scholarly journals Revisiting the Role of Mass and Heat Transfer in Gas–Solid Catalytic Reactions

Processes ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 1599
Author(s):  
Riccardo Tesser ◽  
Elio Santacesaria
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Kinetic Studies ◽  
Packed Bed ◽  
Catalytic Reactions ◽  
Catalytic Reactors ◽  
Tremendous Progress ◽  
Mass And Heat Transfer ◽  
Energy Balances

The tremendous progress in the computing power of modern computers has in the last 20 years favored the use of numerical methods for solving complex problems in the field of chemical kinetics and of reactor simulations considering also the effect of mass and heat transfer. Many classical textbooks dealing with the topic have, therefore, become quite obsolete. The present work is a review of the role that heat and mass transfer have in the kinetic studies of gas–solid catalytic reactions. The scope was to collect in a relatively short document the necessary knowledge for a correct simulation of gas–solid catalytic reactors. The first part of the review deals with the most reliable approach to the description of the heat and mass transfer outside and inside a single catalytic particle. Some different examples of calculations allow for an easier understanding of the described methods. The second part of the review is related to the heat and mass transfer in packed bed reactors, considering the macroscopic gradients that derive from the solution of mass and energy balances on the whole reactor. Moreover, in this second part, some examples of calculations, applied to chemical reactions of industrial interest, are reported for a better understanding of the systems studied.

scholarly journals Rivlin-Ericksen Fluid in Tube of Varying Cross-section with Mass and Heat Transfer

2002 ◽  
Vol 57 (11) ◽  
pp. 863-873 ◽  
Author(s):  
Nabil T. El Dabe ◽  
Galal M. Moatimid ◽  
Hoda S. M. Ali
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Cross Section ◽  
Perturbation Technique ◽  
Equations Of Motion ◽  
Steady Motion ◽  
Physical Parameters ◽  
Mass And Heat Transfer

In this paper, the problem of heat and mass transfer due to the steady motion of a Rivlin- Ericksen fluid in tubes of varying cross-section is considered. Suction at tube walls is taken into account. Under the assumption that the deformations of the boundaries are small, the equations of motion have been solved by using a perturbation technique. The temperature and concentration distributions are obtained. The effects of various physical parameters are discussed. The Nusselt and Sherwood numbers are obtained. A set of figures for a quantitative illustration is presented.

Changed Heat and Mass Transfer Evaluation of a Gas-to-Gas Type Membrane Humidifier by Mass Collection

2010 ◽  
Author(s):  
ByungJun Kim ◽  
SangSeok Yu ◽  
YoungDuk Lee ◽  
KookYoung Ahn
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Steady State ◽  
Heat And Mass Transfer ◽  
Humidity Sensor ◽  
Transient State ◽  
Air Flow Rate ◽  
Dry Air ◽  
Mass And Heat Transfer ◽  
Mass Collection

In this paper, a technique of the humidity measurement is developed to identify the performance of membrane humidifier. The technique is designed to measure the performance of membrane humidifier during steady state and transient state. In particular, the measurement technique is very useful to understand dynamic behavior of humidifier because the response of commercial humidity sensor is too slow to capture the transient response of mass and heat transfer through the membrane. Accordingly, the heat and mass transfer characteristics of membrane humidifier are figured out with the experimental analysis. The parameters used in experiment are dry air pressure, humid air temperature and dry air flow rate.

scholarly journals Twente mass and heat transfer water tunnel: Temperature controlled turbulent multiphase channel flow with heat and mass transfer

2019 ◽  
Vol 90 (7) ◽  
pp. 075117
Author(s):  
Biljana Gvozdić ◽  
On-Yu Dung ◽  
Dennis P. M. van Gils ◽  
Gert-Wim H. Bruggert ◽  
Elise Alméras ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Channel Flow ◽  
Water Tunnel ◽  
Mass And Heat Transfer ◽  
Temperature Controlled

The Catalytic Hydrogenation of Aromatic Nitro Ketone in a Microreactor: Reactor Performance and Kinetic Studies

2009 ◽  
Vol 6 (1) ◽  
Author(s):  
Sunitha Tadepalli ◽  
Adeniyi Lawal
Keyword(s):  
Heat Transfer ◽  
Catalytic Hydrogenation ◽  
Kinetic Studies ◽  
Theoretical Models ◽  
Packed Bed ◽  
Rate Equations ◽  
Batch Reactors ◽  
Reactor Performance ◽  
Mass And Heat Transfer ◽  
Aromatic Nitro

Catalytic hydrogenation of nitro aromatics is an important class of reactions in the pharmaceutical and fine chemical industries. These reactions are extremely fast and highly exothermic in nature; hence, mass and heat transfer limitations play an important role when these reactions are conducted in conventional batch reactors. The use of a micro-channel reactor for such reactions provides improved mass transfer rates which may ensure that the reaction operates close to intrinsic kinetics. In the present study, the hydrogenation of a model aromatic nitro ketone was conducted in a packed-bed microreactor. The effects of different processing conditions were studied using 5%Pd/Alumina catalyst, viz.: hydrogen pressure, substrate concentration, temperature, and residence time on the conversion of substrate, Space Time Yield (STY), and selectivity of product. Internal and external mass and heat transfer limitations in the microreactor were examined. The kinetic study was undertaken in a differential reactor mode, keeping the conversion of the reactant at less than 10%. The overall reaction was treated as comprising two separate reactions: first, the reduction of the nitro compound to hydroxylamine and then, the reduction of the hydroxylamine to amine. Two rate equations for the two consecutive reactions assuming the Langmuir-Hinshelwood mechanism provided the best fit to the experimental data. These two rate equations predicted the experimental rates satisfactorily and the differences were within 10% error. Experiments were also carried out in an integral reactor, and the reactor performance data were found to be in agreement with the predictions of the theoretical models.

Mass and Heat Transfer in Multi-Pulverizing RPB

2011 ◽  
Vol 396-398 ◽  
pp. 311-314
Author(s):  
Hai Hui Chen ◽  
Xu Guang Min
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Transfer Coefficient ◽  
Packed Bed ◽  
Experimental Models ◽  
Transfer Model ◽  
Axial Fan ◽  
Transfer Property ◽  
Rotating Packed Bed ◽  
Mass And Heat Transfer

New typical cross-flow Rotating Packed Bed (RPB) called multi-pulverizing RPB was manufactured. Mass and heat transfer property of the new type PRB were studied by two experimental models. In the mass transfer model, the axial fan pumping gas press is only 100 Pa, mass transfer coefficient is similar to countercurrent RPB. In the heat transfer experiment, the axial fan pumping gas press is only 120 Pa; volumetric heat transfer coefficient is from 75 kW.m-3. K-1 to 100 kW.m-3. K-1.

Hybrid Modeling of Modified Mathematical Model for Gas Phase Olefine in Fluidized Bed Catalyst Reactors Using Artificial Neural Networks

2009 ◽  
Vol 4 (1) ◽  
Author(s):  
Ahmmed Saadi Ibrehem
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Fluidized Bed ◽  
Hybrid Model ◽  
Operating Conditions ◽  
Transfer Coefficients ◽  
Mass And Heat Transfer ◽  
Artificial Neural

The complex flow patterns induced in fluidized bed catalytic reactors and the competing parameters affecting the mass and heat transfer characteristics makes the design of such reactors a challenging task to accomplish. The models of such a process rely heavily on predictive empirical correlations for mass and heat transfer coefficients. Unfortunately, published empirical based correlations have the common shortcoming of low-prediction efficiency compared with experimental data. In this work, an artificial neural network approach is used to capture the reactor characteristics in terms of heat and mass transfer based on published experimental data. The developed ANN-based heat and mass transfer coefficients relations were used in a conventional FCR model and simulated under industrial operating conditions. The hybrid model predictions of the melt-flow index and the emulsion temperature were compared to industrial measurements as well as published models. The predictive quality of the hybrid model was superior to other models. This modeling approach can be used as an alternative to conventional modeling methods.

scholarly journals Electrohydrodynamic Interfacial Stability Conditions in the Presence of Heat and Mass Transfer and Oblique Electric Fields

1999 ◽  
Vol 54 (8-9) ◽  
pp. 470-476
Author(s):  
Mohamed Fahmy El-Sayed
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Electric Field ◽  
Heat And Mass Transfer ◽  
Electric Fields ◽  
Stability Criterion ◽  
Dielectric Constants ◽  
Interfacial Stability ◽  
Mass And Heat Transfer ◽  
The Stability

A novel mathematical formulation to deal with interfacial stability problems of the Kelvin-Helmholtz type with heat and mass transfer in the presence of oblique electric fields is presented. The perturbed system is composed of two homogeneous, inviscid, incompressible, dielectric, and streaming fluids sep-arated by a horizontal interface, and bounded by two rigid planes. The effect of a phase transition on the instability is considered, and the linear dispersion relations are obtained and discussed. It is found that the electric field has a major effect and can be chosen to stabilize or destabilize the flow. For Ray-leigh-Taylor instability problems of a liquid-vapor system it is found that the effect of mass and heat transfer enhances the stability of the system when the vapor is hotter than the liquid, although the clas-sical stability criterion is still valid. For Kelvin-Helmholtz instability problems, however, the classical stability criterion is found to be substantially modified due to the effects of the electric field, mass and heat transfer. A new stability condition relating the magnitude and orientation of the electric field and the dielectric constants is obtained. Oblique electric fields are found to have stabilizing effects which are reduced by the normal components of the electric fields. The effects of orientation of the electric fields and fluid depths on the stability configuration are also discussed.

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