Separation density is one of the most concerned operating parameters in gravity beneficiation.Although equal-errors cut point or distribution density is usually used as practical separation density in gravity benefici...Separation density is one of the most concerned operating parameters in gravity beneficiation.Although equal-errors cut point or distribution density is usually used as practical separation density in gravity beneficiation, the gravity separating process complexly affected by many kinds of factors is actually carried out at a fluctuant density; namely, the practical separation density is essentially a random variable.The studied results show that the equal-errors cut point is the mathematical expectation of this random variable, and the distribution density corresponds to the highest separation efficiency in the gravity separation process.This shows that the distribution density is the best working point of the gravity separation equipment under a particular operating condition.Therefore,in order to fully develop the function of the gravity separation equipment, the distribution density should be close to the theoretical separation density unlimitedly in the range of minimum fluctuation.展开更多
A model that rapidly predicts the density components of raw coal is described.It is based on a threegrade fast float/sink test.The recent comprehensive monthly floating and sinking data are used for comparison.The pre...A model that rapidly predicts the density components of raw coal is described.It is based on a threegrade fast float/sink test.The recent comprehensive monthly floating and sinking data are used for comparison.The predicted data are used to draw washability curves and to provide a rapid evaluation of the effect from heavy medium induced separation.Thirty-one production shifts worth of fast float/sink data and the corresponding quick ash data are used to verify the model.The results show a small error with an arithmetic average of 0.53 and an absolute average error of 1.50.This indicates that this model has high precision.The theoretical yield from the washability curves is 76.47% for the monthly comprehensive data and 81.31% using the model data.This is for a desired cleaned coal ash of 9%.The relative error between these two is 6.33%,which is small and indicates that the predicted data can be used to rapidly evaluate the separation effect of gravity separation equipment.展开更多
In the field of aerospace, minimum and seal of equipments cause the increase in the thermal loading sharply. Due to the lack of driving force, the performance of conventional condenser deteriorates greatly under the s...In the field of aerospace, minimum and seal of equipments cause the increase in the thermal loading sharply. Due to the lack of driving force, the performance of conventional condenser deteriorates greatly under the small gravity environment, which leads to reduction in the service life of equipments. In this study, a passive condenser, developed on basis of the phase separation concept,is utilized to improve the performance of the condensation heat transfer under the small gravity environment. As a result of the limitation of experiments, the mechanisms of heat transfer enhancement of the phase separation condenser tube are revealed through numerical simulation based on the volume-of-fluid(VOF) method. The following conclusions could be obtained:(1) A novel phase distribution of ‘‘gas near the tube wall and liquid in the tube core'' is formed. The thin liquid film is indeed created after the flow pattern modulation by inserting mesh cylinder.(2)The condensation quantity for single bubble in the annular region increases about 16 times greater than that in the bare tube region in the case of Jl= 0.0574 m/s and Jg= 0.0229 m/s.(3) Gas volume fraction affects the parameters of liquid film thickness, bubble length and liquid bridge length. The increase in the gas volume fraction results in the decrease in the evaluation index from21.56 to 12.82. The evaluation index is defined as the ratio of the condensation quantities per unit tube length of the annular region and the bare tube region.展开更多
基金Supported by the Young Science Foundation of China(50025411)the Doctoral Science Research Foundation of University(20030290015)
文摘Separation density is one of the most concerned operating parameters in gravity beneficiation.Although equal-errors cut point or distribution density is usually used as practical separation density in gravity beneficiation, the gravity separating process complexly affected by many kinds of factors is actually carried out at a fluctuant density; namely, the practical separation density is essentially a random variable.The studied results show that the equal-errors cut point is the mathematical expectation of this random variable, and the distribution density corresponds to the highest separation efficiency in the gravity separation process.This shows that the distribution density is the best working point of the gravity separation equipment under a particular operating condition.Therefore,in order to fully develop the function of the gravity separation equipment, the distribution density should be close to the theoretical separation density unlimitedly in the range of minimum fluctuation.
基金National Natural Science Foundation of China (No. 51174202)Doctoral Fund of Ministry of Education of China (No. 20100095110013)
文摘A model that rapidly predicts the density components of raw coal is described.It is based on a threegrade fast float/sink test.The recent comprehensive monthly floating and sinking data are used for comparison.The predicted data are used to draw washability curves and to provide a rapid evaluation of the effect from heavy medium induced separation.Thirty-one production shifts worth of fast float/sink data and the corresponding quick ash data are used to verify the model.The results show a small error with an arithmetic average of 0.53 and an absolute average error of 1.50.This indicates that this model has high precision.The theoretical yield from the washability curves is 76.47% for the monthly comprehensive data and 81.31% using the model data.This is for a desired cleaned coal ash of 9%.The relative error between these two is 6.33%,which is small and indicates that the predicted data can be used to rapidly evaluate the separation effect of gravity separation equipment.
基金supported by the National Natural Science Foundation of China(51476054 and 51506026)the Program for New Century Excellent Talents in University(NCET-13-0792)
文摘In the field of aerospace, minimum and seal of equipments cause the increase in the thermal loading sharply. Due to the lack of driving force, the performance of conventional condenser deteriorates greatly under the small gravity environment, which leads to reduction in the service life of equipments. In this study, a passive condenser, developed on basis of the phase separation concept,is utilized to improve the performance of the condensation heat transfer under the small gravity environment. As a result of the limitation of experiments, the mechanisms of heat transfer enhancement of the phase separation condenser tube are revealed through numerical simulation based on the volume-of-fluid(VOF) method. The following conclusions could be obtained:(1) A novel phase distribution of ‘‘gas near the tube wall and liquid in the tube core'' is formed. The thin liquid film is indeed created after the flow pattern modulation by inserting mesh cylinder.(2)The condensation quantity for single bubble in the annular region increases about 16 times greater than that in the bare tube region in the case of Jl= 0.0574 m/s and Jg= 0.0229 m/s.(3) Gas volume fraction affects the parameters of liquid film thickness, bubble length and liquid bridge length. The increase in the gas volume fraction results in the decrease in the evaluation index from21.56 to 12.82. The evaluation index is defined as the ratio of the condensation quantities per unit tube length of the annular region and the bare tube region.
