scholarly journals Application of inverse concepts to drying

2005 ◽  
Vol 9 (2) ◽  
pp. 31-44 ◽  
Author(s):  
Ljubica Kanevce ◽  
Gligor Kanevce ◽  
George Dulikravich
Keyword(s):  
Optimization Method ◽  
Temperature Fields ◽  
Convective Drying ◽  
Simultaneous Estimation ◽  
Transfer Coefficients ◽  
Sensitivity Matrix ◽  
Unknown Parameters ◽  
Body Dimension ◽  
Drying Time ◽  
Single Temperature

This paper deals with the application of inverse approaches to estimation of drying body parameters. Simultaneous estimation of the thermo physical properties of a drying body as well as the heat and mass transfer coefficients, by using only temperature measurements, is analyzed. A mathematical model of the drying process has been developed, where the moisture content and temperature fields in the drying body are expressed by a system of two coupled partial differential equations. For the estimation of the unknown parameters, the transient readings of a single temperature sensor located in an infinite flat plate, exposed to convective drying, have been used. The Levenberg-Marquardt method and a hybrid optimization method of minimization of the least-squares norm are used to solve the present parameter estimation problem. An analysis of the influence of the drying air velocity, drying air temperature, drying body dimension, and drying time on the thermophysical properties estimation, that enables the design of the proper experiments by using the so-called D-optimum criterion was conducted. In order to perform this analysis, the sensitivity coefficients and the sensitivity matrix determinant were calculated for the characteristic drying regimes and the drying body dimensions.

Inverse Approaches to Drying of Thin Bodies With Significant Shrinkage Effects

2006 ◽  
Vol 129 (3) ◽  
pp. 379-386 ◽  
Author(s):  
Gligor H. Kanevce ◽  
Ljubica P. Kanevce ◽  
Vangelce B. Mitrevski ◽  
George S. Dulikravich ◽  
Helcio R. B. Orlande
Keyword(s):  
Information Matrix ◽  
Optimization Method ◽  
Moisture Diffusivity ◽  
Temperature Fields ◽  
Convective Drying ◽  
Simultaneous Estimation ◽  
Transfer Coefficients ◽  
Unknown Parameters ◽  
Shrinkage Effect ◽  
Single Temperature

This paper deals with the application of inverse concepts to the drying of bodies that undergo changes in their dimensions. Simultaneous estimation is performed of moisture diffusivity, together with the thermal conductivity, heat capacity, density, and phase conversion factor of a drying body, as well as the heat and mass transfer coefficients and the relative humidity of drying air. This was accomplished by using only temperature measurements. A mathematical model of the drying process of shrinking bodies has been developed where the moisture content and temperature fields in the drying body are expressed by a system of two coupled partial differential equations. The shrinkage effect was incorporated through the experimentally obtained changes of the specific volume of the drying body in an experimental convective dryer. The proposed method was applied to the process of drying potatoes. For the estimation of the unknown parameters, the transient readings of a single temperature sensor located in the midplane of the potato slice, exposed to convective drying, have been used. The Levenberg–Marquardt method and a hybrid optimization method of minimization of the least-squares norm are used to solve the present parameter estimation problem. Analyses of the sensitivity coefficients and of the determinant of the information matrix are presented as well.

scholarly journals Optimization Method for the Evaluation of Convective Heat and Mass Transfer Effective Coefficients and Energy Sources in Drying Processes

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6577
Author(s):  
Marcin Stasiak ◽  
Grzegorz Musielak ◽  
Dominik Mierzwa
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Great Influence ◽  
Optimization Procedure ◽  
Optimization Method ◽  
Multistep Method ◽  
Drying Kinetics ◽  
Convective Drying ◽  
Transfer Coefficients ◽  
Effective Coefficients

A new optimization method for the assessment of the coefficients existing in a model of drying kinetics is developed and presented in this article. This method consists of matching the drying kinetics resulting from the mathematical model with the drying kinetics resulting from the experiments. Both the heat and mass transfer coefficients, the critical relative humidity, and the additional ultrasound energy (heat) source are included in the optimization procedure. The Adams–Bashforth multistep method of solving nonlinear ordinary differential equations is used. The inverse problem of model parameter estimation is solved by the Rosenbrock optimization method. The methodology is illustrated by the example of the ultrasound-assisted convective drying of apple and carrot. A high level of agreement between the results obtained experimentally and numerically was found. The obtained results confirmed the great influence of ultrasound on the drying kinetics. It was found that ultrasound application improved the mass transfer by 20–80% and heat transfer by 30–90%. It was also found that the heating effect caused by the ultrasound’s absorption was very small, with a value below 1%.

The Effect of Regulating Elements on Convective Heat Transfer along Shaped Heat Exchange Surfaces

2013 ◽  
Vol 34 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Jozef Cernecky ◽  
Jan Koniar ◽  
Zuzana Brodnianska
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Cfd Simulation ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Temperature Fields ◽  
Transfer Coefficients ◽  
Heat Transfer Intensification ◽  
Heat Transfer Coefficients ◽  
Forced Air

Abstract The paper deals with a study of the effect of regulating elements on local values of heat transfer coefficients along shaped heat exchange surfaces with forced air convection. The use of combined methods of heat transfer intensification, i.e. a combination of regulating elements with appropriately shaped heat exchange areas seems to be highly effective. The study focused on the analysis of local values of heat transfer coefficients in indicated cuts, in distances expressed as a ratio x/s for 0; 0.33; 0.66 and 1. As can be seen from our findings, in given conditions the regulating elements can increase the values of local heat transfer coefficients along shaped heat exchange surfaces. An optical method of holographic interferometry was used for the experimental research into temperature fields in the vicinity of heat exchange surfaces. The obtained values correspond very well with those of local heat transfer coefficients αx, recorded in a CFD simulation.

scholarly journals Energetic and exergetic analysis of a convective drier: A case study of potato drying process

2020 ◽  
Vol 5 (1) ◽  
pp. 563-572
Author(s):  
Iman Golpour ◽  
Mohammad Kaveh ◽  
Reza Amiri Chayjan ◽  
Raquel P. F. Guiné
Keyword(s):  
Energy Consumption ◽  
Research Work ◽  
Specific Energy Consumption ◽  
Exergy Efficiency ◽  
Operating Conditions ◽  
Energy Utilization ◽  
Convective Drying ◽  
Drying Time ◽  
Energy And Exergy ◽  
Exergy Losses

AbstractThis research work focused on the evaluation of energy and exergy in the convective drying of potato slices. Experiments were conducted at four air temperatures (40, 50, 60 and 70°C) and three air velocities (0.5, 1.0 and 1.5 m/s) in a convective dryer, with circulating heated air. Freshly harvested potatoes with initial moisture content (MC) of 79.9% wet basis were used in this research. The influence of temperature and air velocity was investigated in terms of energy and exergy (energy utilization [EU], energy utilization ratio [EUR], exergy losses and exergy efficiency). The calculations for energy and exergy were based on the first and second laws of thermodynamics. Results indicated that EU, EUR and exergy losses decreased along drying time, while exergy efficiency increased. The specific energy consumption (SEC) varied from 1.94 × 105 to 3.14 × 105 kJ/kg. The exergy loss varied in the range of 0.006 to 0.036 kJ/s and the maximum exergy efficiency obtained was 85.85% at 70°C and 0.5 m/s, while minimum exergy efficiency was 57.07% at 40°C and 1.5 m/s. Moreover, the values of exergetic improvement potential (IP) rate changed between 0.0016 and 0.0046 kJ/s and the highest value occurred for drying at 70°C and 1.5 m/s, whereas the lowest value was for 70°C and 0.5 m/s. As a result, this knowledge will allow the optimization of convective dryers, when operating for the drying of this food product or others, as well as choosing the most appropriate operating conditions that cause the reduction of energy consumption, irreversibilities and losses in the industrial convective drying processes.

Turbulent Heat and Momentum Transports in an Infinite Rod Array

1987 ◽  
Vol 109 (3) ◽  
pp. 599-605 ◽  
Author(s):  
An-Shik Yang ◽  
Ching-Chang Chieng
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Equation Model ◽  
Temperature Fields ◽  
Turbulent Heat ◽  
Fluid Temperature ◽  
Transfer Coefficients ◽  
Anisotropic Factor ◽  
Flow Through ◽  
Rod Array

An anisotropic factor is carefully selected from eleven distributions and adopted to the k–ε two-equation model of turbulence to obtain detailed velocity and temperature fields for steady-state, fully developed turbulent flow through infinite triangular/square rod array. The present study covers the ranges of pitch-to-diameter ratio from 1.123 to 1.5, and Reynolds number from 2.4 × 104 to 106. Velocity and wall shear stress are calculated and compared to experimental data. Normalized fluid temperature, friction factor, and heat transfer coefficient are also computed. The correlations of friction factor and heat transfer coefficients for flow inside circular pipe and flow through finite rod arrays are compared with the results for flow through infinite rod arrays.

Development of Convective Heat Transfer Near Suddenly Heated, Vertically Aligned Horizontal Wires

1987 ◽  
Vol 109 (4) ◽  
pp. 912-918 ◽  
Author(s):  
J. R. Parsons ◽  
M. L. Arey
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Fluid Layer ◽  
Convective Motion ◽  
Transient Behavior ◽  
Temperature Fields ◽  
Heat Sources ◽  
Transfer Coefficients ◽  
Vertically Aligned ◽  
The Wire

Experiments have been performed which describe the transient development of natural convective flow from both a single and two vertically aligned horizontal cylindrical heat sources. The temperature of the wire heat sources was monitored with a resistance bridge arrangement while the development of the flow field was observed optically with a Mach–Zehnder interferometer. Results for the single wire show that after an initial regime where the wire temperature follows pure conductive response to a motionless fluid, two types of fluid motion will begin. The first is characterized as a local buoyancy, wherein the heated fluid adjacent to the wire begins to rise. The second is the onset of global convective motion, this being governed by the thermal stability of the fluid layer immediately above the cylinder. The interaction of these two motions is dependent on the heating rate and relative heat capacities of the cylinder and fluid, and governs whether the temperature response will exceed the steady value during the transient (overshoot). The two heat source experiments show that the merging of the two developing temperature fields is hydrodynamically stabilizing and thermally insulating. For small spacing-to-diameter ratios, the development of convective motion is delayed and the heat transfer coefficients degraded by the proximity of another heat source. For larger spacings, the transient behavior approaches that of a single isolated cylinder.

Method of calculating the convective drying time for gypsum molds

1989 ◽  
Vol 46 (11) ◽  
pp. 456-459
Author(s):  
Yu. N. Kryuchkov ◽  
G. Z. Komskii
Keyword(s):  
Convective Drying ◽  
Drying Time

scholarly journals Convective Drying of Sewage Sludge Layer in Through-flow

2020 ◽  
Vol 66 (9) ◽  
pp. 481-493
Author(s):  
Andraž Lipolt ◽  
Brane Širok ◽  
Marko Hočevar ◽  
Lovrenc Novak
Keyword(s):  
Sewage Sludge ◽  
Drag Force ◽  
Layer Structure ◽  
Measured Data ◽  
Matter Content ◽  
Convective Drying ◽  
Coefficient Of Determination ◽  
Dry Matter Content ◽  
Drying Time ◽  
Drying Rates

Drying of the sewage sludge layer was investigated in a convective laboratory dryer at air temperatures of 65 °C and 80 °C and air speeds of 0.53 m/s and 0.83 m/s. The sludge layer was formed by loading cylindrical extrudates on a grate of 0.5 m × 0.5 m size. The drying air was directed through the layer, as typically encountered in industrial belt dryers. Under such setup, the sludge layer structure and porosity significantly affect the air flow conditions and thus the drying rates. Shrinkage and cracking of the material during drying caused changes in the layer’s porous structure, that affected the pressure drop and the drag force due to passing of air through the layer. The decreasing of drag force over time was modeled by a simple function that showed excellent agreement to the selected measured data. The sludge layer drying kinetics was determined by fitting the measured data to the most common drying models. Two models, the modified Nadhari and the Wang Singh model, were determined as most suitable for modeling of drying curves. The total drying time per kilogram of sludge was modeled as a function of drying air temperature, drying air velocity and initial sludge dry matter content. The coefficient of determination (R2) of the model is 0.944. Total drying times between 43 minutes per kilogram and 76 minutes per kilogram of sludge were obtained for the investigated range of drying air conditions.

scholarly journals The influence of ethanol on the convective drying and on the nutritional quality of dekopon slices

2018 ◽  
Author(s):  
Ronaldo Elias de Mello-Júnior ◽  
Nathane Silva Resende ◽  
Jefferson Luiz Gomes Corrêa ◽  
Leila Aparecida Salles Pio ◽  
Elisângela Elena Nunes Carvalho
Keyword(s):  
Antioxidant Activity ◽  
Phenolic Compounds ◽  
Vitamin C ◽  
Nutritional Quality ◽  
Quality Parameters ◽  
Nutritional Composition ◽  
Convective Drying ◽  
Total Phenolic ◽  
Drying Time ◽  
Citrus Reticulate

Dekopon or Hallabong (Citrus reticulate “Shiranui”) is a hybrid fruit that belongs to the citrus fruits. The scientific and commercial interests in dekopon is due to its nutritional composition. The objective of the study was to verify the influence of ethanol as a pretreatment in reducing drying time as well as maintaining nutritional quality (vitamin C, total phenolic compounds, and antioxidant activity) of dekopon slices. The drying with ethanol at 70 °C promoted the greatest reduction in drying time, but the processed pretreated samples at 50 °C presented the highest level of nutritional quality parameters. Keywords: drying time; vitamin C; phenolic compounds; antioxidant activity 

scholarly journals Mathematical modeling of pequi pulp drying and effective diffusivity determination

2017 ◽  
Vol 21 (7) ◽  
pp. 493-498 ◽  
Author(s):  
Elisabete P. de Sousa ◽  
Rossana M. F. de Figueirêdo ◽  
Josivanda P. Gomes ◽  
Alexandre J. de M. Queiroz ◽  
Deise S. de Castro ◽  
...  
Keyword(s):  
Experimental Data ◽  
Effective Diffusivity ◽  
Drying Kinetics ◽  
Convective Drying ◽  
Drying Time ◽  
Air Speed ◽  
Drying Curves ◽  
Increasing Temperature ◽  
Kinetics Of ◽  
Best Fit

ABSTRACT The aim of this work was to study the drying kinetics of pequi pulp by convective drying at different conditions of temperature (50, 60, 70 and 80 °C) and thickness (0.5, 1.0 and 1.5 cm) at the air speed of 1.0 m s-1, with no addition of adjuvant. The experimental data of pequi pulp drying kinetics were used to plot drying curves and fitted to the models: Midilli, Page, Henderson & Pabis and Newton. Effective diffusivity was calculated using the Fick’s diffusion model for a flat plate. It was found that, with increasing thickness, the drying time increased and, with increasing temperature, the drying time was reduced. The Midilli model showed the best fit to the experimental data of pequi pulp drying at all temperatures and thicknesses, presenting higher coefficients of determination (R2), indicating that this model satisfactorily represents the pequi pulp drying phenomenon. There was a trend of increase in the effective diffusivity with the increase in pulp layer thickness and temperature.

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