ISSN:0001-1541    

DOI:10.1002/aic.690160602

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

ISSN:0001-1541    

DOI:10.1002/aic.690160603

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

AbstractOptimal control of concurrent nonlinear tubular reactors for complex reaction system is studied. The jacket side temperature is allowed to vary along the reactor length and with time. The optimal control possesses feedforward component only, and the nonlinear gain may be precomputed. For a Denbigh type of reaction system, if the heat generation is negligible, the control temperature is insensitive to feed concentration variations. With heat generation effect present, the optimal control is time dependent, and the nonlinear feedforward gain is obtained. The gain may be approximated by a linear function to construct a simple linear feedforward control loop which contains a synchronized time delay.

ISSN:0001-1541    

DOI:10.1002/aic.690160607

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

AbstractDetailed data are reported for blend time and turnover time with a 17‐in. impeller operating in an 18‐in. diameter tank. Above 1,500 centipoises, viscosity had no effect on blend time at constant speed. Blend time was inversely proportional to speed.The inner flight of a helical impeller is of value when blending pseudoplastic fluids but has no effect on blend time with Newtonian fluids. The ratio of blend time to turnover time is given, as well as the effect of several different helical impeller geometry variab

ISSN:0001-1541    

DOI:10.1002/aic.690160608

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

AbstractA parallel plate rheometer has been devised which permits measurements of shear stresses of 102to 105dynes/sq.cm. and shear rates of 10−5to 1 sec.−1. A linear, air lubricated bearing is used to align the apparatus, and a linear variable differential transformer is used to sense changes in position. With a sample of polyisobutylene and with several samples of poly(dimethyl siloxane), it has been established that a Hookean range exists for each sample at low stresses. Hooke's law in shear states that the modulus is independent of stress, where the modulus is defined as the ratio of the shear stress in steady, creeping flow to the strain which can be recovered after the stress is removed. Other conclusions supported by the present work are that the Hookean range does not extend to stresses which are high enough to cause non‐Newtonian flow, that the modulus decreases with increasing molecular weight although not in direct proportion, and that a sample with a broad molecular weight distribution has a lower modulus than one with a narrow distrib

ISSN:0001-1541    

DOI:10.1002/aic.690160609

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

AbstractA novel feedback control system, called apredictive feedback control system, is developed for the regulation of the exit composition of a continuous flow stirred tank reactor (CFSTR). The control system utilized two basic feedback signals. One is the effluent concentration of the composition to be controlled. This is measured by a batch type of composition analyzer such as a chromatograph. The other is a predictive feedback signal which continuously predicts the difference between the actual value of the controlled variable and the measurement supplied by the analyzer. The predictive signal is generated from a plant model which approximately relates the controlled variable and the continuously measured reactor temperature.Unlike direct feedback control systems, the stability of the predictive system is unaffected by the periodic sampling and time delays introduced by the batch analyzer. Moreover, at steady state the predictive feedback signal disappears, and, like direct feedback systems, predictive feedback systems yield very accurate steady state control.A computer simulation of the predictive feedback control of a particular CFSTR has shown that predictive control is considerably more effective in composition control than conventional direct feedback control, is more effective than conventional temperature control, and retains the advantages of direct feedback control while partially eliminating the undesirable effects caused by the batch analyzer.

ISSN:0001-1541    

DOI:10.1002/aic.690160610

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

AbstractThe time optimal control problem for jacket cooled continuous flow stirred tank reactor (CSTR) with an exothermic, irreversible, second‐order, homogeneous, liquid‐phase reaction (the saponification of ethyl acetate) was solved with the maximum principle and phase plane analysis. Both experimental studies and analogue computer simulation studies were conducted.The overall performance of the experimental system agreed very well with the performance of the corresponding system simulated on an analogue computer. However, there were enough differences in the observed and predicted operating states and switching curves to warrant the conclusion that the experimental performance can be significantly improved if experimental results are used to modify the results predicted with computer analysis. These differences were attributed to uncertainties in the model and the values of the model parameters as well as nonrandom (and unforeseen) measurement err

ISSN:0001-1541    

DOI:10.1002/aic.690160611

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

AbstractA new one‐term withdrawal expression for power law fluids is developed from theoretical equations. Comparison with film thickness data for three carbopol fluids of α = 1.79 to 2.68 indicates agreement similar to that observed with valid Newtonian theories. The agreement was verified by comparison with independent measurements of entrainment flow ra

ISSN:0001-1541    

DOI:10.1002/aic.690160612

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

AbstractMicroconductivity probes were used for the measurement of point values of mean concentrations and root‐mean‐square concentration fluctuations for mixing of salt solutions in turbulent shear flows. Mixing studies covered a range of flow conditions, with Reynolds numbers on the order of 104, and included ducted turbulent jets, dispersion in turbulent pipe flow, a plane mixing zone, and several multiple injection systems. The test sections all had characteristic dimensions of about 2 cm. The results for mixing experiments are compared with available previous work. Lack of resolution for root‐mean‐square concentration fluctuations in some previous work is indicated.Reaction product concentrations for a rapid, second‐order, irreversible reaction in multiple injection systems, the plane jet, and the mixing zone were also obtained. The relation between conversion in reaction experiments and fluctuation level and decay in the equivalent mixing experiments is il

ISSN:0001-1541    

DOI:10.1002/aic.690160613

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY

摘要:

AbstractMost processes have more storage levels to control than there are production rates for changing inventories, a situation known aspartial controllability. Necessary and sufficient conditions under which all levels can be held within predetermined limits are presented. A control law maximizing the probability of satisfactory operation is developed, together with the computational steps required for its implementation. A simple numerical example is given.

ISSN:0001-1541    

DOI:10.1002/aic.690160614

出版商:American Institute of Chemical Engineers    

年代:1970

数据来源: WILEY