摘要:

AbstractThe fully developed region for a two‐phase jet exhibits similarity for velocity and concentration. A power law expression approximates the velocity distribution and the square root of this profile coincides with the concentration distribution. Measurements show that particle dispersion decreases with increase in particle concentration and the gas mixing rate is lower than the particle mixing rate. The turbulent Schmidt Number remains constant at a value equal to 0.4

ISSN:0008-4034    

DOI:10.1002/cjce.5450620201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractA photometric technique is being developed to study bubble behaviour in three‐phase fluidized beds constituted by fine particles. A custom made U‐shaped single core silica fiber (400 μm diameter) is used as the bubble sensor. A helium‐neon laser beam is introduced at one end of the U probe and the variation of the light intensity, occurring when a gas bubble contacts the sensor, is detected at the other end of the fiber. The velocity and axial length (cord) of the bubbles were measured by four such probes in a two dimensional bed. This technique could be applied to study the bubble behaviour and to provide experimental data for estimating the performance of reactors with severe operating conditions of high temperature and pr

ISSN:0008-4034    

DOI:10.1002/cjce.5450620202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractMeasurements are reported on pressure drop, holdup and interfacial area in a vertical column where a multi‐liquid jet ejector has been used for gas dispersion. Studies have been carried out in the bubble zone up to the onset of slugging. Correlations in terms of physical and dynamic variables have been developed to predict irreversible loss and holdup in such systems. Extensive statistical analysis showed that the correlations are highly significant at the 99 per cent confidence level. Measurements of interfacial area have been carried out by the chemical method. The measured values of the interfacial area were in the range of 5000 to 25000 m2/m3in the ejector and 450 to 2650 m2/m3in the total system. A correlation for predicting interfacial area has also been proposed as a function of the holdup in the syste

ISSN:0008-4034    

DOI:10.1002/cjce.5450620203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractA theoretical and experimental study of the errors arising in sampling through probes projecting into the flow has been conducted. Water–sand slurries with particles of surface‐mean diameter between 0.165 and 0.72 mm were considered. Theoretical predictions were performed assuming the mixture could be described by the axisymmetric potential flow relationship. Satisfactory agreement in the important intermediate K value region was achieved for tapered or thin‐walled probes. However, significant errors arise when thick‐walled blunt probes a

ISSN:0008-4034    

DOI:10.1002/cjce.5450620204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThe liquid velocity profile induced by a chain of bubbles is studied theoretically and a comparison with measurements is made. The wake velocity and the bubble shape involved in the theoretical development are considered based on the wake theory and the previous empirical relation for single bubbles, respectively.The shape and wake volume of chain bubbles can be treated in the same manner as those of single bubbles by using relative velocity. As a result, using the previous results of the drag coefficient and shape of single bubbles enables the prediction of the rising velocity of chain bubbles.

ISSN:0008-4034    

DOI:10.1002/cjce.5450620205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractHeat transfer in co‐current two‐phase upflow and downflow of air–water has been investigated in a 25.8 mm electrically heated vertical pipe at 172.3 kPa for water mass velocities of 54 to 172 kg/m2s and gas flow rates of 0 to 1.322 × 10−2m3/s. It was found that although the injection of air in the liquid flow increased the two‐phase heat transfer coefficients significantly for both systems, upflow coefficients were generally higher than those for downflow for the same liquid flow rate. This could have important implications in the design of some chemical reactors and heat engineering processes. Changes in heat transfer rates were found to occur at the flow pattern transition boundaries. Two‐phase heat transfer coefficients were well correlated by an expression based on dimensional analysis for both upflow

ISSN:0008-4034    

DOI:10.1002/cjce.5450620206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractWall to bed heat transfer has been studied in three‐phase fluidized beds with a cocurrent up‐flow of water and air. Six sizes of glass beads, two sizes of activated carbon beads and one size of alumina beads, varying in average diameter from 0.61 to 6.9 mm and in density from 1330 to 3550 kg/m3, were fluidized in a 95.6 mm diameter brass column heated by a steam jacket. Complementary heat transfer experiments have been performed also for a gas–liquid cocurrent column and liquid–solid fluidized beds.The wall‐to‐bed coefficient for heat transfer in the gas–liquid–solid fluidized bed is evaluated on the basis of the axial dispersion model concept. The ratio of the wall‐to‐bed heat transfer coefficient in the gas–liquid–solid fluidized bed to that in the liquid–solid fluidized bed operated at the same liquid flow rate is correlated in terms of the ratio of the velocity of gas to that of liquid and the properties of solid particles. A correlation equation for estimating the wall‐to‐bed heat transfer coefficient in the liquid–solid

ISSN:0008-4034    

DOI:10.1002/cjce.5450620207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThe variables affecting the peformance of the Domtar pilot plant dryformer have been examined using experimental design techniques. A total of fifteen variables were incorporated in a 215−11fractional factorial design with a reverse sign design to obtain the main effects of variables free of aliasing with other main effects and two‐factor interactions. An estimate of experimental error was obtained from repeated runs of the primary 215−11design conditions.The experiments were performed with bleached softwood kraft pulp and the dependent variables included the production rate at good formation, the production rate with adequate nit removal, the machine direction basis weight variation and the average formation characteristics of the dryformed web product. Of the fifteen variables examined, all but three have some effect on at least one of the dependent variables and there were strong indications that two‐factor interactions played an important role in describing the operation of this dr

ISSN:0008-4034    

DOI:10.1002/cjce.5450620208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractMeasurements of dispersed phase holdup and flooding conditions have been carried out in a 5 cm diameter reciprocating plate extraction column. A simplified predictive model for holdup and flooding has been developed assuming uniform hydrodynamic conditions throughout the column. The model has been confirmed for several systems but may be limited in application by the following factors: (a) mass transfer, particularly from dispersed to continuous phase (coalescence effect), (b) wettability of plates by dispersed phase, (c) axial non‐uniformity of holdup (noticed particularly for high interfacial tension systems), (d) the use of exceptionally high frequencies or low amplitudes of agitatio

ISSN:0008-4034    

DOI:10.1002/cjce.5450620209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThe effect of gas sparger type, clear liquid height, liquid viscosity and addition of electrolyte on fractional gas hold‐up in a 0.38 m i.d. sectionalised bubble column (SBC) was studied for superficial gas velocities ranging from 0.03 to 0.15 m s−1. A study of the wall side solid–liquid mass transfer coefficient,kSL, has been made by considering the dissolution of copper in acidic dichromate solutions. The variation ofkSLwith axial distance in a section for different gas velocities has been explained. A comparison between the performance of sectionalised bubble columns and conventional bubble columns has been presented. In some cases, the SBC may prove to be superior to bubble columns in pra

ISSN:0008-4034    

DOI:10.1002/cjce.5450620210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY