摘要:

AbstractExperiments conducted in 0.15 m diameter bubble columns using water and non‐aqueous liquids have shown that the gas velocity at which transition from the bubbly flow to the churn‐turbulent flow regime occurs is a function of gas density. The transition velocity increased with increasing gas density. The direct effect of gas density on gas holdup in the bubbly flow regime is small with only a slight increase in holdup being observed at higher densities (ϵGα ρg0.04). In the churnturbulent region a much greater effect of gas density on gas holdup was observed. These differences were found to be a direct function of the differences in holdup values at the transition points. Gas holdup was found to be a function of the gas phase momentum. In the bubbly flow regime holdup was directly proportional to momentum while in the churn‐turbulent regime holdup was proportional to momentum to the one third power.Reasons for this behaviour are discussed, as well as the implied effects on liquid mixing in bubble column slurry reactors. The effects of gas density may offer an explanation for some apparently anomalous published

ISSN:0008-4034    

DOI:10.1002/cjce.5450720102

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe size distribution of drops formed from four different diameter nozzles (d=l.O, 1.6, 2.6 and 3.5 mm) was measured over the flow rate range of 0.17 to 3.0 cm3/s (below jetting). Kerosene was used as the dispersed phase and distilled water was used as the continuous phase. The experimental drop size distributions were described adequately by the upper limit number and volume distributions. Plots of the maximum and the minimum diameters versus the mean diameter yielded straight line with slopes of 1.11 and 0.87, respectively.

ISSN:0008-4034    

DOI:10.1002/cjce.5450720103

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe motions of the granular bed inside a rotary furnace are governed by complex dynamics consisting of two modes. The axial velocity of the active layer on top of the bed represents the fast mode, while the overall velocity in the bed follows a slower mode. The proposed nonlinear model focuses on the dynamics of the slow mode. The difficulties of an analytic solution are avoided by a numerical method that employs several correlations. The model can reproduce the experimental transient responses. It is concluded that rotary furnaces respond better to small amplitude excitations than to large ones; consequently, closed‐loop control is well suited for this type of furnac

ISSN:0008-4034    

DOI:10.1002/cjce.5450720104

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

年代:1994

数据来源: WILEY

摘要:

AbstractA mechanistic model has been developed for determining the stratified boundary for condensing flows in horizontal and slightly inclined tubes. Two formulations, a complete and a simplified version are considered for the equilibrium liquid level. Good agreement is found between the two formulations and generalized results were derived from the simplified version of the model. From these results, the effect of condensation is shown to be equivalent to adding a small upward inclination in adiabatic gas‐liquid flow. The predicted transition line is compared with flow‐regime data of different fluid properties, tube diameters, and inclinations. The predictions agreed reasonably well with the d

ISSN:0008-4034    

DOI:10.1002/cjce.5450720105

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

年代:1994

数据来源: WILEY

摘要:

AbstractThis work investigates analytically the wall effect on the mixed convection from a horizontal plate embedded in porous media. Variable surface heat flux is assumed at the plate. The wall effect due to no‐slip boundary condition at the wall is introduced using the Brinkman model. Two sets of transformations are used, one for the forced convection dominating regime (FCDR) and the other one for the natural convection dominating regime (NCDR). The wall effect is found to be characterized by the boundary parameters L = DaxPex/ϵ in FCDR and by M = DaxRa x2/3:/ϵ in NCDR. Velocity as well as temperature profiles are calculated at different values of governing parameters. Local Nusselt number variation for the entire mixed convection regime is also calculated and presented. Accurate correlations for local and average Nusselt number valid for the entire regime of mixed convection and for the range of boundary‐parameter from 0 to 100 are o

ISSN:0008-4034    

DOI:10.1002/cjce.5450720106

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

年代:1994

数据来源: WILEY

摘要:

AbstractA new type of ring‐shaped temperature sensor for packed‐bed heat transfer studies is presented. This ring‐shaped sensor is easy‐to‐build and allows one to filter the experimental angular temperature fluctuations. This device is more effective for beds of small tube‐to‐particle diameter ratio. The proposed device is able to eliminate the effect of the angular position on temperature measurements in packed beds. This sensor property is confirmed both experinientally and theoretically. For demonstration purpose, packed beds of six different materials were studied. Effective thermal radial parameters obtained using the ring‐shaped sensors have shown trends similar to published packed‐bed h

ISSN:0008-4034    

DOI:10.1002/cjce.5450720107

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe local mass transfer rate to tubes immersed in gas‐liquid two‐phase systems was studied using the electrochemical method. It was found that the mass transfer distribution around the tube perimeter is not uniform and depends on the geometry of the system, the properties of the liquid phase and the superficial gas velocity.Taking into account the analogy between heat and mass transfer, these results may be useful in both fie

ISSN:0008-4034    

DOI:10.1002/cjce.5450720108

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

年代:1994

数据来源: WILEY

摘要:

AbstractCrystallization in the presence of high pressure gas as antisolvent could be applied for the recovery of valuable compounds from liquid solution. A study of separation behavior is presented here for a mixture of anthracene (AN) and anthraquinone (AQ) in cyclohexanone (CX) expanded with a gaseous antisolvent, CO2. The pressure range was 0.1 to 12 MPa; the temperature was either 292 or 313K. Separation factors were obtained from the measured salted‐out yields and the supersaturation of each solute could be also obtained for this pressure‐tuning crystallization. The separation factor varies almost linearly with relative supersaturation ratio in the crystallization of anthracene‐anthraquinone from cyclohexanone an

ISSN:0008-4034    

DOI:10.1002/cjce.5450720109

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

年代:1994

数据来源: WILEY

摘要:

AbstractA method is developed for the calculation of the saturation temperature of a KCI‐NaCI aqueous solution, based on the measurement of the density and temperature of a sample solution, and prior knowledge of the NaCl concentration. Experimental density and solubility data for solutions saturated with KCI in the temperature range of 299 to 321 K with concentrations of NaCl greater than 0.200 kg/kg H2O were used to develop the empirical correlation allowing the calculation of the solution saturation level.The method is applicable in the on‐line determination of the level of supersaturation in a KCI crystallizer in which the NaCl concentration is known. Knowledge of the prevailing supersaturation is necessary for the control of crystal purity and crystal size distribution in industrial potash crystalliz

ISSN:0008-4034    

DOI:10.1002/cjce.5450720110

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe effect of adding a water‐soluble chelating agent, diethylenetriaminepentaacetic acid (DTPA), to the feed phase was studied on the selective permeation of rare earth metal ions (Ln3+) through a supported liquid membrane (SLM) containing 2‐ethylhexyl phosphoric acid mono‐2‐ethylhexyl ester (PC‐88A). High selectivity of Pr to Nd was observed at a pH of 2.0 in the stripping phase, and selective permeation of La was observed at higher pH values. The permeation mechanism of the Ln3+was analyzed, and the above results were explained by the change in the concentrations of free Ln3+in the feed phase and Ln3+/PC‐88A complexes in the

ISSN:0008-4034    

DOI:10.1002/cjce.5450720111

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

年代:1994

数据来源: WILEY