreases at high circulation flow velocity.The enhancement factor decreases with the increase in heat flux.The enhancement factor in Na_(2)SO_(4) solution is superior to that in water at high amount of added particles.The empirical correlation for heat transfer is established,and the model results agree well with the experimental data.展开更多
A cold-model vertical multi-tube circulating fluidized bed evaporator was designed and built to conduct a visualization study on the pressure drop of a liquid–solid two-phase flow and the corresponding particle distr...A cold-model vertical multi-tube circulating fluidized bed evaporator was designed and built to conduct a visualization study on the pressure drop of a liquid–solid two-phase flow and the corresponding particle distribution.Water and polyformaldehyde particle(POM)were used as the liquid and solid phases,respectively.The effects of operating parameters such as the amount of added particles,circulating flow rate,and particle size were systematically investigated.The results showed that the addition of the particles increased the pressure drop in the vertical tube bundle.The maximum pressure drop ratios were 18.65%,21.15%,18.00%,and 21.15%within the experimental range of the amount of added particles for POM1,POM2,POM3,and POM4,respectively.The pressure drop ratio basically decreased with the increase in the circulating flow rate but fluctuated with the increase in the amount of added particles and particle size.The difference in pressure drop ratio decreased with the increase in the circulating flow rate.As the amount of added particles increased,the difference in pressure drop ratio fluctuated at low circulating flow rate but basically decreased at high circulating flow rate.The pressure drop in the vertical tube bundle accounted for about 70%of the overall pressure drop in the up-flow heating chamber and was the main component of the overall pressure within the experimental range.Three-dimensional phase diagrams were established to display the variation ranges of the pressure drop and pressure drop ratio in the vertical tube bundle corresponding to the operating parameters.The research results can provide some reference for the application of the fluidized bed heat transfer technology in the industry.展开更多
A novel vapor-liquid-solid circulating fluidized bed evaporator, meaning for enhancing heat transfer and preventing fouling, is applied to wheat straw black liquor, which is the primary pollutant in China’s papermaki...A novel vapor-liquid-solid circulating fluidized bed evaporator, meaning for enhancing heat transfer and preventing fouling, is applied to wheat straw black liquor, which is the primary pollutant in China’s papermaking industry. It is treated by alkali recovery, in which evaporation is a key process. The experimental results show that the vapor-liquid-solid three-phase boiling heat transfer coefficient is enhanced by 20%~40% than that of vapor-liquid two-phase boiling flow, also, the novel evaporator exhibits an excellent function of fouling prevention.展开更多
A circulating fluidized bed evaporator(including down-flow, horizontal, and up-flow beds) was constructed to study the effect of flow directions on multiphase flow boiling heat transfer. A range of experimental invest...A circulating fluidized bed evaporator(including down-flow, horizontal, and up-flow beds) was constructed to study the effect of flow directions on multiphase flow boiling heat transfer. A range of experimental investigations were carried out by varying amount of added particles(0-2%), circulation flow rate(2.15-5.16 m^3/h) and heat flux(8-16 kW/m^2). The comparison of heat transfer performance in different vertical heights of the horizontal bed was also discussed. Results reveal that the glass bead particle can enhance heat transfer compared with vapor-liquid two-phase flow for all beds. At a low heat flux(q = 8 kW/m), the heat-transfer-enhancing factor of the horizontal bed is obviously greater than those of the up-flow and down-flow beds. With the increase in the amount of added particles, the heat-transfer-enhancing factors of the up-flow and down-flow beds increase, whereas that of the horizontal bed initially increases and then decreases. However, at a high heat flux(q=16 kW/m), the heat-transfer-enhancing factors of the three beds show an increasing tendency with the increase in the amount of added particles and become closer than those at a low heat flux. For all beds, the heat-transfer-enhancing factor generally increases with the circulation flow rate but decreases with the increase in heat flux.展开更多
基金This work is supported by the open foundation of State Key Laboratory of Chemical Engineering(SKL-ChE-18B03)the Municipal Science and Technology Commission of Tianjin,China under Contract No.2009ZCKFGX01900.
文摘The particle collision behavior and heat transfer performance are investigated to reveal the heat transfer enhancement and fouling prevention mechanism in a Na_(2)SO_(4) circulating fluidized bed evaporator.The particle collision signals are analyzed with standard deviation by varying the amount of added particles ε(1%–3%),circulation flow velocity u(0.37–1.78 m·s^(-1)),and heat flux q(7.29–12.14 kW·m^(-2)).The results show that the enhancement factor reach up to 14.6%by adding polytetrafluoroethylene particles at ε=3%,u=1.78 m·s^(-1),and q=7.29 kW·m^(-2).Both the standard deviation of the particle collision signal and enhancement factor increase with the increase in the amount of added particles.The standard deviation increases with the increase in circulation flow velocity;however,the enhancement factor initially decreases and then increases.The standard deviation slightly decreases with the increase in heat flux at low circulation flow velocity,but initially increases and then decreases at high circulation flow velocity.The enhancement factor decreases with the increase in heat flux.The enhancement factor in Na_(2)SO_(4) solution is superior to that in water at high amount of added particles.The empirical correlation for heat transfer is established,and the model results agree well with the experimental data.
基金supported by the open foundation of State Key Laboratory of Chemical Engineering (SKL-ChE-18B03)the Municipal Science and Technology Commission of Tianjin (No. 2009ZCKFGX01900)
文摘A cold-model vertical multi-tube circulating fluidized bed evaporator was designed and built to conduct a visualization study on the pressure drop of a liquid–solid two-phase flow and the corresponding particle distribution.Water and polyformaldehyde particle(POM)were used as the liquid and solid phases,respectively.The effects of operating parameters such as the amount of added particles,circulating flow rate,and particle size were systematically investigated.The results showed that the addition of the particles increased the pressure drop in the vertical tube bundle.The maximum pressure drop ratios were 18.65%,21.15%,18.00%,and 21.15%within the experimental range of the amount of added particles for POM1,POM2,POM3,and POM4,respectively.The pressure drop ratio basically decreased with the increase in the circulating flow rate but fluctuated with the increase in the amount of added particles and particle size.The difference in pressure drop ratio decreased with the increase in the circulating flow rate.As the amount of added particles increased,the difference in pressure drop ratio fluctuated at low circulating flow rate but basically decreased at high circulating flow rate.The pressure drop in the vertical tube bundle accounted for about 70%of the overall pressure drop in the up-flow heating chamber and was the main component of the overall pressure within the experimental range.Three-dimensional phase diagrams were established to display the variation ranges of the pressure drop and pressure drop ratio in the vertical tube bundle corresponding to the operating parameters.The research results can provide some reference for the application of the fluidized bed heat transfer technology in the industry.
文摘A novel vapor-liquid-solid circulating fluidized bed evaporator, meaning for enhancing heat transfer and preventing fouling, is applied to wheat straw black liquor, which is the primary pollutant in China’s papermaking industry. It is treated by alkali recovery, in which evaporation is a key process. The experimental results show that the vapor-liquid-solid three-phase boiling heat transfer coefficient is enhanced by 20%~40% than that of vapor-liquid two-phase boiling flow, also, the novel evaporator exhibits an excellent function of fouling prevention.
基金supported by Tianjin Municipal Science and Technology Commission, China (No. 2009ZCKFGX01900)
文摘A circulating fluidized bed evaporator(including down-flow, horizontal, and up-flow beds) was constructed to study the effect of flow directions on multiphase flow boiling heat transfer. A range of experimental investigations were carried out by varying amount of added particles(0-2%), circulation flow rate(2.15-5.16 m^3/h) and heat flux(8-16 kW/m^2). The comparison of heat transfer performance in different vertical heights of the horizontal bed was also discussed. Results reveal that the glass bead particle can enhance heat transfer compared with vapor-liquid two-phase flow for all beds. At a low heat flux(q = 8 kW/m), the heat-transfer-enhancing factor of the horizontal bed is obviously greater than those of the up-flow and down-flow beds. With the increase in the amount of added particles, the heat-transfer-enhancing factors of the up-flow and down-flow beds increase, whereas that of the horizontal bed initially increases and then decreases. However, at a high heat flux(q=16 kW/m), the heat-transfer-enhancing factors of the three beds show an increasing tendency with the increase in the amount of added particles and become closer than those at a low heat flux. For all beds, the heat-transfer-enhancing factor generally increases with the circulation flow rate but decreases with the increase in heat flux.