REPRESENTATION OF THE SPECIFIC SURFACE AREA OF A POROUS MEDIUM BY STATISTICAL CONTINUOUS MONOMIAL FUNCTIONS

2021 ◽  
Author(s):  
В.Г. ЖУКОВ ◽  
В.М. ЧЕСНОКОВ ◽  
Н.Д. ЛУКИН
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Food Systems ◽  
Transfer Processes ◽  
Pore Length ◽  
Mass Transfer Processes ◽  
Size Groups

Удельная поверхность пористых сред является важным геометрическим параметром в расчетах процессов пищевых систем и оборудования для их переработки. Расчетные формулы процессов тепло- и массообмена в настоящее время содержат осредненные значения геометрических параметров, получаемые в эксперименте. Использование формул удельной поверхности по осредненным характеристикам пористой среды существенно ограничивает точность и надежность расчетов. Получены непрерывные одночленные по всему диапазону размеров сообщающихся пор расчетные формулы удельной поверхности, основанные на функции распределения плотности вероятности размеров сообщающихся пор разных модельных конфигураций в полиразмерной дисперсной (несцепленной) и связной (сцепленной) пористых средах для двух видов исходных формул удельной поверхности, различных видов модельных поперечных сечений и длины пор. Проведен их сравнительный анализ. Установлено, что на расчет удельной поверхности влияет моделируемая длина пор. Вид поперечного сечения не влияет на расчет удельной поверхности. Полученные формулы позволяют вычислять удельную поверхность для ансамбля отдельных размерных групп пор и в целом для всей совокупности их размеров. Приведен пример расчета по полученным формулам. The specific surface area of porous media is an important parameter in the calculations of the processes of food systems and equipment. The calculated formulas of the heat and mass transfer processes currently contain the averaged values of the geometric parameters obtained in the experiment. The use of formulas the specific surface area based on the averaged characteristics of a porous medium significantly limits the accuracy and reliability of calculations. Continuous monomial calculated formulas for the specific surface and based on the function of the probability density of the size distribution open pores ware obtained. Their comparative analysis is carried out. It was found that the transverse shape is not reflected in the formulas for the specific surface area, but the simulated pore length does. The specific surface area formulas allow calculating the specific surface area for an ensemble of separate size groups of pores and, in general, for the entire set of their sizes. An example of calculation by the obtained formulas is given.

Direct molecular hydrogen sulphide scrubbing with hollow fibre membranes

2001 ◽  
Vol 44 (9) ◽  
pp. 135-142 ◽  
Author(s):  
N. Boucil ◽  
B. Jefferson ◽  
S.A. Parsons ◽  
S.J. Judd ◽  
R.M. Stuetz
Keyword(s):  
Mass Transfer ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Flow Rate ◽  
Hydrogen Sulphide ◽  
Gas Flow ◽  
Hollow Fibre ◽  
The Other ◽  
Gas Flow Rate

The emission of hydrogen sulphide is a major problem associated with anaerobic treatment of sulphate and sulphite containing wastewaters. Conventional absorbing processes, such as packed towers, spray towers or bubble columns, are all constrained by factors such as flooding and foaming. Membrane systems, on the other hand, enable independent control of the liquid and gas flow rate and a step change order of magnitude increase in the specific surface area of the contact process. The membrane acts as a gas absorber with a design similar to a shell and tube heat exchanger. On the other hand, they are limited by facets of the membrane such as its resistance to mass transfer and permselectivity, as well as its cost. The work presented in this paper refers to an absorption process based on a non-wetted hollow fibre membrane for the scrubbing of hydrogen sulphide from air, with water as the contact solvent. Results presented describe the performance of the unit in terms of overall transfer and outlet liquid concentration as a function of circulation regime, gas flow rate, liquid flow rate and specific surface area. In particular, results are presented using traditional plots of Sherwood number (Sh) against Graetz (Gr) number for the liquid flowing in the lumens, such that experimental and available empirical descriptions of the process performance are directly compared. Results suggest that, as expected, very efficient mass transfer is obtained. However, the mass transfer was found to reach a maximum value against Gr, contrary to available empirical models.

Mathematical Modeling of Biodiesel Production under Intense Agitation

2016 ◽  
Vol 14 (1) ◽  
pp. 445-451
Author(s):  
Aliakbar Roosta ◽  
Jafar Javanmardi ◽  
Elham Sadat Behineh
Keyword(s):  
Mass Transfer ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Rapeseed Oil ◽  
Catalyst Concentration ◽  
Biodiesel Production ◽  
Transfer Coefficients ◽  
Increasing Temperature ◽  
Intense Agitation

AbstractIn this study, a new approach is proposed to investigate the kinetics of sunflower oil and rapeseed oil transesterification in the presence of potassium hydroxide. Transesterification is a heterogeneous process which affected by a number of parameters, that are not readily available in the literature, such as mass transfer coefficients, partition coefficients, and specific surface area of the dispersed phase. However, under intense agitation condition, mass transfer restrictions may be neglected, and the two phases are supposed to remain in thermodynamic equilibrium, during the process. Therefore, a model was developed independent of the mass transfer coefficient and specific surface area, which is reliable for the intense agitation condition. According to the results, the model is valid at least for mixing rates over 500 rpm. The results of the model were used to study the effects of temperature, methanol-to-oil ratio, and catalyst concentration on the biodiesel conversion. Biodiesel production rate increases with increasing temperature, although rapeseed oil transesterification is more temperature dependent. The results show that the maximum amount of catalyst concentration is less than 1% (by weight); however, the optimum value depends on the operating temperature. The optimum value of the methanol-to-oil-ratio decreases with increasing temperature. Thus, at higher temperatures, less amount of methanol and catalyst are required, which leads to easier purification of biodiesel.

scholarly journals Numerical model of mass transfer processes using fractional derivatives

2019 ◽  
pp. 26-32
Author(s):  
Nazariy Lopuh
Keyword(s):  
Finite Element Method ◽  
Mass Transfer ◽  
Finite Element ◽  
Porous Medium ◽  
Numerical Model ◽  
Fractional Derivatives ◽  
Gas Filtration ◽  
Transfer Processes ◽  
Mass Transfer Processes ◽  
Derivative Order

The article describes the scheme of construction and application of finite element method using Grunwald-Letnikov algorithm. Obtained results make it possible to estimate influence of fractional derivative order in terms of time and space on process of gas filtration in porous medium. Numerical ecperification and analysis performed

scholarly journals Metal Foams as Novel Catalyst Support in Environmental Processes

Catalysts ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 587 ◽  
Author(s):  
Anna Gancarczyk ◽  
Katarzyna Sindera ◽  
Marzena Iwaniszyn ◽  
Marcin Piątek ◽  
Wojciech Macek ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Pressure Drop ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Mechanical Stability ◽  
Packed Bed ◽  
Metal Foams ◽  
High Porosity ◽  
Slow Kinetics

Metal foams are considered as promising catalyst carriers due to their high porosity, large specific surface area, and satisfactory thermal and mechanical stability. The study presents heat transfer and pressure drop experiments performed for seven foams of different pore densities made from diverse metals. Mass transfer characteristics are derived using the Chilton–Colburn analogy. It was found that the foams display much more intense heat/mass transfer than a monolith, comparable to packed bed. Next, the foams’ efficiencies have been compared, using 1D reactor modeling, in catalytic reactions displaying either slower (selective catalytic reduction of NOx) or faster kinetics (catalytic methane combustion). For the slow kinetics, the influence of carrier specific surface area at which catalyst can be deposited (i.e., catalyst amount) was decisive to achieve high process conversion and short reactor. For this case, monolith appears as the best choice assuming it’s the lowest pressure drop. For the fast reaction, the mass transfer becomes the limiting parameter, thus solid foams are the best solution.

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