摘要:

A mathematical model of fluid flow and mass transfer in a packed bed was derived and used to evaluate the liquid phase axial dispersion and mass transfer coefficients under high pressure conditions. The least-squares method was used to evaluate the rate parameters from experimental breakthrough curves, and the agreement between the concentration curves predicted from rate parameters and those measured experimentally was good. Experiments were performed at 20 and 200°C with water as a solvent and nonporous soda-lime glass beads as packing. Although the axial dispersion coefficient was independent of temperature and pressure, the mass transport parameters were found to be pressure dependent.

ISSN:0098-6445    

DOI:10.1080/00986449308936189

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Liquid phase axial backmixing in the riser and downcomer sections of an airlift loop reactor with non-Newtonian fluids was investigated and determined by dynamic response technique with pulsed tracer input, dual probe detection and computer on-line analysis system under different superficial gas velocity conditions. This method was used to obtain the dispersion coefficient Dzfor the individual sections of the reactor.

ISSN:0098-6445    

DOI:10.1080/00986449308936190

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The viscocapillary model of slot coating is used to estimate the values of a key operating variable: the differential pressure that must be applied between the gas phases located upstream and downstream of the coating station.

ISSN:0098-6445    

DOI:10.1080/00986449308936191

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Ultrasonic cleaning is an established method for removing micron-size particles or larger from hard substrates. This paper presents the effect of the ultrasonic frequency and time functions on submicron particle removal effectiveness. The effect of the particle size, concentration and the cleaning liquid temperature is also investigated. The removal efficiency is shown to be dependent on the ultrasonic time and frequency functions. The liquid temperature is shown to have a major effect on the ultrasonic cleaning process. The removal efficiency is shown to decrease with decreasing particle diameter. The results show that the ultrasonic cleaning technique can effectively remove particles of sizes 0.3 μm and larger.

ISSN:0098-6445    

DOI:10.1080/00986449308936192

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A two-part mathematical model has been developed to describe the transport processes in a nucleation chamber designed for condensation of refractory vapors in a microgravity environment. The model solves the transient diffusion equations for temperature and concentration fields in cylindrical coordinates using finite differences and the alternating direction implicit method. Vapor supersaturation ratios are then computed from the evolving concentration profiles thus permitting one to estimate the conditions at the location in the chamber where nucleation is observed in experiments.

ISSN:0098-6445    

DOI:10.1080/00986449308936193

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Experimental measurements for the heat and mass transfer in laminar wavy film absorption with the presence of non-absorbables are presented. Water vapor was absorbed into a falling film of aqueous lithium chloride solution on a vertical tube with the air present in the gas phase acting as the non-absorbable whose concentration was accurately detected by a mass spectrometer gas analyzer. Although the depressing effect of the air on the absorption rate was much more significant in the low air concentration range, the absorption reduction rate with increasing air concentration was found to be lower than that reported previously. The reduction was found to be continuous even up to 30% of air content. Besides the non-absorbables, the effects of other operational parameters such as solution flow rate, inlet solution temperature, inlet solution concentration, absorber wall temperature, absorber water vapor pressure, and effective contact length on the absorption rate were also tested. These effects were shown to follow trends similar to those predicted by a numerical solution for smooth film absorption. The heat and mass transfer coefficients were correlated by using Reynolds number, Prandtl number, Schmidt number, capillary-buoyancy coefficient and air concentration.

ISSN:0098-6445    

DOI:10.1080/00986449308936194

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A theoretical analysis has been developed to study the effects of liquid subcooling and velocity on the film boiling heat transfer process from a horizontal cylinder to a binary liquid mixture of various concentrations in a porous medium. The governing equations are solved by means of similarity transformations. The resulting set of ordinary differential equations are numerically solved by the fourth-order Runge Kutta method combined with a shooting technique. Heat transfer results are obtained for a range of operating conditions.

ISSN:0098-6445    

DOI:10.1080/00986449308936195

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A neural network trained with responses to a step input in concentration for a vessel with various percentages of perfect mixing, short circuiting, and distance-velocity lag classifies accurately flow patterns that the program has not encountered previously. Flow responses digitized at a selected sequence of times were the inputs and the percentages of three modes of flow were the outputs for a commercial program for neural networking. Default values of the program worked quite well for the layout of the network and for the convergence error for training, and tweaking these values had little effect on training time or performance.

ISSN:0098-6445    

DOI:10.1080/00986449308936196

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Adsorption of nitrogen dioxide on activated carbon is found to be followed by reaction with the carbon surface at temperatures higher than 373 K. The dynamics of the nitrogen dioxide reaction with the carbon are measured gravimetrically over the temperature range 423-623 K. At small particle sizes (0.014 cm radius) the overall gasification kinetics are controlled by the surface reaction step, and are first order in nitrogen dioxide concentration. Using the random pore model to describe the evolution of reaction surface with porosity, the experimental data are fitted by a kinetic control gasification model, giving an activation energy of 86.2 kJ/mole.

ISSN:0098-6445    

DOI:10.1080/00986449308936197

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Critical loci of 1hexene/CO2and (hexene isomer pseudo-component)/CO2binary mixtures, along with the critical properties of the ternary mixture of CO2/l-hexene/(hexene isomer pseudo-component) were predicted using Gibbs' thermodynamic criteria for criticality in conjunction with the Peng-Robinson (P-R) EOS. Maximum deviation in the critical pressures of the l-hexene/CO2binary mixture is less than 2% from reported experimental values. The addition of hexene isomer to the l-hexene/CO2binary and the path of approach to mixture critical points are shown to have surprisingly strong effects on predicted mixture critical properties. For a given ternary mixture, multiple critical points are predicted depending upon the isopleth (either constant CO2mole fraction path or constant 1-hexene mole fraction path) along which the critical point is approached. Critical densities predicted along the CO2isopleth of approach to critical points are always smaller than the ones predicted along the 1-hexene isopleth of approach. Furthermore, upon hexene isomer addition to the l-hexene/CO2binary, whereas the predicted critical property surfaces of the ternary system vary monotonically along the CO2isopleth of approach, extrema in these surfaces are predicted when approaching the mixture critical points along 1-hexene isopleths. These anomalous predictions are attributed to the inability of the cubic EOS to accurately model the phase behavior near the critical point.

ISSN:0098-6445    

DOI:10.1080/00986449308936198

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor