摘要:

AbstractAn experimental program has been initiated to use a reciprocating plate column for aerobic fermentations. This paper reports the results of the initial phase consisting of the hydrodynamic studies and the evaluation of the power consumption as a function of the level of agitation and gas superficial velocity. The variation of the gas holdup is presented and compared to a correlation. It is shown that a simple correlation can predict adequately the gas holdup when water is used. The power consumption, necessary for scale‐up and design considerations, was evaluated using the pressure variation at the base of the column, the pressure difference across the column and the force exerted on the central shaft to reciprocate the plate stack. Results for the power consumed by the fluid mixture obtained with the three methods are presented and analyzed. The three methods give approximately the same value of the power consumptio

ISSN:0008-4034    

DOI:10.1002/cjce.5450710401

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

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper deals with the experimental study of mixing characteristics by means of steady and unsteady jets. Investigations were carried out with one and two steady jets, and with two alternate intermittent jets, supplying 0.1 m3and 70 m3tanks. From the data obtained from several sensors put into the tank, the signification of the mixing time as applied to the tank is discussed. A Reech‐Froude similarity appears to be a good way in scaling the results obtained on either 0.1 m3or 70 m3models. Combining the specific momentum of the jets and the tank characteristics, a mixing time factorMis deduced which permits the evaluation of the mixing time. The efficiency of different configurations of jets are then compared through a degree of transient inhomogeneity and required powe

ISSN:0008-4034    

DOI:10.1002/cjce.5450710402

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

年代:1993

数据来源: WILEY

摘要:

AbstractHeat transfer in dense fluidized beds have been extensively studied. However, there is not much detailed information about the mechanism of surface‐to‐suspension heat transfer in the freeboard region. In the present work, a newly designed heating plate was used to measure the plate‐surface‐to‐particle‐suspension heat transfer coefficients in the freeboard.The experimental unit consisted of a 30 cm i.d. fluidized bed reactor packed with fluidized catalytic particles of mean particle size 90 μm. Three types of plate orientations were used to test directional effects of surface on heat transfer rate. Height of the freeboard was 171 cm, and the superficial gas velocity was varied from 0.28 to 0.64 m/s. Local solids concentrations in the freeboard were also obtained by a nozzle‐type sampling probe. Data on axial distribution of solids concentration were used to find out the solids kinematics in the freeboard region. Finally, a surface‐to‐suspension heat transfer model was developed to elucidate the surface to particle heat transfer mechanism in this lean phase system.The model is based on the transient gas‐convective heating of single particles when sliding over the heating plate and the assumption of instantaneous attachment–detachment equilibrium between particles

ISSN:0008-4034    

DOI:10.1002/cjce.5450710403

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

年代:1993

数据来源: WILEY

摘要:

AbstractAn analysis is presented of a 1‐2 divided flow exchanger where the temperature of shell and tube streams depend on tube arrangement. Effect of having unbalanced tube passes is assessed for two possible cases. Graphs are plotted that show the variation of thermal effectiveness and logarithmic mean temperature difference correction factor with ratio of heat capacity rates and number of transfer units. Combination of such exchangers is also studie

ISSN:0008-4034    

DOI:10.1002/cjce.5450710404

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

年代:1993

数据来源: WILEY

摘要:

AbstractRecently the absorption heat pumps and chillers have received considerable attention due to their low electricity consumption rate. Therefore, it is important to understand the transport mechanism of an absorption process. In this paper, a numerical study of the heat and mass transfer taking place on a wavy falling liquid film of an absorption process is presented. With previously solved periodic wavy film flow solutions, the finite difference method is employed to solve the heat and mass transport equations. The numerical solution indicates that the waves significantly increase the transport rates. A comparison of the transfer rates of the wavy film to that of the smooth film is presented to show that the mass transfer rate can be doubled.

ISSN:0008-4034    

DOI:10.1002/cjce.5450710405

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

年代:1993

数据来源: WILEY

摘要:

AbstractExtraction of crystallization kinetics, the fundamental information which governs the performance of a crystallization process, is characterized by experimental difficulties in MSMPR and mathematical difficulties in batch crystallization. Here, a rigorous approach is taken to estimate kinetic parameters from a batch crystallizer. The two step LaxWendorff technique is adapted for the solution of the population balance in a batch crystallizer and an iterative self‐correcting least squares algorithm is implemented for the estimation of the kinetic parameters. The need for multi‐response estimation as opposed to single‐response from terminal CSD is demonstrated. The kinetics extracted are average ones, representing primary and secondary nucleation kinetics. It is found that the kinetic parameters estimated by multi‐response technique have a superior predictive capability as opposed to those obtained using the terminal CSD only. An advantage of the proposed algorithm is that the measurement of course of supersaturation, which is difficult to perform, is not r

ISSN:0008-4034    

DOI:10.1002/cjce.5450710406

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

年代:1993

数据来源: WILEY

摘要:

AbstractA mathematical model of biomass gasification in a fluidized bed has been developed. It considers axial variations of concentrations and temperature in the bubble and emulsion phases. The mass balance involves instantaneous oxidation and equilibrium devolatilization of the biomass, kinetics of solid‐gas gasification reactions as well as of gaseous phase reactions and interphase mass transfer and gas convection. The energy balance is solved locally for each vertical volume element, and globally on the reactor by iteration on the temperature at the bottom of the bed. Three parameters have been adjusted based on the experimental results: the heat transfer coefficient at the wall, the weighting of the kinetics of the water‐gas shift reaction and the fraction of biomass carbon remaining as char after devolatilization. The model is used to simulate a pilot scale (50 kg/h) biomass gasifier, and its predictions compared to experimental measurements. The temperature and gaseous concentrations are estimated with good accuracy for the experiments using a wood feedstock, except for the concentration of hydrogen which is overestima

ISSN:0008-4034    

DOI:10.1002/cjce.5450710407

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

年代:1993

数据来源: WILEY

摘要:

AbstractSelective toluene disproportionation has been studied over ZSM‐5 zeolites modified withP, Si and Cs compounds. For thePand Si modified samples,p‐xylene proportion in the primary product was 100% due to the diffusional control on the internal xylene isomerization. The number and strength of the acid sites are reduced by the three modifier agents but a relationship between para‐selectivity and the decrease of the acid strength has not been observed. The most para‐selective samples have been those modified with Si which has been related to the deposition of this agent on the external surface of the zeolite crystals avoiding the primary product isomer

ISSN:0008-4034    

DOI:10.1002/cjce.5450710408

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

年代:1993

数据来源: WILEY

摘要:

AbstractNickel electrodes were prepared by electrodeposition in electrolytes of various anionic compositions. The deposition conditions and bath types were evaluated with special emphasis on the electrocatalytic properties for the oxygen evolution reaction (OER). Electrochemical characterizations in a 5 mol/L KOH solution at 25°C showed that the electrode deposited from the chloride bath, having a low Tafel slope of 50 mV/dec and an overpotential of 396 mV at 100 mA/cm2, is the most catalytically active among electrodes prepared in electrolytes of various anionic compositions. The electrode activity for the OER is related to the real surface areas, which depend on the anion compositions in the deposition bath and the deposition conditions

ISSN:0008-4034    

DOI:10.1002/cjce.5450710409

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

年代:1993

数据来源: WILEY

摘要:

AbstractNickel‐cobalt and nickel‐iron electrodeposits were characterized as hydrogen electrodes in alkaline water electrolysis (6 mol/L KOH, 25°C). The nickel‐based codeposits were fabricated with different bath compositions and at different current densities. The hydrogen evolution in water electrolysis on the nickel‐based codeposits was apparently enhanced as compared with that on nickel. The improvement of the electrocatalytic behaviour of the hydrogen electrodes is attributed to their composition and an increase of their active surface, which are dependent on the electrodeposition co

ISSN:0008-4034    

DOI:10.1002/cjce.5450710410

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

年代:1993

数据来源: WILEY