A comprehensive review of thin-layer drying models used in agricultural products

Ertekin, Can; Fırat, Mehmet Ziya

doi:10.1080/10408398.2014.910493

Cited by 196 publications

(154 citation statements)

References 224 publications

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“…The most commonly used statistical parameters for solar drying are R 2 , χ 2 , and RMSE . The moisture ratio obtained from experiments in three drying conditions are applied to these models to determine the best fit based on lower values of χ 2 and RMSE and higher value of R 2 (Ertekin & Firat, ).…”

Section: Methodsmentioning

confidence: 99%

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Performance comparison of mixed mode and indirect mode parallel flow forced convection solar driers for drying Curcuma zedoaria

Lakshmi

Muthukumar

Ekka

et al. 2019

J Food Process Engineering

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This study focuses on energy and drying kinetic analyses of Curcuma zedoaria (white turmeric) dried in mixed and indirect active parallel flow solar dryers. Dryer efficiency, specific energy consumption and drying rate are studied. The overall dryer efficiency of mixed mode (MFSCD) is 26.5% higher than indirect mode (IFSCD) solar dryer. Two term model and Verma model fit best for Curcuma zedoaria drying in MFSCD and IFSCD, respectively, and Logarithmic model is quite suitable for open sun drying (OSD). The effective moisture diffusivity of the product dried under MFSCD is highest as compared to IFSCD and OSD products. The quality analyses show that higher values of TFC (78.11 mg GAE/g of sample) and DPPH (120.56 μ mol of TE/g of sample) are reported in the samples dried in MFSCD as compared to IFSCD and OSD samples. Practical applications Conventional open sun drying is a common practice followed by small farmers for drying herbs and spices. Products dried under open sun lose their nutritional and medicinal values due to slow drying rate and improper heating. The present work focusses on the development of a low cost solar dryer for drying of high value medicinal herbs like Curcuma zedoaria, curcuma caesia, and black cardamom. Study of drying kinetics helps in improving the design aspects of solar dryer and optimization of the drying systems. Drying time of the Curcuma zedoaria dried in the developed dryer is about 60% less than the open sun drying and the retention of color, antioxidant, and texture of the solar dried products is excellent. The developed solar dryer will be suitable for small small‐scale farmers and can be scaled up to any size.

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Section: Methodsmentioning

confidence: 99%

“…The analytical solution for the Fick's equation is given in Equation 14 (Ertekin & Firat, )

MR = A_{1} \sum_{n = 0}^{\infty} \frac{1}{{((), 2 n + 1)}^{2}} \times \exp ([], - \frac{{(2 n + 1)}^{2} π^{2} D_{eff}}{A_{2}} t)

…”

Section: Methodsmentioning

confidence: 99%

Performance comparison of mixed mode and indirect mode parallel flow forced convection solar driers for drying Curcuma zedoaria

Lakshmi

Muthukumar

Ekka

et al. 2019

J Food Process Engineering

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“…Equation (1) is analytically solved using the assumptions and the initial and boundary conditions are: symmetrical and uniform moisture distribution, internal movement of moisture as the major resistance, absence of shrinkage in the product during the process, occurring evaporation only at the surface, the moisture equilibrium on the surface, one‐dimensional, and constant effective moisture diffusivity for the duration of moisture content changes (Erbay & Icier, ; Ertekin & Firat, ). Analytical solution of Equation (1) is presented below for an infinite slab in Equation (2) (Erbay & Icier, ; da Silva et al, ):

M R = \frac{8}{π^{2}} {false\sum}_{n = 0}^{\infty} \frac{1}{{(2 n + 1)}^{2}} \exp [- \frac{{()(, 2 n + 1)}^{2} π^{2} D_{eff} t}{L^{2}}]

…”

Section: Introductionmentioning

confidence: 99%

“…It has been proved that semi‐theoretical and empirical models are only useful and practical when designing dryers. Semi‐theoretical models are derivative either from Fick's second law and or from Newton's law of cooling (Ertekin & Firat, ). The empirical models are obtained from a direct relevance of moisture content with drying time without attention to fundamentals of the drying process (Beigi et al, ).…”

Section: Introductionmentioning

confidence: 99%

Mathematical modeling of infrared radiation thin‐layer drying of pumpkin samples under natural and forced convection

Sadeghi

Movagharnejad

Asl

2019

J Food Process Preserv

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A comparative study was carried out between a large number of mathematical models and artificial neural networks to estimate the drying curves. Diamente et al. model and modified two‐term exponential‐V model were determined as the best ones describing drying curves for natural and forced drying air systems, respectively. The ANNs with 4‐9‐9‐1 and 3‐9‐1 topologies, log‐sigmoid, and hyperbolic tangent sigmoid transfer functions, and Levenberg–Marquardt training algorithm presented the best results for the former and latter systems, respectively. Furthermore, it was found that ANN modeling had much better performance in prediction of drying curves with respect to statistical analyses. Moisture diffusivity values were obtained in a range of 0.932×10-10-11.976×10-10normalm2/s and 2.209×10-10-9.848×10-10normalm2/s for the systems, respectively. Activation energies were determined as 88,509, 60,344, and 44,806 W/kg for the former system and 36.88, 29.66, and 18.59 kJ/mol for the latter system with an increase in the thickness of samples. Practical applications The main aim of drying food products is the reduction of moisture content up to a certain level to achieve the smallest possible amount of the microbiological spoilage. This process has a considerable effect on the drying kinetics and quality of the dried product as well. Infrared (IR) heating, as an alternative drying method for agricultural products, is efficient to preserve the main characteristics and to shorten drying time. It is important to investigate the effect operating parameters of IR dryer on the mentioned cases. Our studies have clearly displayed that IR heating of pumpkin samples can result in high heating rate and fast drying. Therefore, this alternative approach could be employed as an energy saving drying method along with improved drying efficiency and better product quality in comparison with the common drying methods. Study results are useful for producers of not only dried pumpkins but also other agricultural products.

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“…Among the different methods of drying, natural drying [18], convective drying [19] and solar drying [20] are conventionally used. Natural drying has the lowest installation cost, but requires a high storage volume.…”

Section: Introductionmentioning

confidence: 99%

Olive Mill Wastewater: From a Pollutant to Green Fuels, Agricultural Water Source and Bio-Fertilizer—Part 1. The Drying Kinetics

et al. 2017

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Abstract:Olive Mill Wastewater (OMWW) treatment is considered to be one of the main challenges that Mediterranean countries face. Although several procedures and technologies are mentioned in the literature, these techniques have several disadvantages or have been limited to laboratory pilot validation without posterior industrial projection. Recently, an advanced environmental friendly strategy for the recovery of OMWW was established involving the impregnation of OMWW on dry biomasses, drying of these impregnated samples, and finally green fuels and biochar production. This established strategy revealed that the drying step is crucial for the success of the entire recovery process. Hence, two impregnated samples were prepared through OMWW impregnation on sawdust (IS) and olive mill solid waste (ISW). The drying kinetics of OMWW and impregnated samples (IS and ISW) were examined in a convective dryer (air velocity range from 0.7-1.3 m/s and the temperature from 40-60 • C). The experimental results indicated that the drying of the impregnated samples occurred twice as fast as for the OMWW sample. Such behavior was attributed to the remaining thin layer of oil on the OMWW surface Furthermore, the Henderson and Pabis model showed the suitable fit of the drying curves with a determination coefficient R 2 above 0.97. The drying rates were extracted from the mathematical models and the drying process was analyzed. The coefficient of effective diffusivity varied between 2.8 and 11.7 × 10 −10 m 2 /s. In addition, the activation energy values ranged between 28.7 and 44.9 kJ/mol. These values were in the same range as those obtained during the drying of other agrifood byproducts. The final results could be very helpful to engineers aiming to improve and optimize the OMWW drying process.

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A comprehensive review of thin-layer drying models used in agricultural products

Cited by 196 publications

References 224 publications

Performance comparison of mixed mode and indirect mode parallel flow forced convection solar driers for drying Curcuma zedoaria

Performance comparison of mixed mode and indirect mode parallel flow forced convection solar driers for drying Curcuma zedoaria

Mathematical modeling of infrared radiation thin‐layer drying of pumpkin samples under natural and forced convection

Olive Mill Wastewater: From a Pollutant to Green Fuels, Agricultural Water Source and Bio-Fertilizer—Part 1. The Drying Kinetics

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