scholarly journals МАТЕМАТИЧЕСКАЯ МОДЕЛЬ И МЕТОД РАСЧЕТА ДИНАМИКИ СУШКИ И ТЕРМОДЕСТРУКЦИИ БИОМАССЫ

2018 ◽  
Vol 82 (1) ◽  
Author(s):  
Наталья Николаевна Сороковая ◽  
Дмитрий Николаевич Коринчук
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Thermal Decomposition ◽  
Numerical Method ◽  
Heat And Mass Transfer ◽  
The Body ◽  
Physical Factors ◽  
Deformation Equation ◽  
The Mathematical Model ◽  
Kinetics Of

Разработана математическая модель и численный метод расчета динамики тепломассопереноса, фазовых превращений и усадки при сушке коллоидных капиллярно-пористых тел цилиндрической формы в условиях равномерного обдува теплоносителем. Математическая модель строилась на базе дифференциального уравнения переноса субстанции (энергии, массы, импульса) в деформируемых системах. Проведены экспериментальные исследования кинетики обезвоживания частиц энергетической вербы в потоке воздуха с целью верификации математической модели. Обоснована возможность ее использования для расчета совместных процессов сушки и начального этапа термического разложения биомассы. С использованием ранее полученных данных по значениям энергии активации Аэф(Т) для различных видов биомассы проведено математическое моделирование динамики и кинетики высокотемпературной сушки в потоке дымовых газов энергетической вербы, которая сопровождается термодеструкцией гемиоцеллюлозы. Результаты численных экспериментов свидетельствуют об адекватности предложенного подхода, эффективности математической модели и метода ее реализации. На их основе возможно проводить исследование динамики тепломассопереноса при сушке частиц различных видов измельченной биомассы; определение температуры начала и окончания первой стадии термического разложения; момента достижения равновесного влагосодержания в зависимости от свойств материала и сушильного агента. Эти данные позволяют выбирать оптимальные с точки зрения сохранения энергии и качества высушиваемого продукта  режимные параметры процесса.         A mathematical model and a numerical method for calculating the dynamics of heat and mass transfer, phase transformations and shrinkage during the drying of colloidal capillary-porous cylindrical bodies under conditions of equitable winding by a coolant are developed. The mathematical model was based on the differential equation of substance (energy, mass, impulse) transfer in deformable systems. It includes the equations diffusion-filtration transfer of energy for the system as a whole, and the mass transfer of the liquid, vapor and air phases in the pores of the body. Expressions for the intensity of evaporation of a liquid, capillary pressure, and the diffusion coefficients are presented. The relative volume strain was found by means of an analytical solution of the thermoconcentration deformation equation. Based on the explicit three-layer counting difference scheme and the procedure splitting of algorithm  by physical factors, a numerical method for realizing this mathematical model is developed.Experimental studies of the kinetics of dehydration of energy willow particles in the airflow were carried out to verify the mathematical model. Its applicability for calculating combined processes of drying and of the initial stage of thermal decomposition of biomass is substantiated. Using the previously obtained data on the activation energy values for various types of biomass, a mathematical simulation of the dynamics and kinetics of high-temperature drying in the flue gas flow of energy willow was carried out, which is accompanied by thermal destruction of hemiocellulose. The results of numerical experiments indicate the adequacy of the proposed approach, the effectiveness of the mathematical model and the method of its implementation. On their basis, it is possible to study the dynamics of heat and mass transfer when drying particles of different types of ground biomass; determination of the temperature of the beginning and ending of the first stage of thermal decomposition; the moment when the equilibrium moisture content is reached, depending on the properties of the material and the drying agent. These data allow choosing the process parameters that are optimal in terms of energy saving and quality of the dried product.

Numerical Analysis of Heat and Mass Transfer Performance of the Packed-Type Parallel Flow Dehumidifier

2014 ◽  
Vol 989-994 ◽  
pp. 3100-3104
Author(s):  
Rui Hang Zhang ◽  
Zi Ye Wang ◽  
Run Ping Niu
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Parallel Flow ◽  
Transfer Performance ◽  
Transfer Coefficients ◽  
Simulation Results ◽  
Set Up ◽  
The Impact ◽  
The Mathematical Model

TA mathematical model describing heat and mass transfer performance of packed-type parallel flow dehumidifier was set up. The numerical solution of differential equations was derived. Taking the heat and mass transfer coefficients obtained by experiments as the input parameters of the model, the impact of solution inlet parameters on outlet parameter of air was described. The simulation results indicated that the mathematical model could be used to predict the performance of liquid dehumidification. The results showed that the mathematical model can be of great value in the design and improvement of dehumidifier.

scholarly journals Numerical and experimental investigation of heat and mass transfer within bio-based material

2019 ◽  
Vol 23 (1) ◽  
pp. 23-31 ◽  
Author(s):  
Mounir Asli ◽  
Frank Brachelet ◽  
Alexis Chauchois ◽  
Emmanuel Antczak ◽  
Didier Defer
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Water Vapour ◽  
Test Facility ◽  
Good Prediction ◽  
Vapour Permeability ◽  
Hygroscopic Properties ◽  
Good Concordance ◽  
The Mathematical Model

In this paper, the coupled heat and mass transfer within porous media has been studies. First, the studied materials have been characterized experimentally and than evaluated their thermal properties, namely thermal conductivity and specific heat in different states (dry-wet). The hygroscopic properties, namely water vapour permeability, water vapour sorption. At second time, we present and validate the mathematical model describing heat and mass transfer within bio-based materials, by the confrontation with the experimental results. The materials properties obtained from the characterisation part are used as model?s input parameters. Moreover, a test facility is mounted in the laboratory in order to compare the numerical and experimental data. The founded results show a good concordance between the simulated and measured data. According to this results the mathematical model of Philip and de Vries gives a good prediction of hygrothermal behaviour of bio-based material. This model will allow us to save money and time of the experimental part in the future.

scholarly journals The Mathematical Model and Numerical Study of Heat and Mass Transfer Processes in the Combustion Chamber of Diesel-Generator Units with a Valve-Inductor Generator

2020 ◽  
pp. 611-625
Author(s):  
Dmitriy V. Guzei ◽  
Andrey V. Minakov ◽  
Vasiliy I. Panteleev ◽  
Maksim I. Pryazhnikov ◽  
Dmitriy V. Platonov ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Combustion Chamber ◽  
Heat And Mass Transfer ◽  
Operating Conditions ◽  
Diesel Generator ◽  
Transfer Processes ◽  
Mass Transfer Processes ◽  
Actual Geometry ◽  
The Mathematical Model

The mathematical model of heat and mass transfer processes in the combustion chamber of diesel generator units with valve inductor generators has been developed. The mathematical model takes into account the actual geometry of the combustion chamber and the operating conditions of the diesel engine. A study of the main characteristics of a diesel generator in a wide range of modes of operation has been carried out. In addition to energy characteristics, environmental parameters have been considered

Numerical Modeling of Wet Cooling Towers—Part 1: Mathematical and Physical Models

1983 ◽  
Vol 105 (4) ◽  
pp. 728-735 ◽  
Author(s):  
A. K. Majumdar ◽  
A. K. Singhal ◽  
D. B. Spalding
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Water Temperature ◽  
Heat And Mass Transfer ◽  
Computer Code ◽  
Hot Water ◽  
Physical Models ◽  
Cooling Towers ◽  
Transfer Rates ◽  
The Mathematical Model

The paper discusses the limitations of current practices of evaluating thermal performance of wet cooling towers and describes a more advanced mathematical model for mechanical and natural draft cooling towers. The mathematical model computes the two-dimensional distributions of: air velocity (two components); temperature, pressure, and moisture content; and water temperature. The downward direction of water flow is presumed. The local interphase heat and mass transfer rates are calculated from empirical correlations for which two options are provided. In the first option, only one constant (Ka, based on Merkel’s approximations) is employed; in the second option, two separate constants for heat and mass transfer are used. Boundary conditions can be either of the prescribed cooling range or of the prescribed hot water temperature types. The governing equations are solved by a finite difference method. The model is embodied into a computer code (VERA2D) which is applicable for the natural and mechanical draft towers of both the crossflow and counterflow arrangements. Several applications of the code are described in Part II of the paper.

scholarly journals ANALYSIS METHOD OF CALCULATION PARAMETERS OF HEAT AND MASS TRANSFER PROCESSES IN THE STIRLING ENGINE

2017 ◽  
Vol 3 ◽  
pp. 298
Author(s):  
Sergej Semyonov ◽  
Sergej Tikhonov ◽  
Mihail Donchenko ◽  
Jurij Lukyanov ◽  
Andrej Perminov
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Analysis Method ◽  
Calculation Methods ◽  
Method Of Calculation ◽  
Transfer Processes ◽  
Mass Transfer Processes ◽  
The Mathematical Model ◽  
Optimal Calculation

The article highlights the optimal calculation methods for determining the parameters of heat and mass transfer processes occurring in the rotary-vane engine with an external supply of heat. It is shown that the mathematical model of working processes must consist of two parts. One part describes the processes occurring in the isolated volume. The second part describes the processes of mass exchange between the working chambers of two modules, as well as a heater or a cooler.

scholarly journals The Mathematical Model of Hydrodynamics and Heat and Mass Transfer at Formation of Steel Ingots and Castings

2015 ◽  
Vol 15 (1) ◽  
pp. 13-16 ◽  
Author(s):  
V.I. Bondarenko ◽  
V.V. Bilousov ◽  
F.V. Nedopekin ◽  
J.I. Shalapko
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Expert System ◽  
Heat And Mass Transfer ◽  
Computational Algorithm ◽  
Transfer Processes ◽  
Mass Transfer Processes ◽  
Steel Ingots ◽  
The Mathematical Model

Abstract The generic mathematical model and computational algorithm considering hydrodynamics, heat and mass transfer processes during casting and forming steel ingots and castings are offered. Usage domains for turbulent, convective and non-convective models are determined depending on ingot geometry and thermal overheating of the poured melt. The expert system is developed, enabling to choose a mathematical model depending on the physical statement of a problem.

scholarly journals Modelling of Coupled Heat and Mass Transfer in a Water-Cooled Falling-Film Absorber Working with an Aqueous Alkaline Nitrate Solution

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1804
Author(s):  
María E. Álvarez ◽  
Mahmoud Bourouis
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Theoretical Model ◽  
Flow Regime ◽  
Heat And Mass Transfer ◽  
Nitrate Solution ◽  
Droplet Formation ◽  
Solution Temperature ◽  
Falling Film ◽  
The Mathematical Model

A theoretical model was developed to investigate a falling-film absorber on horizontal tubes with an aqueous alkaline nitrate solution as working fluid. The absorbent, composed of an aqueous solution of nitrates (Li, K, Na) in salt mass percentages of 53%, 28%, and 19% respectively, offers favourable thermal stability, corrosiveness, and heat and mass transfer conditions which can be appropriate for absorption cooling cycles driven by high-temperature heat sources. The mathematical model developed characterises the heat and mass transfer processes and the flow regime effect (droplet-formation, droplet-fall, and falling-film) on the falling-film absorber. The results show the importance of the falling-film and droplet-formation flow regimes in the absorption process. The solution temperature and concentration profiles inside the absorber were established together with their values at the exit. The results obtained by the theoretical model were well in agreement with the experimental data obtained by the authors in a previous study. Deviations in predicting the solution and cooling water temperatures at the absorber exit were around 1 °C and for the concentration of the solution leaving the absorber, around 0.49%. The mathematical model also predicts the absorption rate at 4.7 g·m−2·s−1 for the absorber design and operating conditions used in the present work. This value is 22% higher than the experimental value obtained by the authors in their previous experimental work. The deviation is attributed to approximations incorporated into the model, especially as regards surface wettability and calculation of the mass transfer coefficients for each flow regime.

Modeling and Numerical Simulation of Dehumidifier Using LiCl Solution as the Liquid Desiccant

2011 ◽  
Vol 383-390 ◽  
pp. 6568-6573 ◽  
Author(s):  
Run Ping Niu
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Parameter Distribution ◽  
Liquid Desiccant ◽  
Transfer Coefficients ◽  
Data Simulation ◽  
Simulation Results ◽  
Set Up ◽  
The Mathematical Model

The performance of air dehumidifier using LiCl solution as the Liquid desiccant was studied with numerical methods. A mathematical model describing heat and mass transfer performance of air dehumidifierwas set up. The numerical solution of differential equations were derived. Taking the heat and mass transfer coefficients obtained by experiments as the input parameters of the model，the parameter distribution of air and solution was described. The simulation results corresponds very well to experimental data. Simulation results indicated that the mathematical model could be used to predict the performance of air dehumidifier. The results showed that the mathematical model can be of great value in the design and improvement of air dehumidifier.

scholarly journals Modeling of kinetics of drying process of polycaproamide granules considering its sorption properties

2018 ◽  
Author(s):  
Marina Sergeevna Maklusova ◽  
Maria Konstantinovna Kosheleva ◽  
Olga Roaldovna Dornyak
Keyword(s):  
Mathematical Modeling ◽  
Mathematical Model ◽  
Mass Transfer ◽  
Moisture Content ◽  
Gas Phase ◽  
Heat And Mass Transfer ◽  
Sorption Properties ◽  
Convective Drying ◽  
Drying Process ◽  
Kinetics Of

The object of research is a fiber-forming polymer - polycaproamide. The process of drying of polycaproamide granules, after aqueous extraction of low-molecular compounds from them, is an important stage of producing of polyamide fiber nylon and largely determines the quality of the target product. To obtain a high-quality fiber, the drying of the granules should provide a sufficiently high degree of its dehydration. The average final moisture content of the material should be no more than 0.1%. With a low moisture content, the drying process slows down, so the calculation of the kinetics of dewatering of granules can not be carried out using a constant effective mass-transfer coefficient (moisture diffusion). In this paper we present a calculation technique for determining two local parameters of mass transfer: the water diffusion coefficient in polycaproamide (as a liquid) and the so-called criterion for phase transitions, which depend on the moisture content of the material and are determined by its sorption properties. The report presents the results of numerical calculations illustrating the development of two-dimensional fields of moisture content, temperature, pressure and vapor concentration in the vapor-gas phase for cylindrical granules in convective drying. To describe the processes of heat and mass transfer during the drying of granules, a nonstationary nonlinear 2D model is used that includes transport equations averaged over the microvolume of the material: the liquid phase transfer equation; heat equation; equation for vapor-gas phase pressure; equation for the concentration of the vapor component. The nonstationary nonlinear conjugate mathematical model is studied numerically. A feature of the presented model is the possibility of an analytical calculation of the local mass transfer coefficients of a liquid, taking into account the sorption properties of the material, the permeability coefficient and the local values ​​of humidity and temperature. Determination of the local coefficients of moisture transfer is carried out on the basis of the formulas obtained in the analysis of a more general mathematical model of heat and mass transfer carried out based on the mechanics of multiphase systems developed in the works of R.I. Nigmatulin, and S. Whitaker. The structure of the samples was investigated by three independent methods in order to obtain the most complete idea of ​​it and to compare the obtained characteristics. The isotherms of the sorption of polycaproamide were obtained experimentally on a vacuum sorption plant with Mac-Ben-Bakr weights. Comparison of the results of mathematical modeling of heat and mass transfer in the granule and data of the laboratory experiment on the kinetics of polycaproamide granule drying showed good agreement between the calculated and experimental data. The constructed mathematical model allows to form energy-efficient resource-saving regimes for drying granules of polycaproamide.Keywords: convective drying, mathematical modeling, polycaproamide.

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