摘要:

The lack of accurate modeling of solid oxide fuel cells (SOFC's) and their systems has resulted in limitations in identifying key operating parameters and allowing for system configuration. The purpose of this study is to address each level of modeling needed to identify key parameters as well as integrating each level of modeling. The first level deals with the single cell and its electrochemical and thermal issues. The second level deals with the bundling of cells to form an SOFC stack while the third level incorporates the stack results into an overall thermal system.

ISSN:0098-6445    

DOI:10.1080/00986449608936491

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Experiments were conducted to demonstrate that spent powder activated carbon can be regenerated for reuse by microwave radiation. The spent powder activated carbon tested was prepared from the aqueous solutions of ethanol and acetone. The changes in the temperature and weight of spent activated carbon under microwave radiation were monitored. The results show that microwave regeneration of spent powder activated carbon consist of four steps: heating of wet carbon, evaporation of adsorbate, diffusion of adsorbate, and heating of dry carbon.

ISSN:0098-6445    

DOI:10.1080/00986449608936492

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper deals with a pilot plant study on the catalytic combustion of propane in a membrane reactor with separate feed of reactants. The importance of the amount of catalyst (1% b.w. Pt on γ-Al2O3), deposited on the pore walls of the membrane, is investigated. Two membranes were prepared by the so called urea method, intruding different amounts of the above catalyst (2% and 4% b.w., respectively) in anα-Al2O3basic porous tubular structure (pore diameter: 0.7 μm; length: 100 mm; internal radius 7 mm; thickness: 3 mm). The performance of the two membranes was tested in a pilot plant, feeding air at one membrane side and a propane/N2mixture at the other side. Either the kinetics- or the transport-controlled operating regimes were investigated, and, in this last case, operation was considered both in presence and in absence of trans-membrane pressure gradients. From this study the catalyst load of the membrane seems to affect seriously the reactor performance. The more the catalyst deposited in the membrane pores, the higher the conversion attainable in the kinetics controlled regime (low temperature operation), and the easier to reach the transport-controlling condition at higher temperatures. However, this last feature is achieved at the price of relatively low overall propane conversions due to the entailed lowering of membrane permeability. Therefore, provided the propane feed concentration and the eventual trans-membrane pressure gradient are not too high, a limited catalyst amount should be employed thus allowing higher membrane permeability and propane conversions, with minor slip of reactants through the membrane.

ISSN:0098-6445    

DOI:10.1080/00986449608936493

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The Rayleigh's capillary instability of a cylindrical fluid interface can be suppressed by the centrifugal force due to coaxial rotation when the outer fluid is heavier than the inner one. Thus, wave motions on the rotationally stabilized cylindrical interfaces can occur in natural and technological processes, notwithstanding the lack of coherent treatment in the literature. This work provides a supplementary linear analysis of various wave motions in a three-dimensional framework for two-phase inviscid fluid systems with cylindrical interfaces stabilized by rotation. Many previous results found in the literature are recast in a general from. With gravity acting perpendicularly to the rotation axis, the interface disturbance is considered as an externally forced wave motion. The condition for the stability of the gravity-induced interface displacement in a two-phase rotating system is found to be exactly the same as that for the one-phase case such as an air column in a rotating liquid.

ISSN:0098-6445    

DOI:10.1080/00986449608936494

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A grid model describing the gas flow and interchange in the grid zone of jetting fluidized beds is proposed. Based on this model, longitudinal gas concentration profiles in the jet and annulus are calculated. The longitudinal gas concentration distribution is also experimentally investigated in a jetting fluidized bed with an inside diameter of 50 mm at the ambient temperature, and a jetting fluidized bed with an inside diameter of 80 mm at high temperatures. Comparison between the calculated and experimental results has shown that the experimental profiles can be qualitatively predicted by the grid model. The results indicated that the concentration in the grid zone depends on the gas exchange between the jet and the annulus, and the net gas flow from the jet to the annulus. The gas exchange rate is mainly affected by the inlet gas velocity from the nozzle. The present study is thought to be helpful to understand the grid gas behavior in the jetting fluidized bed coal gasifier.

ISSN:0098-6445    

DOI:10.1080/00986449608936495

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

An analysis of the correlations proposed in the literature for calculation of the drag coefficient (CD) and the terminal velocity of a falling rigid sphere has been made. Among the correlations describingCDvs. Re, that of Turton and Levenspiel fits the experimental data almost perfectly. However, it is not explicit in the terminal velocity. The available explicit correlations do not fit the experimental data well. The present paper shows that a simple and precise explicit correlation can be developed ifCDis related to the Archimedes instead of the Reynolds number. The precision of the correlation proposed is similar to that of the Turton and Levenspiel (1986), while it is explicit in the terminal velocity. On the basis of this correlation, a model is proposed to calculate the drag coefficients and the terminal velocities of free falling or rising spherical particles in an infinite fluid as well as gas bubbles with any volume and shape rising in a contaminated liquid.

ISSN:0098-6445    

DOI:10.1080/00986449608936496

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Previous experimental work shows that velocity ratio is the principal independent variable to determine the flow behavior of coaxial jets. This study focusing on the effect of velocity ratio on the flow characteristics such as the velocity and kinetic energy profiles, centerline velocity decaying, flow growing and entraining of the jet, presents a detailed numerical simulation of a coaxial jet with a secondary parallel moving stream. It is found that radial profiles of the mean velocity componentudepending on the velocity ratio show good similarity in the fully developed zone. Compared with available experimental data, the results show that the use of standard κ-ϵ model leads to good agreement between the numerical results and experimental data.

ISSN:0098-6445    

DOI:10.1080/00986449608936497

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A reactor-separator combining immobilized penicillin acylase (IPA) and electrodialysis was developed for the production of 6-aminopenicillanicacid (6-APA)from the enzymatic hydrolysis of penicillin G (Pen-G) accompanying the continuous removal of by-product phenylacetic acid (PAA). The kinetics of Pen-G hydrolysis by IPA, the separation of PAA, 6-APA and Pen-G with electrodialysis, as well as the reaction-separation phenomena of Pen-G hydrolysis with IPA in the electrodialyzer were studied. The products inhibition mechanism and rate equation of Pen-G hydrolysis by IPA were obtained. The separation of PAA, 6-APA and Pen-G with electrodialysis was dependent on their molecular size and affinity toward the anion exchange membrane. The transport rates of three components decreased in the sequence PAA > 6-APA > Pen-G. Strong concentration polarization of Pen-G was observed in the vicinity of anion exchange membrane. An increase in Pen-G concentration enhanced the selectivity factor of PAA to 6-APA but reduced both the transport rates of PAA and 6-APA. The increase of current density promoted both the transport rates of PAA and 6-APA but reduced the selectivity of PAA to 6-APA. The utilization of electrodialysis was shown to have an improvement in the efficiency of Pen-G hydrolysis by IPA.

ISSN:0098-6445    

DOI:10.1080/00986449608936498

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Currently available information on droplet coalescence and break-up rates in turbulent flows in mixing vessels can be used to control drop sizes in dispersed phase equipment. The effect of drop size distributions on the selectivity and productivity in multi-reaction systems is examined in this paper.

ISSN:0098-6445    

DOI:10.1080/00986449608936499

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A mini pilot coal gasification plant (4–10 kg/h coal feed), incorporating a novel Compartmented Fluidised Bed Gasifier (CFBG) for gasification and combustion has been used for hot experiments. An important operating requirement for steady operation is maintaining the correct solids circulation rate (SCR) between the two compartments. A new technique has been developed for measuring the SCR and can be applied equally easily to hot and cold operation. The method has been applied in a 24factorial experiment with 2 replicates to obtain a statistical model for SCR as a function of the operating variables over the whole practical operating range. The model derived from the factorial experiment has been further tested against a vareity of operating conditions, including hot experiments at typical operating conditions.

ISSN:0098-6445    

DOI:10.1080/00986449608936500

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor