摘要:

AbstractThe process of gas absorption in freely falling films of dilute polymer solutions under different kinematic conditions shows some hitherto unreported and dramatic differences. The absorption rates are reduced when films are generated under rapid stretch conditions over axisymmetric bodies of revolution, whereas they are enhanced when films are generated in a long, wetted wall column. Absorption rates are enhanced on polymer addition in freely falling turbulent films. Possible mechanistic explanations have been offered for these phenomena.

ISSN:0001-1541    

DOI:10.1002/aic.690300302

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractFlatter velocity profiles and more uniform thermal environents are extremely desirous factors for improved performance in flow reactors and heat exchangers. One means of achieving this in laminar flow systems is to use mixers and flow inverters. These improve performance but at higher initial and operating costs. This paper introduces a new and more effective device for flow inversion which is achieved by changing the direction of centrifugal force in helically‐coiled tubes. Transient response experiments carried out under the conditions of both negligible and significant molecular diffusion reveal drastic narrowing of the residence time distribution (RTD). The effectiveness of the present device can be assessed by the fact that even at a Dean number of 3 the value of dispersion number as low as 0.0013 is obtained under the condition of significant diffusion, and in the case of negligible diffusion the value of dimensionless time at which the first element of tracer appears at the outlet is as high as 0.8

ISSN:0001-1541    

DOI:10.1002/aic.690300303

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractOne of the difficulties encountered in the operation of an activated sludge process is the phenomenon of bulking sludge.In an activated sludge process which is composed of a completely mixed aeration tank and a sedimentation vessel, the dynamic behavior of the system can be analyzed using a mathematical model. The model developed here is based on the kinetics and settleability of the combination of floc‐forming sludge and bulking sludge. The operating conditions that cause the bulking phenomenon are clarified on the phase plane. It is also shown that a type of nonlinear state feedback regulator makes the system stabl

ISSN:0001-1541    

DOI:10.1002/aic.690300304

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractA two‐dimensional model for stratified turbulent‐turbulent gas‐liquid flow in inclined pipes is proposed. The gas phase is treated as bulk flow, but an exact solution is carried out for the liquid phase, applying the eddy viscosity theory to model the turbulent viscosity. The interfacial structure is taken into consideration using appropriate correlations for the interfacial shear stress. The model is capable of predicting the liquid velocity field, holdup and pressure drop given gas and liquid flow rates, physical properties, pipe size, and angle of inclination. The results are substantially better than the prediction of Lockhart and Martinelli (1949) correlation and better than the Taitel and Dukler (1976) model for stratified

ISSN:0001-1541    

DOI:10.1002/aic.690300305

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractA new flow mixing calorimeter has been used to make measurements of the excess enthalpy of water vapor + methane at temperatures up to 698.2 K and pressures up to 12.62 MPa. Tests on the calorimeter and consistency tests on the measurements suggest that the results are free from significant error. The measurements are fitted to an equation from which excess volumes and compressibility factors for the mixture are calculated.

ISSN:0001-1541    

DOI:10.1002/aic.690300306

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractLiquid‐side mass transfer coefficients were measured for cocurrent two‐phase downflow in 5 and 10 cm diameter columns pakced with 2.5 and 4 mm Raschig rings. Experiments were specifically carried out in the pulsing flow regime. The mass transfer coefficients were determined via absorption of CO2into buffer solutions with the advantage of a high absorbing capacity. Thus columns of 1 m length could be used. Relations are proposed based on the hydrodynamic phenomena observed in pulsing flow. From these relations a correlation forkLis found in terms of flow rates and packing characteristics that satisfies the experimental d

ISSN:0001-1541    

DOI:10.1002/aic.690300307

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractBy the use of a perfectly mixed model and an imperfectly mixed one for lowdensity polyethylene vessel reactors, we show that increases in the initiator consumption with polymerization temperature are due to mixing limitations at the initiator feed. With all its parameters independently estimated, the imperfectly mixed model provides an excellent agreement with experimental data for several initiators, feed flow rates and polymerization pressures. In the temperature region of industrial interest for each type of initiator, the open‐loop reactor dynamics drastically change from open‐loop unstable, at low temperatures, to open‐loop stable at high polymerization tempera

ISSN:0001-1541    

DOI:10.1002/aic.690300308

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractBy the use of an imperfectly mixed model developed for LDPE vessel reactors, we show that a linear controller cannot perform satisfactorily in the entire range of operating conditions of industrial interest. Based on the concept of reaction rate control, a novel controller is developed which provides satisfactory closed‐loop dynamics independent of steady‐state conditions. A nonlinear controller is shown to be more effective in avoiding reactor light

ISSN:0001-1541    

DOI:10.1002/aic.690300309

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractA comprehensive mathematical model for the finishing stages of polyethylene terephthalate (PET) synthesis is developed. The model takes into account the variables which have significant influences on polymerization but have not been hitherto taken into account, e.g., changing interfacial concentration and the presence of side reactions. The model is applicable to industrial polymerizations, and the predictions agree well with the literature and with certain pilot‐plant and commercial dat

ISSN:0001-1541    

DOI:10.1002/aic.690300310

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractThe reduction in distillation tray efficiency caused by uniform weeping of liquid from the tray has been calculated. Numerical results are presented for all three Lewis cases over the range of variables of interest to tray designers. Analytical equations are given for Lewis' cases 2 and 3 for plug flow of liquid on the tray.

ISSN:0001-1541    

DOI:10.1002/aic.690300311

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY