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1
Content available A simple method of determination of the degree of gas mixing by numerical Laplace inversion and Maple®
Wójcik M., Szukiewicz M.
Bulletin of the Polish Academy of Sciences. Technical Sciences
|
2019
|
Vol. 67, nr 2
235--240
EN
This article presents a new efficient method of determining values of gas flow parameters (e.g. axial dispersion coefficient, DL and Pèclet number, Pe). A simple and very fast technique based on the pulse tracer response is proposed. It is a method which combines the benefits of a transfer function, numerical inversion of the Laplace transform and optimization allows estimation of missing coefficients. The study focuses on the simplicity and flexibility of the method. Calculations were performed with the use of the CAS-type program (Maple®). The correctness of the results obtained is confirmed by good agreement between the theory and experimental data for different pressures and temperature. The CAS-type program is very helpful both for mathematical manipulations as a symbolic computing environment (mathematical formulas of Laplace-domain model are rather sophisticated) and for numerical calculations. The method of investigations of gas flow motion is original. The method is competitive with earlier methods.
2
Content available Doświadczalne wyznaczanie współczynników dyspersji wzdłużnej w hybrydowym aparacie fluidyzacyjnym airlift
Prończuk M., Bizon K., Tabiś B.
Prace Naukowe Instytutu Inżynierii Chemicznej Polskiej Akademii Nauk
|
2018
|
nr 22
31--40
PL
W pracy przedstawiono wyniki badań dotyczących eksperymentalnego wyznaczania wartości liczby Pecleta dla wybranych stref hybrydowego fluidyzacyjnego aparatu airlift z zewnętrzną cyrkulacją cieczy. W tym celu przeprowadzono badania znacznikowe metodą bodziec-odpowiedź. Liczbę Pecleta wyznaczono przy użyciu metody momentów oraz algorytmu optymalizacyjnego sprzężonego z jednowymiarowym modelem dyspersyjnym.
EN
This paper presents the results of experimental research concerning determination of Peclet number for selected zones of a hybrid fluidized-bed airlift apparatus with external liquid circulation. For this aim, the tracer stimulus-response experiments were carried out. Peclet number was then determined using the method of moments and optimization algorithm coupled with the one-dimensional dispersion model.
3
Content available Modelling the gas flow in permeate channel in membrane gas separation process
Szwast M.
Chemical and Process Engineering
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2018
|
Vol. 39, nr 3
271–-280
EN
This paper analyses the real behaviour of the fluid in the channels of a three-end membrane module. The commonly accepted mathematical model of membrane separation of gas mixtures in such modules assumes a plug flow of fluid through the feed channel and perfect mixing in the permeate channel. This article discusses the admissibility of accepting such an assumption regarding the fluid behaviour in the permeate channel. Throughout analysis of the values of the Péclet number criterion, it has been demonstrated that in the industrial processes of membrane gas separation, the necessary conditions for the perfect mixing in the permeate channel are not met. Then, CFD simulations were performed in order to establish the real fluid behaviour in this channel. It was proved that in the permeate channel the fluid movement corresponds to the plug flow, with the concentration differences at both ends of the module being insignificant. In view of the observations made, the admissibility of concentration stability assumptions in the mathematical models for the permeate channel was discussed.
4
Content available remote Solidification of quasi-regular eutectic
Trempczyńska-Łent M.
Archives of Foundry Engineering
|
2007
|
Vol. 7, iss. 3
171-178
EN
The quasi-regular eutectics, one from the groups of the division, accomplished on the basis of the geometry of eutectic phase. The ledeburite eutectic is one from the most commercial eutectics of this group. In the case of rapid solidification, the foundation near which formulate the right growth eutectic they are. One of the measures separating the conditions of low solidification from the rapid one, can be the Peclet number Pe. Decide to observe solidification eutectic in relationship from the size of the Pe.
5
Content available remote Refined analysis of thermal effects for the hydrodynamic lubrication
Bhatt V. K.
International Journal of Applied Mechanics and Engineering
|
2002
|
Vol. 7, Spec. is
215-224
EN
The behavior of hydrodynamic Newtonian lubricant film at the die-workpiece interface in plane strain forging, when the conduction and convection mode of heat transfer is taking place has been theoretically investigated. A complete analysis of plane strain forging process for the case when die extends beyond the workpiece is developed. Viscous shear in the film, friction between the tool and the workpiece and the energy released by the plastic deformation, all contribute to rise in the temperature of the film. As a result, thermal gradient is established and heat transfer takes place, also the physical properties of the fluid is effected due to temperature and pressure rise. An attempt is made in the present work to develop a more sophisticated mathematical model using thermal Reynold's equation developed by Bhatt and Sengupta (1996) and analysis developed by Bhatt (2000). Further equation of plastic equilibrium is solved with appropriate boundary conditions. From this solution mean die pressure for plane strain forging process have been obtained. The variation in mean die pressure with reduction at different Peclet numbers has been investigated. On the basis of this analysis, it can be concluded that mean die pressure decreases with increase in Peclet number. Some basic conclusions have been drawn and suggestions are given for future to enhance the utility of the results of these investigations.
6
Content available remote Application of refined thermal Reynolds equation in the analysis of hydrodynamic lubrication of strip rolling
Bhatt V. K.
International Journal of Applied Mechanics and Engineering
|
2002
|
Vol. 7, no 4
1125-1139
EN
A refined thermal Reynolds equation considering conduction and convection modes of heat transfer across the film for inlet zone of the liquid lubricated strip rolling, developed by Bhatt and Sengupta, is applied in this analysis. It is known that inlet zone plays a dominant role in fixing the lubricant film thickness in the work zone. Hence, for the present analysis the effect of conduction and convection across the film in the inlet zone is studied on the work zone as well as the effect of variation of convection effect in the form of variation of the Peclet number. It is observed that the roll separating force and torque decrease with increasing the Peclet number.
7
Content available Measurement of liquid holdup and axial dispersion in trickle bed reactors using radiotracer technique
Pant H., Saroha A., Nigam K.
Nukleonika
|
2000
|
Vol. 45, nr 4
235-241
EN
The holdup and axial dispersion of aqueous phase has been measured in trickle bed reactors as a function of liquid and gas flow rates using radioisotope tracer technique. Experiments were carried out in a glass column of inner diameter 15.2´10-2 m column for air-water system using three different types of packings i.e. non-porous glass beads, porous catalysts of tablet and extrudate shape. The range of liquid and gas flow rates used were 8.3´10-5-3.3´10-4 m3/s and 0-6.67´10-4 m3/s, respectively. Residence time distributions of liquid phase were measured and mean residence times were determined. The values of liquid holdup were calculated from the measured mean residence times. It was observed that liquid holdup increased with increase in liquid flow rates and was independent of increase in gas flow rates used in the study. Two-parameter axial dispersion model was used to simulate measured residence time distribution data and values of mean residence time and Peclet number were obtained. It was observed that values of Peclet number increases with increase in liquid flow rate for glass beads and tablets and remains almost constant for extrudates. The values of mean residence time obtained from model simulation were found to be in good agreement with the values measured experimentally.
8
O dwóch zagadnieniach optymalizacyjnych w projektowaniu reaktorów rurowych
Tabiś B., Grzywacz R.
Inżynieria i Aparatura Chemiczna
|
2000
|
Nr 1
16-19
PL
Analizowano dwa popularne modele nieizotermicznych reaktorów rurowych, a mianowicie model z dyspersją wzdłużną i model przepływu tłokowego. Wykazano istnienie optymalnej wartości liczby Pecleta w politropowym reaktorze rurowym z dyspersją wzdłużną. Podjęcie analizy ekonomicznej prowadzi również do zagadnienia optymalnej temperatury surowca w reaktorze adiabatycznym o przepływie tłokowym nawet dla reakcji nieodwracalnych.
EN
Two common models of nonisothermal tubular reactors were analysed, i.e. the model with axial dispersion and the plug flow model. The existence of optimal values of the Peclet number in a polytropic tubular reactor with axial mixing was shown. Undertaking of the economic analysis leads also to the problem of optimal feed temperature in a plug flow reactor even for irreversible chemical reactions.
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