摘要:

For calculation of the thermodynamic properties of refrigerants it is proposed that the extended corresponding states principle (ECSP) should be used using two specific reference fluids, CFC12 (CCI2F2) and HFC134a (CF3CH2F), in order to cover the field of interest for most refrigerants. The specific parameters of these refrigerants have been determined for the Lee-Kesler modification of the Benedict-Webb-Rubin equation of state. In the parameter estimation, it has been taken into accounl that all variables are subject to errors by using the so-called Error-in-Variables-Model (EVM). The parameters have been estimated from experimental pressure-volume-temperature data, vapour pressure and saturated liquid and vapour volume data for CFC12 and HFC134a.

ISSN:0098-6445    

DOI:10.1080/00986449308936199

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A general model is presented for recombinant fermentation in a chemostat in which micromixing may be imperfect. Using the production of tryptophan synthetase as an example and the dilution rate,D, as the bifurcation parameter, conditions are first derived for Hopf bifurcation in a perfectly mixed chemostat. The bifurcation surfaces in three-dimensional space are such that oscillatory solutions exist above the surfaces and washout conditions below. A similar analysis is done for imperfect mixing. The bifurcation region is a concave hyperboloid in the [D,f, n]-space, wherefandn; are model parameters. It is argued that poor macromixing reduces the range ofDover which bifurcation to periodic solutions is possible.

ISSN:0098-6445    

DOI:10.1080/00986449308936200

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A new application of the fixed bed catalytic reactor with flow reversal for combustion of natural gas is investigated by mathematical modeling and computer simulation. Comparison between the results obtained for this new reactor and those for a classic catalytic fixed bed is made. Inexpensive perovskite type catalysts containing no noble metals were used. It is shown that an appropriate choice of operating parameters (concentration and temperature of input gas mixture, superficial gas velocity, size and shape of catalyst and inert material, volumetric ratio between catalyst and inert material in the bed) allows for a methane combustion at must lower temperatures in the reactor with flow reversal than in a classic catalytic reactor. Under such a low temperature combustion, no nitrogen oxides are produced.

ISSN:0098-6445    

DOI:10.1080/00986449308936201

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In many applications swirling flow is used to enhance heat and mass transfer. One of the problems of modelling a turbulent swirling flow is the choice of the turbulent closure model which is acceptable for engineering purposes. To evaluate which model performs best, numerical results are compared with experimental data. Local velocity measurements are carried out on a swirling flow in a circular tube. The measurement method is hot-wire anemometry combined with visualization techniques. The numerical analysis is carried out using thek-εmodel and the Algebraic Stress Model. In the experiment a symmetrical swirl was observed, Comparing the experimental data with the numerical results shows that the Algebraic Stress Model represents the experimental data quite well, whereas thek-εmodel fails.

ISSN:0098-6445    

DOI:10.1080/00986449308936202

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This paper is a study to solve the practical problem of comparing two catalysts experimentally. The process under discussion is the isomenzation of aromalics of C8 in non-equilibrium mixtures lo near equilibrium concentrations to allow a greater yield in the production of ortho- and para-xylene. To define the zone of work of each catalyst, the experimental strategy used was the Response Surface Methodology. The catalytic parameters studied were the activity, and selectivity through the analysis of the operating variables influence, the reaction products and the building of empirical models.

ISSN:0098-6445    

DOI:10.1080/00986449308936203

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Crystallizations of KCl from water and reagent grade potassium chloride solution with and without magnesium sulfate and magnesium chloride as impurities were conducted in a one liter continuous MSMPR cooling crystallizer. A series of experiments at a constant operating temperature, various feed temperatures and magnesium and sulfate ions concentrations were carried out to investigate the effect of the type and concentration of impurities on the width of the meta-stable zone, crystal size distribution, crystal habit, crystal purity, growth rate, nucleation rate, and aggregation index. The width of the meta-stable zone increased with impurity concentrations of both magnesium and sulfate ions alike. Sulfate ion increased the mean crystal size at all concentrations, whereas the initial increase in mean crystal size at low magnesium concentrations was moderated at higher concentrations. Polycrystals formation was significant with and without impurities. The crystal surface became irregular at higher sulfate ion concentrations. The impurity incorporation within KCl crystals decreased with crystal size and was much higher in the case of magnesium sulfate. Secondary nucleation rate was unaffected and growth rate was altered in the presence of both impurities, and the influence was apparently independent of the effect upon the meta-stable zone width. The effect of impurities was suppressed with increase in suspension density.

ISSN:0098-6445    

DOI:10.1080/00986449308936204

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A four-phase model for fluidized-bed catalytic reactors is developed. The bed is divided into four phases, i.e., bubble, cloud-wake, emulsion upflow, and emulsion downflow phases. In the model, gas back mixing in the emulsion phase and gas interchange as well as gas cross flow between phases are all considered. Model predictions are shown to compare well with various published experimental data on both axial concentration profiles and overall conversions. Parameters effects on the reaction performance were also illustrated. It was found that neglecting cross flow will result in 13% lower on the predicted conversion.

ISSN:0098-6445    

DOI:10.1080/00986449308936205

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor