scholarly journals Development of Nonlinear Analytical Models for the Study of Heat/Mass Transfer Properties in the Drying of Porous Type Fabric

2012 ◽  
Vol 326-328 ◽  
pp. 593-598
Author(s):  
Ralph W.L. Ip ◽  
Elvis Iok Cheong Wan
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Moisture Diffusion ◽  
Analytical Models ◽  
Model Parameters ◽  
Drying Process ◽  
Drying Characteristics ◽  
Experimental Findings ◽  
Transfer Properties ◽  
Describe Heat Transfer

Designing a drying process for porous type fabrics using traditional linear heat transfer models may be inefficiency because the drying characteristics in the process are usually nonlinear. Using nonlinear approaches to describe the heat/mass flow could be better for many industrial application cases. The paper as presented here is a study for an analytical model using differential form nonlinear equations to describe heat transfer and moisture diffusion process using air as the processing medium. Experimental findings were used to evaluate the performance of the studied model. Relationships between the model parameters and fabric physical properties were determined for further used in the design of drying equipment.

scholarly journals Estimation of the Biot Number Using Genetic Algorithms: Application for the Drying Process

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2822 ◽  
Author(s):  
Krzysztof Górnicki ◽  
Radosław Winiczenko ◽  
Agnieszka Kaleta
Keyword(s):  
Mass Transfer ◽  
Biot Number ◽  
Moisture Diffusion ◽  
Absolute Error ◽  
Heat Fluxes ◽  
Coefficient Of Determination ◽  
Drying Process ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Multi Objective Genetic Algorithm

The Biot number informs researchers about the controlling mechanisms employed for heat or mass transfer during the considered process. The mass transfer coefficients (and heat transfer coefficients) are usually determined experimentally based on direct measurements of mass (heat) fluxes or correlation equations. This paper presents the method of Biot number estimation. For estimation of the Biot number in the drying process, the multi-objective genetic algorithm (MOGA) was developed. The simultaneous minimization of mean absolute error (MAE) and root mean square error (RMSE) and the maximization of the coefficient of determination R2 between the drying model and experimental data were considered. The Biot number can be calculated from the following equations: Bi = 0.8193exp(-6.4951T−1) (and moisture diffusion coefficient from D/s2 = 0.00704exp(-2.54T−1)) (RMSE = 0.0672, MAE = 0.0535, R2 = 0.98) or Bi = 1/0.1746log(1193847T) (D/s2 = 0.0075exp(-6T−1)) (RMSE = 0.0757, MAE = 0.0604, R2 = 0.98). The conducted validation gave good results.

A simulation tool for mass transfer inside compressed air vessel for water networks pressurisation

2019 ◽  
Author(s):  
Andrea Volpi ◽  
Eleonora Bottani
Keyword(s):  
Mass Transfer ◽  
Water Distribution ◽  
Water Distribution Network ◽  
Analytical Models ◽  
Model Parameters ◽  
Cyclic Loading And Unloading ◽  
Level Measurement ◽  
Controlling System ◽  
Mass Transfer Phenomenon ◽  
Reliable Solution

Feeding a water distribution network with the correct pressure is a fundamental requirement for its proper operation; to this end, a simple and reliable solution commonly adopted in small and medium industrial plants is the adoption of a pressure vessel. For small systems, a membrane seals the system water from the gas compartment, anyway, as the size of the vessel increases, the adoption of sealing diaphragm or bladder is no longer feasible, and thus there is a direct contact between air and water. The high pressure of the vessel, combined with the cyclic loading and unloading phases, which replace the water inside the tank, leads to a considerable mass transfer phenomenon of air inside water. The loss of air mass cannot be monitored and detected by simply controlling system pressures; to this extent, water level measurement and reference analytical models are required. Since there is a lack in scientific literature of these models, the present study presents a model for mass transfer estimate in the systems described, starting from a real pilot plant. The main results of the model implementation in a spreadsheet, in terms of the trend of the key model parameters in time, are also reported and discussed.

Analytical Simulation of Annular Two-Phase Flow Considering the Four Involved Mass Transfers

2012 ◽  
Vol 134 (8) ◽  
Author(s):  
Zahra Baniamerian ◽  
Ramin Mehdipour ◽  
Cyrus Aghanajafi
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Fluid Flow ◽  
Analytical Model ◽  
Two Phase Flow ◽  
Experimental Models ◽  
Analytical Models ◽  
Phase Flow ◽  
Two Phase Flows ◽  
Two Phase

Efficiently employing two-phase flows for cooling objectives requires comprehensive knowledge of their behavior in different conditions. Models, capable of predicting heat transfer and fluid flow trends in this area, are of great value. Numerical/analytical models in the literature are one-dimensional models involving with many simplifying assumptions. These assumptions in most cases include neglecting some mechanisms of mass transfer in two-phase flows. This study is devoted to developing an analytical two-dimensional model for simulation of fluid flow and mass transfer in two-phase flows considering the all mass transfer mechanisms (entrainment, evaporation, deposition and condensation). The correlation employed for modeling entrainment in this study, is a semiempirical correlation derived based on physical concept of entrainment phenomenon. Emphasis is put on the annular flow pattern of liquid vapor two-phase flow since this regime is the last encountered two-phase regime and has a higher heat transfer coefficient among other two-phase flow patterns. Attempts are made to employ the least possible simplification assumptions and empirical correlations in the modeling procedure. The model is then verified with experimental models of Shanawany et al., Stevanovic et al. and analytical model of Qu and Mudawar. It will be shown, considering pressure variations in both radial and axial directions along with applying our semiempirical entrainment correlation has improved the present analytical model accuracy in comparison with the accuracy of available analytical models.

A Model for Eddy Conductivity and Turbulent Prandtl Number

1973 ◽  
Vol 95 (2) ◽  
pp. 227-234 ◽  
Author(s):  
T. Cebeci
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Prandtl Number ◽  
Turbulent Flows ◽  
Pressure Gradients ◽  
Turbulent Prandtl Number ◽  
Temperature Distributions ◽  
Type Flow ◽  
Prandtl Numbers ◽  
Experimental Findings

This paper presents a model for eddy conductivity and turbulent Prandtl number based on the considerations of a Stokes-type flow. The expressions obtained by the model provide continuous velocity and temperature distributions for turbulent flows and are applicable to flows with pressure gradients, mass transfer, and heat transfer. Close to the wall the turbulent Prandtl number appears to be strongly affected by the molecular Prandtl number; away from the wall it is constant, that is, it is independent of the molecular Prandtl number. Calculated results agree well with experiments, including those with fluids having both low and high Prandtl numbers. In addition the results confirm recent experimental findings, in that the mass transfer has no effect on turbulent Prandtl number.

Drying Characteristics of Several Agricultural Product: Effect of Drying Temperature

2013 ◽  
Vol 465-466 ◽  
pp. 472-479
Author(s):  
Mohd Nazif Farhan ◽  
Mohd Faizal Mohideen Batcha ◽  
Sulastri Sabudin
Keyword(s):  
Mass Transfer ◽  
Inner Core ◽  
Particle Surface ◽  
Agricultural Product ◽  
Drying Process ◽  
Moisture Migration ◽  
Drying Characteristics ◽  
Surface Moisture ◽  
Simultaneous Heat ◽  
Product Effect

Drying is essentially a process of simultaneous heat and mass transfer, in general, to remove moisture from a wet material to give a long shelf-life or to facilitate further processing. The drying medium flowing around the material serves to remove the moisture. In most drying operations, water is the liquid evaporated using air as the drying medium [. For each individual particle, the drying process involves moisture migration from the inner core regions to the particle surface. The surface moisture is then vaporized or evaporated into the drying medium.

scholarly journals Study of the drying kinetics and calculation of mass transfer properties in hot air drying of Cynara cardunculus

2020 ◽  
Vol 5 (1) ◽  
pp. 740-750
Author(s):  
Raquel P. F. Guiné ◽  
Maria João Lima
Keyword(s):  
Mass Transfer ◽  
Thin Layer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Moisture Diffusion ◽  
Equation Model ◽  
Convective Drying ◽  
Cynara Cardunculus ◽  
Thin Layer Drying ◽  
Transfer Properties

AbstractIn the present work, mass transfer properties of thistle flower (Cynara cardunculus L.) were evaluated for the convective drying carried out at temperatures between 35 and 65°C, with an air flow of 0.5 m/s. The calculations followed two different algorithms, based on mathematical models derived from the thin layer drying equation and Fick’s second law of diffusion. The results obtained indicated that different methodologies resulted in different values of mass transfer properties, which is an alert that care must be taken when choosing which calculation method might be more appropriate in a specific practical application. In all cases, the values of moisture diffusion and mass transfer coefficient were found to increase with increasing operating temperature. The values of diffusivity increased from 2.7866 × 10−9 to 1.4027 × 10−8 m2/s for the thin layer model-based algorithm and from 1.9256 × 10−10 to 1.2033 × 10−9 m2/s for Fick’s equation model. The values of the mass transfer coefficient increased from 8.4335 × 10−8 to 8.4400 × 10−7 m/s and from 5.8277 × 10−9 to 7.2398 × 10−8 m/s, respectively, for the thin layer and Fick’s law-based models.

scholarly journals Features of heat and mass transfer at drying of ceramic products with overglaze paints

2021 ◽  
pp. 7-12
Author(s):  
O.M. Nedbailo ◽  
O.G. Chernyshyn
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Flux ◽  
Heat And Mass Transfer ◽  
Heat Flux Density ◽  
Heat Dissipation ◽  
Mass Transfer Process ◽  
Drying Process ◽  
Air Velocity ◽  
The Heat Transfer Coefficient

The basic results of researches of process of a heat exchange are instanced and parsed at drying glasour ceramic colors. Character of change of importance number of Rebinder is established at drying colors and dependence of intensity of a heat dissipation on velocity of air is spotted. The main results of researches of heat and mass transfer process at drying of overglaze ceramic paints in a stream of drying agent are resulted and analyzed. The nature of the change in the value of the Rebinder number for drying paints is established and the dependence of the heat transfer intensity on the air velocity is determined. Analysis of the temperature coefficient of drying and Rebinder's number determined the directions of heat consumption in the drying process of overglaze ceramic paints. It is established that the heat flux density depends on the temperature and velocity of the coolant and does not depend on the chemical composition of the paints. It is shown that the heat transfer coefficient depends on the velocity of the coolant. Compared with heat transfer during laminar flow around the plate during drying, the intensity of heat transfer increases by 75%.

scholarly journals Dynamics of convective hot air drying of filiform Lagenaria siceraria

2013 ◽  
Vol 19 (4) ◽  
pp. 485-492 ◽  
Author(s):  
Aishi Zhu ◽  
Kai Xia
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer Coefficient ◽  
Lagenaria Siceraria ◽  
Drying Process ◽  
Air Velocity ◽  
Drying Temperature ◽  
Hot Air

In this study, a laboratory convective hot air dryer was used for the thin-layer drying of filiform Lagenaria siceraria and the influences of the drying temperature and air velocity on the drying process were investigated. The drying temperature and the air velocity were varied in the range of 60-80?C and 0.6-1.04 m?s-1, respectively. The experimental data of moisture ratio of filiform Lagenaria siceraria were used to fit the mathematical models, and the dynamics parameters such as convective heat transfer coefficient ? and mass transfer coefficient kH were calculated. The results showed that the drying temperature and air velocity influenced the drying process significantly. The Logarithmic model showed the best fit to experimental drying data. It was also found that, the air velocity and the drying temperature influence notable on both of the convective heat transfer coefficient ? and the mass transfer coefficient kH. With the increase of hot air velocity from 0.423 to 1.120 ms-1, the values of ? varied from 111.3 to 157.7 W?m-2?K-1, the values of kH varied from 13.12 to 18.58 g?m-2? s-1??H-1. With the increase of air temperature from 60 to 80?C, the values of ? varied between 150.2 and 156.9 W?m-2?K-1, the values of kH varied between 18.26 and 18.75 g?m-2?s-1??H-1.

scholarly journals Drying kinetics and mass transfer properties in the drying of thistle flower

2019 ◽  
Vol 22 ◽  
Author(s):  
Raquel P. F. Guiné ◽  
Luísa Fontes ◽  
Maria João Reis Lima
Keyword(s):  
Mass Transfer ◽  
Effective Diffusivity ◽  
Moisture Diffusion ◽  
Convective Drying ◽  
Milk Clotting ◽  
Constant Rate ◽  
Different Temperatures ◽  
Drying Conditions ◽  
Transfer Properties ◽  
Natural Drying

Abstract Thistle flowers, and particularly their stigmas, are used to coagulate milk in the production of a number of traditional Portuguese cheeses due to their high milk-clotting activity provided by the high content of aspartic proteases. The aim of the present work was to determine the mass transfer properties of thistle flower under different drying conditions: natural drying and convective drying. Convective drying took place in a convection chamber set at different temperatures (35 to 65 °C) and the process was terminated when the sample presented a moisture content of about 5% or less. The traditional drying method was also used, placing the thistle flowers in a dry place sheltered from the sun, and leaving them to dehydrate at the variable room temperature. The present work allowed for the conclusion that convective drying was much faster than natural drying, and that the drying rate increased with temperature. The drying curve revealed an initial constant rate period followed by a falling rate. All the five thin layer models tested to fit the experimental data were shown to adequately describe the drying of the thistle flowers, but the best one was the Page model. The drying constant increased with temperature as did the effective diffusivity and the mass transfer coefficient. The results allowed one to estimate the activation energy for moisture diffusion (57 kJ/mol) and for convective mass transfer (78 kJ/mol). Thus this study showed the possibilities for designing efficient drying processes for the thistle flower used for milk-clotting in the manufacture of traditional cheeses.

scholarly journals FORMALIZATION OF THE COTTON DRYING PROCESS BASED ON HEAT AND MASS TRANSFER EQUATIONS

2020 ◽  
Vol 21 (2) ◽  
pp. 256-265
Author(s):  
Sayyora Yunusnova, Toshkenboyevna ◽  
Davron Holmatov, Abdalimovich ◽  
Muhiddin Atajonov, Odiljonovich ◽  
Ulugjon Huzanazarov
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
A Priori ◽  
Management Theory ◽  
Drying Process ◽  
Transfer Equations ◽  
Cotton Seeds ◽  
The Mathematical Model ◽  
Transfer Properties ◽  
Heat Agent

The paper deals with the construction of a mathematical model of the cotton drying process, taking into account the thermal and mass transfer properties of raw cotton components. To determine changes in the temperature of the fibre and raw cotton seeds, the application of Fourier's law is proposed. The mathematical dependence of the change on the humidity of the cotton fibre and seeds along the length of the drum is determined. The rational value of the heat agent consumption in the process of drying raw cotton is also determined. Research methods are based on the provisions of modern trends in management theory and identification. Mathematical models are constructed using analytical methods and equations that describe the physical properties of an object. Methods for constructing a mathematical model usually rely on experimental methods, in particular, the method of acceleration curves, and as a result, the mathematical description becomes a priori inaccurate. It is shown that the mathematical model used is quite adequate for the dynamics of a real object, fully describes it, and characterizes it over the entire range of changes. The analysis of the developed mathematical model based on simulation showed the adequacy of the obtained mathematical dependence of the temperature regime of the cotton drying process with the consumption of heat agent. ABSTRAK: Kajian ini membincangkan tentang penciptaan model matematik bagi proses pengeringan kapas, dengan mengambil kira terma dan sifat-sifat pindah jisim komponen kapas mentah. Bagi mendapatkan perubahan suhu fabrik dan biji benih kapas mentah, penggunaan hukum Fourier telah dicadangkan. Kebergantungan matematik pada perubahan kelembapan fabrik kapas dan biji benih sepanjang drum telah diperolehi. Nilai bersesuaian menggunakan ejen haba dalam proses pengeringan kapas kering mentah didapati. Kaedah kajian berdasarkan tren moden dalam teori pengurusan dan pengenalpastian. Model matematik dibina dengan menggunakan kaedah analisis dan persamaan yang menerangkan ciri-ciri fizikal pada objek. Kaedah bagi membina model matematik selalunya bergantung pada kaedah eksperimen, khususnya, kaedah pecutan melengkung, dan hasilnya, penyataan penaakulan matematik menjadi tidak tepat. Model matematik yang digunakan adalah cukup bagi objek dinamik sebenar, dengan penerangan penuh dan perincian ke atas keseluruhan perubahan. Analisis model matematik yang terhasil berdasarkan simulasi, dilihat cukup kebergantungan matematik terhasil melalui proses pengeringan kapas pada aturan suhu dengan ejen haba.

Sign in / Sign up

Export Citation Format

Share Document